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, crystalline, 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. 
