384 Dr. Austin on the 
Dr. Priestley. This change is accounted for by the for- 
mation of the alkali, which deprivingthe nitrous air of its phlo- 
giflicated part leaves a greater proportion of dephlogifticated 
air. 
This experiment alio fucceeds in atmofpheric air, though a 
longer time is neceffary to produce a fenfible alteration in the 
colours employed as tefts of the alkali; but the change is very 
evident in a day or two. Hence we may conclude, that when- 
ever iron ruffs in contadl with water in the open air, or in the 
earth, volatile alkali is formed. PhlogiAicated air is prefent 
in all parts of the terraqueous globe, and operations are con- 
ftantly going on, by which inflammable air is feparated from 
water, and perhaps from other bodies. Thus we may account 
for the frequent appearance of volatile alkali in the earth, par- 
ticularly where inflammable matters abound, among coals and 
volcanic productions, as alfo in animal and vegetable lubflances. 
When iron, water, and fulphur a£t upon each other in 
atmofpheric air, volatile alkali is produced. The eudiometer 
recommended bv Scheele is, for this reafon, incorrect. Some 
phlogifticated air difappears, and volatile alkali is formed. 
This method therefore feems to have milled that great che- 
mift in his anaiyfls of the atmofphere, and induced him to 
fuppofe, that the quantity of phlogiflicated air in the atmo- 
fphere is only 2f times that of dephlogifticated air. 
There is a combination of light inflammable air with ful- 
phur forming hepatic air. It has been cbferved by the cele- 
brated Mr. Kirwan, that if nitrous air be mixed with he- 
patic air volatile alkali will be formed. I have often repeated this 
experiment, and marked the formation of the volatile alkali by 
the change of the vegetable blue to a green colour. I11 hepatic 
air 
