A NEW CONSTITUENT OF THE ATMOSPHERE. 231 
correct. In the wide tube, C,:C,::1°61:1. Hence the conclusion must be 
accepted that the ratio of specific heats is practically 1°66 : 1. 
Tt will be noticed that this is the theoretical ratio for a monatomic gas, that is, a 
gas in which all energy imparted to it at constant volume is expended in effecting 
translational motion. The only other gas of which the ratio of specific heats has 
been found to fulfil this condition is mercury at a high temperature.* The extreme 
importance of these observations will be discussed later. 
15. Attempts to induce Chemical Combination. 
A great number of attempts were made to induce chemical combination with 
the argon obtained by use of magnesium, but without any positive result. In such a 
case as this, however, it is necessary to chronicle negative results, if for no other 
reason but that of justifying its name, ‘“‘argon.” These will be detailed in order. 
(a) Oxygen in Presence of Caustic Alkali.—This need not be further discussed 
here; the method of preparing argon is based on its inactivity under such con- 
ditions. | 
(b) Hydrogen.—It has been mentioned that, in order to free argon from excess of 
oxygen, hydrogen was admitted, and sparks passed to cause combination of hydrogen 
and oxygen. Here again caustic alkali was present, and argon appeared to be 
unaffected. 
A separate experiment was, however, made in absence of water, though no special 
pains was taken to dry the mixture of gases. The argon was admitted up to half an 
atmosphere pressure into a bulb, through whose sides passed platinum wires, carrying 
pointed poles of gas-carbon. Hydrogen was then admitted until atmospheric pressure 
had been attained. Sparks were then passed for four hours by means of a large 
induction coil, actuated by four storage cells. The gas was confined in a bulb closed 
by two stop-cocks, and a small V-tube with bulbs was interposed, to act as a gauge, 
so that if expansion or contraction had taken place, the escape or entry of gas would 
be observable. The apparatus, after the passage of sparks, was allowed to cool to 
the temperature of the atmosphere, and, on opening the stop-cock, the level of water 
in the V-tube remained unaltered. It may therefore be concluded that, in all 
probability, no combination has occurred ; or, that if it has, it was attended with no 
change of volume. 
(c) Chlorine.—Exactly similar experiments were performed with dry, and after- 
wards with moist, chlorine. The chlorine had been stored over strong sulphuric acid 
for the first experiment, and came in contact with dry argon. Three hours sparking 
produced no change of volume. A drop of water was admitted into the bulb. After 
four hours sparking, the volume of the gas, after cooling, was diminished by about 
* Konpt and Warsure, ‘ Pogg. Ann.,’ 157, p. 353, 1876. 
