An Analyjis of huo Mineral Springs, &c. 351 



ance was not fo ftrong, nor the. precipitate fo copious, as 

 when nitrat of filver is dropped into ordinary rain water.— 

 Thefe experiments evince, that this fait either does not de- 

 compofe the falts of lead and filver, or that the new com- 

 pounds are foluble in water. The firft is abfolutely con- 

 clufive : as to the fmall appearance of decompofition in 

 Exp. a and 3, be it confidered how difficult it is to prevent a 

 minute quantity of common acid from pafling over in the 

 diftillation of the oxygenated acid ; and how readily this acid 

 itfelf is decompofed : add to this the imperfecl: oxydation,, 

 perhaps, of the iron. If thefe circumftances are duly weigh- 

 ed, it feems probable, that this fait, when quite pure, would 

 not at all fenfibly decompofe nitrat of filver. A flight im- 

 purity cannot be detected by acetite of lead, as a fmall quan- 

 tity of muriat of lead is foluble in water. 



XII. FURTHER CONSIDERATIONS ON THE HEPA- 



TISKD SOLUTIONS. 



Befides the oxygenated falts, I think it probable, that 

 thefe foliations retain fome fulphur; but under what form, 

 or in. what combination, it is not eafy to fay. The renduum, 

 after evaporation, has a peculiar fmefl, whereas the pura 

 falts are inodorous. The ftain left upon filver by the refi- 

 duum ought, perhaps, to be attributed to this caufe. Alfo, 

 the white matter formed by the decompofition of oxygenated 

 muriat of mercury feems to be a combination of fulphur 

 and mercury. In proof of this it may be remarked, that 

 the precipitate of this fait diflolved in fimple hepatifed wa- 

 ter is white. Further, it is doubtlefs true, that if hepatifed 

 water have a fmall quantity of acid mixed with it, the folu- 

 tion of iron ftrikes a purple colour with galls. To point out 

 the origin of this colour, mix iron filings and fulphur not 

 wafhed, and form them into a pafte with a little water, and 

 let them remain together for fome hours : put the pafte in- 

 to water, and filtrate: this water now ftrikes a purple colour 



with 



