Gold, Chlorides of:

["1. =Monochloride.= AuCl. _Syn._ AUROUS CHLORIDE, PROTOCHLORIDE OF GOLD. A yellowish-white mass, formed when a solution of trichloride of gold is evaporated to dryness, and the residuum is exposed to a heat of about 440° Fahr., until fumes of chlorine cease to be evolved. It is insoluble in water, which decomposes it, slowly when cold, but rapidly by the aid of heat, into metallic gold and the trichloride.", "2. =Trichloride.= AuCl_{3}. _Syn._ AURIC CHLORIDE, TERCHLORIDE OF GOLD, TRICHLORIDE OF GOLD, AURI CHLORIDUM. _Prep._ Gold, 1 part, dissolved by aid of heat in nitro-hydrochloric acid, 8 parts, and evaporated down to near dryness, and allowed to crystallise.", "_Prop._ Orange-red crystalline needles, or ruby-red prismatic crystals; deliquescent; soluble in water, ether, and alcohol, forming a deep-yellow solution; at the heat of 500° Fahr. it suffers decomposition, chlorine being given off and pure gold left behind. It is reduced by ferrous sulphate, oxalic, sulphurous, formic and phosphorous acids, as well as by most of the metals, to metallic gold. It combines with several of the metallic chlorides, forming a series of double salts, which are mostly yellow when in crystals, and red when deprived of water.", "_Uses, &c._ It has been employed by Duportal, Chrestien, Niel, Cullerier, Legrand, and others, as a substitute for mercury, in scrofula, bronchocele, chronic skin diseases, &c.; also as a caustic.--_Dose_, 1/20 gr., dissolved in distilled water, or made into a pill with starch; or, in frictions on the gums, in quantities of 1/16 to 1/10 gr. Its most important use, however, is as a reagent in photography, large quantities being manufactured for use as a chief agent in toning photographic prints.", "To some extent it is also used for electro-gilding, and mixed with excess of bicarbonate of potassium, it forms a good yielding solution for small articles of copper. These are to be first cleaned with dilute nitric acid, and then boiled for some time in the mixture.", "The above is the salt generally referred to under the name of the 'chloride of gold,' or in commerce occasionally as the 'muriate of gold.'", "Gold, Chloride of, and Sodium.= AuCl_{3}. NaCl. 2Aq. _Syn._ AUROCHLORIDE OF SODIUM; SODII AUROCHLORIDUM. _Prep._ Auric chloride, 85 parts; chloride of sodium, 16 parts; dissolve in a little distilled water, evaporate until a pellicle forms, then put it aside to crystallise. It forms beautiful orange-coloured rhombic prisms.", "_Dose, &c._ 1/20 to 1/12 gr., made into a pill with starch or lycopodium, in the same cases in which the terchloride is ordered. Mixed with 2 or 3 times its weight of orris powder, it has been used in frictions on the tongue and gums, and an ointment made with 1 gr. of the salt, mixed with 36 gr. of lard, has been applied to the skin deprived of the epidermis by a blister.", "Gold, Cyanide of.= AuCy_{3}. _Syn._ AURIC CYANIDE. _Prep._ Add a solution of pure cyanide of potassium to a solution of pure auric chloride as long as a precipitate forms, carefully avoiding any excess; wash, and dry the precipitate.", "_Prop., Uses, &c._ The salt is a pale-yellow powder, insoluble in water, but very soluble in a solution of cyanide of potassium, forming the double cyanide of gold and potassium so largely used in the electrotype process. Cyanide of gold is employed to a certain extent in medicine.--_Dose_, 1/12 to 1/10 gr., made into a pill, in the usual cases in which gold is administered. The first formula is essentially similar to that of the French Codex.", "Gold, Extraction of, by Sodium Amalgam.= (Crookes' Method, Patented.) In the extraction of gold by amalgamation serious difficulties are often occurring through the 'flouring' or 'sickening' of the mercury employed, and the prevention of the amalgamation by a coating of tarnish on the gold. So much is this the case that losses of from 30 to 60 per cent. of the gold are usually incurred, and, in many cases a still more serious loss of mercury.", "When certain minerals, as tellurium compounds, pyrites, &c., occur in the gold ore, the mercury is apt, on trituration, to become subdivided into excessively minute globules, which, owing to their tarnished condition, refuse to unite, and are consequently washed away, it being almost impossible to separate them from the heavier portions of the ore. This is technically called 'flouring,' 'granulating,' &c. Besides this, certain of these minerals affect the mercury in another way, that is, by 'sickening' it, or causing it to lose its bright surface and fluidity, and prevents its amalgamating with the gold. Besides the inconvenience and loss thus caused, a further loss of gold takes place from the inability of the ordinary mercury to touch or amalgamate tarnished gold, unless it is ground with it, for a more lengthy period than is found practicable in most cases.", "Mr Crookes, F.R.S., has, by means of the addition of a certain proportion of sodium, in the form of an amalgam, to the mercury, effectually prevented this serious loss of gold and mercury. By adding certain quantities of amalgams B and C, an amount which, differing from each ore, is ascertained by experiment, the 'flouring' and 'sickening' of the mercury is effectually prevented, the mercury remaining throughout in the best condition. The addition of about one tenth per-centage of amalgam A, at intervals of some hours, increases most powerfully the affinity of the mercury for the precious metals, and secures a more thorough amalgamation.", "This invention has met with general approval, and experiments conducted at many mines show its great practical value, giving an increase of from 5 to 30 per cent. in the yield of gold, and, in fact, with many pyrites that yielded no gold to the ordinary amalgamation process, gave a considerable yield of gold to the sodium amalgamation process. This has led to its use in most mines, both silver and gold, in America.", "Gold, Iodide of.= AuL_{3}. _Syn._ AURIC IODIDE, TRI-IODIDE OF GOLD, GOLD TERIODIDE, AURI IODUM. _Prep._ Add a solution of trichloride of gold to one of iodide of potassium. The resulting precipitate is at first redissolved on agitation, a soluble double iodide being formed; subsequently the iodide of gold is precipitated, leaving the supernatant liquor free of colour.", "_Prop., Uses, &c._ A dark-green powder, easily soluble in hydriodic acid. It is occasionally employed as a medicine, and, like other preparations of gold, is of an alterative character.--_Dose._ About 1/16th of a grain.", "Gold, Oxides of=:--", "1. =Monoxide.= Au_{2}O. _Syn._ AUROUS OXIDE, PROTOXIDE OF GOLD. _Prep._ Formed by treating the aurous chloride with strong potassium hydrate. Green powder, somewhat soluble in potassium hydrate solution, and readily decomposing into metallic gold and auric oxide.", "2. =Trioxide.= Au_{2}O_{3}. _Syn._ AURIC OXIDE, OXIDE OF GOLD, PEROXIDE OF GOLD, AURIC ACID, AURI OXIDUM. _Prep._ Magnesic oxide, 4 parts; auric chloride, 1 part; water, 40 parts; mix, boil, and wash the precipitate with water, dilute nitric acid, and again with water. It must be dried in the shade.", "Reddish-yellow powder, easily decomposed by heat; readily soluble in hydrochloric and hydrobromic acids and strong nitric acid, but insoluble in water and the other acids. Forms unstable salts with the alkalies.", "_Uses, &c._ Trioxide of gold has been given in scrofula, &c., in doses of 1/12 to 1/2 gr., or 1 gr., in scrofula, syphilis, &c., made into a pill with extract of mezereon.", "Gold, Ammoni'uret of*.= _Syn._ AURATE OF AMMONIA, BERTHOLLET'S FULMINATING GOLD; AURUM AMMONIATUM, AMMONIÆ AURAS, L. _Prep._ By adding ammonia to a solution of gold in aqua regia (trichloride), as long as a reddish-yellow precipitate (fulminating gold) forms; the latter must be collected, washed, and dried with the greatest possible caution.", "_Obs._ Ammonia fails to precipitate trioxide of gold from solutions which are not tolerably concentrated, and in those containing free acid or ammoniacal salts the precipitate only forms upon boiling the solution. Before adding the ammonia, it is, therefore, proper to drive off the excess of acid, if any, by the application of heat. See FULMINATING COMPOUNDS.", "Gold, Sul'phide of.= Au_{2}S_{3}. _Syn._ SULPHURET OF GOLD, TERSULPHURET OF G.; AURI SULPHURETUM, L. _Prep._ Transmit a current of sulphuretted hydrogen gas through a solution of terchloride of gold in water; or add hydrosulphuret of ammonia to the same solution; collect the precipitate, wash it with cold distilled water, and dry it in the shade.", "GOLD DETER'GENT.= _Prep._ (Upton.) Take quicklime, 1 oz.; sprinkle it with a little hot water to slake it, then gradually add boiling water, 1 pint, so as to form a milk. Next dissolve pearlash, 2 oz., in boiling water, 1-1/2 pint; mix the two solutions, cover up the vessel, agitate occasionally for an hour, allow it to settle, decant the clear, put it into flat half-pint bottles, and well cork them down.", "_Use._ To clean gilding, &c., either alone or diluted with water. It is applied with a soft sponge, and then washed off with clean water. It is essentially a weak solution of potassa, and may be extemporaneously prepared by diluting solution of potassa (Ph. L.) with about 5 times its volume.", "GOLD SHELLS.= Gold leaf or powdered gold ground up with gum-water, and spread upon the insides of shells. Used by artists.", "GOLD SIZE.= _Syn._ GILDING SIZE, GILDER'S S., GOLD COLOUR. _Prep._ 1. (OIL SIZE.) Drying or boiled oil thickened with yellow ochre or calcined red ochre, and carefully reduced to the utmost smoothness by grinding. It is thinned with oil of turpentine. Improves by age. Used for oil gilding.", "2. (WATER SIZE.) Parchment or isinglass size, mixed with finely ground yellow ochre. Used in burnished or distemper gilding.", "GOLD-BEAT'ER'S SKIN= is prepared from the peritoneal membrane of the cæcum of the ox. It is used to separate the leaves of gold whilst under the hammer, as a nearly invisible defensive dressing for cuts, as a fabric for court plaster, &c.", "GOLDEN SEAL.= See HYDRASTIS CANADENSIS.", "GONG METAL.= See BELL METAL.", "GONIOM'ETRY.= The art of measuring the angles of crystals, by means of a GONIOMETER; a most important matter in _chemistry_ and _mineralogy_. The only accurate and simple instrument of this kind is the REFLECTING GONIOMETER invented by Dr Wollaston. Facility in using this instrument is readily acquired by a few trials.", "GOOSE.= This bird, the _Anser domesticus_, is a favourite article of food almost everywhere, and may fairly claim a similar position amongst poultry to that occupied by \"good Sir Loin\" among joints of meat. The vulgar inuendos occasionally heard to its prejudice should be directed against the cook rather than the bird, as it is only when it is unskilfully dressed and too highly seasoned that it is apt to disagree with that \"irascible member of the interior,\" a delicate or overloaded stomach. Undue susceptibility in that quarter may, however, be generally allayed by an oblation, in the shape of a little '_eau de vie_,' used as sauce or gravy. Formerly, almost miraculous virtues were attributed to this bird. Its flesh was said to promote longevity, to cure hydrophobia, and to be aphrodisiac. The fat (GOOSE GREASE; ADEPS ANSERIS), mixed with honey, was supposed to be \"good against the bitings of a mad dog.\" At the present day it is occasionally used in clysters, and, when scented, as a pomade to make the hair grow, for which purpose it is said to be superior to bear's grease. In quantity it is an emetic of very easy action. The large feathers of the wings (quills) are used for writing. The small feathers form the common stuffing of our beds.", "GOOSE'BERRY.= The fruit or berry of _Ribes grossularis_. Unripe fruit, cold and acidulous; ripe fruit, wholesome and slightly laxative; but the seeds and skins should not be eaten, as they are very indigestible; the juice of the green fruit is made into wine (ENGLISH CHAMPAGNE); the seeds, washed and roasted, were formerly used as a substitute for coffee (GOOSEBERRY COFFEE). Gooseberries are preserved by simply bottling them, and keeping them in a very cold place. See CHEESE, FOOL, FRUIT, &c.", "GOULARD.