of locating Sugars in Plant Tissues. 
38 i 
When 
Levulose. 
Dextrose. 
examined. 
After Slides. 
47 days. 
Much the same. 
Slide. i*o% Crystals more clearly de¬ 
fined. 
After Slides. 
57 days. 
Little further change. 
Crystal formation did 
not appear to have pro¬ 
gressed as with dextrose. 
Very hazy and turbid or 
granular, except at centres 
of clusters. 
Slides, c-i % Little change. 
1.0 % Crystal formation appa¬ 
rently complete. Innu¬ 
merable very minute 
crystals everywhere, be¬ 
sides larger clusters. 
From these results it would appear that the osazones are fairly soluble 
in hot glycerine, but that on cooling they come down as crystals readily in 
mixtures of 1 per cent, concentration and above, but less readily in 01 per 
cent, mixtures. 
In the 1 per cent, mixtures the actual crystal clusters of levulose were 
ultimately less sharply defined than those of dextrose in this particular 
instance. 
It is also seen that a 01 per cent, mixture of levulose phenylosazone 
deposits crystals more rapidly and copiously than a corresponding mixture 
of the osazone yielded by dextrose. 
The two osazones are almost insoluble in glycerine, 1 but in weak con¬ 
centrations crystallization seems to be retarded by the viscosity of the 
glycerine. Naturally in a viscous medium the rate of diffusion of particles 
to form crystals is slower than in a medium such as water. Clearly, too, 
the process of crystallization will be slower when the particles are highly 
dispersed throughout the medium than when they are present in greater 
concentration. 
On the whole, then, although there may be some irregularity at times, 
it may be held that if the preparations are allowed due time for equilibrium 
to be attained, the use of glycerine in the reagent as it is ordinarily employed 
has no very serious effect upon the delicacy of the test as far as levulose is 
concerned. In the case of dextrose, however, it may occasionally happen 
that crystals will fail to appear. 2 
The presence of other sugars may affect the reaction given by any 
particular sugar, but before dealing with this point the results may be 
described which were obtained by mixing maltose phenylosazone with 
glycerine and treating the mixtures as in the above experiment. 
Experiment IV. Tubes were prepared containing the osazone mixed 
1 The actual solubility has not been determined, but it is obviously less than 1 in 1,000. 
2 Grafe states ( 1 . c., p. 17) that a 0*015 per cent, solution of dextrose yields positive results. It is 
not clear, however, whether this concentration means 15 parts in 100,000 of the reagent or of water 
previous to the addition of reagent. 
