V.c. iii. ON SOLUBILITY.” 833 
tion the ratios of the absolute temperatures at which the substances 
have an equal solubility are represented by R and R’, C is a constant 
with a small positive or negative value, and t¢ and ¢? are the temperatures 
at which the solubility of the second substance is known. Satisfactory 
results were obtained with such salt pairs as zinc chloride and bromide 
and potassium chloride and bromide. Koppel'*°® found that the 
solubility of sodium sulphate is increased by the presence of copper 
sulphate owing to the formation in solution of a double-salt, CuSO,, 
Na,SO,.2H,O. Seidell1*® determined the solubility of various mix- 
tures of sodium sulphate and sodium chloride at temperatures between 
10° and 30°C. During their examination of the solubility of calcium 
carbonate in aqueous salt solutions, Cameron and Seidell }*7 obtained 
some seemingly anomalous results: for instance, sodium sulphate was 
found to increase the solubility of calcium carbonate to a greater extent 
than sodium chloride, although from the great solubility of calcium 
chloride the reverse would not have been surprising. These authors 
advanced a tentative hypothesis of complex ‘ion’ formation as a 
possible explanation of these results. | Bodldnder and Storbeck \** 
made a study of the solubility of cuprous chloride in solutions of 
hydrogen chloride and potassium chloride, and arrived at certain con- 
clusions regarding the complex ‘ions’ which may possibly exist in 
such solutions. They also gave values for the ‘ solubility product’ of 
the three cuprous halides. 
Finzi 48 found that when mercuric chloride and silver nitrate 
solutions are mixed together a considerable quantity of silver chloride 
remains in solution. This may be precipitated by adding any of a 
large number of salts, the chlorides and nitrates being particularly 
efficacious. 
The influence of salts, especially alkali nitrates, on the solubility 
of ammonia was examined by Abegg and Riesenfeld.'** In almost 
all cases the addition of salts was found to bring about an increased 
partial pressure of ammonia. In this respect, polyvalent anions have 
greater effect than monovalent anions, and a greater tendency to 
hydration of the anion occasions an increase of the partial pressure of 
ammonia. Gaseous absorption was also investigated by Fozx,??° who 
made an extensive study of the effect produced on the solubility of 
sulphur dioxide in water by the addition of various electrolytes to the 
solvent. Solutions of iodides, ammonium, potassium, and sodium 
bromide, potassium chloride and potassium nitrate, for example, were 
found to dissolve more gas than does water alone, whilst some salts, 
sodium chloride, sodium sulphate, calcium chloride, &c., decrease the 
solubility of the gas. The increased solubility was attributed to the 
formation of complexes in solution, but it is not made clear why, for 
instance, this property should be attributed to potassium chloride and 
not to sodium chloride. 
Rimbach 11° determined the transformation point * of a number of 
double-salts including those of rubidium-cadmium and ammonium-cad- 
mium chloride. 
* The temperature at which the two solutions, saturated respectively with double 
salt and one of its components, become identical in composition. 
1912. 38 
