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VIII, 
Of the effect of the calcination of me- 
tals, AND OF the EFFLUVIA OF PAINT MADE 
WITH WHITE-LEAD AND OIL, ON AlR. 
Having been led to fufpedi, from the experiments 
which I had made with charcoal, that the diminu- 
tion of air in that cafe, and perhaps in other cafe3 
alfo, was, in fome way or other, the confequence 
of its having more than its ufual quantity of phlo- 
gifton, it occurred to me, that the calcination of 
metals, which are generally fuppofed to con Aft of 
nothing but a metallic earth united to phlogifton, 
would tend to afcertain the fadt, and be a kind of 
experimentum cruris in the cafe. Accordingly, I fuf- 
pended pieces of lead and tin in given quantities of 
air, in the fame manner as I had before treated the 
charcoal and throwing the focus of a burning mir- 
ror or lens upon them, in foch a manner as to make 
them fume copioufly, I prefently perceived a dimi- 
nution of the air. In the firffc trial that I made, I 
reduced four ounce meafures of air to three, which 
is the greateft diminution of common air that I had 
ever obferved before, and which I account for, by 
fuppoAng that, in other cafes, there was not only a 
caufe of diminution, but caufes of addition alfo, either 
of fixed or inflammable air, or fome other perma- 
nently elaftic matter, but that, the effedt of the 
calcination of metals being Amply the efcape of phlo- 
pifton, the caufe of diminution was alone and un- 
controuled. 
The 
