CONVERSION OF THE SULPHATES OP THE ALKALIES. 223 



boiling-point; the solution will then contain only carbonate 

 of potash. 



The reaction is readily understood; the carbonic acid in the 

 water dissolves a little carbonate of baryta, which is imme- 

 diately precipitated in the form of sulphate, carrying down 

 a portion of the sulphuric acid of the soluble sulphate, and 

 replacing the same with carbonic acid ; this is rapidly repeated 

 through the agency of the free carbonic acid, until the decom- 

 position of the sulphate is complete. 



Among many experimental results I will give the following : 

 Five grammes of the sulphate of potash dissolved in carbonic- 

 acid water, to which was added seven grammes of precipitated 

 carbonate of baryta, after four and a half hours' shaking (being- 

 attached to a suitable piece of machinery), on testing showed 

 not a trace of sulphuric acid, care being taken to wipe the neck 

 of the bottle near the end of the stopper before pouring out the 

 liquid. 



Other experiments, varying in proportion, gave similar re- 

 sults. I tried to substitute the natural for the precipitated 

 carbonate of baryta, but with very unsatisfactory results. 



DIRECTIONS FOR CONVERSION OF THE ALKALINE SULPHATES INTO 

 TARTRATES, OXALATES, ETC. 



As the tartrate and oxalates of baryta are but very slightly 

 soluble in water, we can not form the alkaline salts of these acids 

 by direct double decomposition of the sulphates of the alkalies 

 and the tartrate, etc., of baryta, as in forming the alkaline chlo- 

 rides from the sulphates ; but it is easily done by the following 

 indirect process. 



Add to the alkaline sulphates in solution, in a porcelain 

 capsule, carbonate of baryta rubbed up into a thick cream in 

 the proportion of about five of the sulphate to seven of the 

 carbonate of baryta; heat the mass and add little by little the 

 requisite quantity of tartaric or oxalic acid; solution of the 

 baryta and precipitation of the sulphuric acid take place rap- 

 idly, and the decomposition is soon completed. 



I have used this process in forming the bitartrates in the 

 process of separating potassium, rubidium, and caesium, that 

 were in the form of sulphates. 



