446 REPORTS ON THE STATE OF SCIENCE. 



Van Laar 22i contributed a mathematical paper containing calcula- 

 tions relating to change of solubility, heat of solution, &c. 



V. B. — Influence of Pressure. 



From observations made on the solubility of the permanent gases 

 1803. hi liquids, Henry 3 formulated the law that the solubility of a gas 

 1SG7. m an y hquid is proportional to the pressure of the gas used.* 



In a publication entitled ' Heat Disengaged in Chemical and 

 1854. Molecular Attraction ' Favre and Silberman 16 express the opinion 



that pressure only influences the solubility of a substance by 

 virtue of an accompanying rise of temperature. The opinion expressed 

 by Carius that Henry's law held good for the absorption of ammonia in 

 1859. wa t' er was disproved by Roscoe and Dittmar, 119 who showed this 



process to be far more complicated than was supposed. 

 1861. M oiler 3U showed change of pressure influenced solubility 



quite independently of any accompanying temperature change. 

 He found the solubility of sodium chloride and potassium sulphate in- 

 creased with increase of pressure, while sodium sulphate decreased in 

 solubility as the pressure was increased. These results were verified 

 mfi9 ky Sorby, 33 who went further by showing a connection between 



change of solubility by pressure and change of volume when the salt 

 separated from solution. If the solution of a substance is accompanied 

 by expansion, and the separation of the same from solution by contrac- 

 tion, as in the case of ammonium chloride, then the solubility of that 

 substance is decreased by pressure. Conversely, if, like sodium 

 chloride or copper sulphate, solution is attended by volume contraction, 

 the solubility is increased by pressure. 

 1867 Khanikof and Louguinine 41 carried out measurements of gas 



absorption as a continuation of Bunsen's researches, and con- 



sidered that the results were incompatible with Henry's law. 

 ■ Sims ' 15 recorded experiments on the absorption of ammonia and 

 sulphur dioxide which supported those obtained by Roscoe and Dittmar. 

 Naccari and Paglktni 83 detected an error in the work of 

 ' Khanikof and Louguinine, and used their results to show agree- 

 ment with Henry's law. Further work was published 83 later on to the 

 same end. 



Etard 1 " 7 determined the solubility of certain salts in closed 



tubes at high temperatures, and found the results were practically 

 a continuation of those at ordinary pressures, concluding therefrom that 

 the pressure influence, within the limits of his experiments, was very 

 small. 



Roozeboitm lls made an extensive investigation of the solu- 



bility of hydrogen bromide under pressures varying from to 

 760 mm., at six different temperatures; when plotted, his results for 

 each temperature form a series of similar curves, which are apparently 

 parabolic. 



* In the case of gaseous mixtures Dallon* discovered that each gas dissolved 

 in accordance with its own partial pressure. 



