BULLETIN OF THE BUSSEY INSTITUTION. oy 
benzyl-phenylhydrazin, in alcoholic solution, for precipitating 
mannose, instead of the simple phenylhydrazin reagents above 
described, but the results of these trials gave no encouragement 
to proceed with them. 
In Testing for Mannose, in products of hydrolysis, allowance must 
be made for the ultimate appearance of crystals of Dextrose- 
osazone. 
- In studying the composition of woods, the precipitation and 
recrystallization of mannose-hydrazone as above described would 
be a fairly satisfactory test in solutions of adequate strength, 
were it not for the circumstance that when dextrose is present — 
and a certain quantity of dextrose must necessarily appear 
whenever wood or any other substance containing cellulose is 
hydrolyzed — there will be formed, on the addition of the pheny]l- 
hydrazin reagent, a quantity of soluble dextrose-hydrazone, some 
part of which will on standing be oxidized sooner or later to 
dextrose-osazone, the crystals of which might readily confuse or 
even mislead an imexperienced seeker of mannose; for this 
dextrose-osazone is a yellow precipitate, very difficultly soluble 
in water, which, under the microscope, is often seen to be com- 
posed of masses of crystals in the shape of balls, covered with 
numberless sharp-pointed spines or needles, which recall forcibly 
the appearance of the common sea-urchin (Echinus). Although 
to an experienced eye these ‘‘sea-urchins” are seen usually to 
differ not a little from the mannose-hydrazone balls covered with 
blunt crystals, as above mentioned, there are occasions or circum- 
stances where the resemblance between the two species is really 
very close, and, as a general rule, the similarity is sufficient to 
confuse an uninstructed person. In point of fact, the liability of 
dextrose-hydrazone to be oxidized to an osazone on standing for 
any length of time in the air in contact with phenylhydrazin 
makes it imperative — when testing for mannose in presence of 
dextrose — to proceed in such manner that the risk of confusion 
through the presence of osazones shall be excluded. Even in 
cases where mannose is present, and where satisfactory crystals 
of mannose-hydrazone have been obtained on testing with phenyl- 
hydrazin compounds, it may happen constantly that the balls 
with sharp-pointed spines or the needles of dextrose-osazone will 
