BULLETIN OF THE BUSSEY INSTITUTION. 25 
treated became turbid, and after some hours the yellow precipi- 
tates just now described settled out. In numerous instances 
these yellow, amorphous, dust-like precipitates were removed by 
filtration soon after they had formed, and additional drops of the 
phenylhydrazin reagent were added to the clear filtrates. Some- 
times this process of fractional precipitation and filtration was 
repeated again and again, but small quantities of the yellow pre- 
cipitate formed anew as often as the trials were made, and after 
the lapse of some time crystalline balls of dextrose-osazone were 
almost sure to appear. In these trials, it seemed as if the phenyl- 
hydrazin acetate acted somewhat more quickly and more strongly 
to favor the oxidation of the dextrose-hydrazone and to induce 
the formation of the osazone crystals than the mixture of pheny]l- 
hydrazin hydrochlorate and sodium acetate did. 
It is noticeable that for the oxidation of dextrose-hydrazone 
time seems to be a more important factor than momentary heating 
of the materials upon the water-bath. Thus, when 1 cc. of a 
1 per cent. solution of pure dextrose was boiled for half a minute 
with five drops of a dilute aqueous solution of phenylhydrazin, — 
prepared by dissolving 1 cc. of the phenylhydrazin in 15 ce. of 
water, nothing but a small quantity of minute, dust-like particles 
separated; and a similar reaction occurred when 1 cc. of the 
1 per cent. dextrose solution was boiled for half a minute with 
one, drop of pure phenylhydrazin. On boiling half a cc. of a 
10 per cent. dextrose solution with a drop of phenylhydrazin, 
some crystals of dextrose-osazone separated in the course of two 
or three days. In an instance where eight drops of a mixture of 
phenylhydrazin hydrochlorate and sodium acetate (prepared as 
on page 14) and 1 ce. of a solution of 0.2 grm. dextrose in 5 cc. 
of water were heated for one hour on a boiling water-bath, no 
crystals of dextrose-osazone were obtained, but only the usual 
yellow amorphous dust. These results are noticeably different 
from those obtained every day in the application of the common 
clinical test for dextrose, for the presence of common salt in this 
case would naturally elevate the temperature at which the liquid 
boils, and so accelerate the transformation of dextrose-hydrazone 
to dextrose-osazone. 
Although the number and size of the mannose-hydrazone balls 
and crystals, which appear on the addition of the phenylhydrazin 