= _Syn._ GOULARD'S EXTRACT. See SOLUTION OF DIACETATE OF LEAD.", "GOUT.= _Syn._ ARTHRITIS, L. A painful disease that chiefly attacks the male sex, particularly those of a corpulent habit and robust frame. Persons who live temperately and take much exercise are seldom troubled with gout. Indolence, inactivity, luxurious habits of life, and free living, are the chief exciting causes of this disease; but excessive study, grief, watchfulness, exposure to cold, and the too free use of acidulous liquors, also occasionally bring it on. In some persons it is an hereditary disease.", "_Symp._ Gout is generally preceded by unusual chilliness of the feet and legs, and a numbness or a sensation of prickling along the lower extremities; the appetite fails, flatulency, indigestion, torpor, and languor ensue, and extreme lassitude and fatigue follow the least bodily exercise; the bowels become costive, and the urine pallid. The fits usually come on in the night; the patient is awakened by the severity of the pain, generally in the first joint of the great toe, or occasionally in the heel, whole foot, or calf of the leg. The pain resembles that of a dislocated joint, accompanied by a sensation resembling the effusion of cold water; the pain increases, rigors and febrile symptoms ensue, accompanied with local throbbing and inflammation. Sometimes both feet and legs are attacked; at others, only one. Towards morning the patient generally falls asleep, and sinks into a state of copious perspiration, from which he awakes comparatively recovered. This constitutes what is called a 'fit of gout.' These fits or paroxysms are apt to return at intervals, commonly every evening, with more or less violence; and when frequent, the disease usually extends its action, the joints become affected, and concretions of a chalky nature (chalk stones, gout stones) are formed upon them, and they become stiff and nearly immovable.", "_Treat._ A plain or vegetable diet, moderate exercise, and the use of warm laxatives, gentle tonics, diaphoretics, and diuretics, are among the best preventives. The moderate use of alkaline remedies, as potassa and magnesia, has also been recommended. To relieve the fit of gout, or to check it at its commencement, the affusion of cold water will be often found effective. The use of the '_eau médicinale_', or the '_vinum colchici_' of the Pharmacop[oe]ia, may also be had recourse to; a due dose of which taken at bedtime will frequently carry off the paroxysm, and nearly always mitigate the symptoms. The effect of the above remedies do not greatly differ from each other. The action of both medicines is accompanied with great languor, and a deadly nausea or sickness, which terminates in vomiting or a discharge from the bowels, or both. These symptoms have often reached an alarming extent, and in some constitutions follow even a moderate dose. This method of cure should not, therefore, be unadvisedly and incautiously adopted.", "Another remedy which has been recommended for gout is lemon juice, but experience has proved that this agent is not to be depended on. The dose proposed by Dr O. Rees, who originated this treatment, was 2 or 3 fl. oz., twice or thrice a day.", "To ensure the efficacy of lemon juice, it must be expressed from the fruit into the glass shortly before being taken. That purchased at the shops is generally stale and disagreeable, and is often worse than useless. In some cases it is advisable to take the juice undiluted, but the more common practice is to mix it with about an equal quantity of water. See RHEUMATISM, COLCHICUM, DRAUGHT (Anti-arthritic), LEMON JUICE, VINEGAR OF COLCHICUM, WINE OF COLCHICUM, &c.", "Gout Cor'dial.= _Prep._ Rhubarb, senna, coriander seed, sweet-fennel seed, and cochineal, of each 2 oz.; liquorice root and saffron, of each 1 oz.; raisins, 2-1/2 lbs.; rectified spirit of wine, 2 gals.; digest for 14 days, press, and filter. Used in gout and rheumatism. Aromatic and slightly laxative.--_Dose_, 1 to 3 table-spoonfuls.", "Gout Med'icine.= (Duncan's.) A mixture of wine of colchicum, wine of opium, and tincture of saffron.", "Gout Rem'edy.= (Alexander's.) According to Dr Paris, this contains--aniseed, cumin seed, ginger, hermodactyles, pepper, and scammony.", "Gout Specific.= (Murray's.) A mixture of iodide of potassium, sulphate of magnesia, and wine of colchicum, disguised with an aromatic tincture.", "GOUTTES AMERES.= [Fr.] See DROPS (Bitter).", "GRAD'UATOR.= See VINEGAR.", "GRAFTING COM'POST.= Clay tempered with water, to which a little linseed oil is sometimes added. Used to cover the joint formed by the scion and stock in grafting.", "GRAINS OF HEALTH, Dr Franck's--Gesundheitspillen--Grains de Santé, ou Grains de Vie=, du Docteur Franck. Silvered pills, containing 1 part gamboge and 4 parts aloes. (Hager.)", "GRAINS OF PAR'ADISE.= _Syn._ GUINEA GRAINS, MELEGUETTA PEPPER. The seeds of the _Ammomum meleguetta_. Grains of paradise are hot, acrid, and aromatic, and in general properties similar to the other peppers. In some parts of the world they are used as a condiment. They are principally employed in these countries to impart a false strength to wine, beer, spirits, and vinegar.", "GRANIL'LA.= A small inferior variety of cochineal (which _see_).", "GRANULA'TION.= The act or process of forming, or breaking into, grains or small masses.", "The granulation of MEDICINES has of late years received considerable attention from both foreign and British pharmaceutists. In France, granulated powders (POUDRES GRANULÉES) are coming into general use in place of impalpable powders, the most unpleasant of all forms of medicine. The French process consists in enveloping the particles of medicines in syrup by means of heat and constant stirring. Mr Banner, of Liverpool, has lately introduced a method of granulating medicines far preferable to that of the French pharmaceutists. The powder to be granulated is placed in a mortar, and mucilage of gum acacia is gradually added until a crumbly mass is made; this is then rubbed through a wire sieve (about 12 meshes to the inch), and the granules produced are spread out on paper, and left to dry spontaneously, or they are placed in a copper pan, and kept in constant motion over a stove until dry; when perfectly dry, they are placed in a mortar, and sufficient quantity of strong tincture of tolu (3 dr. to 1 oz.) is added to them, until by constant stirring they all appear glossy and shining; they are then dried again by a gentle heat, being kept in constant motion. The granules thus formed keep well, are tasteless, and are much more elegant and agreeable preparations than pills or ordinary powders. Many saline substances are granulated by the simple process of dissolving the salt in water, and evaporating to dryness with constant stirring.", "METALS are granulated (reduced to drops, grains, or coarse powder) by pouring them, in the melted state, into water. In many cases they are allowed to run through the holes of a species of colander or sieve to produce minute division; and in order to render the drops spherical, they are allowed to fall from a sufficient height to permit of their acquiring the solid state before striking the water. Lead shot is made in this way. Shot towers are often upwards of 100 feet in height. See COPPER, GUNPOWDER, POWDER, ZINC, &c.", "GRAPES.= _Syn._ UVÆ, L. The fruit of _Vitis vinifera_, or the common grape vine. Ripe grapes are cooling and antiseptic, and in large quantities diuretic and laxative. They are very useful in bilious affections and dyspepsia, and in all febrile, putrid, and inflammatory complaints. The skin and seed, which are indigestible, should be rejected. \"Grapes which contain a large quantity of sugar are, if taken without the husks, the safest and most nutritive of summer fruits.\" (Cullen.) \"The subjects of pulmonary affections, who pass the summer in Switzerland, may try the effects of a course of grapes, '_cure de raisins_,' a remedy held in high estimation in several parts of the Continent.\" (Sir J. Clark.)", "Grapes, in bunches are preserved by wrapping them in silver paper, and packing them in dry bran. Each bunch is suspended by the stem with the fingers of one hand, whilst the bran is poured round it with the other; the jar being occasionally gently shaken as the process of packing proceeds. Some paper is then laid over the top of the jar, the mouth or cover of which is, lastly, tied firmly over with bladder, to exclude the air and moisture. See FRUIT, &c.", "GRAPH'ITE.= See PLUMBAGO.", "GRATE.= A frame of iron bars used for burning coal as fuel. In the construction of a grate it is desirable to make the perpendicular height of the fuel as great as is consistent with safety. A stratum of burning coal will radiate considerably more heat into an apartment if placed vertically than if arranged horizontally; besides which a great saving of fuel will be effected in proportion to the heat radiated. Hence the faulty construction of the old-fashioned wide grates. The fuel should also be so divided in a fireplace as to be easy of ignition, and so placed as to give free access of air to all its parts, as the smoke is then more likely to be burnt.", "GRAV'EL.= A collection of small pebbles commonly mixed with sand or clay, or both. Gravel for garden walks is chosen for its fine colour and binding properties. The gravel of Kensington and Wimbledon is esteemed the finest in the world. Gravel walks when once in order, may be rendered nearly equal to asphalt by pouring over them tar or a mixture of tar and pitch, absorption being promoted, if required, by the application of a hot iron.", "Gravel.= In _pathology_, a term popularly applied to calculous matter formed in the kidneys, and passing off in the urine; and sometimes to distinct calculi or concretions in the bladder itself.", "An attack of gravel, as commonly understood, is accompanied by a deposit of red, gritty, sand-like particles in the urine, which do not dissolve when the urine is heated. The deposit consists of uric acid. Pains in the loins are a common accompaniment of gravel, and there is also sometimes pain in passing water.", "_Treat._ Give twenty minims of solution of potash (of the B. P.) three times a day in barley water; or twenty grains of bicarbonate of soda, also three times a day. If the attack be attended with much pain a brisk dose of Gregory's powder should be additionally taken every morning. Vichy Water will also be found a useful remedy. See CALCULUS.", "GRAVIM'ETER.= See HYDROMETER.", "GRAV'ITY.= _Syn._ GRAVITATION. The attractive force by which bodies fall towards the centre of the earth. Weight is the measure of gravity. The determination of the relative weight of bodies with reference to a given standard, is explained under SPECIFIC GRAVITY.", "GRA'VY.= The juice or liquid matter that drains from dressed meat after it is placed on the dish for serving. The common practice among cooks is to pour a spoonful or two of boiling water or broth over the joint, to increase the quantity. The natural gravy that oozes from the meat after it is cut is the richest and most wholesome. Made gravies are prepared by adding spice and flavouring to the foregoing, or to strong meat soup.", "The gravy for roast meat is usually made by sprinkling a little salt on the joint after it is placed in the dish, and then pouring some boiling water over it; this washes off some of the brown, and makes a coloured liquid in the dish.", "Another method for making gravy for roast meat is the following:--Take any bones, scraps of cold meat, or trimmings of the joint, put them in a half pint of water, with a little salt and half an onion, let them stew all the time the meat is roasting; colour with a little burnt sugar. When the meat is done, pour the dripping from it carefully into a basin, leaving the gravy at the bottom of the tin; strain the gravy you have made into this, let it boil, and pour round (not over) the meat. If the gravy is liked thick, put a dessert-spoonful of flour, mixed into a smooth paste, with two of cold water, into the saucepan five minutes before you strain it. See SAUCE.", "GRAY.