416 COMPOUNDS OF HYDROGEN. 



valent of ammonia with the greatest avidity, and forms a green 

 fusible matter, which the close analogy between copper and 

 hydrogen would lead us to view as analogous in constitution to 

 the compound formed by chloride of hydrogen and ammonia, or 

 chloride of ammonium. It will, therefore, be represented as 

 composed of chlorine united with ammonium, containing an 

 atom of copper, in place of the fourth atom of hydrogen, or as 

 N H 3 Cu, Cl, which may be called chloride of cuprammonium. 

 The sulphate of copper, in like manner, retains half an equiva- 

 lent of ammonia with great force, and forms a compound which 

 may be represented as sulphate of copper combined with sul- 

 phate of cuprammonium : 



CuO, S0 3 + (NH 3 Cu 



which is analogous to the double sulphate of copper and am- 

 monium : 



CuO, SO 3 + (NH 4 , O-f S O 3 ). 



Chloride of mercury forms a similar compound with half an 

 equivalent of ammonia : 



HgCl + NH 3 Hg,Cl 



analogous to sal alembroth, or the compound of chloride of 

 mercury and sal ammoniac : 



HgCl + NH 4 ,Cl. 



A different view of these and the other ammonium compounds 

 is advocated by Dr. Kane. Sal ammoniac is considered by 

 him as a species of double salt, as amide of hydrogen with 

 chloride of hydrogen, II Ad + H Cl ; and the salt I have named, 

 chloride of cuprammonium, as a corresponding amide of hydro- 

 gen with chloride of copper, H Ad -f Cu Cl. We agree in sup- 

 posing these two salts to have the same constitution, but differ 

 as to what that constitution is. To adapt the same expla- 

 nation to the oxygen acid compounds, such as sulphate 

 of ammonium, Dr. Kane assimilates them to the salts of the 

 magnesian class, which contain two equivalents of oxide. 

 Adopting the hypothesis that two atoms of that class (in which 

 water is included) are equivalent in combination to one of the 

 potash class, he views sulphate of copper, possessing what I 

 term its atom of constitutional water, as a compound of sul- 



