ARGON, A NEW CONSTITUENT OF THE ATMOSPHERE. 37 



It will be noticed that this is the theoretical ratio for a iiioiiatomic <fas, that is, 

 a gas ill which all enei'gy imparted to it in raising its temperature at constant 

 volume is expended in generating translation al iiH^tion. 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 obser\ations Avill be dis- 

 cussed later. 



15. Attempts to Induce Chemical Cojibina'jion. 



A great number of attempts were made to induce chemical combination with 

 the argon obtained by use of magnesinm, 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 the name, argon. Tiiese will be detailed in order. 



(a) Oxygen in preseTwe of caustic alkali. — This need m)t be fui-ther 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 pi'esent, and argon a[)- 

 [)eared 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 plati- 

 num wires, carrying pointed poles of gas-cai-bon. Hydrogen was next admitted 

 until atmospheric i)ressure had been obtained. 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 stopcocks, and a small U-tube with bulbs, 

 like that shown in Fig. 4 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 stopcock the level of water in the U-tube 

 remained unaltered. It may therefore be concluded that, in all probability, no com 

 biuation had occurred ; or that if it had, it was attended with no change of volume. 



(c) Chlorine. — Exactly similar experiments were performed with dry, and 

 afterwards with moist, chlorine. The chlorine had been stored over strong sulphu- 

 ric 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' spai'king, the volume of the gas, after cooling, was 



' Kundt and Warburg, Fogg. Ann., 127, p. 497, and 135, pp. 337 and 527, and 157, p. 353. 



