ARGON, A NEW CONSTITUENT OF THE ATMOSPHERE. 



27 



cient idea of the method if we describe an experiment in which a tulei'ably good 

 account was Icept of the air and oxygen employed. The working vessel was a class 

 flask of abont 1500 o. c. capacity, and stood neck downwards over a large jar of 

 alkali. As in the small scale experiments the leading-in wires were insulated by 

 glass tubes, suitably bent and carried thi-ough the liquid up the neck. For the 

 greater part of the length iron pipes wei'e employed, but the internal exti'emities 

 were of platinum, doubled upon itself at the terminals from which the dischai-ge 

 escaped. The glass projecting tubes must be carried up for some distance above 

 the internal level of the liquid, but it is desirable that the arc itself should not be 

 much raised above that level. A general idea of the disposition of the electrodes 

 will be obtained from the figure (5). To ensure gas tightness these bends were 

 occupied by mercury. A tube for the supply or \vithdravval of gas was carried 

 in the same way through the neck. 



Fig. 5. 



The Ruhmkorff employed in this operation was one of medium size. When 

 the mixture was rightly proportioned and the arc of full length, the rate of absorp- 

 tion was about 700 c. c. per hour. A good deal of time was lost in starting, for 

 especially when there is soda on the platinum, the arc is liable to go out if length- 

 ened prematurely. After seven days the total quantity of air led in amounted to 

 7925 c. c. and of oxygen (prepared from chlorate of potash) 9137 c. c. On the 

 eighth and ninth days oxygen alone was added, of which about 500 c. c. was con- 

 sumed, while there remained about 700 c. c. in the flask. Hence the [)roportion in 

 which the air and oxygen combined was as 79 : 96. On the eighth day there was 

 about three hours' work, and the absorption slackened off to about one-quarter of 

 the previous rate. On the ninth day (September 8th) the rate fell off still more, 



