46 THE SECRETIONS.: 



tated by rennet from non-acidulated milk does in reality exist 

 in this condition. 



If we precipitate the casein of cow's milk by sulphuric acid, 

 and decompose the sulphate by carbonate of lime or baryta, we 

 shall obtain soluble compounds of casein with lime or baryta. 

 The casein of woman's milk is very imperfectly precipitated by 

 sulphuric acid. 



If albumen is present in milk, which is sometimes the case, 

 it must be determined by a separate experiment. The milk 

 must be boiled, and the coagulum must be collected and ex- 

 tracted with boiling spirit, in order to remove the sugar and 

 fat ; it must then be dried, and its weight estimated. The 

 amount of albumen obtained in this manner is deducted from 

 the amount of casein obtained by the method which has been 

 described, and which must clearly include both the casein and 

 albumen. 



[Haidlen 1 has recently proposed a new method for analysing 

 milk. It consists in coagulating the milk by gypsum, by which 

 means the error in the determination of the casein that resulted 

 from all former methods, is avoided. 



When milk is stirred with about one fourth of its weight of 

 finely-pulverized gypsum, and heated to 212, it is entirely 

 coagulated ; and if the whole is then evaporated to dryness, 

 a brittle mass is obtained, which is easily reducible to powder. 

 From this powder the butter may be extracted by ether ; the 

 sugar of milk and soluble salts may be removed by hot alcohol 

 of 0*85 ; while the caseate and sulphate of lime, and insoluble 

 salts, remain undissolved. The alcoholic solution scarcely ex- 

 hibits any perceptible opacity on the addition of chloride of 

 barium, showing that no error in the result is occasioned by 

 any of the gypsum being taken up by the alcohol. 



About 100 grains of gypsum and four times its weight of 

 milk answer very well. The soluble salts extracted from the 

 milk by the alcohol may easily be determined by incineration ; 

 and since their amount is to that of the insoluble salts in the 

 average proportion of 5 to 7, the amount of the latter may at 

 least be found approximately, and the ascertained weight of 



1 Simon's Beitrage, p. 358. 



