APPENDIX II TO CHAPTER V 155 



might cool. The mixture of argon and nitrogen remaining in 

 the system was pumped out through a Sprengel pump through 

 F, collected in a large test-tube and re-introduced into the gas- 

 holder B through the side tube G, which requires no description. 

 The magnesium tube was then replaced by a fresh one ; the 

 system of tubes was exhausted of air ; argon and nitrogen were 

 admitted from the gasholder B ; the copper tube and the mag- 

 nesium tube were again heated ; and the operation was repeated 

 till absorption ceased. It was easy to decide when this point 

 had been reached, by making use of the graduated cylinder H, 

 from which water entered the gasholder B. It was found 

 advisable to keep all the water employed in these operations, 

 for it became saturated with argon. If gas was withdrawn 

 from the gasholder, its place was taken by this saturated water. 

 By means of magnesium about 7 litres of nitrogen can be absorbed 

 in an hour. The changing of the tubes of magnesium, however, 

 takes some time ; consequently the largest amount absorbed in 

 one day was nearly 30 litres. 



From the result of a special quantitative experiment it may 

 be concluded, with probability, that argon forms approximately 

 1 per cent, of the atmospheric nitrogen. 



FIGURE 2 OXYGEN METHOD. 



The vessel A is a large globe of about 6 litres capacity and 

 stands in an inclined position. It is about half-filled with a 

 solution of caustic soda. The neck is fitted with a rubber stopper 

 B y provided with four perforations. Two of these are fitted 

 with tubes (7, Z), suitable for the supply of withdrawal of gas or 

 liquid. The other two allow the passage of the stout glass 

 tubes E, F, which contain the electrodes. For greater security 

 against leakage the interior of these tubes is charged with water 

 held in place by small corks, and the outer ends are cemented 

 up. The electrodes are formed of stout iron wires, terminated 

 by thick platinums G, H, triply folded together and welded at 



