

490 REPORT OF THE CHEMIST OF THE 
Statement of results —The data presented in the preceding 
table indicate : 
First, that in one sample 0.5 cc. of acid gave a maximum 
amount of nitrogen in the precipitate, while in two other samples, 
the amount of nitrogen obtained in the precipitate was very low. 
In each instance where the lowest results were given, the filtrate 
was milky in appearance. 
Second, that in three samples out of four, the use of 1.0 cc. of 
acid gave highest results, the filtrate being clear or only faintly 
cloudy. 
Third, that, in most instances, the use of 1.5 cc. of acid gave 
the highest results, with a clear filtrate in every case. 
Fourth, that the use of two cc. of acid gave very nearly the 
same results as the use of 1.5 cc. of acid in most cases, the filtrate 
being clear. 
Fifth. That the use of 2.5 cc. or more of acid gave lower results, 
the decrease becoming greater with increase of acid and the char- 
acter of the filtrate becoming more turbid in appearance. 
Siath. That, with fresh milk, the best results can be secured in 
determining casein by using from one to two ce. or in general, 
1.5 cc. of a ten per cent. solution of acetic acid. 
Seventh. That the completeness of precipitation is quite fairly 
indicated by the character of the filtrate. When the precipita- 
tion is incomplete as a result of using too little acid, the filtrate 
will be more or less turbid, varying from opaque milkiness to 
barely preceptible cloudiness. If, on the other hand, an excess 
of acid is used, thereby causing more or less casein to remain in 
solution, the filtrate will be more or less turbil according to the 
amount of casein in solution. In some cases, a filter paper may 
allow some precipitated casein to pass through and render the 
filtrate turbid. In such cases, two or three repeated filterations 
generally serve to remove the casein and to give a clear 
filtrate. 7 
(3.) The use of different acids in precipitating casein.—In - 
order to ascertain whether some other acid could be used to pre- 
cipitate casein more effectively than acetic acid, comparative 
trials were made with solutions containing ten per cent. of the 

