A NEW CONSTITUENT OF THE ATMOSPHERE, 219 
The oxygen, being too much for convenient treatment with hydrogen, was usually 
absorbed with copper and ammonia, and the residual gas was then worked over again 
as already described in an apparatus constructed upon a smaller scale. 
It is worthy of notice that with the removal of the nitrogen, the arc-discharge from 
the dynamo changes greatly in appearance, bridging over more directly and in a nar- 
rower band from one platinum to the other, and assuming a beautiful sky-blue colour, 
instead of the greenish hue apparent so long as oxidation of nitrogen is in progress. 
In all the large-scale experiments, an attempt was made to keep a reckoning of the 
air and oxygen employed, in the hope of obtaining data as to the proportional 
volume of argon in air, but various accidents too often interfered. In one successful 
experiment (January, 1895), specially undertaken for the sake cf measurement, the 
total air employed was 9250 cub. centims., and the oxygen consumed, manipulated 
with the aid of partially de-aerated water, amounted to 10,820 cub. centims. The 
oxygen contained in the air would be 1942 cub. centims. ; so that the quantities of 
“atmospheric nitrogen” and of total oxygen which enter into combination would be 
7308 cub. centims., and 12,762 cub. centims. respectively. This corresponds to 
N + 1°75O0—the oxygen being decidedly in excess of the proportion required to form 
nitrous acid—2HNO,, or H,0+N,+30. The argon ultimately found on absorption 
of the excess of oxygen was 75'0 cub. centims., reduced to conditions similar to 
those under which the air was measured, or a little more than 1 per cent. of the 
‘atmospheric nitrogen” used. It is probable, however, that some of the argon was 
lost by solution during the protracted operations required in order to get quit of the 
last traces of nitrogen. 
[In recent operations at the Royal Institution, where a public supply of alternating 
current at 100 volts is available, the scale of the apparatus has been still further 
‘increased. 
The capacity of the working vessel is 20 litres, of which about one half is 
occupied by a strong solution of caustic soda. The platinum terminals are very 
massive, and the flame rising from them is prevented from impinging directly upon 
the glass by a plate of platinum held over it and supported by a wire which passes 
through the rubber cork. In the electrical arrangements we have had the advantage 
of Mr. SwInBuRNE's advice. The transformers are two of the “hedgehog” pattern, 
the thick wires being connected in parallel and the thin wires in series. In order to 
control the current taken when the arc is short or the platinums actually in contact, 
a choking-coil, provided with a moyable core of fine iron wires, is inserted in the 
thick wire circuit. In normal working the current taken from the mains is about 
22 amperes, so that some 24 h. p. is consumed. At the same time the actual 
voltage at the platinum terminals is 1500. When the discharge ceases, the voltage 
at the platinum rises to 3000,* which is the force actually available for re-starting 
the discharge if momentarily stopped. 
* A still higher voltage on open circuit would be preferable. 
7, 0! 
