186 



Prof. W. Eamsay and Dr. M. W. Travers. 



sufficed for the complete removal of all oxygen. The oxidised copper 

 was reduced between each operation by means of coal-gas. 



By closing the stop-cock b, and opening the stop-cock c, the gas- 

 holder A could be placed in communication with the apparatus in 

 which the preliminary absorption of nitrogen took place. By placing 

 weights on the top of the gas-holder, the nitrogen was driven through 

 the vessel M, and the U"^ ll ^ e N, both of which contained strong 

 sulphuric acid, into the tube G, which contained magnesium. This 

 tube was a piece of steam-barrel, 1*5 inches in diameter, connected at 



