18 Improvements in Physical Science (Jan. 
two atoms azote. This gives us 100 parts of air composed by 
weight of 
Oxygen ..... 22°222 | Rootes. ea er eae 
These two suppositions obviously give us the specific gravities 
above stated by a common algebraic equation; but if we suppose 
the weight of an atom of azote to be 1°803, as I have stated it in 
a preceding number of the Annals of Philosophy, in that case the 
specific gravities would turn out differently. Our author, no 
doubt, borrowed 1°75 as the weight of an atom of azote, from Dr. 
Wollaston’s paper on chemical equivalents. 1 am disposed to con- 
sider it as nearer the truth than my own number. 
‘The specific gravity of hydrogen gas is deduced by calculation 
from that of ammonia, which has been shown to consist of three 
volumes of hydrogen and one of azote condensed into two volumes, 
and the specific gravity of ammoniacal gas is 0°5502. From these 
data the specific gravity of hydrogen gas is shown to be 0:0694. 
The only doubt in this calculation is whether the specific gravity of 
azotic gas, as assumed, be correct. At all events, 1 have no 
doubt that-it is nearer the truth than the previous results obtained 
by weighing. 
It deserves attention, that if the specific gravity of oxygen, 
azotic, and hydrogen gases be 
Oxygen.... 11111 | Azotic..... 0:9722 | Hydrogen .. .0°0694 
Then oxygen is just 16 times heavier than hydrogen, and azotic 
gas 14 times heavier. Water is a compound of 1 hydrogen + 8 
oxygen by weight. Supposing it composed of one atom hydrogen 
and one atom oxygen, then the atom of oxygen is eight times 
heavier than the atom of hydrogen. 
The specific gravity of chloric gas he makes 25. That of other 
substances is founded entirely upon calculation. His method is to 
find the weight of an atom of the substance in question, and to 
multiply it by half the specific gravity of oxygen gas ; the product 
gives the specific gravity of the substance, supposing it in the state 
of gas: 
Jodine.......... 8611111 or 124 times that of hydrogen. 
Carbon: since .... O'4166 12 ditto. 
Sulphure .\s:e56 «8s WLLL 16 ditto. 
Phosphorus ..... 0°9721 14 ditto. 
Calcium ......«. 1°8888 20 ditto. 
Sodium ic. cise 1°6666 24 ditto, 
Tron. +6 siewelaas ax 1°9444 28 ditto. 
ZAG hd icdiwit sp 2°2222 32 ditto. 
-. Potassium ....... Ea bb br 40 ditto, 
Barytium ....... 4°8611 70. ditto. 
On this table I may make a few remarks. He considers the 
‘weight -of an atom of iodine 155. This agrees very nearly with 
