818 REPORTS ON THE STATE OF SCIENCE.—1912. V.A. li. 
' The accuracy of these expressions was discussed in a communication 
1898 by Goldschmidt and Maarseveen.** These authors determined 
* all three quantities experimentally for some sparingly soluble 
salts—silver salts of fatty acids—and found that the observed heat of 
dissolution lay between the values calculated from the above two 
1900 equations. Not long afterwards van Laar7* published a paper 
* dealing mathematically with this subject ; he developed a formula 
connecting heat of dissolution and solubility, and showed by experi- 
ments the nature of the difference between his and the formula pro- 
posed by Van’t Hoff. 
1901 Campetti 1"! derived a somewhat complex equation which 
* represented the relationship between solubility and heat of dis- 
solution, which was based upon van’t Hoft’s study of the influence of 
temperature on chemical equilibrium. The equation is only valid for 
those cases in which the substance is not dissociated when dissolved. 
He applied it to the cases of carbamide and mannitol with success. 
Holsboer }°* pointed out that if the solubility of a compound in- 
creases with rise of temperature, the theoretical heat of dissolution— 
the heat of dissolution in a saturated solution—must be negative and 
vice versd. This being so, where the solubility curve of a substance 
passes through a minimum the heat of dissolution should be zero. This 
he found experimentally was true of cadmium sulphate CdSO,, 8/3H,O. 
Holsboer also argued that if the thermal capacity of a solution is an 
additive property, heat of dissolution should be independent of tem- 
perature. 
1903 Van’t Hoff’s equation connecting heat of dissolution and 
* change of solubility with change of temperature in the case of 
electrolytes was tested experimentally by Noyes and Sammet.*** In 
the case of o-nitrobenzoic acid agreement was not good, but in that of 
potassium perchlorate the agreement was sufficiently close to be 
regarded as evidence that conductivity is a correct measure of dis- 
sociation. 
1904 The relationship between solubility and heat of dissolution 
* in the case of gaseous absorption was theoretically discussed by 
Richardson.24* A mathematical equation was deduced by him con- 
necting the variations of solubility of a gas dissolving in a liquid and 
ai the same time undergoing dissociation, with the difference between 
the heats of dissolution of the dissociated and non-dissociated gas. 
V. B.—Influence of Pressure. 
1896 v. Stackelberg ® investigated the influence of pressure on 
©*°° solubility. He experimentally determined the solubility of 
sodium chloride, of ammonium chloride, and of alum at 18° C. under 
different pressures up to 500 atmospheres, and compared the results so 
obtained with those calculated from a thermodynamic equation which 
he had evolved, and which was independent of the temperature co- 
efficient | Approximate agreement was observed between the calcu- 
lated and the experimental results, although in some cases there were 
large divergencies. The solubilities of sodium chloride and of alum were 
