324 -BIOT ON THE EMPLOYMENT OF POLARIZED LIGHT 
We then fall back on the equation which we have already found 
in § 20, for the case of complete saturation of the whole active 
mass P, as ought evidently to be the case, since we thus return 
to the same circumstances. 
25. We might, lastly, conceive another variable mode of non- 
saturated constitution, which would enter into that which we 
have considered in § 21, except that it would not remain fixed. 
This would consist in supposing that for each weight E of in- 
active liquid associated with the same weight P of the active 
substance, P forms a certain number of combinations of different 
orders, saturated or supersaturated, which remain stable both 
with respect to their composition and their number, until the 
portion of E, which is in excess relatively to them, attains a cer- _ 
tain value; after which a new division of P would take place, 
giving rise to other saturated combinations, and consequently to 
a new state of the system, which would in like manner be main- 
tained up to a certain limit of E relatively to P, after which it 
would change anew. On applying the reasoning in § 21 to each 
of the temporarily fixed systems which would compose such a suc- 
cession, we find that the characteristic function —— varies 
by abrupt intervals, between each of which its value will remain 
constant; and this mode of variation, if observed, would show 
the existence of the successively changing mode of constitution, 
to which it corresponds. 
26. I have consulted very experienced chemists on the differ- 
ent forms of combinations which may be considered supposable, 
under the circumstances which we have admitted, that is to say 
when an active substance is placed in presence of an inactive 
liquid, at a constant temperature, without mutual decomposi- 
tion, and for all relative proportions of the two bodies compati- 
ble with the state of fluidity. They have not indicated others 
than those which I have just specified, attributing to them very 
different probabilities of realization. For this reason I shall 
collect here the different propositions bearing on the subject, as 
well as the optical characters derived from them, so that their 
connection may become more apparent, and that it may suffice 
to recall them when required. 
27. When a constant weight P of an active substance is dis- 
solved at a constant temperature in a variable weight E. of an 
inactive liquid, with which it may enter into a more or less inti- 
