On Some Criticisms of the Osazone Method. 237 
“ The fact that Mangham should claim to distinguish between 
^-glucose and ^-fructose in the plant by means of the osazone test, 
when their phenyl osazones are of course identical, is not very re¬ 
assuring as to the degree of reliability of his results.” 
It is assumed by the above writers that in the papers dealt 
with, a chemical difference is considered to exist between the 
osazone yielded by dextrose and that yielded by laevulose. Surely 
this is somewhat gratuitous! It really looks as if sufficient atten¬ 
tion could not have been given to that section of the later paper 
headed “ Effects of Glycerine,” a section occupying some fourteen 
pages. A few extracts may perhaps serve to make this clear. 
“The use of glycerine in the reagent has several advantages. 
.On the other hand it has some effect upon the reaction 
with sugars, a point which does not appear to have received 
adequate attention at the hands of other botanical workers or 
critics who have dealt with it.” 1 
“ .... it has been found that the glycerine tends to 
hinder or prevent crystal formation to an extent which varies with 
the different sugars.” 2 
“ This effect appears to be more pronounced with maltose and 
dextrose than with levulose.” 3 
A number of experiments were described in which the effect of 
glycerine was observed upon the production of osazones from 
sugars present in various concentrations. In the case of 1% 
mixtures the following result was recorded. 4 
“The osazone came down more rapidly with levulose than 
with dextrose [this difference was observed by Senft], and in the 
former consisted of sheaves of long, fine, acicular crystals which 
contrasted strongly with the more spherical and somewhat feathery 
clusters of smaller though acicular crystals given by dextrose.” 
The actual extent of the “ claim ” to distinguish between dex¬ 
trose and levulose by the use of Senft’s reagent may be gathered 
from the footnote occurring on the same page : 
“ It may be remarked that these two types of crystal clusters 
can hardly be regarded as altogether distinctive characters for 
dextrose and levulose. In low concentrations the difference is less 
pronounced and may quite disappear.” 
Similarly in the summary: 
“Too much reliance should not be placed on the crystal 
cluster form as a feature distinguishing dextrose from levulose.” 5 
1 l.c., p. 371. 8 l.c., p. 372. 3 l.c., p. 374. 4 l.c., p. 376. ‘ l.c., p. 388. 