= _Syn._ GREY; GRIS, Fr. A mixture of black and white. Delicate grays result from mixture of the three elementary colours, red, yellow, and blue, in which the blue preponderates to a greater or less extent.", "GRAY DYE.= _Syn._ TEINTE GRISE. Gray is dyed with the same materials as black, but both the bath and mordaunt are used in a more diluted state. COTTON goods may be worked in sumach and then in copperas; this gives rather a bluish grey, which may be modified to any particular hue by the addition of suitable colouring matter. To make it yellowish, a small amount of fustic and alum are employed; to make it 'fuller,' peachwood and Lima-wood with alum are used. The methods of obtaining grey on SILK and WOOL are very numerous; they are similar in principle to the above, all depending on the blending of the three primary colours, or on the modification of weak blacks. See BLACK DYE.", "GREASE.= A general term applied to soft animal fats; as BEAR'S GREASE, GOOSE GREASE, &c.", "Grease.= An inflammatory affection of the heels of horses, which produces dryness, scurfiness and stiffness. The _treatment_ consists of emollient poultices, accompanied with physic and diuretic balls, to subdue the inflammation, followed by mild astringent lotions or ointments.", "GREAVES.= _Syn._ GRAVES. The sediment of melted tallow, consisting chiefly of animal membranes mixed with fat, made up into cakes. Used as a coarse food for dogs.", "GRE'CIAN WATER.= See HAIR DYES.", "GREEN.= _Syn._ VIRIDIS, L.; VERT, Fr. Of the colour of the leaves of growing plants; _subst._ a green colour.", "GREEN DYE.= _Syn._ TEINTE VERTE, Fr. All the green dyes in use, with the practically unimportant exception of Chinese green and oxide of chromium green, are compounded of blue and yellow. The goods, in practice, are generally dyed blue first, observing to regulate the shade according to that of the intended green; they are then dried, rinsed, and passed through a yellow bath, with the like precautions, until the proper shade is obtained. See BLUE DYE, YELLOW DYE, &c.", "GREEN PIG'MENTS.= Several of the green pigments of commerce are obtained from copper. Oxide of chromium furnishes some which are very beautiful. Many are formed by the mere mechanical admixture of blue and yellow pigments. The bright blues and yellows, when mixed in this way, produce the liveliest greens; orange, or red and blue, and the yellowish browns and blue, the more dingy greens. In this way are produced all the extemporaneous greens of the artist. Nickel and titanium also furnish green colours, but these are not in common use. The following list embraces all the best-known and most useful green pigments:--", "Green Arsen'ical.= Arsenite and aceto-arsenite of copper. See GREEN, SCHEELE'S and SCHWEINFURT (_below_).", "Green, Barth's.= From yellow lake, Prussian blue, and clay, ground together.", "Green, Bice.= Same as mountain green.", "Green, Bremen.= This is properly green verditer, but other preparations are frequently sold under the name.", "Green, Brighton.= A mixture of impure acetate of copper and chalk, prepared as follows:--", "To sulphate of copper, 7 lbs., add sugar of lead, 3 lbs.; each separately dissolved in water, 5 pints; mix the solutions, stir in of whiting, 24 lbs., set the resulting paste on chalk stones, and when dry grind it to powder.", "Green, Brunswick.= This is probably a crude chloride of copper, but a mixture of carbonate of copper and alumina or chalk is now commonly sold under the name in the shops.", "_Prep._ 1. A saturated solution of sal ammoniac, 3 parts, is poured over copper filings or shreds, 2 parts, contained in a vessel capable of being closed up, and the mixture is kept in a warm place for some weeks, when the newly formed green pigment is separated from the unoxidised copper, by washing the mixture on a sieve; it is then edulcorated with water, and slowly dried in the shade. Colour very deep and rich. The lighter shades are produced by the addition of sulphate of baryta.", "2. A solution of crude carbonate of ammonia or bone spirit is added to a mixed solution of alum and blue vitriol, as long as it affects the liquor; in a short time the precipitate is collected, washed and dried. The various shades of green are produced by using different quantities of alum, which pales and cheapens it.", "Green, Chrome.= The superb green pigment used by enamellers under this name is the green oxide or sesquioxide of chromium. A hydrated oxide of chromium forms the emerald green of Pannetier; it is prepared by melting in a crucible equivalent quantities of anhydrous boracic acid and bichromate of potassium, and treating the fused mass with water. The hydrated oxide thus produced is washed and finely triturated.", "The chrome green of the oil and colour shops is a mixture of chrome yellow and Prussian green.", "Green, Cop'per.= Green bice or mountain green, Brunswick green, emerald green, verditer, and several other well-known pigments, may be thus named.", "Green, Em'erald.= This term is commonly applied to the aceto-arsenite of copper, as prepared in England. It is the same compound, chemically speaking, as Schweinfurt green (which _see_).", "_Prep._ A pulp is formed with verdigris, 1 part, and boiling water q. s., and after being passed through a sieve, to remove lumps, is added gradually to a boiling solution of arsenious acid, 1 part, in water, 10 parts, the mixture being constantly stirred until the precipitate becomes a heavy, granular powder, when it is collected on a calico filter, and dried on chalk stones.", "Green, Frise.= _Syn._ FRIEZLAND GREEN. This resembles Brunswick green.", "Green, Gellart's.= A mixture of cobalt blue and flowers of zinc with some yellow pigment.", "Green, Impe'rial.= Schweinfurt green (see _below_).", "Green, Iris.= A pigment prepared by grinding the juice of the petals of the blue flag with quicklime. It is very fugitive.", "Green Lake.= See LAKE.", "Green, Min'eral.= This is the same as mountain green.", "Green, Mitis.= Another of the many synonyms of Schweinfurt green.", "Green, Mountain.= This pigment is properly the native green carbonate or bicarbonate of copper (malachite) ground to powder, either with or without the addition of a little orpiment or chrome yellow. That of the shops is commonly prepared by adding a solution of carbonate of soda, or of potassa, to a hot mixed solution of sulphate of copper and alum. Green verditer is commonly sold for this article. According to Watts, mountain green is the same as Neuwieder green.", "Green, Neuwieder.= Schweinfurt green mixed with gypsum or sulphate of baryta.", "Green, Prussian.= The sediment of the process of making Prussian blue from bullock's blood or horns, before it has had the hydrochloric acid added to it. It is also prepared by pouring liquid chloride upon freshly precipitated Prussian blue. As now sold, this pigment is generally a mixture of Prussian blue and gamboge.", "Green, Rinman's.= This resembles that of Gellert.", "Green, Sap.= A very fugitive pigment, prepared from the juice of buckthorn berries. The berries are allowed to ferment for a week or eight days in a wooden tub. The juice is then pressed out, strained, a little alum added, and the whole evaporated to a proper consistence; it is next run into pigs' bladders, and hung up in a dry situation to harden. An inferior article is made from the juice of black alder, and of evergreen privet. It is a common practice to add 3/4 pint of lime water and 1/2 oz. of gum Arabic to every pint of either of the above juices.", "Green, Scheele's.= This is arsenite of copper.", "_Prep._ 1. White arsenic (in powder), 1 part; commercial potash, 2 parts; boiling water, 35 parts; dissolve, filter, and add the solution gradually, whilst still warm, to a filtered solution of sulphate of copper (cryst.), 2 parts, as long as a precipitate falls; lastly, wash the newly formed pigment with warm water, and dry it.", "2. (Ure.) Powdered arsenious acid, 11 oz.; carbonate of potassa, 1-1/2 lb.; boiling water, 1 gall.; dissolve, filter, and add the solution, as before, to another solution of crystallised sulphate of copper, 2 lbs., in water, 3 galls. _Prod._ 1-1/2 lb. A very fine grass-green colour.", "Green, Schweinfurt.= This splendid green pigment is the aceto-arsenite of copper.", "_Prep._ 1. Acetate of copper and arsenious acid, equal parts, are each dissolved separately in the least possible quantity of boiling water, and the solutions mixed whilst still as hot as possible; an olive-green precipitate falls, which, by being boiled in the liquor 5 or 6 minutes, changes to a dense granular powder of a superb green colour.", "2. Instead of boiling the solution containing the precipitate, it is allowed to cool and stand for several hours, or until the powder assumes a granular and beautiful tint. Very rich.", "3. (Kastner.) Arsenious acid, 8 lbs., is dissolved in water as before, and added to verdigris, 9 or 10 lbs., diffused through water q. s., at 120° Fahr., the pap of the other being first passed through a sieve; the mixed ingredients are then set aside till the mutual reaction produces the proper shade.", "4. (Dr Ure.) Sulphate of copper, 50 lbs., and lime, 10 lbs., are dissolved in good vinegar, 20 galls., and a boiling hot solution of white arsenic, 50 lbs., is conveyed as quickly as possible into the liquor; the mixture is stirred several times, and then allowed to subside, after which it is collected on a filter, dried and powdered. The supernatant liquor is employed the next time for dissolving the arsenic.", "5. See GREEN, EMERALD (_above_).", "_Obs._ This is a very fine, permanent green pigment. \"A great deal of needless alarm has been excited about its supposed deleterious effects. It is extensively employed for staining wall-papers, and persons inhabiting rooms thus papered are said to have had their health seriously deranged by the arsenical fumes evolved from it. Now, it is utterly impossible that arsenic could volatilise from such a compound at ordinary temperatures; it does not decompose at any temperature below redness.\" (Watts.) [It is, however, probable that the air of such apartments is sometimes charged with the poisonous pigment through its becoming mechanically detached from the paper. To breathe an atmosphere so impregnated would be dangerous. The use of papers coloured with Scheele's green, especially of the kind called 'flock,' should, therefore, be carefully avoided.--ED.]", "Verd'igris.= See COPPER (Acetates) and VERDIGRIS.", "Green, Verd'iter.= This is essentially a mixture of oxide and carbonate of copper in uncertain proportions, with chalk. Factitious green bice and mountain green have a like composition. See VERDITER.", "Green, Verona.= The mineral called green earth.", "Green, Vienna.= The same as Schweinfurt green.", "GREEN SICKNESS.= See CHLOROSIS.", "GREEK FIRE.= This compound, so much used in ancient warfare, is believed to have had naphtha for its chief ingredient. According to some authorities, it was a mixture of asphalt, nitre, and sulphur.", "GREGORY'S SALT.= The crude hydrochlorate of morphia, prepared by Gregory's process. It is a double hydrochlorate of morphia and codeia.", "GRINDELIA ROBUSTA.= A perennial plant belonging to the natural order _Compositæ_; a native of California, in which state it is largely used against poisoning by the \"poison oak\" (the _Rhus toxicodendron_). Of late years it is said to have been in American medical practice used with excellent effect in asthma and kindred diseases. Dr Q. C. Smith, writing to the 'Pacific Medical and Surgical Journal' for April, 1875, states one patient to whom pills made of the solid extract were administered, had suffered from severe and frequent attacks of asthma since childhood, and had found no relief from various remedies. Dr Smith gave his patient the extract of the grindelia in pills of three grains each, one three times a day for two or three days, then a pill at bedtime only, for eight or ten days longer. Under this mode of treatment the attacks are said to have been much less severe, and less frequent; the patient not only gaining in strength and general health in the meantime, but having experienced an immunity from attack for four months. The parts of the plant used are the selected leaves and tops.", "GRIND'ING.