MERCURY, Other Preparations of.

Mercury, Hahnemann’s.= _Syn._ HAHNEMANN’S SOLUBLE MERCURY, H.’S BLACK OXIDE OF M., BLACK PRECIPITATE OF M.; HYDRARGYRI PRÆCIPITATUM NIGRUM, MERCURIUS SOLUBILIS HAHNEMANNI, L.——_a._ By dropping weak ammonia into a solution of mercurous nitrate as long as the precipitate formed is of a black colour; the powder is washed, dried in the shade without artificial heat, and then preserved from the light and air.

(Ph. Bor. 1847.) Solution of mercurous nitrate (recent; sp. gr. 1·1), 9-1/4 oz.; distilled water, 2 lbs.; mix, filter, and add to the solution of ammonia (sp. gr. ·960), 1/2 oz., diluted with water, 4 fl. oz.; collect the powder immediately on a filter, wash it with water, 3 fl. oz., and dry it, &c., as before. A very black powder.——_Dose_, 1/4 to 1 gr.

Mercury, Precipitates of.= 1. BLACK PRECIPITATE, Hahnemann’s soluble mercury (basic mercurous and ammonium nitrate). 2. GREEN P. (MERCURIUS PRÆCIPITATUS VIRIDIS, LACERTA VIRIDIS), from equal parts of mercury and copper, separately dissolved in nitric acid, the solutions mixed, evaporated to dryness, and then calcined until red fumes cease to arise. Caustic. 3. RED P., mercuric oxide. 4. WHITE P., ammonio-chloride of mercury.

Mercury, Ward’s.= _Syn._ AMMONIO-NITRATE OF MERCURY; HYDRARGYRI AMMONIÆ NITRAS, L. To nitric acid, 4 parts, contained in a spacious bolt-head or matrass, add, gradually, ammonium sesquicarbonate, 2 parts; afterwards add of mercury, 1 part, and digest in a gentle heat, until the solution is complete.

Mercury with Chalk.= _Syn._ HYDRARGYRUM CUM CRETÂ. GREY POWDER (B. P.) _Prep._ Rub 1 oz. (by weight) of mercury, and prepared chalk, 2 oz., in a porcelain mortar, until metallic globules cease to be visible to the naked eye and the mixture acquires a uniform grey colour.——_Dose._ From 3 to 8 gr.

A little water is said to aid in the extinction of the mercury. Mr Bottle suggests a slight departure from the Grey _modus operandi_ followed by the British Pharmacopœia in the above preparation. He proposes to substitute for the tedious process of trituration in a porcelain mortar the agitation of the mercury with the chalk in a wide-mouthed glass bottle; by which means the metal may be minutely subdivided, at a considerably less expenditure of time and labour.

Mercury with Magnesia.= (Ph. D.) _Syn._ HYDRARGYRUM CUM MAGNESIÂ. Pure mercury, 1 oz., carbonate of magnesia, 2 oz. Rub together in a porcelain mortar until the globules cease to be visible and the mixture acquires a uniform, grey colour.——_Dose_, 3 to 8 grains.

Mercury, Yellow Oxide of.= (Ph. B.) _Syn._ HYDRARGYRI OXYDUM FLAVUM. _Prep._ Perchloride of mercury, 4 oz.; solution of soda (Ph. B.), 2 pints; distilled water, q. s. Dissolve the perchloride in 4 pints of distilled water, adding the solution by the application of heat, and add this to the solution of soda. Stir them together, allow the yellow precipitate to subside, remove the supernatant liquor by decantation, thoroughly wash the precipitated oxide on a calico filter with distilled water, and finally dry it by the heat of a water bath.

MES′LIN.= A mixture of various kinds of grain. (Brande.)

METAGAL′LIC ACID.= Obtained by heating dry gallic acid, by a quick fire, to about 480° Fahr., or until it froths, melts, and becomes black and solid, then dissolving the residuum in an alkali, filtering, and precipitating by an acid. An insoluble, black powder.

ME′TAL.= _Syn._ METALLUM, L. See METALS.

METAL′LICA.= [L.] Preparations of the metals. One of the divisions of the Ph. L.

METAL′LIC TREES.= See VEGETATION (Metallic).

METAL′LO-CHROMES.= A name given by Nobili to extremely thin films of peroxide of lead deposited by electrolytic action upon plates or polished steel, so as to produce an iridescent play of colours. The effect is often very beautiful.

MET′ALLOIDS.= A name sometimes applied to the NON-METALLIC ELEMENTS.

METAL′LURGY.= “The art of extracting metals from their ores, and adapting them to various processes of manufacture.” (Percy.)

“Notwithstanding the striking analogy which exists between common chemical and metallurgic operations, since both are employed to isolate certain bodies from each other, there are essential differences which should be carefully noted. In the first place, the quantity of materials being always very great in metallurgy, requires corresponding adaptations of apparatus, and often produces peculiar phenomena; in the second place, the agents to be employed for treating great masses must be selected with a view to economy, as well as chemical action. In analytical chemistry, the main object being exactness of result and purity of product, little attention is bestowed upon the value of the reagents, on account of the small quantity required for any particular process. But in smelting metals upon the large scale, profit being the sole object, cheap materials and easy operations are alone admissible.”[35]

[Footnote 35: ‘Ure’s Dict. of Arts, Manufactures, and Mines,’ 4th edit.]

