514 
Proceedings of the Royal Irish Academy. 
Denoting by the quantities of free base, and by 8^ S, the 
quantities of each salt respectively, the equation of equilibrium is 
necessarily of the form 
U=F{B,, B,, 8:, S,)= 0. 
The object of the present investigation is to determine the form 
of the function F. 
The bases selected for experiment v^^ere quinia and brucia. These 
alkaloids possess in solution, as is well known, the power of rotating 
the plane of polarization of a transmitted ray. It is known, more- 
over, that in the case of quinia the rotatory power of any of its salts 
exceeds the rotatory power of the base, while in the case of brucia the 
rotatory power of the salt is less than that of the base. 
These facts being premised, the mode of investigation may be de- 
scribed as follows : — 
First Fxperiment. 
One of the tubes of the saccharometer is filled with a -solution 
containing quinia and brucia, to which has been added a quantity of 
hydrochloric acid, insufficient to convert the whole of both bases into 
salts. The other tube is filled with the same solution diluted with 
» a certain amount of the solvent used (proof spirit). 
The actual rotation being determined for each, it is found that 
that caused by the second fluid is less than that caused by the first, in 
the exact ratio of the dilution. Hence it may be inferred that equi- 
lilrium is not trouhled hj dilution. 
For such disturbance could only arise either by a transference of 
a certain quantity of acid from the quinia to the brucia, or vice versa by 
a transference of acid from the brucia to the quinia. Eut it is evident 
that either transference would alter the rotation. The former would 
substitute for a certain portion of hydrochlorate of quinia a cor- 
responding quantity of free quinia, thus diminishing the rotation, 
and for a quantity of free brucia a corresponding quantity of hydro- 
chlorate of brucia, thus further diminishing the rotation. The 
second transference would evidently augment the rotation. If then 
the rotation undergo no change but that caused by the dilution, it is 
plain that there is no transference, or, according to the definition, no 
rupture of equilibrium. Equilibrium depends, therefore, only on the 
ratios of the four substances. Hence 
\iS B2 J 
