484 Proceedings of Royal Society of Edinburgh. [sess. 
Equilibrium between Sulphuric Acid and Sulphates in 
Aqueous Solution. By Sydney A. Kay, B.Sc. Com- 
municated by Professor Walker. 
(Read December 19, 1898.) 
In the year 1847, as one of the results of an investigation to deter- 
mine the part played by the mass action of water in chemical reactions, 
H. Rose ( Pogg . Ann., lxxxii. 545) showed that an acid sulphate in 
aqueous solution is progressively decomposed into free acid and 
neutral sulphate by increasing quantities of water. His observations 
were confirmed and extended by the thermo-chemical researches of 
Thomsen {Pogg. Ann. 1869, cxxxviii. 72), and Berthelot {Ann. 
Chim. Phys., 1873, x.xix, 433), who indicated more exactly the 
course and extent of this decomposition, and from whose work it 
is known that in the solution of an acid sulphate there exist free 
sulphuric acid, neutral sulphate and acid sulphate. Finally Ostwald, 
in his first memoir on chemical affinity {Jour, prakt. Chem. 1879, 
xix. 483), showed how to determine the magnitude of this decom- 
position, and was able to approximately measure the quantity of 
free acid in solutions of the acid sulphates at different dilutions. 
In a later paper {ibid., 1880, xxii. 305), Ostwald investigated the 
question of the influence of water on the action between sulphuric 
acid and a neutral sulphate. He measured the changes of volume 
which occurred when solutions of sulphuric acid and sodium 
sulphate were mixed in varying proportions, and at different 
dilutions, and obtained results in agreement with his previous 
work. He also pointed out, that if the mutual action between the 
acid and neutral sulphate obeyed the general law of mass action, 
it should follow that, for example, one molecule sodium sulphate 
plus three molecules sulphuric acid, give the same quantity of acid 
sulphate as one molecule sulphuric acid, and three molecules sodium 
sulphate, the volume of the mixture being the same in each case. 
This, however, he showed was not true, little agreement being found 
