1806.] Sulpho-Naphthalic Acid. 187 



a dense flame, leaving common sulphate of potash, mixed with 

 some sulphuret of potassium, 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 alcohol, 

 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 solu- 

 tion 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. 



The barytic salt in solution was now very carefully decom- 

 posed, by successive additions of sulphuric acid, until all the 

 baryta was separated, no excess of sulphuric acid being per- 

 mitted. Being filtered, a pure aqueous solution of the peculiar 

 acid was obtained. It powerfully reddened litmus paper, and 

 had a bitter acid taste. Being evaporated to a certain degree, 

 a portion of it was subjected to the continued action of heat ; 

 when very concentrated, it began to assume a brown colour, 

 and on cooling became thick, and ultimately solid, and was 

 very deliquescent. By renewed heat it melted, then began to 

 fume, became charred, but did not flame ; and ultimately gave 

 sulphuric and sulphurous acid vapours, and left charcoal. 



Another portion of the unchanged strong acid solution was 



