14 ARfiON, A NEW CONSTITUENT OF THE ATMOSPHERE. 



oxide Jiiul alfsorht'd by the pliosplmiic peiito.xiile. A gauge attae-lied to a SiJi-eiigel's 

 pump, connected witli the appaiatus, .showed when a vacuum had been reached. 

 A quantity of nitrogen was tlieii mea.sured in E, and admitted into contact with 

 the red-hot magnesium. Absorption took place lapidly at first and then slowly as 

 shown liy the gauge on the Sprengel's i)ump. .\ iVoli (piantity was tlien measured 

 and admitted, and these operations wei-e i-epeated until no more could be absorl»ed. 

 The system of tubes was then pumped empty by means of the Sprengel's pump, 

 and the gas was collected. The magnesium tube was then detached and replaced 

 by another. The unabsorbed gas was returned to the measuring-tube by a device 

 shown in tlie figure (G), and the absorption recommenced. After 1094 cubic 

 centimetres of gas had thus been treated, thei'e was left about 50 cubic centimetres 

 of gas, which resisted rapid absoi-ption. It still contained nitrogen, howevei", 

 judging by the diminution of volume which it e.xperienced when allowed to stand 

 in contact with ledliot magnesium. Its density was, nevertheless, determined by- 

 weighing a small bulb of about 40 cubic centimetres capacity first with air, and 

 afterwards with the gas. The data are these : 



(a) Weight of bulb and air — that of glass counterimise 0.8094 gramme 



Weight of bulb alone — " " " 0.7588 " 



Weight of air 0.0506 gramme 



(b) Weight of bulb and gas — that of glass counterpoise 0.8108 gramme 



Weight of bulb alone— " " '" 0.7588 " 



Weight of gas 0.05 20 gramme 



Taking as the weight of a litre of air 1.29347 gramme, the mean of the latest 

 results, and of oxygen (=10) I.429(J1 gramme,' the density of the residual gas 

 is 14.88. 



' The results on which this and the subsequent calculations are based are as follows (the 

 weights are those of i litre) : 



Air. Oxygen. 



Regnault 129349 1.43011 



Von Jolly 1.29383 1.42971 



Leduc 1.29330 1. 42910 



Rayleigh 1.29327 1.42952 



Regnault's numbers have an approximate correction applied to them by Crafts. The mean of 

 these numbers is taken, that of Regnault for nitrogen being omitted, as there is reason to believe 

 that his specimen was < oni.uninated with hydrogen. 



Air. Oxygen. Nitrogen. Hydrogen. 



1.29347 1. 42961 1.25749 0.08991 



This ratio gives for air the composition by volume : 



Oxygen 20.91 j). c. 



Nitrogen 7909 " 



a result verified by experiment. 



It is of course to be understood that these densities of nitrogen refer to atmospheric nitrogen, 

 that is, to air from which o.wiicii, water vapor, carbon dioxide, and ammonia have been removed. 



