New York AGRICULTURAL EXPERIMENT STATION. 253 
tar he was able to remove the acid completely from the proteid. 
We have abundantly confirmed his statement that the acid can 
be removed from the proteid by trituration, but in view of recent 
developments in chemistry, this argument has no weight, since 
we can do the same thing in the case of some well-known and 
well-established inorganic salts. For example, the sulphuric 
acid radical of mercuric sulphate can be completely removed by 
trituration with water. 
EXPERIMENTS SHOWING COMBINATION OF CASEIN AND ACIDS. 
In order to show that there is actual combination between base- 
free casein and acids, we used the following method: We sus- 
pended in 50 cubic centimeters of distilled water .5 gram of 
finely-ground base free casein and allowed the mixture to stand 
one hour, with occasional shaking. At the end of this time, we 
added hydrochloric aeid of known strength in definite quantities, 
after which the volume was made to 100 cubic centimeters by 
water and filtered. The residue was not washed. Aliquot parts 
of the filtrate were titrated with .", sodium hydroxide, using 
phenolphthalein as indicator. The difference between the amount 
of acid added and that found in the filtrate represents the 
amount of acid combining with the easein, plus the amount ad- 
hering mechanically to the casein. It was necessary to use dilute 
solutions of acid in order to avoid dissolving the proteid by an 
excess of acid. The materials used in this work were the four 
preparations of base-free casein which have been already de- 
scribed on pp. 247-49. 
Amount of acid used kept constant in relation to proteid.—In 
the experiments, the results of which are given in Table I, we 
used different solutions of hydrochloric acid of varying dilution, 
but varied the quantity of acid used so that the same absolute 
amount of acid was used in each case, which was equal to 20 
cubic centimeters of aa hydrochloric acid for one gram of base- 
free casein. The work was carried on at room temperature, 17° 
ts” O. 

