THE DISSOCIATION OF DOUBLE SALTS. 
HAROLD L. MAXWELL AND NICHOLAS KNIGHT. 
The 'purpose of this work is to study the condition of double 
salts in aqueous solutions. Graham 1 was the first to show that 
the double sulphates of the alums could be separated by diffu- 
sion. Marignac confirmed this work soon after and reached the 
conclusion “That double salts are found as such only at the 
moment of crystallization.” Later in 1882, Riidorff made a 
study of the diffusion of some of the double bromides and chlor- 
ides. He diffused the double salt solutions, using gold beater’s 
skin for a membrane, 2 and then analyzed the diffusate and in 
this way determined the proportion in wdiich the double salts 
came through. If the diffusate contained the various elements 
in the same proportion that they would be found in the double 
salt, it would be evident that the double salt did not dissociate 
in the solution, but if the diffusate contained the elements in a 
different proportion from that found in the double salt it would 
be plain that the salt had dissociated in the solution. 
From these determinations it is possible to classify double 
salts in two general classes. First, those which suffer decom- 
position in aqueous solution and second, those which are not 
broken down when in a water solution. To the first class be- 
long : 
Copper Potassium Chloride 2KC1. CuCl 2 +2PI 2 0. 
Magnesium Potassium Chloride KC1. MgCl 2 +6H 2 0. 
Copper Ammonium Chloride 2NH 4 C1. CuC1 2 +2H 2 0. 
Sodium Cadmium Chloride 2NaCl. CdCL-f 3H 2 0. 
Zinc Potassium Chloride 2KC1. ZnCl 2 +H 2 0. 
Barium Cadmium Chloride BaCL. C'dCl 2 +4H 2 0. 
The following three double chlorides are not decomposed in 
the presence of water: 
Sodium Platini! Chloride 2NaCl. PtCl 4 . 8PLO. 
Potassium Platinie Chloride 2KC1. PtCL. 
Mercuric Ammonium Chloride 2NH 4 C1. HgCl 2 . 
iChem. Pharm. In, 56. 1851. 
e Ber., 21, 4. 1888. 
