Manchester Memoirs, Vol. x/vni. (igo4), No. t^. 5 



the maximum quantity of seleniuretted hydrogen pro- 

 duced is a function of the temperature, and increases 

 from 250°C. to 520^C., and then decreases regularly to 

 700°C. On trying the experiment in a bent tube similar 

 to the one used for hydrogen and sulphur, I found that 

 combination took place much more readily, and the 

 solution of soda rose rapidly in the tube. The sodium 

 selenide formed was found to be insoluble in soda of the 

 strength used (i part soda to 15 parts water), and 

 crystallized out in beautiful needle - shaped crystals, 

 sometimes over an inch in length. These have been 

 investigated by Fabre,^who determined their composition, 

 and found that the selenide crystallizes with different 

 amounts of water depending on the strength of the soda 

 and the temperature. Salts corresponding to the follow- 

 ing formulae have been obtained : 



Na.SegHp, Na,Sei6H„0, 2Na,Se9H,0, 



and an anhydrous one, Na2Se is obtained by heating any 

 of the above in a current of nitrogen. These crystals are 

 extremely unstable when removed from the soda solution. 

 They become red in a few seconds owing to separation of 

 selenium, and on exposure to air rapidly change to a 

 mixture of sodium carbonate, selenium, and sodium 

 selenite. 



Hydrogen and Tellurium. 



Tellurium also combines readily with hydrogen. 

 When the experiment in the bent tube was made, using 

 hydrogen and tellurium, the reaction took place in a 

 precisely similar manner, but even more readily than 

 when selenium was used. There was, however, no 

 formation of sodium telluride crystals, either with soda 

 of the same strength or when a stronger solution was used. 



^ Coinpt. Rend. vol. 102, p. 613. 



