3 S6 Dr. Austin on the 
to the refult of M, Berthollet’s experiments. If we take 
the fpecific gravities of thefe airs, given in Mr. Kir wan’s 
late publication, 
ico cubic inches contain 18,16 grains of alkaline air. 
. 30,535 — of phlogifticated air. 
. 2,613 — of inflammable air. 
According to M. Berthollet alkaline air is expanded upon 
decompofitiom from 1,7 to 3,3. Its fpecific gravity after de- 
compolition muff therefore be leftened in the fame proportion ; 
and 100 cubic inches will be found to contain only 9,355 
grains of alkaline air thus expanded. I11 what proportion muft 
the phlogifticated and inflammable airs be, in order to form a 
mixture of this fpecific gravity ? 
Let x reprefent the number of grains of phlogifticated air 
in 100 cubic inches of the mixture : then 9,355 — ^ will ex- 
prefs the number of grains of inflammable air. As the weight 
of one cubic inch is to a cubic inch, fo will the weight of 
either air in the mixture be to the cubic inches of that air in 
the mixture ; and therefore the weight of a cubic inch 
of phlogifticated air, or which is the fame, >30535 flaall be 
which miift be the number of cubic 
to 1 , as x is to 
X 
.30535 
inches of phlogifticated air in 100 cubic inches of the mixture; 
and the weight of a cubic inch of inflammable air, that is, 
or ,02613 : 1 :: o, 355 -x : ~ the cubic inches 
100 J ,02613 
of inflammable air in 100 cubic inches of the mixture. Thus 
we have an expreftion for the cubic inches of each air ; thefe 
two quantities taken together are equal to 100 cubic inches by 
fuppofition. We have then, 
A X 
i$°535 
