THE USE OF LIQUID AMMONIA AS A SOLVENT in 



tetrad nitrogen; diammonium, H 4 N — NH lt however, could be 

 formed by the union of the two ammonium radicles in just the 

 same way as cyanogen is formed by the union of two cyanide 

 radicles. It has already been mentioned that the substituted 

 alkali-ammoniums probably exist in this form, although they 

 are extremely easily dissociated. Ammonium also, if it is 

 capable of existence, would probably be easily dissociated and 

 therefore it seems necessary to carry out any attempts that 

 might be made to isolate it at as low a temperature as possible. 



In order to ascertain whether ammonium can exist at 

 a temperature of about — ioo° C, Moissan (9) made use of 

 the interaction of calcium-ammonium and ammonium chloride 

 in the presence of liquid ammonia. Pure dry ammonia was 

 led over a known weight of calcium contained in a U tube one 

 of the arms of which was constricted so as to hold ammonium 

 chloride in the constriction. On cooling the tube to — 40° C, 

 the compound Ca(NH 3 ) 4 was formed and dissolved in the excess 

 of ammonia. The tube was then cooled to — So C, when more 

 ammonia liquefied and the ammonium chloride dissolved in it. 

 The red-brown colour of the calcium-ammonium then dis- 

 appeared rapidly, hydrogen being evolved and collected in a 

 special apparatus. The volume of the hydrogen, which was 

 found to be pure, showed that at a temperature of — 8o° C. 

 ammonium did not exist. 



2NH,C1 + Ca(NH,) 4 = CaCL + 4NH3 + 2(NH, + H). 



Exactly similar results were obtained on using lithium instead 

 of calcium. 



Moissan (10) also prepared the so-called "ammonium- 

 amalgam " by the action of ammonium chloride in ammonia 

 on sodium amalgam. This forms ammonium amalgam and 

 sodium chloride, no gas being evolved. The product was 

 washed with liquid ammonia ; on cooling to — 80° C. a metallic 

 mass was obtained which was washed with ether at — 8o° C. 

 This did not evolve any gas, even in a vacuum. On warming, 

 the mass began to swell, till at 15° C. it occupied twenty-five 

 to thirty times its original bulk. Several determinations of 

 the evolved gases were made ; all of these agreed closely with 

 the theoretical volumes of two volumes of ammonia to one of 

 hydrogen : 2NH4 = 2NH3 + H 2 . Nevertheless Moissan did not 

 regard this as a true ammonium amalgam but from the similar 



