338 BIOT ON THE EMPLOYMENT OF POLARIZED LIGHT 
ture in the mixed system; and the calculation, made as above 
for a thickness of 100™™, gave 
a(P ais E) es °, 
[4], =—pry = + 44359. 
. Considering these experiments as perfectly exact, we should con- 
clude that the sugar here investigated combines with a certain 
proportion of the water in which it is dissolved, and to which it 
communicates the rotatory power; so that the mixed group thus 
formed would be specifically a little more energetic than the 
primitive solid group. Several circumstances independent of 
the foregoing tend to confirm this induction. For, first, the 
solid sugar thus obtained strongly attracts moisture from the 
air, and becomes deliquescent ; and by this absorption, radiating 
centres of crystallization are formed in the interior of the mass, 
which quickly destroy its transparency when left thus exposed. 
These modifications, resulting from its affinity for water, should 
therefore be immediately produced when dissolved in this liquid. 
Moreover, having formerly observed aqueous solutions of the 
same crystallized cane-sugar, where I had introduced this sugar 
in various proportions by weight, from 0°25 up to 0°65, the spe- 
cific rotatory power [«],, calculated by the function es nll see: , 
was found to be progressively somewhat higher in those in which 
the proportion of water was greater, which is also in agreement 
with the foregoing results. Nevertheless, I am not inclined to offer 
these analogies as absolutely decisive, because the experiments on 
which they are founded are of ancient date, and perhaps less mi- 
nutely accurate than they might be made at the present time with 
this special object. But I shall bring forward others more nu- 
merous and striking, in which the same physical result, that is to 
say the communication of the rotatory power to inactive liquids 
by an active substance dissolved in them, will be clearly evident. 
35. The rotatory power of pure cane-sugar, calculated accord- 
ing to its aqueous solutions for the red ray, and for a thickness 
of 100™™, appeared to me, as the mean of several experiments, to 
be [a], = 54°°762, 
It is therefore considerably stronger than that of the same sugar 
decrystallized by fusion just considered. To ascertain to what 
this difference is attributable, I prepared some new plates of the 
decrystallized sugar, and having dissolved them in water in a 
known ponderable proportion, I submitted the solution to the 
test of inversion by hydrochloric acid, to ascertain the propor- 
