THE DISSOCIATION OF DOUBLE SALTS 
491 
This work of Jones and Knight included the following four 
double chlorides and as many double bromides. 
Sodium Zinc Chloride. 
Strontium Cadmium Chloride. 
Ammonium Magnesium Chloride. 
Potassium Magnesium Chloride. 
Barium Cadmium Bromide. 
Potassium Cadmium Bromide. 
Sodium Cadmium Bromide. 
Ammonium Zinc Bromide. 
CONDUCT OF DOUBLE SALTS IN AQUEOUS SOLUTIONS. 
The compounds which we have studied are • 
Sodium Cadmium Bromide 2NaBr. 3CdBr 2 -|-6H 2 0. 
Ammonium Zinc Bromide 3NPI 4 Br. ZnBr 2 . 
Copper Ammonium Chloride CuCl 2 . 2NH 4 C1+2IT 2 0. 
Iron Ammonium Sulphate FeNH 4 (S0 4 ) 2 . 
In the study of these compounds we used the diffusion method. 
We obtained the porous cups from Carl Schleicher and Sell till 
and found that the size, 45 mm. wide and 100 mm. high, gave the 
best results. This article is listed as Diffusions — Hiilsen No. 
597. These cups are Compact enough to permit diffusion only 
slowly, yet porous enough to pass enough material to admit of 
accurate analysis. They are placed in 200 cc, beakers and 50 
cc. of the five per cent solution of the double salt is placed in 
each one. Then distilled water is placed in the beaker until it 
reaches the same level in the beaker that the salt solution has 
in the diffusion cup. 
These beakers must be kept at a constant temperature as 
this factor plays an important part in determining the amount 
of material to pass through the walls of .the cup. By varying 
the temperature at one concentration of the salt solution and 
then by varying the concentration of the salt soltition at each 
temperature, it is possible to secure an endless list of data 
showing the effect of temperature and dilution upon the rate 
of dissociation of the salts. 
