28 Mr. Davy’s Lecture on the Decomposition and Composition 
would be about .0184 grains troy ;* but .0184: .1384: : 
i 3.2 9: 100; and according to this estimation 100 parts of 
potash will consist of 86.7 basis, and 13.3 oxygene nearly. 
In the second experiment .07 grains of the basis absorbed 
at temperature 63° of Fahrenheit, and under pressure equal 
to 30.1 barometer inches, a quantity of oxygene equal in 
volume to 121 grain measures of mercury, and the proper 
corrections being made as in the former case, this gas would 
weigh .01189 grains. 
But as .07 + .01189= .08189: 07 : : 100 : 85.48 nearly, 
and 100 parts of potash will consist of 85.5 of basis and 14.5 
of oxygene nearly. And the mean of the two experiments will 
be 86.1 of basis to 13.9 of oxygene for 100 parts. 
In the most accurate experiment that I made on the com- 
bustion of the basis of soda .08 parts of the basis absorbed a 
quantity of oxygene equal to 206 grain measures of mercury ; 
the thermometer being at 56°Fahrenheit ; and the barometer 
at 29.4; and this quantity, the corrections being made as 
before for the mean temperature and pressure, equals about 
.02 grains of oxygene. 
And as .08 +.02 == .10: .08, : : 100: 80, and 100 parts of 
soda according to this estimation will consist of 80 basis to 
eo of oxygene. 
In all cases of slow combustion, in which the alkalies were 
not carried out of the tray, I found a considerable increase of 
weight, but as it was impossible to weigh them except in the 
* From experiments that I made in 1799* on the specific gravity of oxygene gas, 
it would appear that its weight is to that of water as 1 to 748, and to that of quicksilver 
as 1 to 10142. Researches Chem. and Phil. p. 9; and with this estimation, that dedu- 
ciblefrom the late accurate researches of Messrs. Allen and Pepys on the Combus- 
tion of the Diamond almost precisely agrees. Phil. Trans. 1807, page 275. 
