IN STUDYING QUESTIONS OF CHEMICAL MECHANICS. 361 
tity of the latter increases. But the effect of this action does 
not become mathematically null until the total proportion of the 
water is infinite compared with that of the acid contained in the 
solution. 
I proceed now to prove that the values of the characteristic 
= setae determined by the optical experiments, fol- 
low precisely laws of variation analogous to these, in similar 
solutions; so that they likewise agree in showing that tartaric 
acid dissolved imparts a power to the whole mass of water pre- 
sent, which is not completely satisfied until the proportion of this 
liquid becomes comparatively infinite. Such is the principal ob- 
ject of the following section. 
function 
Section III.—On the action of tartaric acid upon water and 
other bodies exposed to it in the liquid state. 
48. I consider an aqueous solution of tartaric acid in which 
P represents the weight of the acid, E that of the water asso- 
ciated with it. To render its definition independent of the units 
of weight of P and E, I make 
dail P E 
~ P+P 
whence 
savers 
e will be the proportion of acid, e the proportion of water con- 
tained in each unit of weight of the solution. I make, moreover, 
for the sake of shortness, 
a(P + E) oe 
Oley cami rs 
a designating the deviation observed through a red glass, which 
only allows red rays sensibly homogeneous to pass. [a] will be 
the characteristic function, determinable by observation, of which 
we have given, in § 27, the relations with the various possible 
states of the active chemical groups constituting the system under 
consideration. Now, in the investigation contained in vol. xv. of 
the Mémoires de l’?Académie des Sciences, I have established, 
by numerous experiments, the fact, that if we form a series of 
similar systems, in which ¢ and e vary in every degree compatible 
with the state of liquidity, and that we observe the action of 
all these systems on polarized light, at the same temperature, 
VOL. IV. PART XV. 2D 
