EADIATION or HEAT BY GASEOUS MATTEE. 
67 
mentioned does not exceed 
11 , 
while the absorption of hydrobromic acid of the same tension amounts to 
30. 
The hydrobromic acid was prepared by the action of glacial phosphoric acid (for a 
pure specimen of which I have to thank my friend Dr. Feankland) on bromide of 
potassium. If the above figures represent the truth (and I have spared no pains to 
arrive at a right conclusion), w’e have here a most striking instance of transparency to 
light and opacity to obscure heat being promoted by the self-same chemical act 
H- 
In the following Table is given the absorption of a number of gases at a common 
tension of one atmosphere. 
Table I. 
Name. Absorption. 
Air I 
Oxygen I 
Nitrogen I 
Hydrogen 1 
Chlorine 39 
Hydrochloric acid ... 62 
Carbonic oxide .... 90 
Carbonic acid .... 90 
Nitrous oxide 355 
Sulphuretted hydrogen . 390 
Marsh-gas 403 
Sulphurous acid . . . . 710 
Olefiant gas 970 
Ammonia 1195 
Air, oxygen, nitrogen, and hydrogen are all set down as equal to unity in the above 
Table. I do not mean thereby to affirm that there are no differences between these gases 
as regards their powers of absorption, but that the most powerful and delicate tests which 
I have hitherto applied have failed to establish a difference in a satisfactory manner. It 
is not improbable that the action of these gases may turn out to be less even than I have 
found it. For who can say that the best-constructed drying apparatus is really perfects 
Besides, stopcocks must be greased, and hence may contribute an infinitesimal impurity 
to the air passing through them. I cannot even say that sulphuric acid, however pure, 
may not deliver a modicum of vapour to the cun’ent of air passing through it. At all 
* A layer of liquid bromine, sufficiently opake to intercept the entire luminous rays of a gas-flame, is 
highly diathermanous to its obscure rays. An opake solution of iodine in bisulphide of carbon behaves 
similarly. — The details of these experiments shall be published in due time: 'they were publicly shown in 
my lectures many months ago. — June 13th, 1862. 
K 2 