The limits of this work do not permit of more than a general reference to the leading operations of metallurgy under this head. These are——digging, picking or sorting, stamping or crushing, and washing, included under the general term, ‘dressing ore,’——roasting or calcination, which is either performed with the fuel in contact with the ore, or in reverberatory furnaces; and the liquation or reduction to the reguline form. The application of these processes is noticed under the leading metals. Those who desire to study the subject minutely are referred to the treatises of Dr Percy, Robert Hunt, Karsten, and Le Play.

MET′ALS.= _Syn._ METALLA, L. Metals are elementary bodies, which are generally distinguished by their lustre and power of conducting heat and electricity. When their solutions are electrolysed, the metals always appear at the electro-negative surface, and are hence termed electro-positive elements.

Formerly, when science was much less advanced than at present, the metals constituted a well-defined class. The properties which were regarded as specially characteristic were physical, and were not founded on chemical relations; thus, lustre and high specific gravity were considered to be essential characters of all metals. But we are now acquainted with metals which have a lower specific gravity than water (lithium, sodium, &c.), and with so-called non-metallic elements which present a strong metallic lustre (carbon in the state of graphite, crystallised silicon). It will therefore be seen that the term ‘metal’ is rather conventional than strictly scientific. By far the greater number of elementary bodies at present known are metals. Their physical characters and leading chemical properties are noticed under each of them in its alphabetical place. The following table exhibits some useful particulars:——

TABLE _of some of the properties of some of the metals._

Names arranged in the order of their /-----------------------/\----------------------\ Ductility. | Malleability. | Gold. | Gold. Silver. | Silver. Platinum. | Copper. Iron. | Tin. Nickel. | Platinum. Copper. | Lead. Zinc. | Zinc. Tin. | Iron. Lead. | Nickel.

Names arranged in the order of their /-----------------------/\----------------------\ Power of conducting | Power of conducting Heat. | Electricity. | Silver. | Silver. Copper. | Copper. Gold. | Gold. Tin. | Zinc. Iron. | Iron. Lead. | Tin. Bismuth. | Lead. | Antimony. | Bismuth.

METANTIMON′IC ACID.= H_{4}Sb_{2}O_{7}. The name given by M. Fremy to that variety of antimonic acid obtained by decomposing pentachloride of antimony with excess of water. It differs from common antimonic acid in being tetra, and forming two different classes of salts with the acids. The acid metantimoniate of potassium is the only reagent which yields a precipitate with the sodium salts, and is therefore of great value in chemical analysis. It is prepared by fusing antimonic acid with excess of potassa, in a silver crucible, dissolving the fused mass in a little cold water, and allowing it to crystallise in vacuo. The resulting crystals (metantimoniate of potassa), by solution in pure water, are resolved into free potassa and the acid salt. See ANTIMONY.

METAPEC′TIC ACID.= See PECTIN.

METAPEC′TIN.= See PECTIN.

METAPHOSPHOR′IC ACID.= See PHOSPHORIC ACID.

METHEG′LIN.= _Syn._ HYDROMELI, H. VINOSUM, MELLIS VINUM, L. _Prep._ From honey, 1 cwt.; warm water, 24 galls.; stir well until dissolved; the next day add of yeast, 1 pint, and hops, 1 lb., previously boiled in water, 1 gall.; along with water q. s. to make the whole measure 1 barrel; mix well, and ferment the whole with the usual precautions adopted for other liquors. It contains on the average from 7% to 8% of alcohol. See MEAD.

ME′THYL.= CH_{3}. The hypothetical radical of PYROXYLIC SPIRIT (WOOD-SPIRIT, METHYLIC ALCOHOL) and the methyl series. It forms a number of compounds analogous to those of ethyl.

METHYLAMINE.= _Syn._ METHYLIA. CH_{3}H_{2}N. A colourless gas possessing a very powerful odour of ammonia, and a strongly alkaline reaction. It differs from ammonia, however, in being non-inflammable. In other respects it bears a considerable resemblance to it. Water at 55° Fahr. dissolves more than eleven hundred times its bulk of methylamine. It may be easily condensed to a liquid by means of a freezing mixture.

To obtain it nascent hydrogen is made to react on prussic or formic acid. Methylia exists in herring brine, and is a frequent product of the destructive distillation of substances containing nitrogen. Most of its salts are very soluble in water.

METHYLATED SPIRIT.= A mixture of 1 part of methylic alcohol (wood spirit) and 9 parts of ethylic alcohol (spirit of wine). See SPIRIT.

METHYLENE CHLORIDE.= CH_{2}Cl_{2}. _Syn._ METHYLENE BICHLORIDE. There are various methods of obtaining this compound:——1. By heating chloroform with zinc filings and dilute sulphuric acid. 2. By acting on methylene iodide with chlorine. In this process prolonged treatment with chlorine, at ordinary temperatures, is required to remove the last traces of iodine. (Buttlerow.) Chloride of methylene is a colourless mobile fluid, having a smell like chloroform, and a burning taste. It is used as an anæsthetic in place of chloroform. According to Dr Armstrong, the substance known as METHYLENE ETHER is a mechanical mixture of bichloride of methylene and ethylic ether. Dr Richardson says of this latter it is not so quick in its action as the methylene chloride, but that it is safer. See ANÆSTHETICS.

