New YorK AGRICULTURAL EXPERIMENT STATION. 239 
10. Comparison of Properties of Casein and Paracasein and 
their compounds. of Calcitwm.—Basic calcium casein and para- 
casein appear soluble in water forming slightly opalescent solu- 
tions. Neither is coagulated by rennet, but both are precipi- 
tated by soluble calcium salts on warming. Neutral calcium 
casein is coagulated by soluble calcium salts on warming to 35° 
to 10° ©, but not at ordinary room temperature, while neutral 
calcium paracasein is completely and quickly coagulated at room 
temperatures by soluble calcium salts. Free casein and free 
paracasein, freshly prepared, possess the same solubilities in 
warm 5 per ct. salt solution and in hot 50 per ct. alcohol; they 
also possess the same peculiar properties of plasticity and ductil- 
ity. The close resemblance of casein and its compounds respec- 
tively to paracasein and its compounds suggests that they are 
chemically alike, paracasein being different only by consisting 
of a larger molecular aggregation than casein. 
11. Relation of Paracasein to Salt-Soluble Substance and to 
Body formed by Treatment with Acid.—Free paracasein appears 
to be identical in characteristic properties with the compounds 
we formerly called paracasein mono-salts of acids used as precipi- 
tants. The compounds which we have heretofore called para- 
casein di-salts of acids appear to be combinations of free para- 
casein and acids used as precipitants, one gram of paracasein 
uniting, for example, with about .5 cc. of decinormal hydrochloric 
acid. 
12. Relation of Salt-Soluble Product of Cheese to Para- 
casein.—F rom water-extracted fresh cheddar cheese we prepared 
one extract by warm 5 per ct. salt solution and another by hot 
50 per ct. alcohol. These preparations have in common with free 
paracasein the characteristic properties of plasticity, ductility, 
and the same combining power with bases and acids, and there- 
fore appear to be free paracasein instead of paracasein mono- 
lactate as we were formerly led to believe. , 
13. Chemical Changes in Calcium Casein resulting from Sour- 
ing of Milk or Addition of Acids——When an acid is formed in 
or added to cows’ milk, the acid first combines with the bases 
of some of the inorganic salts of the milk and then with the 
calcium that is combined with the casein, resulting in the forma- 
tion of a precipitate which is free casein. By further formation 
