42 C.C. NATURAL HISTORY SOCIETY, 



Ammonia "oooSo 



Ozone "00015 



Nitric Acid "00015 



By passing the air through a solution of Potash and then 

 through strong Sulphuric Acid all the gases (except the Nitrogen 

 and Oxygen) may be absorbed. 



By adding sufficient Hydrogen Gas to these and passing an 

 electric spark through the mixture the Oxygen combines with the 

 Hydrogen to form water. The gaseous residue over and above 

 any excess of Hydrogen was considered to be Nitrogen. 



Another method of obtaining Nitrogen from the air is by 

 burning Phosphorus in air which has been purified by passing 

 it through potash solution and strong Sulphuric Acid. The 

 Oxygen all combines with the Phosphorus, and since the residue 

 extinguishes a lighted taper, has no effect on lime water, does not 

 smell, and will not burn in air, it was called Nitrogen, these being 

 the tests which distinguished that gas from all others. 



The first suspicion that this residue contained some other 

 additional substance arose from the very careful researches carried 

 out by Lord Rayleigh on the density of the principal gases. He 

 found that a volume of Nitrogen prepared from the air by the above 

 methods weighed slightly more than the same volume of Nitrogen 

 prepared by heating Ammonium Nitrite and other chemical com- 

 pounds. 



This difference was so very small that elaborate means were 

 taken to ensure freedom from errors of manipulation and observa- 

 tion. Time after time the experiments were repeated. The 

 " chemical " Nitrogen was prepared in every possible way, but in 

 every case this difference between it and " atmospheric " Nitrogen 

 was observable. 



Lord Rayleigh was entirely at a loss for a probable explanation, 

 and in 1893 invited the opinion of others on the point. Noi 

 explanation was forthcoming, but it was pointed out that in 1785 1 

 Cavendish, in experimenting to see whether all or only part of the] 

 Nitrogen in the air would combine with Oxygen to form the brown I 

 Oxide of Nitrogen, came to the conclusion that all, except a nn'mi/e\ 

 quantity, probably tiot more than I-I20th part of the total volume, 

 would do so. 



Lord Raleigh at once repeated Cavendish's experiment, using] 

 an improved form of apparatus and found an obstinate residue] 

 almost of the same amount as Cavendish. The residue, though it I 



