594 Journal of the Asiatic Society of Bengal, [December, 1910. 



Experimental. 



Preparation of Nitrogen free from Nitric Oxide. 

 Nitrogen as ordinarily prepared by heating a mixture of 



ammonium chloride and sodium nitrite contains a good deal of 



nitric oxide which is not wholly removed by ferrous sulphate, 

 as pointed out by Wright. In fact even when four or five wash 

 bottles of the solution are employed, the solution in the last 

 bottle still gives the characteristic black colour. Gibbs (Ber., 

 10, 1387) recommended the addition of potassium bichromate 

 to oxidise the nitric oxide to nitric acid, but we have seen 

 potassium bichromate fails to destroy all the nitric oxide 

 evolved. Wright (loc. cit.) recommended the use of alkaline 

 sulphites which convert nitric oxide to nitrous oxide. His 

 method is extremely tedious, and moreover the presence of 

 nitrous oxide in nitrogen is not desirable. The best method of 

 removing the last traces of nitric oxide is to pass the nitrogen 

 over red hot copper. The nitrogen is prepared in the usual 

 way and collected in a gas-holder after removing the greater 

 part of the nitric oxide by means of ferrous sulphate. The gas 

 is then dried and passed through a combustion tube filled with 

 bright copper turnings, and heated in a combustion furnace. 

 The tube is connected with Muencke's wash-bottle containing 

 ferrous sulphate solution, which now shows no coloration, and 

 the nitrogen thus freed from nitric oxide is collected in a second 

 gas-holder. The gas thus obtained, even when passed for five 

 or six hours through ferrous sulphate, does not in the least 

 affect its colour. Of course nitrogen free from nitric oxide 

 may be prepared from air, but as the complete removal of all 

 oxygen from large quantities of air requires long time and 

 many tubes filled with copper, the method described above 

 seems to be the best and easiest for the purpose of preparing 

 large quantities of nitrogen absolutely free from nitric oxide. 



Nitrogen and Hydrogen in presence of Iron. 



The nitrogen was then mixed with pure hydrogen in a gas- 

 holder in the proportion of one to three, also in the proportion 

 of one to six. Powdered iron (Merck) was taken in a combus- 

 tion tube and heated in a tube heater. By means of a T-tube 

 the tube containing iron was joined to the wash-bottle con- 

 nected with the gas-holder and also to the wash-bottle con- 

 nected with a hydrogen Kipp. The gases were finally passed 

 before entering the tube containing iron through strong sulr 

 phuric acid in order to arrest any adventitious ammonia, and 

 also through water as Ramsay and Young used moist gases. 

 The other end of the tube is connected with a delivery tube 

 which dips in a Nessler's solution. 



