190 LORD RAYLEIGH AND PROFESSOR W. RAMSAY ON ARGON, 
It is of interest to compare the density of nitrogen obtained from chemical com- 
pounds with that of oxygen. We have N,:O, = 2'2996 : 2°6276 = 0°87517 ; so that 
if O, = 16, N, = 14:003. Thus, when the comparison is with chemical nitrogen, 
the ratio is very nearly that of 16:14. But if “atmospheric nitrogen” be substituted, 
the ratio of small integers is widely departed from. — 
The determination by Stas of the atomic weight of nitrogen from synthesis of 
silver nitrate is probably the most trustworthy, inasmuch as the atomic weight of 
silver was determined with reference to oxygen with the greatest care, and oxygen is 
assumed to have the atomic weight 16. If, as found by Stas, Ag NO,:Ag=1°57490:1, 
and Ag:O = 107'930:16, then N:O = 14:049 : 16. . 
To the above list may be added nitrogen, prepared in yet another manner, whose 
weight has been determined subsequently to the isolation of the new dense constituent 
of the atmosphere. In this case nitrogen was actually extracted from air by means 
of magnesium. The nitrogen thus separated was then converted into ammonia by 
action of water upon the magnesium nitride, and afterwards liberated in the free 
state by means of calcium hypochlorite. The purification was conducted in the usual 
way, and included passage over red-hot copper and copper oxide. The following was 
the result :— 

Globe empty, October 30, November 5. . . . . 2°82313 
GlobesullOctober!s = cee eee Seg, 6 O2BO5 
Weightiofsoas) <2 cia. cy eulir Goeiaee ty) epee OOS 
It differs imappreciably from the mean of other results, viz., 2°2990, and is of 
special interest as relating to gas which, at one stage of its history, formed part of 
the atmosphere. 
Another determination with a different apparatus of the density 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 im hydrochloric acid; the 
solution was evaporated to dryness; 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 hydroxide, and through two 
drying-tubes, one containing soda-lime, and the other phosphoric anhydride. 
At 18°38° C, and 754°4 mgs. pressure, 162°843 cub. centims. of this nitrogen 
weighed 0°18963 gram. Hence :— 
Weight of 1 litre at 0° C. and 760 millims. pressure . . . 1°2521 gram. 
