REPORT OF THE CHEMICAL DEPARTMENT. 
SOME OF THE RELATIONS OF CASEIN AND PARA- 
CASEIN TO BASES AND ACIDS, ANDsTHEIR 
APPLICATION TO CHEDDAR CHEESE.* 
L. L. VAN Stykpb AND E; B. Hart. 
SUMMARY. 
1. Object.—The primary object of the work presented is to 
make a further study of the compounds first discussed in Bulletin 
No. 214, casein and paracasein salts of acids, with an extension 
to the free proteids and some of their combinations with bases. 
2. Base-Free Casein.—Preparations of casein free from ash 
ov nearly so were made by precipitating dilute skim-milk with 
acids, removing the acid and inorganic matter by repeated filtra- 
tion and trituration with water in a mortar. The process re- 
quired several days. 
3. Basic Calcium Casein.—Preparations were made with base- 
frce casein in which the proteid combined with about 2.40 per ct. 
of calcium oxide. One such preparation was made by triturating 
together calcium carbonate and the base-free casein suspended 
in water, and another by dissolving base-free casein in lime- 
water and making this neutral to phenolphthalein by acid. 
4. Neutral Calcium Casein.—By treating base-free casein dis- 
solved in lime-water with acid until the reaction is almost neutral 
te litmus, there is formed a compound of casein and calcium 
oxide containing aout 1.50 per ct. of calcium oxide. 
5. Calcium Vasein Compounds in Relation to Rennet Enzym 
axd Soluble Calcium Salts.—Rennet enzym coagulates neither 
neutral nor basic calcium casein. Neutral calcium casein after 
— 
*A reprint of Bulletin No. 261. 