METHYLIC ALCOHOL.= See WOOD SPIRIT.

MEZE′REON.= _Syn._ GAROU; MEZEREON BARK, MEZEREI CORTEX (B. P.); MEZEREON——Ph. L., E., & D. The dried bark of the _Daphne Mezereum_, mezereon; or _Daphne Laureola_, spurge, or wood-laurel. The “bark of the root of _Daphne Mezereum_,” or spurge olive. (Ph. L.) A stimulant and diuretic. It is employed as a sudorific and alterative, in syphilis, rheumatism, scrofula, and chronic cutaneous diseases, usually in conjunction with sarsaparilla. It has also been used as a masticatory in toothache, paralysis of the tongue, &c. On the Continent it is used as a vesicant. For this purpose it is softened by soaking it in hot vinegar, and is then bound on the part, and renewed after intervals of some hours, until vesication is produced.

MICE.= See RATS.

MI′CROSMIC SALT.= NaNH_{4}HPO_{4}, _Syn._ TRIBASIC PHOSPHATE OF SODIUM AND AMMONIUM. _Prep._ 1. Phosphates of soda and ammonia, equal parts; water, q. s.; dissolve separately, mix the solutions, evaporate, and crystallise. A slight excess of phosphate of ammonia aids the crystallisation.

2. (Fownes.) Phosphate of sodium, 6 parts; water, 2 parts; liquefy by heat, and add of sal ammoniac (in powder), 1 part; common salt separates, and after its removal the liquid is concentrated so that crystals may form. Used as a flux in blowpipe assays.

MI′CROSCOPE.= The value of the microscope in chemistry and the collateral sciences is now so generally acknowledged that it would be folly to do more than merely allude to the subject here.

In the COMPOUND MICROSCOPE, which has quite superseded the ‘simple microscope’ as an instrument of research, the object is magnified in the first instance by the object-glass, and then remagnified by the eye-piece. It follows, therefore, that the magnifying power of the instrument may be increased either by increasing the power of the object-glass or that of the eye-piece. It must be borne in mind, however, that in increasing the power of the eye-piece we do not magnify the object itself in a greater degree, but simply increase the image of the object formed by the object-glass. Any imperfections which may exist in the latter are thus greatly increased. At first the great drawback to the use of the compound microscope was its deficiency in achromatism; but the researches of Mr Lester and Dr Goring led to the achromatising of the object-glass, which was the first of the rapid strides towards perfection made by this instrument during the last twenty years. The two most useful object-glasses are the ‘quarter-inch,’ which should magnify from 200 to 220 diameters, and the ‘inch,’ which should magnify from 30 to 40 diameters. The definition of these glasses should be good, and they should transmit plenty of light. Any lines in a structure examined by them should appear sharp and distinct, and there should be no coloured fringes around the object. It is of great importance that the object-glasses are kept perfectly free from dust. A few shreds of wash-leather of the finest quality should be kept in a pill-box for cleaning them. Before rubbing them with the leather they may be breathed upon, but no whiting or liquid of any kind should be used, as each object-glass, being achromatic, is a very delicate piece of workmanship, consisting of two lenses of flint and crown-glass cemented together by Canada balsam. Compound microscopes are now sold by the best London makers at very low prices. A really good instrument, adapted to most of the wants of the chemical, pharmaceutical, o

The following formulæ for the preparation of the chief substances, together with the principal reagents required in the working of the microscope, are from Dr Lionel Beale’s valuable book, ‘How to Work with the Microscope,’[36]

[Footnote 36: Harrison, 59, Pall Mall.]

_Reagents_——

1. Alcohol, of various strengths.

2. Ether, to dissolve oil globules.

3. Nitric acid (1 part of strong acid to 5 of water)

4. Sulphuric acid (1 to 5).

5. Hydrochloric acid.

6. Acetic acid, glacial and dilute (1 to 5).

7. Chromic acid, very dilute, to harden tissues.

8. Solution of potash, saturated and dilute (1 to 10).

9. Solution of soda (25 gr. of fused soda to 1 oz.).

10. Ammonia (1 part of the strongest solution to 3 of water).

11. Nitrate of baryta, a cold saturated solution of.

12. Nitrate of silver (120 gr. to 2 oz.). These two are for the mineral acids.

13. Oxalate of ammonia in solution. Test for lime.

14. Solution of iodine saturated, _i.e._ 1 to 7000 parts of water. Another solution is——1 gr. of iodine and 3 of iodide of potassium in 1 oz. of distilled water.

1. _Cements._——1. _Brunswick Black._ Boil together 1/4 lb. foreign asphaltum and 4-1/4 oz. of linseed oil (previously thickened with litharge), then mix to a proper consistence with oil of turpentine (about 1 pint).

