46 On air heated 



within it was of the flandard of 1.4. This, however, 

 might have been tranfmitted through the water, as in 

 fome former experiments; but to prevent this I placed 

 the open end of the tube (which was a piece of a gun 

 barrel) in a bafon of iiiercury. Still, however, I found 

 after fome time the air was confiderably increafed in 

 quantity, and almoft as pure as the air of the atmofphere. 

 This, therefore, muft have come through the pores 

 of the veffel, which, however, when it was examined 

 in every method that I could think of, appeared to be 

 perfectly air-tight. 



Experiments relatitig to PhlogijVicated Air. 



There is a peculiar difficulty refpeding the conflitution 

 of phlogifticated air ; fince fome of my experiments 

 feem to fhew that it contains the principle of acidity, 

 and others that it is intirely free from it ; fo that except- 

 ing its bafe (which is like that of all other kinds of air, 

 viz. water) it confifts of nothing but fome modification 

 of phlogifton. 



When dephlogifticated air is decompofed together with 

 much inflammable air, phlogifticated air is produced ; 

 and in this cafe there does not appear to be any thing 

 befides this phlogifticated air into which the oxygen of 

 the dephlogifticated air can enter. That the water which 

 is found aiter this experiment does not contain any 

 oxygen, 1 think 1 have fufficiently demonftrated ; fmce 

 it is not contained in finery cinder, where the new the- 

 ory lodges it. 



Alfo when rufted iron becomes black by long ex- 

 pofure to inflammable air, and is thereby converted in- 

 to phlogifticated air, the oxygen in the ruft cannot be 

 found except in this phlogifticated air. 



Notwithftanding 



