VII 



THE BURNING OF INFLAMMABLE AIR 



123 



accurately. This method of analysis had two advantages (i) 

 the hydrogen need not be pure, and (2) the volume of 

 hydrogen added need not be adjusted accurately. 



In the hands of Gay- Lussac, Berthollet, Cruikshank, and 

 others, Volta's eudiometer be- 

 came an important instrument, 

 not only for the estimation of 

 oxygen and hydrogen, but for 

 the examination and analysis 

 of other combustible gases. 



Water is produced by the 

 action of inflammable air on 

 metallic calces. The revivifi- 

 cation of metallic calces by in- 

 flammable air was discovered in 

 1785 by Priestley (Experiments 

 and Observations, 1786, VI. 5). 



By means of a burning 

 glass, he heated red lead in a 

 bell -jar inverted over water 

 and filled with the inflammable 

 gas. As soon as the red lead 

 became dry the inflammable 

 air was absorbed l and metallic 

 lead was produced ; no other 

 product was seen and Priestley 

 concluded that : 



red lead '+ inflammable air 

 (phlogiston) = lead, 



the inflammable air being re- 

 garded by him as pure phlo- 

 giston. 



1 101 volumes of the gas were 

 reduced to 2, which still consisted 

 of inflammable air (loc. cit. p. 7). 



FIG. 27 VOLTA'S EUDIOMETER. 



The funnel at the base was used 

 to collect the gas over water con- 

 tained in the trough C. The ring 

 AD was used to read off the posi- 

 tion of the meniscus, e, on the 

 graduated scales which enveloped 

 the greater part of the tube. Details 

 of the sparking-device are shown at 

 abc. 



