THE ANALYSIS OF MILK. 85 



If it be desired to estimate the casein by itself, 25 grams of milk are 

 diluted with eleven times their volume of water, carefully precipitated 

 with acetic acid, and the precipitate collected on a dried and weighed filter. 

 The precipitate is washed, extracted from fat, and dried at 110 C., till the 

 weight is constant. It is then burned, and the weight of the ash deducted 

 from the first obtained weight. According to the method of J. Lehmann, 

 the casein may be determined by the application of porous clay plates. 

 The albumin is estimated by heating filtrate and wash-water got in the 

 determination of the casein to boiling temperature. The clot thus obtained 

 is collected on a dried and weighed filter, washed, extracted from fat, and 

 dried to a constant weight at 110 C., and the weight of the ash obtained 

 after burning is deducted from the weight thus obtained. The percentage 

 of so-called lacto-protein may be estimated in the filtrate and wash-water 

 from the determination of the albumin by means of the method of 

 Ritthausen, by using copper sulphate and potassium hydrate. 



Determination of Milk-sugar. The determination of the milk-sugar, if 

 not effected by means of the polariscope, is best carried out according to 

 Soxhlet's method. 25 c.c. of milk are weighed out, and diluted with 

 400 c.c. of water, then first treated with 10 c.c. of sulphate of copper solu- 

 tion (69*28 grams of copper sulphate per litre of water), then with 6'5 to 

 7 - 5 c.c. of potash solution of such a strength that one volume of copper is 

 precipitated for every volume of the copper solution. After the addition of 

 the alkali, the solution must be neutralized and rendered slightly acid, and 

 may contain a little copper in solution. It is then made up to 500 c.c. and 

 filtered through a dry folded filter. 100 c.c. of the filtrate is treated with 

 50 c.c. of Fehling solution in a beaker, which is then covered and brought to 

 the boil over a double wire gauze. After it has been boiled for six minutes 

 it is filtered through asbestos, and the reduction of the copper takes place 

 spontaneously in the asbestos tube. A small straight calcium chloride tube 

 (about 12 centim. long and 1*3 centim. wide), whose bulb is half protected 

 by oblique and not too soft asbestos filaments, is washed, then dried over 

 the naked flame while air is drawn through, weighed, and attached to 

 a filter pump. Filtration is then carried on by pouring through an 

 attached glass funnel in the presence of a weak diluted atmosphere, then 

 washing with water, and, after the filter pump has been detached, twice 

 with absolute alcohol and twice with ether. Thereafter the filter tube is 

 removed, stretched, and, after the ether has been for the most part 

 expelled by air, bent on a holder downwards, its upper wide opening 

 connected with a Kipp hydrogen apparatus, then the copper suboxide 

 very carefully heated over a small flame, the top of which is about 5 

 centimetres under the bulb. The reduction is complete in about two or 

 three minutes. After the asbestos tube has been cooled in a stream of 



