relating to Air and Water, 293 



much* This lafl circumftance, however, fome of my experi- 

 ments may ferve to explain. Whenever I had no more water 

 than was fufficient for the produ(5lion of the air, there was 

 never any fenfible quantity of uncombined fixed air mixed with 

 the inflammable air from charcoal. This was particularly the 

 cafe when I produced the air by means of a burning lens in an 

 exhaufted receiver, and alfo in an earthen retort with the appli- 

 cation of an intenfe heat. I therefore prefume, that when the 

 fleam tranfmitted through the hot tube containing the charcoal 

 was very copious, the fixed air in the produce was greater than. 

 it would otherwife have been. The extremes that I have ob- 

 ferved in the proportion of the fixed to the inflammable air have 

 been from one-twelfth to one-fifth of the whole. As I gene- 

 rally produced this air, the latter was the ufual proportion ; and 

 this was exclufive of the fixed air that was intimately combined 

 with the inflammable air, and which could not be feparated 

 from it except by decompofition with dephlogiflicated air ; and 

 this combined fixed air I fometimes found to be one-third of the 

 whole mafs, though at other times not quite fo much. 



To afcertain this, I mixed one meafure of this inflammable 

 air from charcoal (after the uncombined fixed air had been fepa- 

 rated from it by lime-water) with one meafure of dephlogifli- 

 cated air, and then fired them by the ele(^ric fpark. After this 

 I always found that tlie air which remained made lime-water 

 very turbid, and the proportion in which it was now dimi- 

 nifhed, by wafliing in lime-water, fhewed the quantity of 

 fixed air that had been combined with the inflammable. That 

 the fixed air is not generated in this pr.ocefs, is evident from 

 there being no fixed air found after the explofion of dephlogifti- 

 cated ail* aud inflammable air from iron. 



Not with- 



