428 COMPOUND SALTS 



18. Amiiionio-oxalate of copper. This salt 

 copper! may be obtained by mixing together oxalates of 



copper and ammonia in the atomic proportions, 

 and digesting the mixture. By evaporation the 

 salt is obtained in rhomboidal plates ; it has a 

 blue colour, and is insoluble in water. Vogel of 

 Bareuth first formed it. Water decomposes it. 

 When suddenly heated it detonates loudly, ac- 

 cording to Vogel ; but this didjnot take place in 

 my laboratory. Its constituents are 



1 atom oxalate of copper 

 1 atom oxalate of ammonia 

 3 atoms water 



19-5 



19. Efflorescing ammonio-oxalate of copper. 

 This salt was formed by Vogel of Bareuth, by 

 agitating oxalate of copper in caustic ammonia 

 till a saturated solution was obtained. When 

 this solution is placed in a flat dish it deposites 

 dark blue crystals, having the form of six-sided 

 prisms, with two broad and two . narrow faces. 

 When exposed to the air it loses 18 per cent, of 

 its weight ; this loss is partly water partly am- 

 rnonia. The constituents of this salt are as fol- 

 lows : 



1 atom oxalic acid 

 1 atom oxide of copper 

 J atom ammonia 

 1 atom water 



12-75 



