Prepay aiian of the Oxyget'tated Muri'at of Potafb, igr 



Ibmetimes more of the fait, after being purified by feveral cryftallizations. But having mads 

 "fome alteration In the apparatus, I now find that the fame quantity of alkali may remain 

 for three or four diftlliations before fufficient gas be furniflied to form the fait ; except the 

 perfon employed be remarkably inattentive to his duty. I confuler this as a valuable' im- 

 provement, tlie making of the fait being only a fecondary objeft. The fait was chiefly 

 formed during the dlilillation. The alkali became warm toward the latter end of the 

 procefs, cfpecially if the abforption of gas was very rapid, a quantity of caloric being dif- 

 engaged. In this cafe-, a confulerable part of the fait foon cryftallized, on the lixivium be- 

 hig fet In a cool place, and a great deal of gas appeared to efcape ; which on one occafion 1 

 colle(n:ed, and found that it precipitated lime from its felution in water, and extingulflied 

 flame : and tlierefore, though it had a flight fmell of the oxygenated muriatic acid gas, I 

 believe that it confided chiefly of carbonic acid, as the former occafions no precipitation of 

 lime water, which the latter uniformly does. A glafs jar containing 32 ounce meafures 

 of this gas, being left over water one night, was reduced to about one fourth its "bulk. The 

 gas that remained feemed to contain more oxygene than the air of the room ; two mea- 

 fures of it, with one of nitrous gas, gave 1.53, whilft an equal quantity of common air 

 gave i.g. 



Before any of the fait appeared to be formed in the alkaline folutlon, I have conftantly 

 obferved a quantity of earthy matter to be precipitated. This was cai'efully feparated from 

 rive fait, and, after being waflied repeatedly in boiling water, was fufFered to dry ; but not. 

 having examined it with fufllcient minutenefs to fay what it is, I (hall content myfelf atpre- 

 fent with flating fome of its properties. It did not detonate with fulphur, and was totally or. 

 nearly infoluble in water. The fulphuric acid diflblved it, and gave evident figns of 

 muriatic acid, which appeared to be flightly oxygenated. After being expofed to a red 

 heat for half an hour, the above properties ftill appeared the fame, except with the fulphuric 

 acid. I thought the gas that was difengaged had more of the fmell of fimple muriatic acid 

 gas, though along with it a little of the oxygenated gas might be perceived. The muriatic 

 acid did not appear to diflblve any of this fubftance, either before or after its calcination. 

 With the nitrous acid a ftrong fmell of the oxygenated muriatic gas was produced. From 

 a dram of this fubftance in an earthen retort expofed to a ftrong heat, about fix ouncc- 

 meafurcs of gas were produced, confifting of a mixture of carbonic and azotic gas, the 

 latter of which was in the greateft quantity, forming by eftimate about three fourtlis of the 

 whole. 



The form of the cryftals that firft appeared in the folutlon of alkali were quadrangular 

 plates : what were afterwards formed, when the lixivium became cool, were needle-like, as 

 were thofe that were produced by fpontaneoufly evaporating the remainder of the ley : they 

 appear to have the fame property of detonating as the firft. Thefe different forms of 

 cryftals appeared on diffolving the fait in hot water, and, when cold, feparating the fait, and 

 fuffering the water to evaporate fpontaneoufly. 



I frequently obferved, that unlefs the alkali began to part with a confiderable portion of 

 gas without the admifliion of any from the apparatus, little or none of the oxygenated 

 muriat was procured ; and that as this gas (which I have before obferved to be chiefly the 

 carbonic acid) efcaped, the cryftallizatlon took place, and increafed or diminiftied according 

 to the evolution of that gas. This I found uniformly the cafe, whether mild or cauftic 



alkaU 



