204 Report oO THE CHEMIST OF THE 
the cold aS a means of separating peptones from amido-acid com- 
pounds. Babcock, Russell and Vivian in this country have used 
it, as well as tannin, designating the different precipitates as 
“peptones by phosphotungstic acid ” and “ peptones by tannin.” 
In the introductory portion of this paper, when mentioning 
different cleavage products of casein, we included among them 
the hexon bases, viz: arginine, histidine, and lysine, and, in addi- 
tion, certain compounds resulting from their cleavage, such as 
putrescine and cadaverine, and also pyrrolidine-a- carbonic acid, 
all of which are precipitated by phosphotungstic acid. While all 
these products have not been separated from ripening cheese, it 
is probable that they will be sooner or later. “We shall soon 
publish results of work done in this laboratory showing in 
normal ripening cheese the presence of histidine, lysine, putre- 
scine (derived from arginine) and Siegfried’s lysatine, which 
is also precipitable by phosphotungstic acid. The quantities of 
these bases that can be derived from casein are not to be 
neglected, since, for example, in the hydrochloric-acid cleavage 
15.4 per ct. of the nitrogen of the products splits off into the 
hexon bases. Bondzynski has used phosphotungstic acid in hot 
solution with arginine and finds the precipitate soluble when hot, 
separating out on cooling, and this statement we can confirm, the 
solution, however, being complete only on boiling. In the case 
of lysine, histidine, and putrescine, the phosphotungstic acid 
precipitate fails to redissolve completely at the temperature of 
the water-bath or on boiling. This behavior renders worthless 
the use of phosphotungstic acid as a reagent for the separation 
of peptones from those amido-acid compounds that are precipi- 
tated by it. | 
We have seen that tannin-salt solution fails to precipitate pep- 
tones completely and that phosphotungstic acid precipitates, 
in addition to peptones, some amido-acid compounds. When, 
therefore, we use these two reagents in precipitating solutions 
that contain both peptones and amido-acid compounds, as in thé 
case of normal ripening cheese, we should expect to find the 
amount of nitrogen compounds left in the filtrate less with phos- 
138A. Ellinger. Ber. deut. chem. Ges., 31: III: 383 (1898). 

