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4fO INFLAMMABLE SUBSTANCES. Sc&. 2%0. The caufe and manner of their containing ful phur, which was long a problem, has at lafl been happily explained by Mr. Bergman. It plentifully occurs in the neighbourhood of volcanos,. and in feveral mines. Kirwan. 12. But copper and iron become of a blue colour; lead eafily tarnifhes, when immerfed in it; and mercury be comes black. 13. Water, impregnated with hepatic air, turns filver black; precipitates arfenic, from its folvehr, into a powder re- fembling orpigment: precipitates zinc from the vitrio lic acid : and the folution of corrofive fublimatc, into a white powder. The foluttons of filver in nitrous acid and of fait of lead, are precipitated of a black colour. The folution of copper, and of the martial vitriol, as well as that of mercury in nitrous acid, are precipitated by the fame, of a dark brown colour. 14. This water, fo impregnated, diffolves iron filings; and this folution takes a purple colour, if the infufion of galls be added to it. But phlogifticatcd alkali does not produce any change. 15. It does not precipitate lime from lime-water, unlefs a very large quantity of this air paffes through a lmall'one of water. Hepatic air is eafily obtained by art, from all forts of fiver of fulphur, whether the bafe be an alkali, an earth, or a * metal, if any acid is poured upon it: and the better, if life is made of the marine acid, bccaufe it contains phlogifton enough, and does not fo ftrongly attradfs that of the hcpar fulphur is. For this reafon the nittous acid is not fit for this procefs, as it combines itfelf with the phlogifton, and produces nittous air. It may alfo be produced, by diftilling a mixture, of fulphur and povudcred charcoal; or of fulphur and oil, &c. According to Mr. Kirwan (in the firft part of Phil. Tranf. for 1786), hepatic air confiffs of fulphur alone, kept in an aerial ftate by the matter of heat. It has evidently, though weakly, an acidity of the vitriolic kind, as fulphur docs; and no in flammable air can be extracted from it ? unlefs when produced by thofe compounds, which afford the fame, as carbonaceous, and facchaiint compound., &c. The Editor, SECT.
