86 MR. F. C. CALVERT ON THE SOLUBILITY OF 



know all the circumstances which influence the solubility of 

 sulphate of baryta ; and, although I have made several hun- 

 dred experiments, I shall only give here the most striking, 

 and those which tend to demonstrate the influence exercised 

 by masses of matter, upon their chemical affinity. I hope 

 that these last facts will offer the more interest, as we only 

 possess few researches demonstrating, that Berthollet ex- 

 pressed a correct opinion, when he asserted that the quantity 

 of matter present exercised an influence upon chemical affinity. 

 However, since I have commenced these researches, in 1851, 

 several works supporting these views have appeared, those of 

 Messrs. Bunsen, Gladstone, Henry Deville, &c. 



The first idea of these researches was suggested to me by 

 an inquiry which I had undertaken to determine the quantity 

 of sulphur in cast and malleable irons. As the quantity of 

 sulphur to be determined only varied between the limits of 

 0.1 and 0.3, it was indispensable that I should take the greatest 

 precautions ; but, notwithstanding, I still found it impossible, 

 in making two comparative analyses of the same iron, to 

 obtain two sulphates of baryta having corresponding weights. 

 Desiring to know the cause of error I made several experi r 

 ments, and discovered, to my great surprise, that sulphate 

 of baryta was freely soluble in acids, and then the error in 

 my analyses was explained. Some quantitative analyses of 

 water, which I had to make at the same time, led me to the 

 same result ; for having followed the ordinary process which 

 consists in adding, in the case of a water which contains car- 

 bonates and sulphates, nitric acid to the residue left by the 

 evaporation of a known quantity of water, I determined the 

 quantity of sulphuric acid, and was again struck by the 

 divergence of my results. If I had contented myself by 

 taking the mean of the results obtained, I should have been 

 obliged, in calculating the relation of the bases to the acids, 

 to admit, as some chemists have done, that there were silicates 