2. _Gold Size._ Boil 25 parts of linseed oil with 1 of minium and 1/3rd part of umber for 3 hours; pour off the clear fluid, and mix with equal parts of powdered white lead, and yellow ochre, added in small successive portions. Then boil well the whole again, and pour off the clear fluid. It dries slowly, but firmly. Both this and the last are dissolved by turpentine.

3. _Goadby’s Marine Glue._ Dissolve separately in coal naphtha equal parts of shell-lac and india rubber. Mix thoroughly with heat.

4. _Sealing-wax Varnish._ Dissolve the best sealing-wax in enough strong spirit of wine to reduce it to the proper consistence. This is brittle.

5. _Canada Balsam._ This dries spontaneously.

Solutions of shell-lac, gum, and various other cements and glues are employed by microscopic manipulators.

_Preservative Fluids._ Canada balsam, spirit and water, glycerin, solution of gelatin, saturated solution of alum, chloride of zinc, and chloride of calcium, are all used to preserve microscopic objects.

The following formulæ will be found useful:——

1. _Goadby’s Solution._ Bay salt, 4 oz.; alum, 2 oz.; corrosive sublimate, 4 gr.; boiling water, 4 pints. Mix and filter. It may often be more diluted.

2. _Thwaite’s Fluid._ Mix spirit of wine, 1 oz., with creosote sufficient to saturate it; rub up with chalk to form a thin paste, and mix gradually with 16 oz. of water. To this may be added an equal quantity of water, saturated with camphor.

3. _Simple Creosote Solution._ Dissolve creosote, 1 dr., in pyroligneous acid, 1 dr., and mix gradually with cold water, 1 pint.

4. _Passini’s Solution. For blood-globules, nerves, and white tissues generally._ Perchloride of mercury, 1 part; chloride of sodium, 2 parts; glycerin, 13 parts; distilled water, 113 parts.

MIL′DEW.= _Syn._ RUST, BLIGHT. The mouldy appearance on the leaves of plants produced by innumerable microscopic fungi. The hop, wheat, and the choicest garden fruit trees, are those most commonly attacked. The causes are said to be excess of moisture, and absence of the free circulation of air and sunshine. On the small scale, finely powered sulphur is occasionally dusted over the parts affected, as a remedy.

MIL′IARY FEVER.= _Syn._ MILIARIA, L. Among the other symptoms are——anxiety and frequent sighing, the perspiration has a strong and peculiar smell, and there is a sensation of pricking on the neck and breast, followed by an eruption of small red pimples, which in two or three days become white vesicles, dry up, peel off, and are succeeded by others. The moist weather of spring and autumn are the periods in which it is most prevalent; and delicate females, particularly in child-bed, are those most liable to its attacks. Sometimes it assumes a malignant character. The _treatment_ of this affection consists chiefly in combating the depression of the system by a supporting diet; but everything that heats or stimulates the skin should be avoided. The apartment should be kept cool and well ventilated, and cooling saline laxatives and bitter tonics, with cooling drinks, should also be had recourse to.

MILK.= _Syn._ LAC, L. The value of milk as an article of food is clearly shown by the fact of it being sufficient to support, and to increase the growth of, the young of every species of the mammalia; at once supplying materials for the formation of the osseous, fleshy, and liquid portions of the body. “The substances present in milk are wonderfully adapted to its office of producing materials for the rapid growth and development of the animal frame. It contains an azotised matter, casein, nearly identical in composition with muscular flesh, fatty principles, and a peculiar sugar, and, lastly, various salts, among which may be mentioned phosphate of lime, held in complete solution in a slightly alkaline liquid.

“The white and almost opaque, appearance of milk is an optical illusion. Examined by a microscope of even moderate power, it is seen to consist of a perfectly transparent fluid, in which float about numbers of minute transparent globules; these consist of fat surrounded by an albuminous envelope, which can be broken mechanically, as in the churning, or dissolved by the chemical action of caustic potassa, after which, by agitating the milk with ether, the fat can be dissolved.” (Fownes.)

_Comp._ COWS’ MILK, of average quality, contains from 10% to 12% of solid matter when evaporated to dryness by steam heat, and has the mean sp. gr. 1·030; while that of the skimmed milk is about 1·035; and of the cream, 1·0244. (Ure.) The average CREAM of cows’ milk contains 4·5% of butter, 3·5% of curd, and 92% of whey. (Berzelius.) The SKIMMED MILK consists of water, 92·9%; curd, 2·%; sugar of milk, 3·5%; lactic acid, lactate of potassa, and a trace of lactate of iron, ·6%, chloride of potassium, phosphate of potassa, and earthy phosphates (lime), ·2%. (Berzelius.)

The following analysis of fresh milk is by M. Haidlen:——

Water 873·00 Butter 30·00 Casein 48·20 Milk sugar 43·90 Phosphate of lime 2·31 Phosphate of magnesia ·42 Phosphate of iron ·07 Chloride of potassium 1·44 Chloride of sodium ·24 Soda in combination with casein ·42 ———————— 1000.

Professor Wanklyn has devised and published in his excellent little manual ‘Milk Analysis’[37] a process by which a very thorough chemical examination of milk may be accomplished with great facility and expedition.

[Footnote 37: Trubner and Co.]

