220 LORD RAYLEIGH AND PROFESSOR W. RAMSAY ON ARGON, 
With this discharge, the rate of absorption of mixed gases is about 7 litres per hour. 
When the argon has accumulated to a considerable extent, the rate falls off, and after 
several days’ work, about 6 litres per hour becomes the maximum. In commencing 
operations it is advisable to introduce, first, the oxygen necessary to combine with 
the already included air, after which the feed of mixed gases should consist of about 
11 parts of oxygen to 9 parts of air. The mixed gases may be contained in a large 
gas-holder, and then, the feed being automatic, very little attention is required. 
When it is desired to determine the rate of absorption, auxiliary gas-holders of glass, 
graduated into litres, are called into play. If the rate is unsatisfactory, a determina- 
tion may be made of the proportion of oxygen in the working vessel, and the 
necessary gas, air, or oxygen, as the case may be, introduced directly. 
In re-starting the arc after a period of intermission, it is desirable to cut off the 
connection with the principal gas-holder. The gas (about two litres in amount) 
ejected from the working vessel by the expansion is then retained in the auxiliary 
holder, and no argon finds its way further back. The connection between the working 
vessel and the auxiliary holder should be made without india-rubber, which is hable 
to be attacked by the ozonized gases. 
The apparatus has been kept in operation for fourteen hours continuously, and 
there should be no difficulty in working day and night. An electric signal could 
easily be arranged to give notice of the extinction of the arc, which sometimes occurs 
unexpectedly ; or an automatic device for re-striking the arc could be contrived.— 
April, 1895.] 
9. Density of Argon prepared by means of Oxygen. 
A first estimate of the density of argon prepared by the oxygen method was 
founded upon the data recorded already respecting the volume present in air, on the 
assumption that the accurately known densities of “atmospheric” and of chemical 
nitrogen differ on account of the presence of argon in the former, and that during the 
treatment with oxygen nothing is oxidised except nitrogen. Thus, if 
D = density of chemical nitrogen, 
De . atmospheric nitrogen, 
Ca ¥ argon, 
® = proportional volume of argou in atmospheric nitrogen, 
the law of mixtures gives 
ad+(1—e)D=D 
or 
d=D+(D'—D)a. 
