NITROGEN SELENIDE. 263 



2. NITROGEN SELENIDE. 



1. This compound is similar to nitrogen sulphide; it has 

 recently been the subject of careful study on the part of M. 

 Verneuil, 1 who has fixed its formula at NSe. He kindly 

 furnished M. Vieille and the author with a specimen for the 

 experiments which they were making upon explosive substances. 



It is an amorphous powder, of a deep orange colour, very 

 dangerous to handle. It explodes at about 230, according to 

 M. Verneuil. It also explodes either by friction or by a very 

 slight percussion of iron upon iron, or a more violent percussion 

 of wood upon iron. The contact of a drop of sulphuric acid 

 also makes it explode. 



2. Heat of detonation. We effected the explosion in our 

 usual apparatus by the same process as we adopted for nitrogen 

 sulphide. Working with 3 grms. of the substance, two trials 

 gave, for the reaction 



NSe (93 grms.) = 1ST + Se 



+ 42-9 Cal. and -f 42'4 Gal., on an average + 42'6 Gal. with 

 a constant volume, or + 42 '3 Cal. at constant pressure, a value 

 which is only approximate, owing to the difficulty of obtaining 

 this substance quite pure. 



3. Heat of formation. We conclude from these observations 

 that the nitrogen selenide is formed from its elements, with an 

 absorption of heat equal to 42*3 Cal. at a constant pressure. 



4 The heat of combustion. 



NSe + 2 = N + Se0 2 



is equal to + 99'9 Cal. 



5. Thus nitrogen selenide is an endothermal combination 

 ( 42'3). It may, therefore, in this respect be classed with 

 nitrogen oxide ( 21*6 Cal.) and nitrogen sulphide ( 31'9 

 Cal.), the condition of these bodies being almost comparable as 

 regards the nitrogen sulphide and selenide, and the heats 

 absorbed forming a sort of arithmetical progression at the rate 

 of about 10 '5. In all cases they increase in absolute value 

 with the equivalent, in accordance with a relation that is pretty 

 general among the series of similar compounds, 2 such as the 

 series of chlorine, bromine, and iodine ; the series of nitrogen, 

 sulphur, and selenium, etc. It follows that in such series the 

 explosive character of the endothermal compounds becomes more 

 and more pronounced in proportion as their atomic weight is 

 greater. 



1 " Bulletin de la Socie'te' Chimique," 2" se*rie, torn, xxxviii. p. 548. 



2 " Annales de Chimie et de Physique," 5" seVie, torn, xxxii. p. 391. 



