at Lenungton Priori- 163 



of msrnganefe ; but how fmall foever was the quantity ufed, 

 and however much it was diluted, the manganefe was in- 

 ftantly detected by pruffiat of pot-afh. I was therefore forced 

 to conclude that, if oxygenated muriat of iron is really an in- 

 gredient of this water, it muft be formed by a procefs dif- 

 ferent from that which I had imagined. 



Till. THE APPEARANCES IN QUESTION ARE PRODUCED 

 BY THE ACTION OF HEPATIC GAS ON IRON AND MAN- 

 GANESE. 



An obfervation of Bergman, though in part erroneous, 

 lias conducted me, as I think, to the true caufe of thefe ap- 

 pearances ; and I am greatly miftaken if its confequences, 

 when fully purfued, are not of confiderable importance to 

 chemical fcience. Bergman has aflerted that hepatifed water 

 in which iron filings have been kept for fome days, in a well- 

 clofed vefiel, grows purple with tincture of galls : if the iron 

 be diflblved by an acid, the colour approaches more to violet. 

 He moreover adds, that the folution of iron in hepatifed wa- 

 ter is not at all rendered turbid by prujfiat of potafb (Bergman's 

 EJfaySy DiJJcrtation VH. 4. L.) This latter fa£t promifed to 

 throw fome light on the fubject of my enquiry, particularly 

 when it was joined to the fact of the hepatic fmell, which 

 the water has when recently drawVi (1.). I was the more 

 ftrongly induced to pay attention to this combination, from 

 the contradiction of another very eminent chemift. Mr. 

 Kirwan lias denied that hepatic gas can diflblve iron, or any 

 other metal (Pbilofoph. Tranfac. 1786). To afcertain this 

 point, I have made numerous experiments with the greateft 

 caution ?nd accuracy that I have been able to apply. The 

 hepatic gas which I have ufed, was obtained from fulphuret 

 of iron, formed by fufing equal parts of iron and flowers of 

 fulphur •, and (except in fome inftances, which will be par 

 ticularly noticed as they occur) was extricated by diluted 

 fulphuric acid. The gas was collected under water j which 

 method was preferred, to purify it if pofhble from extraneous 

 S 4 acid 



