~ a 
bo 
iN) 
~T 
Kiihne and Chittenden— Peptones. 
trate with sulphuric acid. The peptone solution thus obtained had a 
distinctly acid reaction, and strange to say, contained hydrochloric 
acid, which was hardly to be expected after the very careful washing 
which the precipitate had received. The solution was neutralized 
with ammonia to render the acid harmless on concentration. Then 
we succeeded in obtaining the evaporated residue free from ammo- 
nium chloride by repeated precipitation and boiling with alcohol. 
As already mentioned, the method gives rise to much loss and the 
same holds true of the otherwise excellent precipitation of peptone 
by phosphotungstic acid according to the method of Hofmeister, for 
so far as our experience extends, peptones cannot be completely pre- 
cipitated in this manner. There arises in the filtrate, containing 
excess of phosphotungstic acid, not only additional turbidity and 
precipitation due to peptone, but considerable quantities of peptone 
are still found in the liquid, which has perhaps remained clear for 
months, if treated with barium hydroxide ;—a circumstance which 
we were not able to prevent even by strongly acidifying the solu- 
tion to be precipitated with phosphotungstic acid, with either sul- 
phuric or hydrochloric acid. = 
Behavior of the peptone.—This peptone was also difficult to con- 
vert into a dry state, although we did succeed ultimately in bringing 
it to a constant weight as a fine, exceedingly hygroscopic powder, 
by heating for some time at 105° C. im vacuo. The first difficulty 
was found in commencing the drying, for although we treated the 
glue-like mass repeatedly with absolute alcohol, then for a long time 
with ether and finally boiled it again with alcohol, thereby changing 
it into an almost dry, crumbling condition, we were compelled at last 
to stop its further direct drying, since at 100° C. the preparation 
took on the consistency of pitch and formed a bulky foam trom which 
alcohol vapor continually escaped. Therefore the alcohol was first 
driven out by thorough boiling with water and the latter removed as 
much as possible at 100°C. This was also a tedious performance for, 
although the substance no longer foamed up so violently, it did not 
become dry until after many days of stirring and breaking the cover- 
ing which continually bubbled up. The same proceeding was re- 
peated, although in a less degree, on transferring the substance to 
the air bath at 105° C., and only the single portions taken for analysis 
could be brought to a constant weight without puffing up further at 
105° C. 
While drying, the unpleasant odor noticed from amphopeptone A 
was also observed here, although only in a slight degree. 
