404 Chittenden and Painter— Casein and its 
the preparations. We have already commented on the difficulty, in 
fact, impossibility, of removing certain inorganic salts after they 
have once been brought in contact with a caseose body. Repeated 
precipitation appears to affect the percentage of ash but little. The 
reason for the large percentage of ash lies in the precipitation of the 
caseoses from such large volumes of fluid. We thought it unwise at 
first, to expose the bodies to the long continued evaporation neces- 
sary for precipitation with a small amount of salt. To avoid the 
possible danger of change, therefore, the large volumes of fluid 
resulting from the several digestions were saturated directly with 
salt, and as this involved the use of large quantities, calcium salts 
and some iron as impurities in the sodium chloride, were unavoid- 
ably introduced. These, the caseoses seemed at once to catch hold 
of and retain, in spite of oft-repeated purification. In the digestion 
D, in which the fluid was concentrated somewhat before precipita 
tion, the percentage of ash is seen to be somewhat smaller than in 
preparations from the other digestions. 
In comparing the composition of the individual protocaseoses (see 
the accompanying table) it. is seen that two of the bodies show a 
content of carbon somewhat higher than casein itself, while the 
average of all the others, with one exception, shows a content of 
carbon a little lower than casein. Leaving out the acetic acid pre- 
cipitate C 2, the average of the remaining ten preparations of proto- 
caseose shows the following composition for this substance: 
Cie: H N Ss 0 
erOLOCASGOSO a5. = 7- mae eee 52°89 4-10 15:94. 0°95 23°12 
Wasein= en. ee De a ee 53°30 7-07 15°91 0°82 22°03 
Plainly, the average of our results would indicate that protocaseose 
does not differ essentially in composition, from the casein from which 
it is formed. A slightly smaller content of carbon is the only notice- 
able difference. To be sure the individual results show noticeable 
variation in the percentage of carbon, but bearing in mind the large 
amount of ash present in the preparations, it is evident that the aver- 
age result is of more value than the results obtained in any one case. 
As to the lower content of carbon in so-called protocaseose C 2, it is 
probable that this body is composed mainly of deuterocaseose. The 
two caseoses being precipitated together in this digestion by ammo- 
nium sulphate and then separated afterwards from a fairly concen- 
trated solution by saturation with salt and addition of acetic acid, 
renders it probable that the protocaseose was more completely precip- 
