96 CHEMICJL ANALTSIS 



ftone, fome common fait, which, by this procefs, was decompo- 

 fed, and its acid and alkali colleded feparately ; but whether 

 the whole of the fait was obtained, and what proportion it bore 

 to the earthy parts, I cannot determine, as the ftone itfelf was 

 not analyzed. 



The next fpecimen was taken from a ftratum of fandftone, 

 which lies below the hill of Salifbury Craig ; and I chofe this 

 fpecies, becaufe the whin to which it is contiguous has already 

 been fhown to contain foda. Some of it being reduced to the 

 ftate of fine fand, and treated in every refped as the preceding, 

 gave a portion of muriate of filver, and of carbonate of foda. 

 The exiftence, therefore, of fea-fi\lt in thefe varieties of fand- 

 ftone, is thus fvilly eftabliflied *. 



The celebrated Mr Klaproth of Berlin has already fhown, 

 that potafti enters into the compofition of feveral ftony fubftan- 

 ces ; and by the experiments defcribed in this, paper, the other 

 fixed alkali, foda, has alfo been proved to exift in mineral bo- 

 dies, as it has been feparated from nine different varieties ; all 

 of which alfo contain a certain quantity of muriatic acid. 



As cauftic fixed alkali was much ufed in thefe analyfes, I 

 ftiall conclude this paper by defcribing, in a few words, the me- 

 thod by which I prepare it ; both becaufe its purity is of the 

 greateft importance, and becaufe the procefs I employ differs, 

 in fome circumftances, from that of moft chemifts. Having ob- 

 tained an alkali free from all earthy matter, either by burning 

 white tartar, or by repeated folutions and cryftallizations of car- 

 bonate of foda, I diffolve it in a confiderable quantity of water. 

 The requifite proportion of lime being flacked, and allowed to 

 cool, it is diluted with water, and then mixed with the folution 



of 



* Since thefe experiments were performed, I have feen feveral decompofed 

 iandftones, on the furfaces of which there was an efflorefcence of common fait. 



