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A D U L T E RATION

are closely akin to adulteration, if not actually such, have much engaged the attention of analysts during the last few years—namely, the addition of chemical preservatives and of colouring matters to articles of food. Chemical preservatives are contained in many perishable articles—namely, sulphite of lime in beer, syrups, meat, lime-juice, &c. j salicylic acid sometimes in wines and often in jams; formaldehyde (formaline) in milk. But by far the most frequently used materials are borax and boracic acid, almost universally present in imported butter (with the exception of Danish butter), and in much that is made in Great Britain, in cured ham, in fish, cream, and milk. A preservative acts as a bactericide, and in no case is physiologically inert, although the dose taken at a meal may not be sufficient to produce obvious effects. Medical opinion is, however, at present almost unanimous that the continual use of preservatives cannot fail to be injurious to the human system, and the increasing infant mortality in some towns is attributed to the fact that the milk used by the infants is now so frequently borated. A Committee appointed by the Board of Agriculture has been engaged on this subject, but at the time of writing no report has yet been made public. The employment of preservatives is justified by dealers in perishable articles by pointing to the difficulty which would otherwise be experienced in collecting in distant countries food-materials like butter, shipping them to England, and distributing them to the public without loss of quality; on the other hand, modern means of preserving food, in cold-store, &c., are being pointed to as fully sufficient to meet all wants without the introduction of foreign matters. Colouring matters, quite harmless in themselves, are largely used at the present time in many articles of food and drink. Originally the use of a yellow dye in milk was due to a fraudulent motive, namely, to hide the blueness produced by watering. Gradually the public, especially in London, became accustomed to see their milk of a distinct yellow tint, and all milk, even genuine milk free from added water, sold in London, is now coloured, generally with anatto, often with aniline dye; and it would be almost impossible for a vendor to sell milk of its natural colour. Again, all butter sold in London and the South of England is coloured yellow. Natural butter has often a very faint fawn tint, and the public, educated to see butter yellow, would not purchase such butter; hence the now universal colouring adopted. The Food Act cannot cope with this practice, as long as the object of colouring is not a fraudulent one and the colour itself is harmless. The colouring of preserved peas by the use of a little copper sulphate is on a different basis, as the copper is considered liable to produce injury to health, and many vendors of coppered peas have been fined during recent years; yet the public object to purchase preserved peas of the natural brown colour. Jams are very frequently dyed, and the brilliantly coloured jams now sold owe most of their colour to coal-tar dyes, which are often employed to hide the fact that unripe or inferior fruit has been used by the manufacturer. We will now consider recent forms of adulteration in specific articles, and the means adopted for their detection. Milk.—Although the general qualitative composition of milk has been known for very many years, all quantitative statements concerning the proportion of the several constituents published before 1884 are affected with considerable errors. About 1872 Wanklyn showed that, although, as was well known, the percentage of the fat of milk was subject to very considerable fluctuation, when the percentage of milk-sugar, caseine, and other albuminoids and mineral water was added together, the “solids-not-fat” varied but little, and he proposed to utilize that fact to

determine whether milk was genuine or had been impoverished by the addition of water,—it being evident that water would diminish the percentage of solids-not-fat, the percentage of addition being readily calculated from the amount of the latter. Although the method of ascertaining the proportion of “ solids-not-fat ” adopted by Wanklyn has been shown to be somewhat erroneous, the principle of analysis established by him has remained the basis upon which milk-analysis rests, and public analysts virtually adopted the limits proposed by him—viz., 2-5 per cent, of fat and 9 per cent, of solids-not-fat. In 1884 M. A. Adams showed, however, that the then usual method of analysis did not allow of the complete removal of the fat from the other milk-constituents, that therefore the proportion of fat had been underestimated, the amount of the solids-not-fat being correspondingly too high. By the simple and ingenious expedient of spreading a known volume of the milk to be analysed upon a long strip of blotting-paper and extracting the paper together with the dried milk by a solvent, such as ether or benzene, the fat could be completely removed from all other constituents. After full investigation the Society of Public Analysts altered the limits, in accordance with the new discovery, to 3 per cent, as a minimum for the fat and 8‘5 per cent, for the solids-not-fat. As the average composition of genuine milk, according to Yieth, is 4T per cent, of fat, 8'8 of solids-not-fat, and 12-9 per cent, of total matter other than water, it is obvious that the limits allow for a reasonable departure from the average. The Board of Agriculture’s Departmental Committee has quite recently issued a report, in which the following recommendations are made as to proportions of food constituents which should be present in milk. The percentage of total solids must not be less than 12, the proportion of solids-not-fat not less than 8'5 per cent., and that of fat at least 3-25. If the amounts are smaller, a presumption is raised, unless the contrary is proved, that the milk is adulterated by skimming or watering. The recommendations of the Committee are most valuable, as tending to the improvement in the breed of dairy cattle, and cows yielding milk poorer than the above will probably be weeded out and replaced by superior breeds. A number of means are now known allowing of the complete analytical separation of the fat other than the “Adams” method. The “galactometer”and “lactometer” instruments, referred to in the article in the ninth edition of this work, have long been abandoned. Other far more exact and more rapid means have been found to determine the composition of milk with a degree of accuracy sufficient for practical, especially dairying, purposes. As the fat of milk is its most valuable and most important constituent, it is of high importance to the butter-producer in particular to know the exact proportion of the fat, partly in order to know that he obtains value for his money, and also to check the efficiency of the working of his appliances for separating the cream—centrifugals being now universally employed for that purpose. By centrifugal force alone the fat globules of milk do not coalesce into a layer of pure fat; if, however, an acid, like hydrochloric or sulphuric acid, be added to the milk in sufficient quantity prior to subjecting it to centrifugal force a clear layer of pure butter-fat separates, and if a measured quantity of milk be taken and the volume of the separated fat be determined, generally in a graduated glass-tube, the amount of fat in any sample of milk can be arrived at in a few minutes. Upon this principle a number of instruments have been designed and render excellent service in the creamery and laboratory. As, moreover, a definite relation exists between the specific gravity of a milk and its contents in fat and solids-not-fat, it follows that the