considerable subsidence of the heavier fats. Thus, a kilogram. of pure butter was allowed to cool slowly after melting in a capacious vessel, with constant stirring; when a sample was taken, and the distillate obtained after Reichert's method used, 14 cc. of d. n. soda. The same butter was then remelted, and allowed to cool slowly without stirring, and samples taken from various portions with the following results : The same chemists, applying Reichert's method to various fats, A distillation process was proposed in England before the publication of Reichert's paper by Mr. Perkins:* a solution of oxalic acid was used to decompose the soap, and all the volatile acids were supposed to distil over; but the test experiments given are rather below the total amount which were probably present. There is one advantage of a distillation process which must not be lost sight of-viz., the acids may be identified by fractional titration when treated after Duclaux's process, described in the article on "Wine." A process of saponification has been proposed and practised by Mr. West Knight,t which is based on the insolubility of the oleate, stearate, and palmitate of barium, and the ready solubility of the volatile fatty acid combinations with barium. The butterfat is saponified with alcoholic potash in the ordinary way. The soap solution is diluted to 300 cc., and a solution of chloride of barium added until a curdy precipitate separates, and the liquid is no longer rendered milky by a fresh addition-the insoluble barium fatty acids are collected on a filter, and ultimately transferred to a tube such as is used by Muter (p. 302), and the fatty acids liberated by sulphuric acid and shaken up with ether; Analyst, 1879, 142. + Analyst, 1880. when separation has been effected, a fractional part of the ether is taken, and evaporated in a tared flask. Further Analyses of the Insoluble Fatty Acids.-The insoluble fatty acids are, as already stated, oleic, palmitic, and stearic; it is their total weight which is alone valuable, and to separate the three with accuracy is not easily effected. The first can, however, be very readily isolated by the following process, the details of which have been worked out by Dr. Muter. The process depends upon the well-known fact that the oleate of lead, Pb2C18H3302, can be separated from plumbic palmitate, Pb2C6H3102, and plumbic stearate, Pb2C HO2, by taking advantage of the solubility of the former in ether. 18 35 About 1 grm. of the fatty acids is combined with potash, and the solution well diluted with boiling water, and carefully treated with acetic acid added to the boiling solution until a permanent turbidity is produced; solution of potash is now dropped in with constant stirring, until the liquid just clears again. The solution. is now precipitated by plumbic acetate in slight excess, and is stirred until the precipitated soap settles thoroughly. The supernatant liquid is poured off, and the soap once washed by boiling with a large volume of water and decanting; plumbic oleate, palmitate, and stearate are thus obtained as perfectly neutral salts, the first being soluble in ether, the last two quite insoluble. The lead soap is now transferred to a flask of 100 cc. capacity, and the plumbic oleate dissolved out by ether, the ethereal solution being passed through a filter. The end of the process is known by the washings ceasing to blacken ammonium hydrosulphide. The filtrate and the washings should not exceed 200 cc., a fractional portion of which may be evaporated to dryness in a platinum dish, and weighed as plumbic oleate. To ensure perfect accuracy, the remainder should be ignited and weighed as Pb+ PbO; the residue treated with acetic acid to take up the PbO, and the residual Pb calculated to PbO. By deducting the weight of plumbic oxide thus obtained from the total plumbic oleate, and allowing for the hydrogen displaced, the oleic acid is obtained. Dr. Muter recommends, however, an easier method. This requires a long graduated tube of 250 cc., having a well-ground stopper and a stopcock, which is placed at 50 cc. from the bottom. The ethereal solution is placed in this, the soap decomposed by hydrochloric acid [1:2]; and (when the chloride of lead is fully settled) a known quantity of the supernatant ethereal solution drawn off, evaporated, and weighed as oleic acid. In the majority of adulterated butters, the specific gravity, the melting-point, and the fatty acids are all widely different from that of genuine butter, so that there is no room for doubt. Occasionally, however, a butter may be met with in which a small proportion only of foreign fat has been used, and in such a case the analysis must be repeated several times lest a mistake be made. Of all the above determinations, the percentage of insoluble and soluble fatty acids is of the greatest importance. A marked deficiency or complete absence of soluble, and an increase of insoluble, are the characteristic features of fats other than butter. The following are a few examples of percentages of fatty acids found in genuine butters : It is generally accepted that 88 per cent. of insoluble acids, if associated with 6.3 of soluble acids, is a fair standard of butter calculation, and that if a butter shows anything less than 89.5 insoluble, with 5 soluble, it may be passed as genuine.