V.A. i. ON SOLUBILITY. 815 
1904 The solubility-temperature curves of the hydrates of nickel 
* sulphate were determined by Steele and Johnson,!®° who 
deduced the transition points between the two hexahydrates—blue and 
green—and the transition points between the hexa- and hepta- 
hydrates. 
Stanley *°** compared the solubility curves of hydrates of the 
formates of calcium, strontium, and barium, and showed the difference 
between their temperature coefficients. 
The stability relationship of five different hydrates of cerous sulphate 
was investigated by Koppel?'7 by means of solubility graphs. 
Hudson,?® working with the three forms of milk-sugar, came to the 
conclusion that hydrates change but little with change of temperature, 
the change being in the direction of increased hydration with rise of 
temperature.* In a mathematical paper by Richardson? an equation 
was deduced which expressed the variation of solubility with change 
of temperature when a gas dissolves and at the same time dissociates 
in a liquid. The equation put forward is dependent upon the heats 
of dissolution of the dissociated and of the undissociated gas. 
Later on, in the same year, Kohlrausch ?* published a compilation 
of results of solubility determinations of sparingly soluble silver salts, 
which were arrived at from electrical conductivity measurements. He 
complained that knowledge of the influence of temperature on these 
phenomena was still very incomplete. 
The solubility of anthracene, anthraquinone, and quinol in liquid 
sulphur dioxide at different temperatures further engaged the attention 
of Centnerszwer and Teletoff.21* From calculations based upon the 
phase rule these authors concluded that the ‘mean solubility ’+ of 
a sparingly volatile substance is not of constant magnitude at any 
particular temperature. 
Cantoni and Zachoder?°® determined the solubility of tartrates of 
barium (anhydrous), strontium (+3H,O), and calcium (+4H,O), and 
found a positive temperature coefficient in each case.  Bresler 1% 
plotted solubility-temperature graphs for ( ]-asparagine and 3 l-aspartic 
acid from 0° to 100° C., and derived an equation therefrom expressing 
the relationship between solubility and temperature for those substances. 
The solubilities of a large number of salts over a wide range of 
temperature were determined by the Earl of Berkeley 2**: among the 
salts used were the chlorides, sulphates, and nitrates of sodium, 
potassium, rubidium, cesium, and thallium. 
1905 According to Aten ?%* the solubility curves of mercuric 
* chloride in acetone and in ethylic acetate are nearly parallel to 
the temperature axis. In the case of sulphur dissolving in aqueous 
solutions of sodium sulphide similar observations were made by 
Kiister and Heberlein,*44 who found that between O° and 50° the 
solubility was almost independent of the temperature. 
The solubility of sulphur in benzyl chloride was determined by 
* See also Hudson and Brown. J. Amer. Chem. Soc. [1908], 30, 960. 
+ By the ‘mean solubility’ is meant (S+0) (J+A), in which S and O denote 
respectively the quantities of substance dissolved in liquid SO, of weight 7 and vapour 
of weight A. 
