Primary Cleavage Products. 367 
Lehmann, Riihling, Volckel and others,* varies from 0°85 per cent. to 
1:10 per cent. Ritthausen,t from several analyses of the copper 
compound of casein, found a content of sulphur equivalent to 0°80— 
1:12 per cent. in the free casein. Schwarzenbach,f{ by a study of the 
platinum cyanide compound of casein, ascribed to casein itself a con- 
tent of 0°19-1°10 per cent. of sulphur. Hammarsten, however, found 
by analysis of eight distinct preparations of casein, some of which 
had been reprecipitated even ten times with acetic acid, a content 
of sulphur ranging from 0°619 per cent. to'0°775 per cent.§ Later, 
Hammarsten|| analyzed four other preparations of casein and each 
by six distinct methods. Omitting two or three results, which were 
altogether too low on account of inaccuracies in the method, Ham- 
marsten found in these different preparations of casein, as a result 
of twenty-nine distinct determinations by five different methods, 
0-798 per cent. as maximum, 0°726 per cent. as minimum, or 0°758 
per cent. as the average, content of sulphur. Taking, however, the 
results obtained by what Hammarsten considers as the more correct 
methods the average content of sulphur is raised to 0°77—0°78 per 
cent. Inno case did Hammarsten obtain results in any way con- 
firmatory of Danilewsky’s views. Hammarsten further made a large 
number of phosphorus determinations, and these as well as the results 
obtained for carbon and nitrogen showed too little variation to war- 
rant the idea of a mixture of two bodies of unlike composition. 
While therefore, Hammarsten’s results would seem to point conclu- 
sively to the unit-like nature of casein, we have, however, made quite 
a number of different preparations of the substance, both from fresh 
milk and from skimmed milk, with the idea of obtaining confirmatory 
data, with which to make direct comparisons between the composi- 
tion of,casein and its primary cleavage products. 
Preparation and composition of Casein. 
The casein was precipitated in some cases by acetic and in others 
} p 
by hydrochloric acid. In both cases the acid used was very dilute, 
* See Gmelin-Krauts’ Handbuch der Organische Chemie, Band iv, Abtheilung, iii, 
1870, p. 2254. 
+ H. Ritthausen und R. Pott, Untersuchungen tiber Verbindungen der Kiweisskorper 
mit Kupferoxyd. Journal fiir prakt. Chemie, 1873, Band vii, p. 361. 
t{ Annalen der Chem. u. Pharmacie, Band exxxiii, p. 185. 
§ Zeitschrift fir physiologische Chemie, Pand vii, p. 259. 
|| Ueber den Gehalt des caseins an Schwefel und iiber die Bestimmung des Schwefels 
in Proteinsubstanzen, Zeitschrift fiir physiologische chemie, Band ix, p. 273. 
