and on the Isomeric Modifications of Selenium, 513 



o 



2-1 



2-0 



1-9 



1-7 



1-95 



1-25 



1-4 



1-4 



1-17 



0-88 



0-67 



0-52 



It is seen from this table that up to 93 degrees the ther- 

 mometer rose constantly with a decreasing rapidity, as ought to 

 be the case, for it was thus approximating to the surrounding 

 temperature, which was 100 degrees; but from 94 degrees the 

 ascending march of the thermometer was accelerated, at first 

 feebly, but afterwards with rapidity. At the 61st minute the 

 thermometer exceeded the surrounding medium. From the 71st 

 to the 72nd minute it increased 53 degrees ; its ascending march 

 was then somewhat slower, and it was at the 73rd minute that 

 it reached its maximum of 214 degrees. From thence the 

 thermometer assumed a descending march, which was at first 

 accelerated up to the 78th minute, because the substance still 

 emitted heat which partially compensated for the eflect of the 

 cooling causes : at last the rapidity of the cooling abated, the 

 excess of temperature becoming less and less. It is besides 

 evident that this superelevation of temperature of more than 

 114 degrees, is far less than that which would have taken place 

 if the disengagement of heat, in consequence of the molecular 

 transformation, instead of being successive, had been instan- 

 taneous, and if the substance had not been obliged to divide its 

 heat with foreign bodies, and to lose it by radiation. 



Thus in the experiment before us, the weight of selenium is 

 200 grammes. Assuming that its specific heat is 0*0769, as we 

 have found it between 15 and 90 degrees, this selenium corre- 

 sponds, in its calorific capacity, to 15^'-42 of water. The brass 

 vessel which contains it weighs 81e''-15, and corresponds to 7^-70 

 of water. We may assume that this case is at the same tempe- 

 rature as the selenium which it contains. In this case if x 

 represents the temperature to which selenium would have been 

 raised had it been alone, we should have 



15-42 .a?= (15-42 + 7-70) . 114, whence ^=170°-9. 

 Thus the temperature would have been raised 171 degrees if the 