= The operation of reducing substances to powder by attrition or friction. In the laboratory, the term is chiefly applied to powdering by means of a mill or by mechanical power, in opposition to simple pounding or trituration in a mortar or with a slab and muller. All the principal powders, paints, &c., sold by the druggist, drysalter, and colourman, are reduced in the drug or colour mill. Recently machinery has even been applied to the common mortar. An ingenious and very useful contrivance of this kind is the 'mechanical mortar' of Mr H. Goodhall, of Derby.", "GRIND'STONES. (Artificial).= Washed siliceous sand, 3 or 4 parts; shell-lac, 1 part; melt together, and form the mass into the proper shape whilst warm, with strong pressure. The fineness of the sand must depend on the work the stone is intended for. The same composition is formed upon pieces of wood, as corn rubbers, and for the purpose of sharpening knives, and cutting stones, shells, &c. See EMERY.", "GROATS.= _Syn._ GRITS; GRUTELLUM, AVENA DECORTICATA, AVENÆ SEMINA, AVENA (Ph. L.), L. Common oats, deprived of their exterior integuments or husks. This is generally effected in a mill, which, at the same time, cuts them into two or three pieces. When crushed flat, they are denominated EMBDEN GROATS.", "GROUT.= Mortar reduced to a thin paste with water, used to fill up the joints of masonry and brickwork. A finer kind is used to 'finish off' the best ceilings.", "GRUEL.= _Syn._ OATMEAL GRUEL, WATER G.; DECOCTUM AVENÆ, L. Oatmeal or groats boiled with water to a proper consistence, and strained. It is variously flavoured to suit the palate; but the addition of a little white sugar, and finely powdered Jamaica ginger, with or without a glass of wine, is the least likely to offend the stomach. Nutmegs, cinnamon, &c., frequently disagree with invalids. Sometimes milk or butter is added. Embden groats require less boiling than the common groats. Of oatmeal, the Scotch is commonly said to be the best.", "The following directions for making gruel from oatmeal are given by Dr A. T. Thomson: \"Oatmeal, 2 oz.; cold water, 1-1/2 pint; rub the meal in a basin, with the back of a spoon, in some of the water, pouring off the fluid after the grosser particles have subsided, but whilst the milkiness remains; repeat this with fresh water, unite the washings, and boil until a soft, thick mucilage is formed.\"", "GUA'IACIN.= _Syn._ GUAIACIC ACID, PURE GUAIACUM RESIN. A substance having the nature of an acid, discovered by Trommsdorff in the wood and bark of _Guaiacum officinale_.", "_Prep._ The tincture of guaiacum is treated with hydrate of lime, and the guaiacate of lime thus formed is decomposed with dilute sulphuric acid; it is purified by dissolving it in alcohol.", "_Prop., &c._ Insoluble in water; soluble in alcohol and ether; it unites with the caustic alkalies, forming alkaline guaiacates (guaiacum soaps); air and light turn it green; gluten, mucilage of gum Arabic, &c., turn it blue; nitric acid and chlorine turn it successively green, blue, and brown; tincture of guaiacin, added to hydrocyanic acid and sulphate of copper, produces an intense blue colour. (Pagenstecher.) A delicate photographic paper may be formed by washing unsized paper with an alcoholic solution of guaiacum resin, and afterwards with one of neutral acetate of lead. (Johnston.)", "GUA'IACUM.= _Syn._ GUAIAC, GUM GUAIACUM, GUAIACUM RESIN; GUAIACUM (Ph. L.), (GUAIAC RESIN, GUAIACA RESINA, B. P.). The resin prepared by means of fire from the wood of _Guaiacum officinale_, by natural exudation, by incision, or by heat. (B. P.) This substance is often adulterated. When pure, its \"fresh fracture is red, slowly passing to green; the tincture slowly strikes a lively blue colour on the inner surface of a thin paring of raw potato.\" (B. P.) Adulteration with resin may be generally discovered by the odour evolved when the guaiacum is heated. An alcoholic tincture of guaiacum, rendered milky with water, recovers its transparency on the addition of caustic potassa in excess; but this is not the case when resin is present.", "Guaiacum is stimulant, sudorific, and alterative.--_Dose_, 10 to 30 gr., either in powder or pills; in chronic rheumatism, gout, obstinate chronic skin disease, scrofula, syphilis, &c. It forms the active ingredient of the once celebrated 'CHELSEA PENSIONER,' and the 'GOUT SPECIFIC' of Mr Emerigon. The latter was made by digesting 2 oz. of guaiacum resin in 48 fl. oz. of rum, for seven or eight days. The dose of this was a table-spoonful every morning, fasting, for a twelvemonth. Its other properties are similar to those of GUAIACIN, but are less marked. Sp. gr. 1·20 to 1·22.", "Guaiacum Wood.= _Syn._ LIGNUM VITÆ, GUAIACI LIGNUM (Ph. L.), L. The wood of _Guaiacum officinale_. This is employed under the form of shavings, raspings, and sawdust, in decoctions only. See DECOCTION and BALSAM.", "GUA'NO.= _Syn._ HUANHO, Peruv. This substance, now so extensively used in agriculture, is the partially decomposed excrement of certain aquatic birds, chiefly the common penguin, which congregate in countless numbers on the barren and uninhabited islets and rocks on the western coasts of South America and the coasts of Africa. It abounds in ammonia and the phosphates, and is undoubtedly the richest natural manure known. Under judicious application the increase of the crops of grain, turnips, potatoes, and grass consequent upon its use is said to be about 33%. \"Guano is peculiarly adapted to horticultural and floricultural improvement, by its relative cleanliness and facility of application.\" (Ure.)", "\"According to Denham Smith,[339] South American guano, as imported, presents itself in three distinct states, the three varieties being not unfrequently mixed together in the same bag; the first variety is damp and pulverulent; the second exists as large concretions, presenting various aspects when broken; the third is heavy and crystalline, and is termed 'stone' by the labourers. These three varieties differ widely in composition, as the following comprehensive analysis, by Smith, will show:--", "[Footnote 339: 'Proceedings of the Chem. Soc.,' vol. ii.]", "+--------------------------------------------------------------+ | _Soluble in Water._ | +-----------------------------+------------+---------+---------+ | | I. | II. | III. | | |Pulverulent.|Concrete.| Saline. | | +------------+---------+---------+ |Water | 222·00 | 250·00 | 97·00 | |Chloride of ammonium | 25·50 | -- | 30·30 | |Sulphate of potash | 80·00 | -- | -- | | \" soda | traces | 258·44 | 191·77 | |Oxalate of ammonia | 74·00 | 93·90 | -- | | \" soda | -- | -- | 105·63 | |Phosphate of ammonia | 63·30 | 61·24 | -- | | \" potash | -- | 77·32 | 49·47 | | \" soda | 1·20 | -- | 3·60 | |Chloride of sodium | -- | 29·22 | 286·31 | | \" potassium | -- | -- | 41·63 | |Organic matter | 15·00 | 6·68 | 25·53 | |Urate of ammonia | 154·18 | -- | -- | |Uric acid | 25·16 | -- | -- | |Ammonia phosphate of magnesia| 5·64 | 7·84 | 1·33 | |Animal matter | 11·80 | 8·60 | 7·56 | | | | _Insoluble in Water._ | +-----------------------------+------------+---------+---------+ | | I. | II. | III. | | |Pulverulent.|Concrete.| Saline. | | +------------+---------+---------+ |Oxalate of lime | 25·60 | 109·58 | -- | |Phosphate of lime | 199·30 | 62·70 | 132·23 | | \" magnesia | 20·30 | 8·", "\"Several of the South American guano beds are now exhausted, but new varieties are constantly being introduced; and although the qualities are continually varying, guanos, on the whole, may be divided into two classes, the one characterised by the abundance of ammonia, the other by that of phosphates, the Peruvian and Angamos being characteristic of the former, and the Saldanha Bay and Bolivian of the latter. In selecting a guano, the following points (Anderson) ought to be attended to by the farmer:--", "\"1st. The guano should be light coloured and dry, colouring very slightly when squeezed together, and not gritty.", "\"2nd. It should not have too powerful an ammoniacal smell, and should contain lumps which, when broken, appear of a paler colour than the powder.", "\"3rd. A bushel should not weigh more than from 56 to 60 pounds.", "\"These characters are, however, imitated with great skill, so that they cannot be implicitly relied upon, and they are applicable to Peruvian guano only.\"[340]", "[Footnote 340: The above particulars are from an elaborate paper by Dr H. M. Noad, in the 'Chemist and Druggist,' vol. ii.]", "_Purity, Adulteration._ Guano, owing to its high price, is very commonly adulterated, or is in an advanced stage of decomposition when sold. Much of what is vended under the name is altogether a fictitious article. These artificial mixtures are made to look so like genuine guano, that the mere practical man, who goes only by their appearance, is very often deceived by them, and, owing to the failure of his crops in consequence, is led to distrust the efficacy of guano as a manure. A sample of pretended guano examined by Johnstone was found to contain, in the state in which it was sold, more than half its weight of gypsum, the rest being peat or coal ashes, with a little common salt, crude sulphate of ammonia, and either dried urine or the refuse of the glue manufactories, to give it a smell. \"I could not satisfy myself that it contained a particle of real guano.\"[341] Vessels which sail hence for the guano stations are now very commonly ballasted with rough gypsum or plaster of Paris. This substance is mixed with the guano as it is loaded, and enables the importers to deliver from the vessel a \"nice-looking, light-coloured article.\" Purchasers of guano are very desirous of having it delivered from the vessel, as they believe they thus obtain it pure. The favourite material for the adulteration of guano, at the present moment, is a variety of umber, which is brought from Anglesea in large quantities. The rate of admixture is said to be about 15 cwt. of umber to about 5 cwt. of Peruvian guano, from which an excellent-looking article is manufactured, which is sold under the name of 'African guano.'", "[Footnote 341: 'Elem. of Agric. Chem.']", "Pure guano has a pale-brown colour, a more or less offensive odour, and the average sp. gr. of 1·63 to 1·64. If the sp. gr. exceed 1·75, it is either damaged or adulterated; and if it is less than 1·62, it contains an undue quantity of moisture. The best is neutral to test-paper, and sometimes has even an acid reaction; but that of commerce has generally an alkaline reaction, owing to the presence of free ammonia, and, in consequence, turns turmeric paper brown, and gives white fumes when a glass rod dipped in hydrochloric acid is held over it. Triturated with quicksilver or caustic potassa, good guano evolves a powerful odour of ammonia; digested in water, fully one half of it is dissolved; dried by the heat of boiling water, it does not lose more than from 7 to 9% in weight; and burned upon a red-hot shovel, it leaves a white ash, not a red or dark-coloured one. (See directions for selecting guano given _above_, also _below_.)", "_Analysis_ or _assay_. The quantitative analysis of guano, so as to exhibit the names and proportions of all its numerous component substances, is an extremely tedious and difficult matter in the hands of persons unaccustomed to chemical manipulations. As, however, its value to the agriculturist depends chiefly on its richness in ammonia, potassa, and phosphoric acid, the analysis of guano for practical purposes may be reduced to an assay for these articles. Indeed, the presence of ammonia (the most valuable of them), in the proper quantity, may be fairly taken as evidence of the presence of the rest. The following methods of testing guano are both simple and accurate, and are so arranged as to permit its per-centage richness in one or more of its leading constituents to be determined without much trouble or expense.", "1. _a._ 100 gr. of the sample for examination (fairly selected) are crushed to a powder, and placed on a small, weighed, and perfectly dry paper filter, and then desiccated, by exposure for 2 or 3 hours to the heat of boiling water. The loss in weight, taken in grains, after deducting 9, indicates the quantity per cent. of water or moisture which the sample contains in excess of that present in good or pure guano.