[ i6 3 ] 



The diminution of the quantity of air in which a 

 candle, or brimftone, has burned out, is various ; 

 but I imagine that, at a medium, it may be about 

 one fifteenth, or one fixteenth, of the whole 5 about 

 one third as much as by animals breathing it as long 

 as they can, by animal or vegetable fubftances 

 putrifying in it, by the calcination of metals, or by 

 a mixture of fteel filings and pounded brimftone 

 /landing in it. 



I have fometimes thought, that flame difpofes the 

 common air to depolit the fixed air it contains - y for 

 if any lime-water be expofed to it, it immediately 

 becomes turbid. This is the cafe, when wax candles, 

 tallow candles, chips of wood, fpirit of wine, aether, 

 and every other fubftance which I have yet tried, 

 except brimftone, is burned in a clofe glafs vefTel, 

 flan ling in lime-water. This precipitation of fixed 

 air (if this be the cafe) may be owing to fomething 

 emitted from the burning bodies, which has a ftronger 

 affinity with the other conftituent parts of the atmo- 

 fphere. 



If brimftone be burned in the fame circum- 

 ftances, the lime-water continues tranfparent, but 

 ftill there may have been the fame precipitation 

 of the fixed part of the air; but that, uniting with 

 the lime and the vitriolic acid, it forms a felenetic fait, 

 which is foluble in water. Having evaporated a 

 quantity of water thus impregnated, by burning 

 brimftone ,a great number of times over it, a whitifh 

 powder remained, which had an acid tafte; but re- 

 peating the experiment with a quicker evaporation, 

 the powder had no acidity, but was very much like 

 chalk. The burning of brimftone but once over a 



y 2 quantity 



