and on the Isomeric Modifications of Selenium. 517 



portant corrections; for during all the time which the ther- 

 mometer has taken to rise from 93 degrees to its maximum, the 

 system has lost by radiation a considerable portion of the heat 

 which would become free in consequence of the molecular trans- 

 formation. To be able to calculate this loss of heat, I transcribe 

 the table of observations of temperatures made before the time 

 at which the selenium was lowered into the calorimeter. 



Variation in minutes. 



0-63 

 0-52 

 0-48 

 0-35 

 0-35 

 0-33 

 0-28 

 0-25 

 0-23 

 0-22 

 0-24 

 0-15 

 0-25 

 0-20 

 0-20 

 0-25 

 0-35 

 0-30 

 0-30 

 0-20 

 0-20 

 0-35 

 0-30 

 0-30 



Variation in minutes. 

 69 . . . 961 



0-35 



70 . . . 96-45 



71 . . . 96-7 



72 . , , 97-2 



73 ^^-rr . 97-7 



74 . . . 98-05 



75 . . . 98-5 



76 . . . 99-1 



77 . . . 99-7 



78 . . . 100-3 



79 . . . 101-0 



80 . . . 101-95 



81 . . . 103-1 



82 . . . 104-15 



83 . . . 105-7 



84 . . . 107-8 



85 . . . 110-9 



86 . . . 116-5 



87 . . . 127-6 



88 . . . 147-6 



89 . . . 187-0 



90 . . . 200-4 

 As the thermometer now rose only 



slowly, the system was lowered ; it 



was placed in the calorimeter at the 

 92nd minute. 



VTe see here again that the rapidity of the heating goes 

 on diminishing up to the 58th minute, when the thermometer 

 shows 93 degrees; from the 58th to the 65th minute, this rapidity 

 remains perceptibly constant, assuming then an ascending march. 

 We may therefore suppose then that the molecular transform- 

 ation commences at 93 degrees, and that selenium, during its 

 passage from 93 to 98 degrees, is only heated by the radiation 

 of the enclosure. If it be admitted that the molecular transform- 

 ation has not commenced from 76 to 93 degrees, we might, as- 

 suming Newton's law, calculate from the numbers of this period 

 the heat which the enclosure has communicated to the system, 



0-35 

 0-25 

 0-50 

 0-50 

 0-55 

 0-45 

 0-60 

 0-60 

 0-60 

 0-70 

 0-95 

 1-15 

 105 

 1-55 

 2-10 

 3-10 

 5-60 

 11-10 

 20-00 

 39-40 

 13-4 



