388 Maugham.—Observations on the Osazone Method 
Summary. 
The results of this investigation may now be brought together. 
To carry out the test sections of plant tissues are laid in a mixture of 
glycerine solutions of phenylhydrazine hydrochloride and of sodium acetate, 
and then are heated at 98 °-ioo° C., usually for an hour. 
During the heating to which the tissues are subjected some diffusion of 
cell contents may occur, but this is certainly less than that resulting from 
the use of aqueous reagents such as Fehling’s solution. On the whole 
positive results (osazone formation) may be held to indicate with a fair 
degree of accuracy the distribution of the reacting sugars before treatment 
with the reagent. 
The reaction is affected by the glycerine employed ; the glycerine acts 
mainly by reason of its viscosity and causes a retardation of processes 
depending upon diffusion. 
The amount of this retardation varies with different sugars, and 
apparently is not altogether constant for the same sugar. 
Levulose yields an osazone very readily, and in preparations heated for 
half an hour the crystals are often formed before cooling. Frequently the 
crystals are long and fine, and are arranged in sheaves. 
Dextrose precipitates its osazone less readily than levulose, and with 
very small concentrations of dextrose a positive result may occasionally not 
be given. As a rule the crystals are shorter, and are formed in spherical 
clusters having a feathery outline. With 1 per cent, of the sugars present 
the crystal clusters contrast strongly in the two hexoses, but in low con¬ 
centrations this difference disappears. With o-i per cent, of the osazones 
present the crystals are small and indistinguishable, and are deposited after 
a few hours, but more readily and copiously in the case of levulose. 
Too much reliance should not be placed on the crystal cluster form as 
a feature distinguishing dextrose from levulose. 
Glycerine is known to have a hydrolytic effect on cane sugar and 
maltose. 
Cane sugar, if present in sufficient concentration, may become partly 
hydrolysed after being heated at 98 °-ioo° C. for an hour. In an experi¬ 
ment with 1 per cent, of the sugar present no osazone crystals were formed. 
With 10 per cent, a good crop of dense, lumpy crystal clusters was obtained, 
but the yield was much less than that given by a 1 per cent, dextrose 
mixture. 
It follows that attempts to detect cane sugar in presence of its con¬ 
stituent hexoses by comparing the osazone yield in duplicate preparations, 
one of which only has been heated (hexoses alone react slowly in the cold), 
cannot give very reliable results and may be quite misleading. 
The presence of water appears to accelerate the hydrolysis of cane 