In his preliminary remarks he condemns, as utterly unreliable and misleading, the inferences to be drawn from those hydrometric instruments, the lactometer or lactodensimeter, and creamometer. “A very little consideration,” he says “will suffice to make intelligible the obliquity of the indications of the lactometer and to show how untrustworthy it must be. The lactometer, as of course will be understood, is simply the hydrometer applied to milk; and readings of the instrument are neither more nor less than specific gravities. The more milk-sugar, and casein, and mineral matter there is in a given specimen of milk, the greater (other things being equal) will be its density or specific gravity, and the higher the lactometer reading.

“If, however, fat globules (as happens in the instance of milk) be diffused through the fluid, then, because fat is lighter than water, the effect of the other milk solids on the gravity of the liquid, will be more or less neutralised. The density of milk-fat is about 0·9, water being 1·0. Now, if a solution of casein and milk-sugar, of specific gravity 1·030, be sufficiently charged with fat globules, its specific gravity may be sent down even below the gravity of water. How much would be required to bring about such a result is a matter of simple calculation.

“This being understood, it will be obvious that if the specimens of milk differ in specific gravity, there must be two distinct and equally valid ways of accounting for the difference.

“The milk with the lower gravity may be milk let down with water, or let down with fat, _i. e._ milk let down by being enriched.”

In support of this last assertion Professor Wanklyn quotes corroborative instances afforded by the examination of different specimens of milk known as ‘strippings,’ these being the last portions of milk yielded by the cow at the termination of the milking. All these ‘strippings’ had a lower specific gravity than normal milk.

Further, Professor Wanklyn points out that the specific gravity of organic fluids is a fallacious index of the amount of solids they may contain, as is illustrated by the fact, that whilst a 10 per cent. solution of chloride of potassium has a specific gravity of 1·065 at 15° C., and a 10 per cent. solution of casein and milk sugar, has a specific gravity of only about 1·035.

The creamometer meets with equal condemnation in Professor Wanklyn’s little book, since different specimens of milk vary considerably in their yield of cream, and a perfectly pure sample of milk may yield less cream than one which has been tampered with.

A complete analysis of milk involves the determination of the water, the fat (the essential constituent of the cream), the casein, milk-sugar, and ash.

The following is an outline of Professor Wanklyn’s neat and ingenious method of analysis:——

By means of an accurately graduated pipette, he first places 5 cubic centimetres of the milk in a small weighed platinum dish (about 14 grammes in weight) just previously ensuring the sample from which the milk is taken being thoroughly mixed.

The dish is then placed over a water-bath (the water in which must be kept vigorously boiling the whole time) for three hours, at the end of which time all the water having been driven off, there will remain in the dish a completely dried up residue.

The increase in weight between the empty dish and the residue, will give the weight of the ‘milk solids’ from 5 c.c. of milk. Of course, if this weight be multiplied by 20, the yield from 100 c.c. of milk will be obtained.

To reduce this to a percentage statement it is necessary to remember that 100 c.c. of average milk weigh 102·9 grammes. The next proceeding consists in the determination of the fat. This is done by treating the dried milk solids resulting from the 5 c.c. of milk with ether. There are several important minutiæ necessary to be observed in connection with this part of the process, for the particulars of which the reader is referred to Professor Wanklyn’s book. Suffice it to say, that if properly performed, the whole of the fat is dissolved by the ether, and being separated from the non-fatty portion of the residue is weighed and calculated as ‘fat.’

If, then, the amount found as fat be deducted from the whole of the milk solids previous to their treatment with ether, the ‘milk solids, not fat,’ will be arrived at. Professor Wanklyn estimates the casein[38] as follows:——He treats the milk solids, not fat, with hot alcohol, by which means he dissolves out from them, and removes the milk-sugar and the soluble chlorides. The remaining residue, consisting of casein and phosphate of sodium (chemically combined with the casein), is dried on a water-bath until it ceases to lose weight. It is then weighed along with the vessel containing it, and ignited. The combined weight of the vessel and phosphate of sodium remaining after ignition being deducted from the weight previous to ignition, the difference is the casein.

[Footnote 38: Under the head “Casein” Prof Wanklyn includes the entire nitrogenous materials of milk.]

Another and quicker method, recommended by Professor Wanklyn, for the determination of the casein, is to measure it by the amount of albuminoid ammonia it is capable of yielding when subjected to the ‘albuminoid ammonia process,’ invented by Messrs Wanklyn, Chapman, and Smith.

The alcoholic solution filtered off from the combined casein and phosphate of sodium, contains the milk sugar and soluble chlorides. It is evaporated to dryness on a water-bath, and the residue with the vessel containing it, is weighed. It is then gently ignited, and the weight of the remaining residue being deducted from the total weight before ignition, gives the yield of milk sugar. Or the milk sugar may be determined by titration with a standard copper solution.

For the determination of the ash it is only necessary to ignite the milk solids from 5 c.c. of milk, in the small platinum dish, by which operation all the organic matter being driven off, that which remains behind constitutes the ‘ash’ and is weighed as such.

