312 Report of the Department of Chemistry of the 



4.6 X 10 •* gram equivalents. Their properties resemble those of the 

 corresponding caseinates. 



(11) Valency of paracasein molecule and molecular weight of 

 paracasein. — The valency and molecular weight are shown to be 

 one-half those of casein. 



(12) Action of rennet-enzym on casein in forming paracasein. — 

 When casein is treated with rennet-enzym, the casein molecule 

 appears to be split into two molecules of paracasein. 



(13) Composition of brine-soluble compound in cheese. — During 

 the manufacture and ripening of cheddar and many other kinds of 

 cheese, a protein is always formed which is insoluble in v/ater but 

 soluble in a 5 per ct. solution of NaCl. Former studies led to erro- 

 neous conclusions regarding its identity. Extended study shows 

 that this substance is identical with mono-calcium paracaseinate. 



INTRODUCTION. 



The uncombined protein, casein, shows the characteristic property 

 of an acid in combining with bases of the alkalis and alkaline earths 

 to form salts and in decomposing their carbonates. The compomids 

 thus formed, especially those with calcium, have been studied by 

 numerous investigators, the more important contributions have been 

 made by the following: 



Hammarsten (Zur Kenntniss des Kaseins etc., Upsala, 1877); 

 Soldner {Landw. Versuchs.-Siat., 35: .351, 1888); 

 Courant {Pfluger's Arch. Physiol, 50: 109, 1891); 

 Timpe {Arch. Hijq., 18: 1, 1893); 

 B6champ {Bull. Soc. Chim. (3) 11:, 152, 1894); 

 de Jager {Maly Jahresber. Thierchem., 27: 276, 1897); 

 Salkowski {Zeitschr. Biol., 37: 415, 1899); 

 Kobrak {Pfluger's Arch. Physiol, 80: 69, 1900); 

 Osborne {Jour. Physiol, 27: 398, 1901); 



Laqueur and Sackur {Beitr. Chem. Physiol u. Pathol, 3: 193, 1902); 

 Van Slyke and Hart (Bull. No. 261, N. Y. Agr. Exp. Sta., and Am. Chem. Jour., 

 33:472, 1905); 



Long {Jour. Am. Chem. Soc, 28: 72, 1908); 

 Robertson {Jour. Biol Chem., 2: 317, 1906); 

 Robertson {Jour. Physic. Chem., 13: 469, 1909). 



Without going into details, it is sufficient for our purpose at this 

 point to state that results have been reported in which compounds, 

 formed by treating casein with calcium hydroxide, contain an equiva- 

 lent of calcium oxide varying all the way from . 8 to 3 per ct. (equal 

 to 0.57 to 2.14 per ct. of calcium). 



In the chemical laboratory of this Station, the relation of casein 

 and paracasein to bases has been a subject of continued study for 

 several years, especially in connection with changes taking place in 

 the operation of cheese-making. The results here presented include 



