120 Mr. Cavenpisn’s Experiments on Air. 
think it much moft likely, that the phlogiftication of the air, and 
production of fixed air, in this procefs, is owing to the burning 
of fome inflammable matter in the apparatus. When the 
{park 1s taken from a folution of teurnfel, the burning of the 
tournfol may produce this effet; when it is taken from lime- 
water, the burning of fome foulnefs adhering to the tube, or 
perhaps of fome inflammable matter contained in the lime, 
may have the fame effet; and when quickfilver or metallic 
knobs are ufed, the-calcination of them may contribute to the 
phlogiftication of the air, though not to the produGtion of fixed 
aire 
There is no reafon to think that any fixed air is produced by 
the firft method of phlogiftication. Dr. PrirsTLEY never found 
lime-water to become turbid by the calcination of metals over 
it*: Mr. Lavoisier alfo found only a very flight and {carce 
perceptible turbid appearance, without any precipitation, to take 
place when lime-water was fhaken in a glafs veflel full of the 
air in which lead had been calcined; and even this {mall dimi- 
nution of tranfparency in the lime-water might very likely 
arife, not from fixed air, but only from its being fouled by par- 
ticles of the calcined metal, which we are told adhered in fome 
places to the glafs. This want of turbidity has been attributed 
to the fixed air uniting to the metallic calx, in preference to the 
lime; but there is no reafon for fuppofing that the calx con- 
tained any fixed air; for I do not knew that anyone has ex- 
tracted it from calces prepared in this manner; and though 
moft metallic calces prepared over the fire, or by long expofure 
to the atmofphere, where they are:im contact with fixed air, 
contain that fubftance, it-by no means follows that they muft 
* Experiments on Air, vol. I. .p. 137. 
-de 
