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vin. 



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 fufpecl, from the experiments 

 which I had made with charcoal, that the diminu- 

 tion of air in that cafe, and perhaps in other cafes 

 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 confift of 

 nothing but a metallic earth united to phlogifton, 

 would tend to afcertain the fact, 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 5 and throwing the focus of a burning mir- 

 ror or lens upon them, in fuch a manner as to make 

 them fume copiouily, I prefently perceived a dimi- 

 nution of the air. In the firft trial that I made, I 

 reduced four ounce meafures of air to three, which 

 is the greaterl diminution of common air that Ihad 

 ever obferved before, and which I account for, by 

 fuppoling that, in other cafes, there was not only a 

 caule of diminution, but caufes of addition alfo, either 

 of fixed or inflammable air, or fome other perma- 

 nently elaftic matter, but that, the effect of the 

 calcination of metals being limply the efcape of phlo- 

 giflon, the caufe of diminution was alone and un~ 

 controuled. 



The 