* A few examples of adulterated butter-fat are as follows: Somerset House standard for water in butter. At the Bath Police Court (January, 1879), a dairyman had been summoned for selling butter, the proximate analysis of which showed a considerable addition of water. An appeal to Somerset House elicited the following certificate:-‘ :-"We hereby certify that we have analysed the butter, and declare the results of our analysis to be as follows: "The results of our analyses of numerous samples of ordinary commercial butters obtained from different parts of the country, including the south of England, show that the proportion of water present is very variable, and that it occasionally amounts to as much as 19 per cent." BIBLIOGRAPHY. ANGELL, G., and HEHNER, O.-"Butter: its Analysis and Detection." 1st ed., Lond. 1874; 2nd ed., 1878. BLYTH, A. WYNTER.-Easy and Rapid Method of Manipulating the Fatty On the Figures or Patterns which Liquid Fats assume under certain CROOK, W. G.-A New Method of distinguishing Butter from some other DIETZEL, u. M. G. KRIESNER.-Zeitschrift f. An. Chem., 1879. DUPRE, A.-The Composition and Analysis of Butter-Fat. Analyst, 1, 87, 114. HAGER, H.-Pharm. Central. Halle, xviii., 413. JONES, E. W. T.-Butter-Fat: its Analysis and Composition. Analyst, ii. 1878, 19, 87; Influence from the Decomposition of Butters through Age on the Specific Gravity of the Fat, &c. Analyst, 1879. KOETTSTORFER, J.-Neue Methode zur Untersuchung der Butterfett auf fremde Fette. Zeilschrift f. Anal. Chem., 1879, 199, 431. Analyst, 1879, p. 106. KRETSCHMAR, M.-Deut. Chem. Ges. Ber., x. 2091-2095. MEDICUS, L., u. S. Scherer.-Zeitschrift f. Anal. Chem., 1880, 159. PERKINS, F. P.-Analyst, 1879, 142. REDWOOD.-On the Determination of the Melting-points of Butter and other Fats. Analyst, 1, 1877. REICHERT, E.—Butter-Prüfung nach Hehner's Princip. Zeitschrift f. An. Chem., 18, 64. WEST-KNIGHT, E.-On the Estimation of the Insoluble Fatty Acids in Butter-Fat. Analyst, 1880, 155. WIGNER, G. W.-On Estimation of the Gravities of Fats. 35. -On Butter Analysis by Koettstorfer's Process. Analyst, 1, 1877, Analyst, 1879, 132. BUTTERMILK, § 186. Buttermilk is the thin whey left behind when the fat has been extracted in the process of butter-making. It is never fat-free; it contains all the constituents of milk, but a great portion of the sugar has been changed into lactic acid. It is then essentially a dilute, poor acid milk. The average composition of fresh buttermilk is :— The lactic acid tends ever to increase, so that samples which have stood a little time will contain more lactic acid than the proportion above given. . CHEESE. § 187. Cheese consists essentially of the coagulated albuminous matters of milk, especially of caseine, with a variable quantity of fat, common salt, and alkaline and earthy phosphates. Cheese may be made from the milk of any animal, but the great majority of cheeses in commerce are made from that of the cow. The principle of the manufacture of cheese from fresh milk is very simple: the caseine is precipitated by rennet, and carries down with it most of the milk-fat, as well as some portion of the milk-sugar. The thin whey is allowed to run off, and the precipitated "curds "* submitted to pressure, which has the effect of not only getting rid of the whey, but also of giving to the mass shape and consistency. Cheese may be made from sour milk without the addition of rennet, the lactic acid precipitating the caseine; but most of the cheeses in commerce are made from fresh milk. Cheeses may be divided into two varieties-the soft and the hard; the former are manufactured by precipitating with rennet at a low temperature, and using but little pressure; they have mostly an alkaline reaction. The hard cheeses are subjected to a higher temperature and stronger pressure, and have, when first made, an acid reaction. I. SOFT CHEESES. § 188. Neufchatel Cheese.-This is a Swiss cream cheese; its average composition when fresh is as follows :— * An analysis of curds by M. Rubner is as follows: Per cent. 37.87 17:43 41.30 3:40 Per cent. |