[342]", "[Footnote 342: According to Dr Noad, the proportion of water in genuine guanos ranges from 7 to 20%.]", "_b._ The paper filter, with its contents, is next suspended for some time over concentrated sulphuric acid (oil of vitriol) contained in a wide-mouthed bottle or jar, by means of a thread attached to the cork or stopper, care being taken to exclude the external air. The exposure in this way is continued until the guano ceases to diminish in weight, which is ascertained by weighing it at intervals after the first 3 or 4 hours. When this point is arrived at, the filter and its contents are very carefully weighed. The difference between its present weight and its original weight (before the desiccation in _a_), taken in grains, gives the gross quantity of water per cent.", "_c._ The dried guano from _b_ is next placed in a weighed, smooth crucible or capsule, and exposed to a low red heat until all the organic matter is completely destroyed, and the whole is reduced to a white ash, which is weighed as soon as it has become cold. This weight, in grains, gives the gross weight per cent. of non-volatile matter (fixed alkaline and earthy chlorides, phosphates, and sulphates); the total loss of weight by combustion denotes the gross per-centage of combustible and volatile matter (urea, uric acid, ammoniacal salts, and organic matter). The latter should not be less than 55 to 60%.", "2. _a._ A second 100 gr. of the guano, selected as before, is distilled along with about 75 gr. of fresh-slaked quicklime, and a little water, in a small matrass connected with a tubular, triple bulb-condenser, containing cold distilled water, and immersed in a basin of ice-cold water. (See _engr._) The condenser is charged by plunging one of its extremities into the water, and sucking at the other, until the liquid reaches the level indicated in the margin. A very gentle heat only, cautiously increased, need be employed. After the process is over, the strength of the solution of ammonia found in the condenser is tested, either by taking its density in a small specific-gravity bottle, or by determining its saturating power in the manner described under ALKALIMETRY. This furnishes the per-centage of ready formed ammonia sufficiently accurate for all ordinary purposes, provided proper care is taken.", "When extreme accuracy is required, the condenser is charged with a weighed quantity of dilute hydrochloric acid of a known strength, instead of water, and after the process is over, this is tested as before. The quantity of ammoniacal test-liquor (see ALKALIMETRY) now taken to saturate it, deducted from what it would have taken before the exposure in the condenser, gives the per-centage sought.", "Another method, giving very accurate results, is to use a rather strong hydrochloric acid (sp. gr. about 1·13) for the condenser; after the operation is over, the contents of the latter are poured into a glass or porcelain capsule, a solution of bichloride of platinum is added, in excess, and the whole is then gently evaporated to dryness; the residuum is rubbed to powder, and exhausted with a mixture of two measures of alcohol and one measure of ether; the undissolved portion is next dried at a heat not exceeding 212° Fahr., and weighed. The weight, in grains, of the ammonia chloride of platinum thus obtained, multiplied by ·0763, gives the per-centage of ready-formed ammonia, as before. When hydrochloric acid is used for the condenser, a simple U-tube and beaker glass may be employed, if a bulb-condenser is not at hand. (See _engr._) The advantages resulting from the use of acid instead of water for the condenser is, that with the former no ammonia can possibly escape being absorbed, whilst little care is required to keep the condenser cool.", "_b._ 25 gr. of the guano are next weighed, and after being slightly moistened with a little dilute hydrochloric acid, are thoroughly dried by the heat of boiling water; the dried sample is then mixed in a warm unglazed porcelain mortar with 10 times its weight of a mixture of 2 parts of quicklime to 1 part of hydrate of soda (both quite dry). This mixture is introduced into a combustion tube of hard Bohemian glass, about 16 or 18 inches long, and 3/4 of an inch in diameter (see _engr._) The mortar is rubbed out with a little of the soda-lime mixture, which is also introduced into the tube with that already put there; a little plug of ignited asbestos is then loosely placed over the whole, and the tube is immediately connected with a tubular bulb-condenser, containing moderately strong hydrochloric acid, great care being taken that the joints are made air-tight, which may be determined by the operator sucking a few bubbles out of the apparatus. If, after suction, the liquid remains at a higher level in the furthest bulb (_b_), it is a sign that the connection is sound. This being done, heat is applied to the combustion-tube, by means of spirit-lamps; or, more conveniently, by means of the furnace now usually employed in organic analysis (see _engr._) The tube is next gradually surrounded with red-hot charcoal, by shifting by degrees the screen (_c_), and adding more charcoal, so as to gradually expel the ammonia. The disengagement of gas should take place uninterruptedly, but not too rapidly, in order that the acid may not ascend into the combustion-tube and spoil the experiment. The non-condensable volatile matters which pass off furnish a key to the progress of the operation. The heat is at length increased to a full red. When gas ceases to be evolved, and the mixture in the tube has become quite white, the experiment is at an end. The point (_a_) of the combustion-tube is broken off, and the ammonia which remains in the tube is expelled by sucking gently at the ex", "_c._ The quantity of ready-formed ammonia (see 2, _a_) deducted from the quantity last found (see 2, _b_) gives the quantity of LATENT or POTENTIAL AMMONIA that will be slowly developed by the decomposition of the guano in the soil, and become available for the food of plants. This is the most valuable product of this substance as a manure, and can only be obtained in quantity from well-preserved, dry guano.", "3. _a._ A third quantity of 100 gr. of the guano, selected as before, is triturated and digested for some time with 12 times its weight of hot distilled water, and the whole being thrown on a filter, the undissolved portion is washed with a little warm distilled water; the solution and 'washings' are then mixed together, and acidulated with nitric acid; a solution of pernitrate of iron is next added, and afterwards solution of ammonia, in excess; the liquid is next heated for a short time, and the bulky reddish-brown precipitate is collected, washed with hot water, dried, ignited, and weighed. The weight, in grains, less the weight of the peroxide of iron in the pernitrate consumed, gives the weight of PHOSPHORIC ACID present in the soluble phosphates contained in the sample. The pernitrate of iron is made by direct solution in hot strong nitric acid, of twice as much pure iron wire as there is phosphoric acid suspected to be present in the liquid. A slight excess will not alter the result. The number of grains of metallic iron used to form the solution, multiplied by 1·4286, gives the weight of the peroxide of iron which is to be deducted from the gross weight of the precipitate.", "_b._ The filtrate and 'washings' left from 3 _a_ are mixed, and treated with a little oxalate of ammonia to throw down any lime, and then carefully evaporated to dryness and ignited; the residuum of the ignition, when cold, after being carefully weighed, is treated with the smallest portion of water that will dissolve it; the solution is acidified with hydrochloric acid, and a solution of bichloride of platinum added, in excess; some strong alcohol is next poured in, the precipitate carefully collected on a filter, washed with rectified spirit, dried at 212° Fahr., and weighed. The weight, in grains, multiplied by ·1940, gives the per-centage of POTASSA sought.", "_c._ The weight of the potassa multiplied by 1·852, and deducted from the weight of the ignited residuum in 3 _b_ already found (see _above_), gives the quantity of CHLORIDE OF SODIUM or COMMON SALT (nearly).", "4. _a._ The insoluble residuum from 3 _a_, dried, and ignited, or the ash from 1 _c_, is digested for 10 or 12 hours in 600 times its weight of water (to which a little common salt or sal-ammoniac may be added), after which the whole is thrown upon a filter; a solution of chloride of barium is then added to the filtrate as long as a precipitate (if any) forms; the latter is collected, washed, dried, ignited, and weighed. The weight, in grains, multiplied by ·5843, denotes the quantity of GYPSUM or SULPHATE OF LIME which has been used to adulterate the sample.", "_b._ The insoluble residuum last left on the filter is digested for some time in warm dilute hydrochloric acid; the whole is then thrown upon a filter, and the undissolved portion (SILICA or SAND, with, perhaps, a trace of ALUMINA) is washed, dried, ignited, and weighed. It should not weigh more than 3 to 3-1/2 gr. (3 to 3-1/2%).", "_c._ The filtrate and 'washings' from _b_ are next mixed together; the mixed liquid is acidified with dilute sulphuric acid and heated until all the hydrochloric acid is expelled, and the whole reduced to a soft pasty mass; rectified spirit is now poured in, and after active stirring for some time, the mixture is thrown on a filter, and the solid portion washed with a little more rectified spirit; it is then dried, ignited, and weighed. The weight, in grains, multiplied by ·7650, gives the quantity of PHOSPHATE OF LIME per cent. required.", "_d._ The filtrate from _c_ is diluted with water, and after being boiled for a few minutes, ammonia is added in slight excess, followed by a solution of sulphate of magnesia (previously mixed with as much sal-ammoniac as will prevent ammonia producing a precipitate in it), slowly dropped in as long as it disturbs the liquor; the whole is now allowed to rest for 10 or 12 hours, when the precipitate is collected on a filter, and washed with water alkalised with ammonia, as long as the filtering liquid is rendered turbid by chloride of barium; it is next dried, submitted to intense ignition for some time in a covered platinum crucible, and, when cold, carefully weighed. The weight, in grains, multiplied by ·6429, indicates the per-centage of PHOSPHORIC ACID in the insoluble phosphates (phosphates of lime, magnesia, &c.) in the sample examined.", "5. A fourth 100 gr, of guano is weighed, and exhausted by trituration and digestion with hot water (see 3 _a_); the solution is evaporated to dryness by a gentle heat, and the residuum of the evaporation, after being weighed, is powdered and enclosed in a stout phial with 8 times its volume of alcohol, sp. gr. ·825 (63 o. p.); the plant is next securely corked and guarded, and exposed for some time, with agitation, to the heat of 212° Fahr., the whole is then allowed to cool, the contents of the phial filtered, the undissolved portion washed with hot alcohol, and both the filtrate and the 'washings' gently evaporated to dryness, and weighed. This gives the richness of the sample in UREA, one of the most valuable constituents of the best guano. Its presence is \"a certain proof of its entire soundness.