328 PROCEEDINGS OP THE AMERICAN ACADEMY. 



experiments x and y are expressed in cubic centimeters because they 

 were measured directly as such, and in this way it was not necessary 

 to make determinations of the densities of the liquids used, nor any 

 assumptions in regard to their reacting weights. Equation (o) will 

 not remain unchanged if the reacting weight of ^ or ^ varies, that is, 

 if the ratio of the active mass to the actual mass changes as x ox y 

 changes. The converse of this is also true, that if the system follows 

 the law ic" y = C, the common solvent remaining constant, the react- 

 ing weishts of the substances A and B cannot have varied with the 

 concentration. 



I have found that the equation, x'^if^ Constant, is the expression 

 representing the saturated solutions of two non-miscible liquids in a 

 constant quantity of a consolute lic^uid. I find, however, that in most 

 cases the concentrations cannot be given by one curve, but involve 

 two, so that for one set of concentrations I have the relation x"^y= Ci, 

 for the other set off^y =0^. This cannot be true unless the two sets of 

 saturated solutions correspond to different conditions. This is the 

 case. Duclaux* found that a saturated solution of amylalcohol and 

 water in ethylalcohol became turbid on adding a drop either of amyl- 

 alcohol or of water. In other words the solution was sensitive to an 

 excess of either liquid. f, I have confirmed this result, and it is per- 

 fectly general. It is not proper, however, to draw the conclusion that 

 the solution is saturated' in respect to both liquids. If to a given 

 saturated solution of chloroform, water, and alcohol, for instance, one 

 adds a drop of water or of chloroform, the solution becomes turbid ; 

 but what separates out is the same in both cases. It is analogous to a 

 saturated solution of salt in a mixture of alcohol and water. It is in- 

 different whether one adds alcohol or salt to the solution. In either 

 case, there is a precipitate ; but in both cases the precipitate is salt, and 

 the solution is saturated in respect to salt, not in respect to alcohol. 

 It is not so easy to see what takes place in a system composed of 

 liquids because the precipitate, being itself a liquid, dissolves part of the 

 solution, and the new phase is not composed of pure substance. This 

 need not trouble us, for, theoretically at any rate, the precipitate may 

 be treated as pure liquid, and the final equilibrium looked upon as due 

 to a subsequent reaction. One of the two curves represents, then, the 

 set of solutions which is saturated in respect to chloroform, and not in 

 respect to water. Whether one adds water or chloroform, to these 

 solutions, the precipitate is chloroform. Tne other curve represents 



* Ann. chim. phys , [5.], VII. 264. 1876. t Ostwalcl, Lehrbuch, I. 819. 



