146 Mr. Faraday on the mutual action of sulphuric acid 



became solid, and felt like a piece of soft soap. The salt 

 when dried had no resemblance to sulphate of potash. When 

 heated in the air, it burnt with a dense flame, leaving com- 

 mon sulphate of potash, mixed with some sulphuret of 

 potassum, resulting from the action of the carbon, &c. upon 

 the salt. 



Some of the dry salt was digested in alcohol to separate 

 common sulphate of potash. The solution being filtered 

 and evaporated, gave a white salt soluble in water and alco- 

 hol, crystaUine, neutral, burning in the air with much flame, 

 and leaving sulphate of potash. It was not precipitated by 

 nitrate of lead, muriate of baryta, or nitrate of silver. 



It was now evident that an acid had been formed peculiar 

 in its nature and composition, and producing with bases 

 peculiar salts. In consequence of the solubility of its barytic 

 salt, the following process for the preparation of the pure 

 acid was adopted. 



A specimen of native carbonate of baryta was selected, 

 and its purity ascertained. It was then pulverized, and 

 rubbed in successive portions with a quantity of the impure 

 acid in solution, until the latter was perfectly neutralized, 

 during which the slight colour of the acid was entirely 

 removed. The solution was found to contain the peculiar 

 barytic salt. Water added to the solid matter dissolved out 

 more of the salt ; and ultimately only carbonate and sulphate 

 of baryta, mixed with a little of another barytic salt, remained. 

 The latter salt being much less soluble in water than the 

 former, was not removed so readily by lixiviation, and was 

 generally found to be almost entirely taken up by the last 

 portions of water applied with heat. 



