ARGON, A NEW CONSTITUENT OK THE ATMOSPHERE. 29 



regards its upper portion, in waiei-. In tlie luter expciitncnts ;i glolie of about 

 7 litres capacity, intended foi- sliowintr tlie eonilnistion of phosphorus in oxygen, 

 was employed. Tiie ueclv was inclined u[)wards at an angle of about 45" and was 

 closed air-tight by a coi'k, through which weie led (he necessary tubes. The lower 

 part of the globe is occupied by about .'! litres of a 5 per cent solution of caustic 

 soda, the solution rising to within about half an inch of tlie platinum terminals. The 

 upper half of the globe is kept cold by water a[)plied externally. With this 

 apparatus an absorption of 3 litres of mixed gas per hour can be attained., — about 

 3000 times the rate at which Cavendish could work. 



9. Density of Arciox Prepared by Means of OxY(iEN-. 



No direct determination has yet been made of the density of argon isolated by 

 the oxygen method, but a fair estimate may be founded u[)on the <lata i-elating to 

 the volumes ali'eady I'ecoi-ded, on the assumption that the accui-ately known densi- 

 ties of atmospheric and cheniical nitrogen, differ on account of the presence of argon 

 iu the foi'mer and that during the treatment with o.xygen nothing is oxydized ex- 

 cept nitrogen. Thus if 



D = density of chemical nitrogen, 



D — " atmospheric nitrogen, 



d = " argon, 



T, = proportional volume of argon in atmospheric nitrogen, 



the law of mixtures gives : 



Ld + (i - L) D = D' 



D' - D 



or d = D H 



L 



In this formula D' — D and L are both small, !)ut they are known with fair 

 accuracy. From the data ali'eady given 



65 



•79 X 7925 

 whence if (on an arbiti-aiy scale of reckoning) D = 'J.2990, D' = 2.3102, we find 

 d = 3.378. Thus if N, be 14 or O2 be 16, the density of argon is 20.6. 



It had been hoped that further data might have been obtained respecting the 

 proportional volume of argon in atmospheric nitrogen, but accidents difficult to 

 avoid in t)perations so i-isky and so extended have hitherto stood in the way. 



10. Density of Argon Prepared by Means of Magnesium. 



It has already been stated that the density of the residual gas from the first 

 and preliminary attempt to sepaivate oxygen and iiitix.geu fiom air by means of 



