83 



VI. — On the Solubility of Sulphate of Baryta in Acid 



Solutions. 



By F. Crace Calvert, F.C.S., M.R.A. Turin, &c. 



[Read December 2nd, 1856.] 



There are few substances more frequently met with and 

 which require to be determined with greater precaution than 

 sulphur and its compounds, it is therefore of the highest 

 importance to possess exact means of knowing their pro- 

 portions. 



Up to the present time it has been admitted that sulphate of 

 baryta was so insoluble that it was sufficient to add a soluble 

 salt of baryta to a solution containing a sulphate, with an 

 excess of acid, either nitric or hydrochloric (so as to avoid 

 the precipitation of other acids by the baryta), in order that 

 the sulphuric acid existing in a liquor should be exactly 

 determined. My researches have convinced me that sulphate 

 of baryta is soluble in acids. I have succeeded, as will 

 be seen further on, in dissolving two grains of sulphate of 

 baryta in 1,000 grains of nitric acid of a specific gravity of 

 1.167; whilst it requires 140,000 grains of water to dissolve 

 one grain of sulphate of baryta ; and what is not less interest- 

 ing is, that very weak nitric acid influences the solubility of 

 sulphate of baryta; it is therefore essential not to acidify 

 liquors with nitric acid. 



This fact seemed to me so important for analytical chemis- 

 try, that I made a great number of researches in order to 



