Chemical and Molecular Behavior of Casein. 97 



in Table II. This shows that electrical conductivity, like freezing- 

 point lowering, and the ratio K/A is higher in parasite than in host. 



Thus it appears that there is some mechanism not as yet 

 determined by which the mistletoe accumulates and retains in 

 solution larger quantities of dissociated salts or organic acids 

 than does the host. 



It is possible that higher transpiration from the parasite 

 might result in the accumulation in a purely mechanical manner of 

 larger amounts of salts from the transpiration stream, but this is 

 merely a suggestion requiring further investigation. 



45 (1627) 



Chemical and molecular behavior of casein. 



By Jacques Loeb. 



[From the Laboratories of The Rockefeller Institute for Medical 

 Research, New York City.] 



Two kinds of casein were used, both prepared according to 

 Van Slyke and Baker, the one from skimmed milk, the other 

 from a solution of purchasable "pure casein." Since albumin is 

 soluble near a P H of 4.7 while casein is not, in both cases, casein 

 practically free from albumin was obtained. 



It was possible to show that when HC1 or H3PO4 are added to 

 isoelectric casein, three times as many c.c. of 0.1N H 3 P0 4 as of 

 0.1N HC1 are required to bring I gm. of isoelectric casein in a 

 1 per cent, solution to a given P H . On the other hand, it required 

 equal numbers of c.c. of 0.1N Ca(OH) 2 or Ba(OH) 2 as of 0.1N 

 KOH or NaOH to raise 1 gm. of isoelectric casein in 100 c.c. solution 

 to the same P H . Hence H 3 P0 4 combines with casein in molecular 

 proportion while Ca(OH) 2 and Ba(OH) 2 combine in equivalent 

 proportions with casein. In other words, acids and alkalies 

 combine with casein by the same purely chemical forces of primary 

 valency as they combine with crystalloids. The same fact had 

 been shown by the writer for the combination of these acids and 

 alkalies with gelatin and crystalline egg albumin. 1 



1 J. Loeb, Journ. Gen. Physiol, 1918-19, i, 483, 559; 1920-21, iii, 85; Science, 

 1920, lii, 449. 



