512 M. Regnault on the Specific Heat of Simple Bodies, 



gress, or that a molecular movement is effected which disengages 

 a considerable quantity of heat. But this is not the movement 

 which transforms vitreous selenium into metallic selenium ; for 

 the mass of selenium taken out of the oven after the 165th 

 minute still preserved its vitreous aspect in the fracture, even 

 when quite cool. 



Experiments on the Heat disengaged by Selenium at the moment 

 of its isomeric transformation, 



I wished to determine as exactly as possible the quantity of 

 heat which selenium disengages in undergoing its isomeric trans- 

 formation in the oven heated to 100 degrees. To this end, I melted 

 the selenium in the mould represented in fig. 1, only replacing the 

 cylinder ab by a very fine brass tube open at both ends. The 

 mould thus filled with selenium was suspended, when cool, in 

 the oven heated to 100 degrees, the bulb of the thermometer of 

 the oven being adjusted in the central tubulure. In order to pre- 

 vent the thermometer from being too much cooled by the current 

 of air which must necessarily be established through this tubulure 

 at the moment at which selenium disengages heat, a lute of 

 bread paste was spread on the inferior orifice. The following is 

 the succession of temperatures observed : — 



4-63 

 9-3 

 23-9 



530 



13-5 



o 



-O-l 



-1-9 



-4-0 



7-2 



8-2 

 7-4 

 6-1 

 5-7 



