On a new Constituent of Atmospheric Air. 405 



An abstract of the values obtained is given in the table (p. 404). 



Part II consists of a bolometric study of the radiation emitted by 

 platinum at temperatures ranging from 500 C. to the melting point 

 of the metal. It is shown that for theoretical reasons the true rate 

 of change of the total radiation with temperature lies between the 

 values obtained by measuring the heat lost by the radiating body 

 and those deduced from the readings of any form of bolometer or 

 thermopile. 



By comparing the observations of Dr. J. T. Bottomley and 

 Schleiermacher, based on the first method, with those of F. Paschen 

 and of the author, made by the second method, a reliable criterion 

 is obtained by which to test any formula intended to express the law 

 of thermal radiation. 



The formulae of Dulong and Petit, of Stefan, and of Bosetti fail 

 when tested in this manner ; whilst Weber's formula, from 400 to 

 800 C., gives results in close agreement with the true rate of 

 change of total radiation with regard to temperature. 



The second part of the paper also contains a description of some 

 points of interest in the design of the bolometer which was used 

 during this work. 



Part III refers to the variation of the intrinsic brilliancy of plati- 

 num surface with temperature. 



The results may be expressed by the following formula : 



0-400) = 889-6 yb, 



where i is the temperature in degrees centigrade, and b the intrinsic 

 brilliancy in candle power per square centimetre. The constant 400 

 is taken as the temperature limit at which the visible radiation falls 

 to zero. 



"On a new Constituent of Atmospheric Air." By WILLIAM 

 RAMSAY, F.R.S., and MORRIS W. TRAVERS. Received 

 June 3 Read June 9, 1898. 



This preliminary note is intended to give a very brief account 

 of experiments which have been carried out during the past year 

 to ascertain whether, in addition to nitrogen, oxygen, and argon, 

 there are any gases in air which have escaped observation owing 

 to their being present in very minute quantity. In collaboration 

 with Miss Emily Aston we have found that the nitride of magne- 

 sium, resulting from the absorption of nitrogen from atmospheric 

 air, on treatment with water yields only a trace of gas ; that gas is 

 hydrogen, and arises from a small quantity of metallic magnesium 

 unconverted into nitride. That the ammonia produced on treatment 



VOL. I.X11I. ^ H 



