BULLETIN OF THE BUSSEY INSTITUTION. 20 
usually bring out crystals of mannose-hydrazone if any of this 
substance is really present. Any uncertainty of this sort may be 
remoyed by treating the globules at once with glacial acetic acid, 
which will dissolve the osazone balls and leave those of the hydra- 
zone practically intact. 
Inasmuch as mannose-hydrazone is much less soluble in diluted 
alcohol than dextrose-osazone is, a large proportion of the latter 
will remain dissolved in the alcohol after the mannose-hydrazone 
has crystallized. Yet, again, it happens not infrequently that the 
dextrose-osazone, which forms in and upon a mannose-hydrazone 
precipitate when the latter has been allowed to stand for some 
time under its mother liquor, will be in the form of numerous 
minute, pale green, spiny balls, which are so much lighter and 
more flocculent than the mannose-hydrazone precipitate that they 
can be decanted off with the mother liquors, and also when the 
precipitate is washed with water. ‘The facts that mannose-hydra- 
zone may itself change to an osazone on being boiled with water, 
and that dextrose-hydrazone, when in presence of an excess of 
phenylhydrazin, is apt to be oxidized to dextrose-osazone, espe- 
cially if the mixture be warmed, were pointed out some years ago 
by Fischer. 
Behavior of Dextrose when Tested with Phenylhydrazin Acetate. 
In the course of this research, the oxidation of dextrose-hydra- 
zone to dextrose-osazone has been noticed very frequently when, 
in testing for mannose, the mixture of phenylhydrazin compounds 
and products of the hydrolysis of woods has been left to stand 
during several days. Conspicuous illustrations of it have been 
seen also in experiments where solutions of pure dextrose, as well 
as of ‘‘ glucose” and ‘‘ starch-sugsr,” were treated with phenyl- 
hydrazin compounds. For example, 1 cc. of a 0.2 per cent. 
solution of dextrose, treated with one drop of phenylhydrazin and 
two drops of glacial acetic acid and left to stand for several days, 
gave a small yellow amorphous precipitate in which were to be 
seen under the microscope occasional ‘* sea-urchin”’ balls of 
dextrose-osazone with sharp spines. Similar results were ob- 
tained on repeating the test with a mixture of one drop of phenyl- 
hydrazin and six drops of glacial acetic acid. On removing the 
precipitate by filtration and adding some drops of the reagent to 
