52 Mr. J. Norman Lockyer. On the Appearance of the 



occluded, and the heat evolved represented the true heat of occlusion 

 of this quantity of oxygen. 



Indirectly, the same value was obtained by charging the platinum 

 black up fully and alternately with hydrogen and oxygen, and finally 

 with oxygen. The amount of oxygen really occluded in the last 

 charge, and independent of that which had gone to form water, was 

 then found by exhausting in vacuo at a red heat. The difference 

 between this quantity and the total amount of oxygen used is a 

 measure of the oxygen which formed water with twice as much 

 hydrogen by volume. Knowing these quantities, the total heat 

 evolved, the heat of formation of water, and the heat absorbed on 

 the removal of hydrogen, we have all the data for calculating the 

 heat of occlusion of oxygen. 



In a similar way the amount of heat absorbed per gram of 

 oxygen removed was calculated from the data obtained during the 

 penultimate charge. 



The mean value for the heat of occlusion of oxygen, from the 

 direct and indirect measurements, which did not differ much from 

 each other, is +11 OK (1100 ^-calories) per gram. This value 

 referred to 16 grams of oxygen is +176 K, which is almost identical 

 with Thomsen's measurement of the heat of formation of platinous 

 hydrate Pt(OH) 2 , viz., +179 K. 



This agreement suggests the possibility that the two phenomena 

 may in reality be identical, the necessary water being always present 

 in platinum black dried in vacuo. 



The paper concludes with some speculations on the nature of the 

 occlusion of gases. 



" On the Appearance of the Cleveite and other New Gas Lines 

 in the Hottest Stars." By J. Norman Lockyer, C.B., 

 F.R.S. Received June 15— Read June 17, 1897. 



Introductory. 



In my recent paper on " The Chemistry of the Hottest Stars," * 

 I left for future discussion the spectra of those stars apparently at 

 or near the apex of the temperature curve, for the reason that in 

 them the lines of known gases do not show very great variations, 

 while the enhanced lines cease to be of service as a criterion of 

 temperature. I pointed out, however, that there were several lines, 

 as yet of unknown origin, which are strong in some of these stars 

 and weaker in others, and that the study of these might eventually 

 help us in classifying such stars and arranging them in temperature 



* ' Roy. Soc. Pjoc.,' vol. 61, p. 185. 



