SULPHATE OF BABYTA IN ACID SOLUTIONS. 87 



of magnesia and lime in the water, whilst by avoiding the 

 solution of the sulphate of baryta, I arrived at the conclusion 

 that the bases existed as sulphates and that the silica was 

 free, or combined in small quantity with potash or soda. 



Before giving the results of my experiments, which demon- 

 strate the solubility of sulphate of baryta in acid solutions of 

 different degrees of concentration, and the influence exercised 

 by multiple volumes of nitric acid of specific gravity 1.167 

 on the same solubility, I shall give the method of operating 

 which I followed. 



Having placed in ten jars, of the same size, known quan- 

 tities of perfectly pure sulphate of potash, I added to them a 

 given bulk of nitric acid of sp. gr. 1.305, and a quantity of 

 distilled water, such as when added to that which was em- 

 ployed to dissolve the nitrate of baryta, made a known total, 

 which was in each successive jar a multiple of the quantity of 

 water put in the preceding jar. When, instead of employing 

 acids decreasing in strength, I wished to study the influence 

 of increased volumes of the same acid, that used was of the 

 sp. gr. 1.167 at 60°, or equal to 27.27 of anhydrous nitric 

 acid and 72.73 of water per cent. This strength of acid was 

 employed in preference to any other, because it was that 

 which gave the maximum of solubility to the sulphate of 

 baryta. I also took the precaution to use new jars, in order 

 to avoid scratches, which influence the solubility of the sul- 

 phate of baryta; and equally avoided agitating the intimate 

 mixture of the two salts, in order to be always, as far as 

 possible, placed in the same, circumstances, so that the results 

 might be comparative. 



I will give, first, several series of results which demon- 

 strate the solubility of the sulphate of baryta; and afterwards 

 will examine the facts which have special relation to chemical 

 affinity. 



