1896.] On some Physical Properties of Argon and Helium. 199 



method of Cavendish had not been reached, although a preliminary 

 resnlt (19*7) obtained from a mixture of argon and oxygen* went far 

 to show that the densities of the gases prepared by the two methods 

 were tbe same. In order further to test tbe identity of the gases, it 

 was thought desirable to pursue the question of density ; and I deter- 

 mined, as the event proved, somewhat rashly, to attempt large scale 

 weighings of pure argon with the globe of 1800 c.c. capacity 

 employed in former weighings of gasesf which could be obtained in 

 quantity. 



The accumulation of the 3 litres of argon, required for convenient 

 working, involved the absorption of some 300 litres of nitrogen, or 

 about 800 litres of the mixture with oxygen. This was effected at 

 the Royal Institution with the apparatus already described,^ and 

 which is capable of absorbing the mixture at the rate of about 

 7 litres per hour. The operations extended themselves over nearly 

 three weeks, after which the residual gases amounting to about 

 10 litres, still containing oxygen with a considerable quantity of 

 nitrogen, were removed to the country and transferred to a special 

 apparatus where it could be prepared for weighing. 



For this purpose the purifying vessel had to be arranged some- 

 what differently from that employed in the preliminary absorption 

 of nitrogen. When the gas is withdrawn for weighing, the space left 

 vacant must be filled up with liquid, and afterwards when the gas is 

 brought back for repurification, the liquid must be removed. In 

 order to effect this, the working vessel (Fig. 7)§ communicates by 

 means of a siphon with a 10-litre " aspirating bottle," the ends of 

 the siphon being situated in both cases near the bottom of the liquid. 

 In this way the alkaline solution may be made to pass backwards 

 and forwards, in correspondence with the desired displacements of 

 gas. 



There is, however, one objection to this arrangement which requires 

 to be met. If the reserve alkali in the aspirating bottle were allowed 

 to come into contact with air, it would inevitably dissolve nitrogen, 

 and this nitrogen would be partially liberated again in the working 

 vessel, and so render impossible a complete elimination of that gas 

 from the mixture of argon and oxygen. By means of two more 

 aspirating bottles an atmosphere of oxygen was maintained in the 

 first bottle, and the outermost bottle, connected with the second by a 

 rubber hose, gave the necessary control over the pressure. 



Five glass tubes in all were carried through the large rubber cork 

 by which the neck of the working vessel was closed. Two of these 



* Loc. cit., p. 221. 



f 'Koy. Soc. Proc.,' February, 1888; February, 1892; March, 1893. 

 % * Phil. Trans.,' loc. ext., p. 219. 

 § ' Phil. Trans.,' loc. ext., p. 218. 



