[ *45 ] 
faft. One ounce of tinfoil yields 202 ounce mca- 
fures of inflammable air. 
Thefe experiments were made, when the thermo- 
meter was at 5o°and the barometer at 30 inches. 
All thefe three metallic fubftances diffolve readily in 
the nitrous acid, and generate air; but the air is not at 
all inflammable. They alfo unite readily, with the 
afliftance of heat, to the undiluted acid of vitriol ; but 
very little of the fait, formed by their union with the 
acid, diflolves in the fluid. They all unite to the acid 
with a confiderable effervefence, and difcharge plenty 
of vapours, which fmell flrongly of the volatile ful- 
phureous acid, and which are not at all inflammable. 
Iron is not fenfibly adted on by this acid, without the 
afliftance of heat ; but zinc and tin are in fome 
meafure adted on by it, while cold. 
It feems likely from hence, that, when either of 
the above-mentioned metallic fubflances are diflolved 
in fpirit of fait, or the diluted vitriolic acid, their 
phlogiflon flies off, without having its nature changed 
by the acid, and forms the inflammable air ; but that, 
when they are diflolved in the nitrous acid, or united 
by heat to the vitriolic acid, their phlogiflon unites 
to part of the acid ufed for their folution, and flies off 
with it in fumes, the phlogiflon lofing its inflam- 
mable property by the union. The volatile fulphur- 
eous fumes, produced by uniting thefe metallic fub- 
ftances by heat to the undiluted vitriolic acid, fhew 
plainly, that in this cafe their phlogiflon unites to the 
acid ; for it is well known, that the vitriolic ful- 
phureous acid confifts of the plain vitriolic acid 
Vol. LVI. U united 
