6 Cain, The Constitution of the Ammonium Compounds. 



peroxide O = OH^, and of ozone O = O = O. The general 



formula for salts of ammonia and oxygen acids is 



H3N = OHX, 



thus ammonium sulphate is written 



H,N = O - SO, - O = NH3, 

 H H 



oxygen, of course, being tetrad. 



The obvious question as to the possibility of this 



formula, in view of the isomorphism of the ammonium 



and potassium salts, at once arises. Ought we not, 



however, to expect some difference between these salts 



from the fact that water is always eliminated in the 



formation of, for instance, potassium sulphate, while no 



such reaction takes place in the case of ammonium 



sulphate? The formation of potassium sulphate may, 



however, be exactly analogous to that of ammonium 



sulphate, thus — 



(i) Addition, 



K H H K 



2KOH + H,S04->Hd = 6-SO,-6 = 6H. 



(2) Molecular change, 



K H H K H K K H 



h6 = 6-so3-6 = 6h->h6 = 6-so,-6 = 6h. 



(3) Water split off, 



H K K H K K 



h6=6-so,-6 = o. H->6-so,-6 + 2Hp. 



In the case of ammonium sulphate, the group attached 

 to the tetrad oxygen atom is split off at a higher tem- 

 perature. 



If we have hitherto regarded as isomorphous, com- 

 pounds containing two such differently constituted 

 groups as 



H 



X-0-KandX-O-N ^^^ 



H 



