492 Report oF THE CHEMIST OF THE 
which are tabulated below, the temperature and time of digestion 
were made tojvary, all the other conditions being kept uniform. 







TE nee OF Time of digestion. Character of filtrate. anltrogen ia 
U2 | OR hs eae 5 MINutes ieee 6 acs CGAY ann ities 0.448 
me iawn...) OMIT t@R meriiane aio Ciearsee, bye 0.475 
BOR tains Daa Li mingtene? wae oes Clears sr Wn 0.479 
“Vahl O38 Rane Sees 2. MINES ees eons Clearce seine: 0.481 
SUNY Cie tia a) ere 3 Minutes vow. he Cleartr nt cme. 0.471 
BORO rt, cob 10 minntes wrk ss) Clearees tiiecis 0.477 
CANS G5 Gana! 2 O\aminwles testes & 6.2 Clearsvunaan rN 0.484 
UGS, CATS Res ie O MNEs eoite ss es Oléar> icv alae 0.468 
“NG ig ARS Oa poe ithahhd sof ¢ Roe ae Clear a5. sere 0.476 
Mo a eae BAMINULGR gies orks 8 Cléarscaete es 0.483 

The data presented in the foregoing table shows: 
first. That when the precipitate was digested at thirty degrees 
C. for five minutes the results were lowest. 
Second. That when the precipitate was digested at forty degrees 
C. without standing or with standing one, two, three, ten, or twenty 
minutes, the results were practically uniform. The greatest 
difference obtained by digesting different periods of time did 
not exceed 0.01 per cent. nitrogen. 
Third. That, when the precipitate was digested at 45° C. 
for periods of time varying from a few seconds to five minutes, 
the results were fairly uniform, the greatest difference being 
0.015 per cent. nitrogen. As compared with digestion at 40° C., 
digestion at 45° C. gave essentially the same results. 
Fourth. It would, therefore, seem that a variation of tempera- 
ture two or three degrees above or below 40° C. and variation 
of time of digestion after the addition of acetic acid exercises 
comparatively little influence upon the results. However, in 
practice, I think it is desirable to adhere quite closely to uni- 
formity of temperature. 
(5) The precipitation of casein in the fresh and old miulk.— 
The fact is well known that milk undergoes rapid and complex 
changes when left to itself at ordinary temperatures. In the 
course of our work, it occurred to the writer that, asa result of 
these changes, the casein might be so changed that the method 
used in determining casein in fresh milk might not be entirely 

