A NEW CONSTITUENT OF THE ATMOSPHERE. 221 
In this formula D’—D and @ are both small, but they are known with fair 
accuracy. From the data already given for the experiment of September 8th 
whence, if on an arbitrary scale of reckoning D = 2-2990, D’ = 2°3102, we find 
d = 3378. Thus if N, be 14, or O, be 16, the density of argon is 20°6. 
Agein, from the January experiment, 
75:0 
7308 

oo 
whence, if N = 14, the density of argon is 20°6, as before. There can be little doubt, 
however, that these numbers are too high, the true value of « being greater than is 
supposed in the above calculations. : 
A direct determination by weighing is desirable, but hitherto it has not been 
feasible to collect by this means sufficient to fill the large globe (§ 1) employed for 
other gases. A mixture of about 400 cub. centims. of argon with pure oxygen, 
however, gave the weight 2°7315, 0°1045 in excess of the weight of oxygen, viz., 
2°6270. Thus, if « be the ratio of the volume of argon to the whole volume, the 
number for argon will be 
2°6270 + 0°1045/a. 
The value of «, being involved only in the excess of weight above that of oxygen, 
does not require to be known very accurately. Sufficiently concordant analyses by two 
methods gave « = 01845; whence, for the weight of the gas we get 3°193; so that 
if O = 16, the density of the gas would be 19°45. An allowance for residual nitrogen, 
still visible in the gas before admixture of oxygen, raises this number to 19°7, which 
may be taken as the density of pure argon resulting from this determination.* 
10. Density of Argon Prepared by means of Magnesiui.t 
It has already been stated that the density of the residual gas from the first and 
preliminary attempt to separate oxygen and nitrogen from air by means of mag- 
nesium was 19086, and allowing for contraction on sparking with oxygen the density 
is calculable as 20°01. The following determinations of density were also made :— 
(a.) After absorption in glass tubes, the water circulator having been used, and 
subsequent circulation by means of mercury circulator until rate of contraction had 
* [The proportion of nitrogen (4 or 5 per cent. of the volume) was estimated from the appearance of 
the nitrogen lines in the spectrum, these being somewhat more easily visible than when 3 per cent. 
of nitroger was introduced into pure argon (§ 8).—April, 1895. ] 
+ See Addendum, p. 237. 
