18 BULLETIN OF THE BUSSEY INSTITUTION. 
beneath the cover glass on the slide of the microscope, extraneous 
matters may be removed, and, in case the mannose-hydrazone 
balls had a reddish tinge, the acid will remove this coloration and 
leave them either colorless or pale yellow. . 
By applying the alcohol in the manner above denen it is 
easy to obtain excellent crystals of mannose-hydrazone that leave 
no shade or suspicion of doubt as to their identity. They appear 
as colorless, brilliant rhombic prisms, sometimes as distinct plates, 
often as bunches of rhombic prismatic crystals radiating from a 
central point, and occasionally (when the alcohol has evaporated 
too rapidly) as a multitude of small stars spread like a carpet 
across the field of the microscope, with the points of each star 
touching those of its neighbors. Although this star carpet is an 
object of great beauty, its appearance is not to be encouraged, 
since the stars are not specially characteristic of mannose-hydra- 
zone. In case the liquor resulting from the hydrolysis of the 
wood or other matter to be tested should be very dark colored, it 
might be decolorized by means of bone-black after neutralization 
and before testing with the phenylhydrazin reagents, but in many 
cases this complication is unnecessary. 
It is not strictly necessary that the acid product of the hydro- 
lysis of vegetable matters should be neutralized exactly by the 
soda lye before adding the phenylhydrazin reagent. Good results 
may still be obtained when the point of neutrality has been over- 
stepped and the solution made faintly alkaline, and also when the 
liquor has been left slightly acid. In case phenylhydrazin acetate 
is to be used for testing, it has been found convenient to make 
the liquor from the hydrolysis very slightly alkaline, while, if 
phenylhydrazin hydrochlorate plus sodium acetate is to be used, 
it will be well enough to leave the liquor faintly acid. Perhaps 
rather better results, on the whole, are obtained by testing with 
phenylhydrazin acetate than with the mixture of phenylhydrazin 
hydrochlorate and sodium acetate, though when this last named 
mixture is used there seems to be a smaller liability that the 
reaction may be obscured after a time by the formation of crystals 
of dextrose-osazone. 
The details above mentioned have been tested in this laboratory 
in a multitude of instances and in many different ways by operat- 
ing upon vegetable ivory, date stones, the wood of coniferous 
