U6 Mr. Kihwan’s Experiments 
proved abortive : on the contrary, when the materials could 
previoufly fupply inflammable air, as when martial carbonaceous 
and faccharine compounds were employed, inflammable air, in 
ever fofmall a proportion, was detected : nor could hepatic air 
be procured from the direct union of inflammable air and fiil- 
phur, as we have feen. 
Some have imagined, that this air eonfifts of liver of ful- 
phur itfelf volatilized, and confequently that an alkali enters 
into its compofition ; but many weighty reafons oppofe this 
fuppofition. In the frrft place this air is evidently, though 
weakly acid, fince it reddens litmus, and precipitates acetous 
baro-felenite. 2dly, It may be extradted from materials that 
either contain no alkali at all, or next to none, as iron, fugarj 
oil, charcoal : and, laftiy. It is not decompofedby marine or fixed 
air, by which, neverthelefs, liver of fulphur is decompofable^ 
I formerly thought that fulphur was. held involution in he- 
patic air, either by vitriolic or marine air ; yet though both of 
them may hold fulphur in folution,.as we have feeivftill neither 
of them is- efiential to the conflitution of hepatic air as fuch, 
fince it is producible from materials that contain neither of 
t-hefe acids ; and, from whatever fubjedt it ^obtained, it exhibits 
the charadters of one and the fame acid, namely, the vitriolic 
exceedingly 'weakened ; and fuch an acid we may fuppofe fulphur 
itfelf to be. 
In effect, fulphur, even in its concrete (bate, affords many 
characters of acidity. It unites with alkalies, calcareous and 
ponderous earths, and moft metals, as. a weak acid might: 
and except a m.anifeft folubility in water (a property which 
fome other concrete acids alfo poflefs in a very weak degree) it 
exhibits every character of acidity. But its acidity is the weakeft 
pofiible, fince it decompofes only acetous,, and not marine baro- 
felenite,. 
