1895.] 



The Expansion of Argon and of Helium. 



61 



of Chappuis* was performed entirely at temperatures below 100°, the 

 •gases employed being hydrogen, nitrogen, and carbon dioxide. The 

 experiments of Grunmach and Pernetf were also conducted at tem- 

 peratures below 100°. Crafts^ has compared the readings of a 

 number of mercury thermometers with those obtained by Regnault 

 and by himself with a hydrogen thermometer. Wiebe and B6ttcher§ 

 have determined the boiling points of a number of liquids in terms of 

 the expansion of air. 



In connexion with the work on argon and helium in progress at 

 University College, it was suggested by Professor Ramsay that a 

 comparison should be made between the leadings shown by thermo- 

 meters containing respectively argon, helium, hydrogen, and air. 

 The temperatures used were : the melting point of ice and the boiling 

 points of water, chlorbenzene, aniline, quinoline, and bromnaph- 

 thalene respectively. The gas to be experimented upon was contained 

 in a bulb about 12 cm. long and 22 cm. wide, sealed at one end to a 

 fine capillary tube about 12 cm. long ; this, in turn, was connected 

 with a piece of thick-walled glass tubing, having an inside diameter 

 •of about 0*2 cm. The wider tube was fitted with a stopcock, for con- 

 venience in filling the bulb, and at its lower end was connected with 

 a stout rubber tube, which led to a movable mercury reservoir. Near 

 the point at which the fine capillary tube was sealed to the wider tube, 

 a mark was made on the latter : the mercury was always brought up 

 to this mark in the experiments, and the difference of level in the 

 tube and in the mercury reservoir was read off, with the aid of a 

 telescope, from a glass scale graduated in millimetres, which stood 

 directly behind the apparatus. 



The bulb of the gas thermometer was heated in one of Ramsay and 

 Young's vapour jackets, the mark on the stem being just below the 

 •cork closing the bottom of the jacket : consequently a small portion 

 of the stem was not heated to the temperature of the vapour in the 

 jacket. The error thus introduced "was taken into account, l^o part 

 of the mercury column which compressed the gas in the bulb was 

 heated more than a few degrees above the temperature of the room, 

 screens being employed to cut off radiation : the temperature of the 

 mercury was, however, always determined as accurately as circum- 

 stances would permit, and the readings reduced to 0°. In order to 

 protect the thermometer bulb from the effects of radiation, the jacket 

 was shielded by an outer cylinder of thick j)asteboard, with an air 

 space between. 



* < Archives de Geneve [3], vol. 20, pp. 5— 36, 153—179, 248—262 ; also ' Traites 

 «et Memoires du Bureau International,' vol. 6. 

 t ' Metronomische Beitrage,' No. 3. 

 X ' Comptes Kendus,' vol. 95, pp. 836—839. 

 •§ ' Zeitschrift fur Instrumentenkunde,' vol. 10, pp. 16 and 233. 



