H4 HISTORICAL INTRODUCTION TO CHEMISTRY CHAP. 



times that quantity of common air, and the burnt air made to 

 pass through a glass cylinder eight feet long and three- 

 quarters of an inch in diameter, in order to deposit the dew. 

 The two airs were conveyed slowly into this cylinder by 

 separate copper pipes, "passing through a glass plate which 

 stopped up the end of the cylinder ; and as neither inflam- 

 mable nor common air can burn by themselves, there was 

 no danger of the flame spreading into the magazines from 

 which they were conveyed. Each of these magazines con- 

 sisted of a large tin vessel, inverted into another vessel just 

 big enough to receive it. The inner vessel communicated 

 with the copper pipe, and the air was forced out of it by 

 pouring water into the outer vessel ; and in order that the 

 quantity of common air expelled should be 2\ times that of 

 the inflammable, the water was let into the outer vessels by 

 two holes in the bottom of the same tin pan, the hole which 

 conveyed the water into that vessel in which the common 

 air was confined being 2j times as big as the other." 



" In trying the experiment, the magazines being first filled 

 with their respective airs, the glass cylinder was taken off, 

 and water let, by the two holes, into the outer vessels, till 

 the airs began to issue from the ends of the copper pipes ; 

 they were then set on fire by a candle, and the cylinder put 

 on again in its place. By this means upwards of 135 grains 

 of water were condensed in the cylinder, which had no taste 

 nor smell, and which left no sensible sediment when evapor- 

 ated to dryness ; neither did it yield any pungent smell 

 during the evaporation ; in short, it seemed pure water." 



" By the experiments with the globe it appeared, that 

 when inflammable and common air are exploded in a proper 

 proportion, almost all the inflammable air, and near one- 

 fifth of the common air, lose their elasticity, and are con- 

 densed into dew. And by this experiment it appears, that 

 this dew is plain water, and consequently that almost all the 

 inflammable air, and about one- fifth of the common air, are 

 turned into pure water" (A. C. R. III. 14 15). 



Cavendish prepares water by exploding inflammable 

 air with oxygen. Having thus shown that only one-fifth 

 of the air was condensed by the explosion of ordinary air 