It will be obvious that in order to determine with anything like rigid accuracy the quality of any sample of milk by analysis, not only must a normal standard for the purpose of comparison be adopted, but such normal standard must represent very closely and with but little variation the definite composition of all sound and genuine milk.

Professor Wanklyn says that “the following, which is the result of several concordant analyses of country-fed milk, may be taken as representing normal milk. In 100 grammes of milk——

Solids (dry at 100° C) 12·5 grammes. Water 87·5 —————— 100·0

“The 12·5 grammes consist of 9·3 grammes of ‘solids which are not fat,’ and 3·2 grammes of fat.” The above data, which are founded on the examination of a very large number of different samples of milk, are confirmed by the researches of Müller and Eisenstuck, who were employed by the Royal Agricultural Society of Sweden in a similar investigation. The labours of these chemists extended over a twelvemonth, and the result of them was to show that the milk yielded day by day, for a whole year, by a herd of cows was remarkably constant in composition.

Professor Wanklyn gives the following formulæ for the calculation and statement of the results of milk analysis. He says, treating the question quite rigidly, which I believe is the proper way of dealing with it, we arrive at the following:——

_Problem_ 1. Given the percentage of ‘solids, not fat’ (= _a_), in a specimen of sophisticated milk (_i. e._ milk, either watered, or skimmed, or both)——required the number of grammes of genuine milk which was employed to form 100 grammes of it.

_Answer._ Multiply the percentage of ‘solids, not fat’ by 100, and divide by 9·3.

Or—— (100 / 9·3)_a_.

_Problem_ II.——Given the percentage of ‘solids, not fat’ (= _a_), also the percentage of fat (= _b_), in a specimen of sophisticated milk——required the number of grammes of fat which have been removed by skimming from the genuine milk which was employed to form 100 grammes of it.

_Answer._—— (3·2 / 9·3)(_a_ - _b_).

In translating fat into cream, the rule is that a removal of 0·2 gramme of fat equals a removal of 1·0 gramme of cream. This rule is directly founded on experiment. I do not, however, claim a high degree of accuracy for the measurement of the cream.

Finally, a slight refinement may be noticed. If a specimen of sophisticated milk has been produced by both skimming and watering, it will be obvious, on consideration, that the extraneous waters employed in manufacturing 100 grammes of it is equal to the difference between 100 and the quantity of genuine milk employed to make 100 grammes of sophisticated milk, together with a quantity of water equal to that of fat removed by skimming.

Extraneous water = 100(100 / 9·3)_a_ + (3·2 / 9·3)(_a_ - _b_)

100[(100 + 3·2) / 9·3](_a_ - _b_)

Save for the purpose of finding out the presence of matters other than an excess of water in the milk (a contingency regarded as very improbable), the estimation of the casein and milk sugar is unnecessary. The determination of the ash is for the object of learning if foreign mineral matters, such as chalk or any other inorganic impurity, are present. Professor Wanklyn says he believes that such like extraneous bodies are never employed. The chief, if not the sole, form of dishonesty are watering and skimming.

The amount of ash, however, is a good criterion as to the extent of dilution that has been practised, a deficient amount being, of course, confirmatory of a watered milk.

The determination of the amount of ‘solids, not fat,’ is, in almost every instance, all that is necessary to enable an opinion to be arrived at as to whether the sample of milk has had water added to it or not.

Out of fifty-six samples of milk supplied to the different London unions in 1873, Professor Wanklyn reports that he found only fifteen unwatered, or nearly unwatered. Of these fifteen samples nine had been skimmed, leaving only six that were at once unwatered and unskimmed. These figures, therefore, show that only about 10 per cent. of the milk supplied in the above year to the Metropolitan unions was genuine. He adds——“It is curious to compare the language of the contract under which (as it appears from Mr Rowsell’s report) the dealer supplied the various unions with milk, with the quality of the article as exhibited by the analysis. ‘New unskimmed milk unadulterated,’ ‘genuine as from the cow,’ ‘best new unskimmed milk, to produce 10 per cent. of cream,’ occur in these contracts.”

_Prop._ These are well known. Perfectly fresh milk is slightly alkaline, but soon becomes acid on exposure to the air, and after a time white coagula of casein (CURDS) separate from it. This change is immediately effected by the addition of rennet or an acid. That from the first, when dried and pressed, constitutes cheese.

_Pur., Tests, &c._ The common frauds practised by the milk-dealers are the addition of water and the subtraction of part of the cream. Sometimes potato starch is added to the milk, to give it a creamy or rich appearance, and this addition is still more frequently made to cream, to increase its consistence and quality.

The presence of potato starch may be determined by boiling some of the milk with a little vinegar, and after separating the coagulum by a strainer, and allowing the liquid to become cold, testing it with solution or tincture of iodine. If it turns blue, starch, flour, or some other amylaceous substance, has been used to adulterate it. In most cases it will be sufficient to apply the test to the unprepared suspected milk.

It has frequently been stated that chalk, plaster of Paris, gum, gelatin, sugar, flour, mucilage of hemp-seed, the brains of animals, and other similar substances, are often added to London milk, but there is no reason to suppose there is any truth in these assertions, as some of these articles are too costly to be used, and the presence of others would so alter the flavour or appearance of the milk, or would so soon exhibit themselves by subsidence, as to lead to their detection.

