372 Dr . Prout on the ultimate composition 
ing diabetic sugar in a state of purity.* This, deprived of its 
hygrometric moisture by being placed under a receiver with 
sulphuric acid for several days, was found to consist of 
Carbon - - - 36-36 
Water - - 63-63 
This sugar in the ordinary state of the atmosphere usually 
contains more water than indicated by this analysis ; that is 
to say, generally about 64’ 7 per cent. On the other hand, 
on exposure to a temperature considerably below that of 
boiling water, it rapidly loses about 3 per cent, of water, and 
begins to assume the fluid form ; kept at the temperature of 
boiling water for 30 hours, it lost in one experiment upwards 
of 10 per cent, of its original weight, became of a deep brown 
colour, and seemed to be partially decomposed.-f 
Sugar prepared from starch evidently belongs to this va- 
riety, as is sufficiently indicated both by its sensible properties 
and composition. The same is true in general of diabetic 
sugar, and probably also of the sugar of grapes, figs, &c. 
When pure, all the varieties of this sugar are beautifully 
* Med, Chirurg. Trans, viii. 537. I have little doubt that honey contains a still 
lower sugar, and which is incapable in this country (at least during a great part 
of the year), of assuming the solid form. This is probably the liquid sugar of 
Proust. 
f I observed that after this sugar had been cautiously melted it might be pre- 
served in the state of a transparent fluid, if placed in a perfectly dry atmosphere, 
as under the receiver of an air pump with sulphuric acid ; but that in a few 
hours after exposure to the air, it began to grow opaque and assume the crys- 
talline form, by attracting moisture. Is not this precisely analogous to the dete- 
rioration which is known to take place in the sugars of commerce? See Mr. Daniell 
on this subject in the Royal Institution Journal, v. 32. Dr. Ure supposes that 
this deterioration depends on the absorption of oxygen ; but I have hitherto met 
with no sugar containing an excess of oxygen. 
