CHEMISTEY. 19 



that of normal 'huttor. These tests of the curd consist of the appear- 

 ance of th(> batter on heating, the comparison of the separated curd 

 freed from fat with the curd from normal l)utter, and tests for albu- 

 min in the filtered butter. The ratio of casein to albumins may also 

 be determined. In the process butter this has been found to be about 

 8.6 pai'ts of casein to 1 of albumins. This ratio is determined in the 

 curd which has been thoroughly freed from fat. For determining 

 this ratio 50 giu. of butter is dissolved in ether to a clear solution, the 

 ether solution of fat decanted as far as possible, and the remainder 

 filtered tlirough a separatory funnel. The casein remaining on the 

 filter is washed with water and (\stimated by the Kjeldahl method. 

 The filtrate is macU' slightly acid with acetic acid, brought to a lK)il, 

 and the albumins filtered out and estimated by the same method. 



"These tests serve to diflerentiate between genuine butter and proc- 

 ess butter as it is now found on the market," 



A comparison of reagents for milk proteids ^vith some notes 

 on the Kjeldahl method for nitrogen determination, A. \ ivian 

 (Wisco/isin iSttf. Bpf. 1S99, j>p. 170-lSG). — A comparative study was 

 made of a long list of reagents for separating the nitrogenous com- 

 pounds of milk and their decomposition products into distinct groups. 

 The following method of analysis was adopted and used in investiga- 

 tions on the action of ferments on the proteids of milk: 



In preparing the extracts for analysis cheese was emulsified l)y rub- 

 bing with warm water, acidified with acetic acid, and boiled. Milk 

 was also acidified with acetic acid and boiled. The same quantities of 

 the filtrates in each case were taken for the different reagents. Deter- 

 minations were made of the total nitrogen and of the total soluble 

 nitrogen (nitrogen not precipitated by acetic acid and heat). Por- 

 tions of the extracts were treated with zinc sulphate, tannic acid and 

 sodium chlorid, and phosphotungstic acid, and determinations were 

 made of the nitrogen in the filtrates, the nitrogen in the precipitates 

 l)eing calculated by difference. The nitrogen as ammonia was deter- 

 mined by distilling with magnesium oxid. 



In designating the groups of proteids obtained by this method of 

 analysis the following nomenclature was adopted: Nitrogen in insolu- 

 ble portion (casein, globulin, and albumin — difference between total 

 nitrogen and soluble nitrogen), nitrogen in albumoses (difference 

 between nitrogen in filtrate from zinc sulphate and total soluble nitro- 

 gen), nitrogen in peptones by tannin (difference between nitrogen in 

 filtrates from tannic acid and sodium chlorid and from phosphotungstic 

 acid), nitrogen in peptones by phosphotungstic acid (difference between 

 nitrogen in filtrates from phosphotungstic acid and from tannic acid 

 and sodium chlorid), nitrogen in amids (difference between nitrogen in 

 filtrate from phosphotungstic acid and in ammonia), and nitrogen in 

 ammonia. 