\" (Ure.)", "6. _a._ Another 100 gr. of the guano is taken, and, after being exhausted with water, is dried at 212° Fahr., and weighed; it is then digested with heat in 20 times its weight of borax-water (containing 1% of borax), or in a solution of caustic potassa, and after a time the whole is thrown on a weighed filter, washed with a little cold distilled water, dried by a heat not higher than that of boiling water, and again carefully weighed. The loss, in grains, indicates the proportion per cent. of URIC ACID.", "The accuracy of the result may be verified by adding dilute hydrochloric acid, in slight excess, to the filtrate, collecting the bulky, crystalline precipitate of uric acid which forms, washing it carefully with a little rectified spirit, drying it, and weighing it, as before. This weight, which in general is a very little under that denoted above, is the more accurate of the two. The precipitate is shown to be uric acid by its assuming a rich crimson colour when treated with a little nitric acid, which turns to a rich purple (_murexide_) when it is moistened with ammonia water.", "_b._ The quantity of uric acid last obtained, multiplied by 1·1012, gives the per-centage of URATE OF AMMONIA.", "_Obs._ Amongst the numerous constituents of guano, none are so valuable in an agricultural point of view as the three substances referred to in the last two sections. Indeed, almost all the ammonia furnished by this substance to the soil, after the latter, manured with it, has been exposed to the air and rain, is derived from the slow decomposition of urea, or urate of ammonia. It is these substances from which the store of latent, or, as Dr Ure terms it, potential ammonia, is derived. The ammonia existing in the guano under the form of carbonate, or of soluble salts (ready formed ammonia), is either soon dissipated in air or is washed away by heavy rains, and, therefore, forms the least valuable and durable portion of this manure. It may be even added artificially, a matter almost impossible with the former. An assay, therefore, for the latent ammonia, or the urea, or the urate of ammonia, any one of them singly, at once furnishes us, as we have already hinted, with evidence of the quality of the guano examined, without the expense and trouble of a complete analysis of this substance. Urea and uric acid are only to be found in the very best samples of guano, and their presence is a positive proof of entire soundness and superior quality. The other valuable portions of guano are potassa and phosphoric acid (phosphate of lime chiefly); the rest are of little importance. (See 2 _c_, _above_.)", "GUARANA= (Grimault & Co., Paris). 12 migrain powders, each weighing 1·75 grammes, consisting of guarana, but perhaps also containing an admixture of cocoa seeds, neither prepared nor roasted. (Hager.)", "GUARANA'.= _Syn._ PAULLINIA, BRAZILIAN COCOA. An alimentary and medicinal substance prepared from the seeds of _Paullinia sorbilis_, a Brazilian tree. The dried seeds, deprived of their aril, are pounded and kneaded into a mass, which is afterwards made into oblong or rounded cakes (GUARANA BREAD). These cakes are used as we use chocolate--mixed with water and sugar, and drank as a beverage. In Brazil this beverage is largely consumed, both on account of its nutritive qualities, and for its stomachic, febrifugal, and aphrodisiac effects. See CHOCOLATE, &c., also _below_.", "GUARANINE'.= A crystalline substance discovered by M. Martius in guarana. It appears to be identical with caffeine, the active principle of coffee and tea.", "GUD'GEON.= The _Cyprinus gobeo_ (Linn.), a small fresh-water fish, common almost everywhere. The white is considered the best. It was formerly used in medicine.", "GUM.= _Syn._ GUMMI, L. The general term for an important class of vegetable products. Gums are more or less soluble in cold water, but insoluble in alcohol, ether, and oils. They are obtained from certain plants in amorphous masses; most of them exude spontaneously, or on puncturing the bark. The most perfect type of this class is the substance called GUM ARABIC, or GUM ACACIA. The gums are employed as demulcents in medicines, and are used as cements, and for giving stiffness and gloss to textile fabrics. Among the vulgar the term is often incorrectly applied to the resins and gum resins.", "Gum Acacia.= _Syn._ GUM ARABIC; ACACIÆ GUMMI (B. P.); G. ARABICUM, G. ACACIA, ACACIA (Ph. L.), L. \"From various species\" (of _Acacia_) \"yielding gum\" (Ph. L. & E.), chiefly _Acacia arabica_ and _A. vera_. \"Whitish or yellowish, transparent or cracked on the surface, and opaque; brittle; it dissolves freely in water.\" (Ph. L.) It is scentless, and may be bleached by exposure to the sun and air, at the temperature of boiling water. Sp. gr. 1·355. (Ure.) The pure soluble principle of gum Arabic is termed ARABIN (which _see_). BARBARY or MOROCCO GUM, GUM SENEGAL, and EAST INDIA GUM, are inferior commercial varieties of the same substance from other species of _Acacia_ (see _below_).", "Powdered gum Arabic (PULVIS ACACIÆ) is frequently adulterated with flour or farina, or with Senegal or other inferior gums. The first may be detected by agitating a little of the powder with cold water; the pure gum dissolves rapidly, whilst the starch or flour falls to the bottom of the vessel. Or, a little of the powder may be mixed with boiling water, and when cold, tested with tincture of iodine; if it contains starch or flour, the paste will assume a blue colour. If it contains cherry-tree gum or tragacanth, it will be only partly soluble in cold water, and the paste will be partly coloured, and more or less interspersed with gelatinous clots.", "For the detection of dextrin in gum Arabic Hager finds that when some of the adulterated article is placed in a glass dish, with vertical sides, and a solution of ferric chloride, density 1·48, diluted with an equal volume of water, is poured over it until the grains are just covered, in the course of a minute or so that particles of gum Arabic will adhere to the bottom of the vessel, whilst the grains of dextrin do not.", "Much of the white gum Arabic of the shops is formed by bleaching gum Senegal, by what is called 'Picciotto's process.' The gum is dissolved in water, and sulphurous acid gas passed through the solution. The liquid is afterwards boiled to expel the sulphurous acid, a little of which, however, still remains behind. To obtain the gum in a still whiter state, carbonate of baryta is added, and after agitation the mixture is filtered; it is afterwards shaken with gelatinous alumina, again filtered, and evaporated. The product (BLEACHED GUM) is very white, but lacks the peculiar toughness and adhesiveness of the best gum acacia.", "Gum, Barbary.= _Syn._ MOROCCO GUM. An inferior product, consisting of a mixture of several Acacia gums. It is exported from Mogador.", "Gum, Bassora.= A solution of yellowish gum brought from the neighbourhood of Bassora. It differs from most gums in being nearly insoluble in water. The plant yielding it is believed to be a species of _Mimosa_. It contains the principle BASSORIN, which also exists in gum tragacanth.", "Gum, Bleached.= See GUM ARABIC (_above_).", "Gum, Brit'ish.= _Syn._ DEXTRIN, STARCH GUM. Starch converted by the action of acids, diastase, or heat, into a soluble substance resembling gum.", "_Prep._ 1. Malt (crushed small), 1 lb.; warm water, 2 galls.; mix, heat the whole to 145° Fahr., add of potato starch 5 lbs., raise the heat to 160° or 165° Fahr., and mash for about 25 minutes, or until the liquid becomes thin and clear; it must then be instantly run off, and raised to the boiling point to prevent the formation of sugar; after boiling for 3 or 4 minutes the whole must be filtered, and evaporated to dryness by a steam heat.", "2. By exposing dry potato starch, in a stove, to a heat of about 400° Fahr. Yellow and inferior.", "3. (M. Payen.) Dry starch, 1 ton, is moistened uniformly with concentrated nitric acid, 4-1/2 lbs. (diluted with), water, q. s., and the paste or dough is made up into small bricks or loaves, and dried in a stove; it is next reduced to coarse powder, and exposed in a stove-room for some time to a current of air at 160° to 165° Fahr.; it is next ground, sifted, and exposed, as before, to a heat of about 228° Fahr.; it is, lastly, ground, and passed through the 'bolting machine.' Very white and superior. This process has been patented in France by M. Henzé.", "4. (Pinel.) Water, 100 galls., nitric acid, 1/2 gall., and hydrochloric acid, 1/2 pint, are mixed together, and so much potato starch is mixed as will form a thin paste; in two hours the liquid is drained off, and the solid matter is made up into lumps, which are dried by a gentle heat in a stove-room; they are next coarsely pulverised, and the powder is exposed on three successive days to the respective temperatures of 100°, 150°, and 190° Fahr.; the whole is then sifted, and, lastly, exposed to a heat ranging from 300° to 350° Fahr. Darker coloured than the last. To give it the appearance of gum Arabic, it is made into a paste with water containing 1% of nitric acid, and after being spread on copper plates in layers 3/4 to 1 inch thick, it is exposed to a stove heat ranging from 240° to 300° Fahr.", "_Prop., &c._ White; insipid; transparent; friable; soluble in cold water, and in dilute spirit; insoluble in alcohol and ether; its solution yields a precipitate with acetate of lead. Iodine commonly turns commercial dextrin blue, but does not affect the colour of pure dextrin. It is distinguished from ordinary gum by its right-handed polarization of light, and by yielding oxalic but not mucic acid, when treated with nitric acid.", "Dextrin is nutritive, emollient, and agglutinant. In France it is largely employed by the pastry-cooks and confectioners, and in medicine as a substitute for gum. The French surgeons also commonly employ it as a 'stiffening' for the splints used for fractured limbs. In this country it is chiefly used as a fine dressing for muslins, silk, and other textile fabrics, and in calico printing. Recently it has been made up into tear-like masses, and sold for gum Arabic, to which, however, it is vastly inferior as an agglutinant. See DEXTRIN.", "Gum, Cherry-tree.= _Syn._ FRUIT-TREE GUM, PLUM-TREE G.; GUMMI CERASI, G. PRUNI, L. An exudation from the stems of cherry, plum, and some other of the _Rosaceæ_. It is only partly soluble in water. It contains CERASIN (which _see_).", "Gum, East India.= This product, which consists of inferior kinds of gum acacia, is chiefly exported from Bombay, having been previously conveyed there from the coast of Arabia. It varies greatly in quality. Some samples are quite unfitted for making gum-water.", "Gum, Insoluble.= See BASSORA GUM, CHERRY-TREE GUM, and GUM TRAGACANTH.", "Gum, Seed.= _Syn._ GUMMI SEMINUM, L. A species of soluble gum extracted from the seed of the flax (linseed), quince, &c.", "Gum, Senegal.= This product, which is largely exported from Portendie, Sierra Leone, and the French settlements on the Senegal, ranks next in quality to gum acacia, and for many purposes, as calico-printing for instance, it answers equally well. The transparent and light-coloured pieces are frequently picked out and sold as gum Arabic.", "Gum Trag'acanth.= _Syn._ TRAGACANTH, GUM DRAGON; GUMMI TRAGACANTHA, G. DRACONIS, TRAGACANTHA (Ph. L.), L. The gummy exudation of the _Astragalus verus_, hardened by the air. When digested in water, it swells considerably, a portion is dissolved, and the whole combines to form a thick mucilage. It is totally soluble in boiling water, when some change is supposed to take place in it; a great portion, however, afterwards separates. Sp. gr. 1·384. It is chiefly employed in calico-printing, and by shoemakers and lozenge-makers; by the latter to give toughness to the saccharine mass.", "Powdered tragacanth is often adulterated with flour of starch, and not unfrequently with the commoner varieties of gum Arabic. According to M. Planche, a mixture of pulverised tragacanth and gum Arabic forms, with water, a thinner mucilage than the same quantity of either of these gums alone. This fraud may be detected as follows:--Make a mucilage of the suspected gum, and add thereto a few drops (2 or 3 to the dr.) of alcoholic tincture of guaiacum, taking care to stir it all the while. If the sample contains any gum Arabic, the mixture, in the course of a few minutes, assumes a fine blue colour, whilst it does not change colour if the gum tragacanth is pure, 5% of gum arabic can be thus detected. When the quantity is very small, one to four hours may elapse before the colour is developed. Starch and flour are detected in the manner noticed under GUM ARABIC.", "Gum, Turkey.= Various qualities of gum acacia are sold under this name.", "GUM RES'INS.