_Pres._ Milk may be preserved in stout bottles, well corked, and wired down, by heating them, in this state, to the boiling-point, in a water bath, by which means the oxygen of the small quantity of enclosed air becomes absorbed. It must be afterwards stored in a cool situation. By this method, which is also extensively adopted for the preservation of green gooseberries, green peas, &c., milk will retain its properties unaltered for years. A few grains of carbonate of magnesia, or, still better, of bicarbonate of potassa or soda, may be advantageously dissolved in each bottle before corking it.

Under Bethel’s patent the milk or cream is scalded, and, when cold, strongly charged with carbonic-acid gas, by means of a soda-water machine, and the corks are wired down in the usual manner. The bottles should be kept inverted, in a cool place.

An excellent method of preventing milk from turning sour, or coagulating, is to add to every pint of it about 10 or 12 gr. of carbonate or bicarbonate of soda. Milk thus prepared may be kept for eight or ten days in temperate weather. This addition is harmless, and, indeed, is advantageous to dyspeptic patients. According to D’Arcot, 1/2000th part of the bicarbonate is sufficient for the purpose. An excess of alkali used in this manner may be detected by the milk turning turmeric paper brown, even after it has been kept some hours, and by the ash obtained by evaporating a little to dryness, and then heating it to dull redness, effervescing with an acid. (See _below_.)

⁂ Milk should not be kept in lead or zinc vessels, as it speedily dissolves a portion of these metals, and becomes poisonous.

_Concluding Remarks._ The principal difference between cows’ milk and human milk consists in the former containing more casein and less sugar of milk than the latter. The remarkable indisposition to coagulate is another character which distinguishes human milk from cows’ milk. Prof. Falkland, who has practically investigated the subject has prepared a nutritive fluid for infants from cows’ milk, closely resembling that of the healthy adult woman. His process is, however, unnecessarily complicated, and, therefore, unsuited to those who would have to employ it in the nursery. To remove this objection we have adopted the following formula:——Sugar of milk, 2 oz.; hot water, 1/4 pint; dissolve, and, when the liquor has become quite cold, add it to fresh cows’ milk, 3/4 pint, and stir them together. This quantity, prepared morning and evening, will constitute the proper food for an infant of from 5 to 8 months old. More may be allowed it if it ‘craves’ it; but there must be no ‘cramming.’ At first it will be advisable to remove a little of the cream from the milk before adding to it the saccharine solution; but after a few days this will be found to be unnecessary, and, indeed, injurious. One very important particular to be attended to is, the employment of pure cows’ milk, obtained from a healthy grass-fed animal only. With this precaution, and the use of a good FEEDING-BOTTLE, the infant will thrive nearly as well as on the breast of any human female, excepting its mother’s. (See _below_.)

ASSES’ MILK closely resembles human milk in colour, smell, and consistence, but it contains rather less cream. (See _below_.)

EWES’ MILK closely resembles cows’ milk, than which, however, it is slightly richer in cream.

GOATS’ MILK, for the most part, resembles cows’ milk, but its consistence is much greater, and it contains much more solid matter. (See _below_.)

MARES’ MILK, in consistence; is between that of cows’ and human milk. Its cream is not converted into butter by agitation. See BUTTER, CHEESE, LACTIC ACID, &c.

_Milk as a cause or carrier of disease._——Milk of a mother labouring under strong mental emotion is, as is well known, capable of seriously endangering the health of the suckling babe. Payne narrates the case of a woman suffering under a nervous affection whose milk, two hours after an attack of the disease, became viscid, like the white of an egg. Similarly, a deterioration and consequent alteration in properties is induced in the milk of the cow if she be over driven, exhausted, or harassed. The food of the animal likewise exercises an influence on the quality of its milk; thus when cows are fed on turnips, wormwood, decayed leaves, and plants of the cabbage or onion families, the flavour of these substances is imparted to their milk. The milk of animals that have fed on poisonous or deleterious plants is capable of setting up toxic symptoms in human beings partaking of it. In June, 1875, the inhabitants of a certain quarter of Rome were attacked with an epidemic, distinguished by great gastro-intestinal irritation. The cause of the outbreak was traced to the use of goats’ milk, yielded by goats that had eaten of the meadow saffron, the _Colchicum autumnale_. It also appears that in the Western States of America the milk of cows that have fed on the poison-oak, the _Rhus toxicodendron_, has on several occasions given rise to attacks of illness in children, marked by extreme weakness, vomiting, fall in bodily temperature, swollen and dry tongue, and constipation. Boiling seems to remove the dangerous properties of the milk.

Milk, as has been shown by Fuchs, is sometimes infested by a fungus, the _Oidium lactis_ or _Penicillium_, which is capable of giving rise to gastric irritation, and sometimes to severe febrile gastritis.[39]

[Footnote 39: Parkes.]

Although the evidence as to the power of the milk of animals affected with epizootic diseases to convey the particular affection to human beings is contradictory, there is little reason to doubt that soured milk may become a carrier of infection from the ailing or convalescent subject to the healthy one.

Typhoid and scarlet fever have been known to have originated in this manner.

