V.c. ii. ON SOLUBILITY. 837 
explain the increased solubility of the calcium salt under the conditions 
above referred to. Cameron and Bell?** found that magnesium sul- 
phate lowers the solubility of calcium sulphate, and the curve they ob- 
tained by plotting the concentration of calcium sulphate against that of 
the magnesium sulphate was of remarkable shape. Taber *’4 observed 
that phosphoric acid increases the solubility of calcium sulphate. 
Foote and Levy?" made use of solubility measurements in their 
investigation of double-salt formation,* in the case of mixtures of mer- 
curic chloride with the chloride of sodium ‘potassium and rubidium. In 
this manner several new salts were recognised. 
HE. Fischer *** made the interesting observation that low concentra- 
tions of hydrogen chloride enhance the solubility of }-naphthalene 
sodium sulphonate in water, whereas greater concentrations of hydrogen 
chloride occasion the opposite effect. 
Both hydrogen chloride and sodium chloride increase the solubility of 
silver chloride in water, and Barlow ?78 showed this to be an independent 
and, at the same time, an additive property of these substances. 
The solubility of plumbic sulphate in sulphuric acid solutions of 
various concentrations was examined by Dolezalek and Finckh.?”° 
1907 In the following year this subject was studied by Pleissner *1* 
* from the point of view of its bearing upon the contamination of 
water supplies. He found the solubility of lead sulphate and lead 
chloride is reduced by sulphuric acid and hydrochloric acid respectively, 
whilst that of the carbonate is increased by carbonic acid. The influence 
of hydrogen chloride upon the solubility of various salts in water was 
studied by H. H. Armstrong, Eyre,*°° and others, who showed that a re- 
latively larger effect was produced when only small quantities-of hydro- 
gen chloride were present. Their results indicated a similarity of be- 
haviour when hydrogen chloride and alcohols acted as precipitants for 
salts. The lowering of the solubility of gases in water brought about by 
the addition of electrolytes and non-electrolytes (precipitants) to the 
solvent was examined by Philip,*°* and’as observed by the above- 
mentioned authors the lowering effect was found to be relatively most 
marked when dilute solutions of the precipitants were employed. 
The solubility of calcium carbonate in aqueous solutions of potas- 
sium chloride and potassium sulphate was measured by Cameron and 
Robinson 2*7 and Bell and Taber ?°"4 found that, up to a certain con- 
centration, copper sulphate diminishes the solubility of gypsum, but 
that! higher concentrations increase the solubility of the calcium salt. 
1908 According to Spencer and Le Pla **° thallous chloride is much 
* more soluble in solutions of potassium carbonate than in pure 
water, and Free **7 found that the addition of sodium and calcium car- 
bonates greatly diminished the solubility of basic copper carbonate in 
aqueous solutions of carbon dioxide, whilst the addition of calcium 
sulphate produced no such effect. Work having a similar bearing was 
published by Kernot and Agostine ** in which it was shown that in- 
creasing quantities of potassium chloride at first increase and then 
diminish the solubility of calcium hydroxide in water: the solubility 
* Vide Part II. R. 172. 