= _Syn._ GUMMI RESINÆ, L. Vegetable products in which the properties of gum and resin are combined. They are partly soluble in water, and partly in alcohol. Many of them form a species of emulsion when triturated with the former fluid. The principal gum resins are AMMONIACUM, ASSAF[OE]TIDA, BDELLIUM, GALBANUM, GAMBOGE, MYRRH, OLIBANUM, OPOPONAX, SAGAPENUM, and SCAMMONY.", "GUN BAR'RELS.= See BROWNING.", "GUN COT'TON.= See PYROXYLIN.", "GUN MET'AL.= An alloy containing 90·5% of copper and 9·5% of tin, used for casting pieces of ordnance (erroneously termed 'brass guns'), also those parts of machinery which are subjected to considerable friction. See ALLOYS, BRONZE, STEREO-METAL, &c.", "GUN'POWDER.= This substance is a mechanical mixture of saltpetre, charcoal, and sulphur. It is seldom prepared on the small scale.", "_Prep._ The saltpetre having been trebly refined, by boiling, skimming, filtering, and crystallising, is melted into cakes, which are then brushed to remove any adhering grit or dirt, broken into pieces with a mallet, ground to a fine powder in a mill, and sifted through a fine bolting sieve of brass wire. The charcoal is that of the alder or willow, and is carefully burnt, as already described, and is then reduced to powder. The sulphur is refined by distillation, and ground to the same fineness as the charcoal and saltpetre. The ingredients are weighed out in the proper proportions, and mixed together in a machine consisting of a wooden drum, having a shaft passing through its centre, to which numerous 'flyers' in the shape of knife-blades are attached, the drum and flyers revolving in a contrary direction. When mixed, the charge is carried to the 'incorporating mill,' where it is ground under vertical iron 'mill-stones,' with a small quantity of distilled water, until the ingredients are thoroughly incorporated. The product of this operation is then pressed into a hard cake, which is next broken into pieces, granulated by means of sieves, and after being 'glazed' by friction, and the dust separated, is dried, with proper precautions, in a stove heated to about 130° by steam pipes.", "The proportions of saltpetre, charcoal, and sulphur, used for different kinds of powder, differ very slightly. In 'sporting powders' the proportion of saltpetre is generally from 1 to 3% greater than in the Government powders. In 'miners' powders' it is about 10% less, an excess of sulphur being used. The following are the proportions adopted by European powers:", "Saltpetre. Charcoal. Sulphur. England 75 15 10 France 75 12·5 12·5 Austria 75 15 10 Prussia 75 13·5 11·5 Russia 73·78 13·59 12·63 Spain 76·47 10·78 12·75 Sweden 76 15 9 (Capt. Jervis-White Jervis.)", "_Obs._ The quality of gunpowder is best estimated by actual trial of its power and cleanliness in use. It should be dry, hard, and free from dust; the grains should be of a uniform size, and glossy, and the colour a dark-grey or brownish-grey, not perfectly black. A very little placed on a piece of paper and fired should instantly explode with a flash, and neither leave an appreciable residue on the paper nor burn it. Dried by the heat of boiling water, or in vacuo, it should not lose more than 1/2 to 1% of its weight. Damp powder rapidly 'fouls' the gun. Gunpowder, containing more than 7% of water, does not recover its strength by simply drying it. The sp. gr. ranges between 1·795 and 1·800.", "Karolyi succeeded in analysing the gases of gunpowder which had been fired in conditions closely resembling those which occur in artillery practice. For this purpose he enclosed a charge of powder in an iron cylinder of such strength that it just burst when the powder was fired by means of the electric spark. This charged cylinder was suspended in a hollow spherical bomb, from which the air was exhausted before firing.", "After the explosion had been produced, the gases and the solid residue of the powder were submitted to analysis. The results obtained were the following:[343]", "[Footnote 343: 'Phil. Mag.,' 1863.]", "1. _Composition of the Powder used._", "Ordnance Powder. Small Arms Powder. Nitre 73·78 77·15 Sulphur 12·80 8·63 {Carbon 10·88 11·78 Charcoal. {Hydrogen 0·38 0·42 {Oxygen 1·82 1·79 {Ash 0·31 0·28 ------ ------ 99·97 100·05", "2. _Products of Combustion by Weight._", "Ordnance Powder. Small Arms Powder. { Nitrogen 9·77 } { 10·06 } { Carbonic anhydride 17·39 } { 21·79 } Gaseous. { Carbonic oxide 2·64 } { 1·47 } { Hydrogen 0·11 } 30·58 { 0·14 } 34·18 { Sulph. hydrogen 0·27 } { 0·23 } { Marsh gas 0·40 } { 0·49 }", "{ Ammonic sesquicarbonate 2·68 } { 2·66 } { Potassic sulphate 36·95 } { 36·17 } { \" carbonate 19·40 } { 20·78 } Solid. { \" hyposulphite 2·85 } 69·25 { 1·77 } 65·14 { \" sulphide 0·11 } { 0·00 } {Charcoal 2·57 } { 2·60 } {Sulphur 4·69 } { 1·16 } Loss. 0·17 0·68 ------ ------ 100·00 100·00", "3. _Products of Combustion by Volume in 100 of Gas._", "Ordnance Powder. Small Arms Powder. Nitrogen 37·58 } { 35·33 } Carbonic anhydride 42·74 } { 48·90 } Carbonic oxide 10·19 } { 5·18 } Hydrogen 5·93 } 100 { 6·90 } 100 Sulphuretted hydrogen 0·86 } { 0·67 } Marsh gas 2·70 } { 3·02 }", "It will be seen from the above figures that in addition to the generation of a considerable amount of carbonic anhydride (carbonic acid) by the combustion of gunpowder, there is liberated at the same time a large quantity of solid matter, in the form of sulphate and carbonate of potash, sulphide of potassium, sulphur, charcoal, &c. This will explain why the air of mines is so prejudicial to the health of the miner, particularly when he is engaged in blasting operations, these being carried on in a more or less confined space. See AIR, VITIATED.", "Gunpowder, Schultze.= The subjoined account of Schultze gunpowder is a transcription of a report communicated to the editor of the 'Field' newspaper by Mr F. Toms, A.I.C., F.C.S. After referring to a previous communication on the same subject Mr Toms proceeds as follows:--I have carried out some further experiments, with the aid (by Dr Frankland's kind permission) of apparatus more suited to my requirements than that previously at my disposal; and I now proceed to lay before you the results of these experiments, and the conclusions to which they have led me, respecting the powders formerly received and the new Schultze powder, with a sample of which you have since favoured me.", "The main constituent of the Schultze gunpowder, as you are aware, is wood fibre, which, having first been purified, is then subjected to the action of strong nitric acid (intensified by mixture with sulphuric acid), and thus is converted into a kind of nitro-cellulose or pyroxylin, the ordinary form of which is gun-cotton. The wood fibre undergoes no change in appearance by this treatment; but a change takes place in its chemical composition, which may thus be exemplified:", "CELLULOSE NITRO-CELLULOSE (unconverted cotton or (cotton or wood fibre treated wood fibre). with nitric acid). Carbon 6 parts 6 parts. Oxygen 5 \" 5 \" Hydrogen 10 \" 7 \" or more. Nitroxyl (NO_{2}) none 3 \" or less.", "It will thus be seen that the sole difference between gun-cotton or Schultze powder and ordinary cotton or wood fibre is, that some of the hydrogen is abstracted and has its place supplied by nitroxyl--a substance contained in nitric acid, and composed of one part of nitrogen united with two parts of oxygen. Under the most favorable circumstances, it is possible to replace _three_ of the ten parts of hydrogen by three of the nitroxyl, when the substance produced is explosive, and is called from its composition _tri_-nitro-cellulose. This is the purest form of gun-cotton. If weaker acid is used, less hydrogen is displaced, and the product is called _di_-nitro-cellulose or _mono_-nitro-cellulose, according as it contains _two_ or only _one_ part of nitroxyl. These derivatives are either feebly explosive or not explosive at all. Such are the compounds known as photographic collodion and soluble gun cotton--the latter name distinguishing it from pure gun-cotton, which is not soluble in a mixture of ether and alcohol.", "The Schultze powder contains both the explosive and the non-explosive varieties of nitro-cellulose.", "If the wood fibre, after being carefully purified according to the method described in Schultze's patent of 1864, were thoroughly desiccated and allowed to cool out of contact with air, and then dipped in acid of the strength mentioned in the specification, there seems no theoretical reason why an explosive powder containing at least 90% of true tri-nitro-cellulose should not be produced. As, however, I find on experiment that nothing like that per-centage is arrived at, I can only conclude that, in order to moderate the violence of the explosion, the Schultze Company secure the formation of a large per-centage of \"soluble\" or less explosive nitro-compounds by merely air-drying their wood.", "If this supposition be generally true, it seems probable that the sample of Schultze powder supplied by Messrs Blissett may owe its extra explosive force to exceptional care being taken, during the interval between the drying and the dipping, to prevent the absorption of moisture--with the addition, perhaps, of an increased length of exposure to the action of the acid.", "That some such variation of the ordinary procedure was carried out seems evident from the different proportions of soluble and insoluble gun-cotton in the specimens of Schuitze powder supplied by Messrs Blissett and Messrs Bland; for it was found that on the washed wood fibre from each being submitted to the action of a mixture of alcohol and ether, about one half of the former powder and two thirds of the latter were dissolved out. This shows that while the \"Blissett\" specimen contained about one half its weight of insoluble or explosive nitro-cellulose, the \"Bland\" contained only about one third--a difference which confirms the result obtained by analysis as stated below.", "The _soluble_ gun-cotton, ordinarily non-explosive, may, however, be rendered explosive by saturating it with bodies rich in oxygen, which promote the decomposition and complete the combustion of the fibre. Nitre is used for that purpose, because it parts with its oxygen readily; and nitrate of baryta is also used, because, being more stable than the nitre, it renders the combustion more gradual than would be the case if nitre were alone employed. When both are used, the nitre, I should think, would start, and the nitrate of baryta continue and finish the combustion of the powder. The amount used is, I suppose, the result of calculation and experiment; but a powder containing little true tri-nitro-cellulose should require more of these salts than one containing much tri-nitro-cellulose; and an excess of the salts would lower the rate of burning of the powder.", "I will now give my analysis in full of the three powders, viz.