268 Lord Rayleigh and Prof. Ramsay. [Jan. 31, 



of " chemical " nitrogen from the same source, magnesium nitride, 

 which had been prepared by passing " atmospheric " nitrogen over 

 ignited magnesium, may here be recorded. The sample differed from 

 that previously mentioned, inasmuch as it had not been subjected to 

 treatment with red-hot copper. After treating the nitride with water, 

 the resulting ammonia was distilled off, and collected in hydrochloric 

 acid ; the solution was evaporated by degrees, the dry ammonium 

 chloride was dissolved in water, and its concentrated solution added 

 to a freshly-prepared solution of sodium hypobromite. The nitrogen 

 was collected in a gas-holder over water which had previously been 

 boiled, so as, at all events partially, to expel air. The nitrogen 

 passed into the vacuous globe through a solution of potassium hydr- 

 oxide, and through two drying-tubes, one containing soda-lime, and 

 the other phosphoric anhydride. 



At 18-38 C. and 754'4 mm. pressure, 162'843 c.c. of this nitrogen 

 weighed 0' 18963 gram. Hence, 



Weight of 1 litre at C. and 760 mm. pressure = T2521 gram. 



The mean result of the weight of 1 litre of " chemical " nitrogen 

 has been found to equal 1'2505. It is therefore seen that " chemical " 

 nitrogen, derived from " atmospheric " nitrogen, without any exposure 

 to red-hot copper, possesses about the usual density. 



Experiments were also made, which had for their object to prove 

 that the ammonia produced from the magnesium nitride is identical 

 with ordinary ammonia, and contains no other compound of a basic 

 character. For this purpose the ammonia was converted into 

 ammonium chloride, and the percentage of chlorine determined by 

 titration with a solution of silver nitrate which had been standardised 

 by titrating a specimen of pure sublimed ammonium chloride. The 

 silver solution was of such a strength that 1 c.c. precipitated the 

 chlorine from 0'001701 gram of ammonium chloride. 



1. Ammonium chloride from orange-coloured sample of magnesium 

 nitride contained 66'35 per cent, of chlorine. 



2. Ammonium chloride from blackish magnesium nitride contained 

 66'35 per cent, of chlorine. 



3. Ammonium chloride from nitride containing a large amount of 

 nnattacked magnesium contained 66'30 per cent, of chlorine. 



Taking for the atomic weights of hydrogen H = 1'0032, of nitrogen 

 N = 14'04, and of chlorine Cl = 35*46, the theoretical amount of 

 chlorine in ammonium chloride is 66'27 per cent. 



From these results that nitrogen prepared from magnesium 

 nitride, obtained by passing "atmospheric" nitrogen over red-hot 

 magnesium has the density of " chemical " nitrogen, and that 

 ammonium chloride, prepared from magnesium nitride, contains 

 practically the same percentage of chlorine as pure ammonium chlo- 

 ride it may be concluded that red-hot magnesium withdraws from 



