856 Prof. J. Joly on the 



results these indicate the relative numbers of ions produced 

 in the two constituent gases of a gaseous mixture. In 

 C 2 H 5 Br and air, the relative absorptions of energy were 

 found very closely in agreement with the relative masses of 

 C 2 Hr,Br and air. 



The ionization by X-rays of gaseous mixtures has been 

 shown to differ considerably from the sum of the ionizations 

 in the two individual gases. The difference shows the effect 

 of corpuscles from one gas being absorbed by the other, the 

 nature of the deviation being what could be foretold from 

 our experiments on ionization by corpuscular radiation. The 

 magnitude of the effect, however, is not so great as we should 

 expect on the simplest theory of ionization by ejected 

 corpuscles alone. The possible causes have been discussed. 



1 wish to express my thanks to the Solvay International 

 Institute for a grant in aid of these researches. — 0. Gr. B. 



LXXXVIII. The Temperature of Sublimation. 

 By J. Joly, F.R.S* 



IN a recent number of the Philosophical Magazine (Feb. 

 1913) I described a simple apparatus (which I have 

 called the Apophorometer) by means of which the chemical 

 analysis of many volatile bodies may be effected by so regu- 

 lating the temperature of the finely powdered substance as 

 to volatilize one by one its several constituents in the order 

 of their volatility. The successive sublimates are caught 

 and removed in watch-glasses and weighed; the residue also 

 being weighed when desired. I cited some examples of 

 more or less complex mineral bodies quantitatively analysed 

 by fractional sublimation. 



I was at the time surprised at the apparent sameness of 

 temperature at which certain very different mineral species 

 decomposed, but contented myself with pointing out the 

 probable importance of temperature measurements and with 

 indicating a method of effecting such measurements. This 

 method — that of determining the temperature in terms of 

 the current which heats the hob upon which the substance 

 reposes — has proved very satisfactory and easily applied ; 

 the current and temperature maintaining a rectilinear 

 relation at least so high as 1200° C. 



* Communicated bv the Author. 