--(1) the ordinary powder issued last season, being part of a supply obtained from Messrs Bland, gunmakers, of the Strand; (2) some powder furnished by Messrs Blissett, of Holborn, and alluded to in their letter in the 'Field' of Jan. 19th last, as having damaged a gun made by them; and (3) some of the new powder of 1878, as used at the 'Field' trial of explosives in May last.", "1877 1878 Bland's. Blissett's. Trial or New.", "Moisture, per cent. 2·18 2·39 2·97 {Nitrate of baryta, per cent. 21·50 16·59 22·32 Extracted { \" potash, per cent. 11·46 10·46 6·47 by water. {Yellow coloured organic {substance, trace of chlorides, {&c., undetermined", "{The converted wood fibre } Insoluble { (nitro-cellulose) then } in water. { remaining contained the } 5·0 6·0 2·95 { following per-centage of } { mineral matter }", "The converted wood fibre (after allowing for extraneous mineral matter) possessed the following per-centage composition. I place for comparison Professor Abel's determination of the composition of tri-nitro-cellulose, and two of the impurities found along with it, in a parallel column.", "Bland's. Blissett's. Trial or New. Tri-nitro- Impurities. Cellulose. Carbon 28·75 28·07 28·12 24·24 29·20 30·50 Hydrogen 3·49 3·65 3·54 2·36 -- 2·91 Nitrogen 10·80 15·60 11·66 14·14 11·85 -- Oxygen 56·06 52·68 56·68 59·26 -- --", "These powders exploded at a temperature of about 190° C. (374° F.), the different samples varying but slightly. Pure gun-cotton is stated by Professor Abel to explode at 150° C. (302° F.); and black powders are said, by different authorities, to explode at various temperatures between 500° and 600° F., according to the variation in their composition and manufacture.", "In addition to the difference in chemical composition of these Schultze powders, I would point out that there is a difference in density--the Blissett being heaviest, the Bland next, and the New the lightest of the three. I think this fact also has some bearing on the violence of the explosion. In black powders, I believe, a dense powder, speaking generally, is stronger than a lighter one; and the Schultze patent states that hard woods make more explosive powders--not, I take it, because the composition is thereby altered, but because a denser powder is produced. It would appear to me, from the above analyses, that the new trial powder should contain rather more explosive force than the Bland variety, though considerably less than the Blissett. The result may, however, be modified by the difference in density of the powders; and your practical experiments will show how far this agrees with the results of the shooting.", "I have hitherto only spoken of the explosive force of the powder; now I will touch on another point--its tendency to spontaneous decomposition. Knowing that, in the case of gun-cotton, its stability is injured by a small proportion of resin and other organic impurities, and by the presence of free mineral acids. I did not expect to find this powder (made from a less pure kind of cellulose, from which also it must be somewhat difficult to wash all traces of acid) equal in stability to gun-cotton; and on subjecting the three kinds of Schultze powder to the Government 'heat test' of 150° F. (with a minimum of 10 minutes' duration), it was found that the", "New or Trial (1878) Powder stood the test 12 m. 'Bland's' sample \" 8 \" 'Blissett's' sample \" 7 \"", "This shows that the 'new' powder is very stable, as it stood the test for two minutes beyond the Government minimum, while the other two samples were a good way below it. The officials at Waltham Abbey would accept no gun-cotton which did not stand the test for ten minutes; and I have seen the best gun-cotton stand it for fifteen.", "Whether the loose granulated condition of the Schultze powder, when stored, is sufficient to neutralise this inferiority in purity, and render a sample of Schultze, which only stands the test of seven minutes, as little liable to spontaneous combustion as gun-cotton which stands the test for ten minutes, there is at present no evidence to show.", "To carry out this 'heat test' properly, some practice is required; so, in order to put the matter beyond doubt, I called in the assistance of my friend Mr Arthur Linnell, F.C.S., chemist to the Gun-Cotton Company, Stowmarket, a gentleman who uses the test daily, and who carried out the above three experiments strictly after the manner adopted by himself and by the Government officials.", "In addition to Mr Linnell's experiments, I noted that the aqueous extract of 'Blissett' was very faintly acid; that when heated in a chest at 195° F. moist blue litmus was very quickly reddened.", "I think this serious defect (want of stability) is due to want of care in the washing; and I base this opinion on the following facts:", "(1) The 'Bland' and 'Blissett' samples (the powders of least stability) are of a deeper tint than the 'new' (due to the soluble yellow impurity before mentioned). By continued washing in warm water they become pale, like the more carefully prepared new powder, and the yellow substance is dissolved away. Hence the lighter colour of the 'new' (and most stable) indicates it has less of this organic impurity.", "(2) Sulphuric and nitric acids are used in the dipping of the powder, but should be entirely washed out, as they promote spontaneous decomposition. If left in, the sulphuric acid will, when the salts are added, decompose the nitrate of baryta, forming insoluble baric sulphate and free nitric acid.", "On experiment I ascertained that the abnormally large quantity of mineral matter or ash (5 and 6 per cent.) found in the insoluble part of the 'Bland' and 'Blissett' powders _is_ due to baric sulphate, and I think the acidity of the aqueous extract is due to the nitric acid thus set free.", "Had this baric sulphate been present in the new powder, I should have thought it was purposely formed in all to prevent access of moisture; but, not finding this substance in this carefully prepared sample, I attribute its presence in the other cases to carelessness on the part of the workmen.", "I should state that all these powders consisted of a granulated and consolidated pulp. This improvement must, I think, have considerable advantages over the sawdust form previously adopted by the Schultze Company in as much as it facilitates a more thorough purification being carried out, and produces a more homogeneous and equal powder. It is possible, too, that working with pulp may be of advantage, inasmuch as the company may now, by varying the pressure in forming the cake, obtain grains of any required density.", "In conclusion, I may say that, in my opinion the most difficult task which the Schultze Company have had to encounter is that of obtaining uniformity of strength in their explosive; and the 'Blisset' sample of their powder may he looked upon as an experimental batch in which (by altering the mode of procedure in some such manner as I have indicated) they made a powder with a large per-centage of tri-nitro-cellulose, thus producing a more rapidly burning substance, and consequently a more violent explosion.", "Taking all things into consideration, I think the Schultze Company, in manufacturing a nitro-explosive which gives the uniformity of shooting power shown in your recent experiments, have worked out a most troublesome problem with remarkable success. The difficulty of obtaining such results is evidenced by the fact that so many inventions of a somewhat similar character have been abandoned for sporting purposes from a deficiency in this respect.", "But, however difficult it may be to manufacture a powder giving uniform shooting, it is evidently possible, with suitable care to produce (as the 'new' Schultze shows) a wood powder which is perfectly safe and stable, as far as spontaneous decomposition is concerned. The company, therefore, if they have not already done so, ought to take means to prevent powder of the low stability of the 'Bland' and 'Blissett' samples being again issued from their works.", "P.S.--Since writing the above I have examined cursorily a sample of the 'Dittmar' wood powder, an American variety of 'Schultze,' used by Captain Bogardus in some of his recent shooting competitions. The powder is somewhat darker in tint, and of slightly larger grain, than the Schultze. In density it is intermediate between 'Bland's' and the 'new' powder; and the charge in a twenty-bore cartridge was forty-two grains. This powder would seem to be made from solid cubes of wood (not a pulped mass like the present 'granulated' Schultze, or of sawdust splinters like the old so-called 'cube' Schultze). It contains no nitrate of baryta, but has a small quantity of nitrate of potash and soda. Possessing, as it would seem, therefore, a much smaller proportion of oxidizing salts than the English Schultze, it should contain, to make up for this loss of force, a larger proportion of explosive pyroxylin; but this is a point I have not experimentally determined. ('Field,' August 3rd, 1878, No. 1336, p. 143.)", "Gunpowder, White.= _Syn._ BLASTING POWDER. _Prep._ 1. See BLASTING POWDER, No. 3.", "2. Yellow prussiate of potash and white sugar, of each 1 part; chlorate of potassa, 2 parts; powder each separately, and mix them well, but carefully, with a bone or wooden knife. It may be granulated like gunpowder, by making the powder into a paste with a little water, and pressing the mass through a parchment sieve.[344]", "[Footnote 344: See the precautions noticed under BLASTING POWDER, page 230.]", "GUN'JAH.= See HEMP (Indian).", "GUT.= _Syn._ FISHING GUT, SILKWORM G. This is obtained from the _Bombyx mori_ (Linn.) or silkworm caterpillar. _Prep._ The silkworms, when just ready to spin, are steeped in strong vinegar for 12 hours in warm weather, or 2 or 3 in cold weather, and are then broken in half, and stretched out as far as possible on a board, furnished with slits or pegs to hold them; in this state they are allowed to dry in the sun or a warm place.", "_Obs._ Used by anglers. The worms may be known to be going to spin by refusing food, and by having a fine silken thread hanging from the mouth.", "GUT'TA PERCHA.= The concrete juice of the _Isonandro Gutta_, a tree growing only in the Malayan Archipelago, and of other species of the same genus. The stem of the gutta-percha tree grows to the diameter of 5 or 6 feet, and on being notched yields a milky juice, which, after exposure to the air for some time, solidifies, forming the gutta percha of commerce. It arrives in this country in irregular blocks of some pounds in weight, usually containing a large portion of impurities in the form of pieces of wood, stones, and earth. To prepare this crude product for manufacturing into useful articles, the blocks are first cut into slices, and then torn into shreds. These are softened by hot water, and kneaded in a 'masticator,' the stones, earth, and other impurities, being gradually washed away by water. After several hours the gutta percha is found to be kneaded into a perfectly homogeneous mass, which is rolled or drawn into sheets, bands, or tubes, as required.", "_Prop., &c._ Gutta percha is a tough, inelastic substance, becoming soft and plastic at 212° Fahr., at which temperature two pieces may be firmly welded together. It is one of the best insulators of electricity, is impervious to moisture, and resists the action of acids and alkalies to a great extent. Its best solvents are benzol, chloroform, bisulphuret of carbon, rectified mineral naphtha, and rectified oil of turpentine. All these dissolve it readily. According to the analysis of Payen, the purified gutta percha of commerce consists of 75 to 828 of chemically pure gutta percha, which is insoluble in ether and alcohol, and a white and a yellow resin, soluble in boiling alcohol.", "_Uses._ These are numerous and varied. No substance, perhaps, with the exception of caoutchouc, has been 'tortured' to so many different purposes. Its perfect plasticity when warm, and its capability of receiving the most delicate impressions, render it invaluable in many cases where india rubber would be useless. Beautiful mouldings, picture frames, and a number of ornamental articles, are made from it. To the chemist and photographer it is of great use as a material for making bottles, carboys, photographic baths, and voltaic battery cells. One of the most important uses to which it has been applied is for enclosing the metallic wires used for telegraphic purposes. Its indestructibility by water, its plasticity, and high insulating power, have rendered it particularly valuable for this purpose. At the International Exhibition of 1862 the Gutta Percha Company exhibited one mile of covered wire perfectly insulated, which was hardly thicker than common sewing cotton. Gutta percha may be rolled into thin transparent sheets, which, being perfectly impervious to moisture, are well adapted for surgical purposes. Again, a solution of gutta percha in chloroform forms an excellent dressing for incised wounds, and a protection for abraded surfaces, burns, &c. It is used in the same way as collodion.", "Gutta Percha, Purified.= Dr Cattell, of London, has succeeded in purifying gutta percha so perfectly from all extraneous matter, that it presents the appearance of ivory. The raw material is dissolved in a certain solvent, and the solution most carefully filtered until it leaves on evaporation the gutta percha in a pure milk-white condition.", "GYP'SUM.= This is native sulphate of lime.