The outbreak of the former malady in Marylebone in 1874 was traced to the contamination of milk by the remains of the water which had been used in rinsing the milk pans. This water had been obtained from a well into which the excrete from a typhus patient had percolated from a privy.

At Leeds a similar outbreak was caused by the absorption by the milk of the typhoid effluvium. In the case of scarlet fever the malady has been conveyed by means of the throat-discharges and cuticle falling into the milk from the persons of servants and others employed in dairies.

Milk, Al′mond.= See EMULSION and MIXTURE.

Milk, Arrowroot.= _Prep._ From arrowroot, 1 table-spoonful, first wetted and stirred with a little cold water, afterwards adding, gradually, of boiling water, 1/4 pint; and, lastly, of boiling milk, 1/2 pint; with sugar, spice, wine, &c., to palate. Very nutritious, and excellent in chronic diarrhœa. Some persons employ all milk.

Milk, Choc′olate.= _Prep._ Dissolve chocolate (scraped), 1 oz., in boiling new milk, 1 pint. Nutritious; but apt to offend delicate stomachs.

Milk, Cof′fee.= _Prep._ 1. Coffee, 1 oz.; boiling water, 1/4 pint; infuse for 10 or 15 minutes in a warm situation, and add the strained liquid to boiling milk, 3/4 pint.

2. Coffee, 1 oz.; tie it loosely in a piece of muslin, and simmer it for 15 minutes in milk, 1 pint. Both the above have been recommended for persons of spare habits, and for those disposed to affections of the lungs, more especially for the asthmatic.

Milk, Facti′′tious.= _Syn._ ARTIFICIAL MILK. Of the numerous compounds which have been proposed as substitutes for natural milks, the following are examples:——

1. (FACTITIOUS ASSES’ MILK; LAC ASININUM FACTITIUM, LAC A. ARTIFICIALE, L.)——_a._ Cows’ milk, 1 quart; ground rice, 1 oz.; oringo root (bruised), 1 dr,; boil, strain, and add sugar candy (or white sugar), 1 oz.

_b._ Whites of 2 eggs; lump sugar, 1 oz.; cows’ milk (new), 3/4 pint; mix, then add syrup of tolu, 3/4 oz.

_c._ Water, 1 pint; hartshorn shavings, 1 oz.; boil to a jelly; then add lump sugar, 2 oz.; cool, add new milk, 1 pint; syrup of tolu, 1/2 oz. Used as substitutes for asses’ milk, taken freely as a beverage. A cupful, with or without a spoonful of rum, 3 or 4 times daily, is a popular remedy in consumption and debility.

2. (F. GOATS’ MILK——A. T. Thomson.) Fresh mutton suet (minced), 1 oz.; tie it in a muslin bag, and boil it in cows’ milk, 1 quart; lastly, add of sugar candy, 2 gr. In scrofulous emaciation, and in the latter stages of phthisis. The proportion of suet in the above may be advantageously increased a little. The LAC CUM SERO of Guy’s Hospital is a similar preparation.

3. (F. HUMAN MILK; LAC HUMANUM FACTITIUM, L.)——_a._ See _above_.

_b._ (Rosenstein.) Almonds (blanched), 2 in number; white sugar, 1 dr.; water, 4 fl. oz.; make an emulsion, strain, and add of fresh cows’ milk, 6 fl. oz. As a substitute for the breast in nursing.

Milk, Preserved′.= _Syn._ MILK POWDER; LACTIS PULVIS, LAC PULVERATUM, L. _Prep._ 1. Fresh skimmed milk, 1 gall.; carbonate of soda (in very fine powder), 1-1/2 dr.; mix, evaporate to 1/3rd by the heat of steam or a water bath, with constant agitation, then add of powdered white sugar, 3-1/2 lbs., and complete the evaporation at a reduced temperature; reduce the dry mass to powder, add the cream (well drained) which was taken from the milk, and after thorough admixture put the whole into well-stoppered bottles or tins, which must be at once hermetically sealed.

2. (Legrip.) Carbonate of soda, 1/2 dr.; water, 1 fl. oz.; dissolve, add of fresh milk, 1 quart; sugar, 1 lb.; reduce it by heat to the consistence of a syrup, and finish the evaporation on plates by exposure in an oven.

_Obs._ About an ounce of the powder agitated with a pint of water, forms an agreeable and nutritious drink, and a good substitute for milk at sea. It may also be used for tea or coffee in a solid form. This process, which is very old, has been recently patented. See MILK (_above_).

The condensed or preserved milk, now in such general use, and which is met with in tins as milk which has been more or less deprived of water by evaporation in _vacuo_. It occurs in the market in two forms——in one simply as condensed milk, and in the other as condensed milk mixed with a large quantity of sugar. Milk preserved as above without sugar will keep only for two or three days; whereas with sugar it may be preserved for an almost indefinite time. Either variety mixed with the proper quantity of water becomes normal milk again, the sweetened kind being, of course, milk with the addition of a considerable amount of cane sugar. Professor Wanklyn says he has examined the principal brands of preserved and condensed milk sent to the London market, and finds they contain their due proportion of fat. He gives the following analyses of the produce of the English Condensed Milk Company: