COMPOUND SALTS 



1 atom diphosphate of magnesia 8-5 



1 atom diphosphate of ammonia 7'75 



.5 atoms water . 5-6^5 



11-875* 



Though I have prepared this compound salt 

 many times, and analyzed it repeatedly, I have 

 never met with any salt composed in the same 

 manner as that examined by Riffault. 



14. Amnionio-arseniate f .of soda. This salt 

 soda. was obtained by M. Mitcherlich, by mixing so- 

 lutions of arseniate of ammonia and arseniate of 

 soda together. By evaporation the salt crystal- 

 lizes. The primary form of the crystals is an 

 oblique prism with rhombic bases ; the inclina- 

 tion of the faces of the prism is 38 44'. And, 

 Mitcherlich says, that the ammonio-phosphate of 

 soda crystallizes under the same form. 



From the experiments of Mitcherlich, it is evi- 

 dent that the constituents of this salt are 



1 atom arseniate of soda 11 '750 



1 atom arseniate of ammonia 9'875 



8 atoms water . . 9-000 



S0-625t 



Ammonio- 15. Ammonio-permuriate of iron. This salt is 



permuriate ,,..,;, . . , /? - 



of iron, obtained by mixing permuriate or iron and sal- 

 ammoniac in the atomic proportions, and con- 



Ann. de Chim, et de Phys. XIX. 90. f Ibid. 400. 



