xin THE DECOMPOSITION OF THE ALKALIS 287 



of hydrogen in ammonia ; the decomposition of ammonium 

 nitrite takes place so readily that this salt was separated from 

 its solutions in a crystalline form for the first time in 1909 (P. C. 

 Ray, Trans. Chem. Soc., 95, 345). 



BerzelillS, in 1823, proposed to represent the compound 

 radical ammonium, NH 4 , by the symbol Am, thus : 

 ammonium chloride = NH 4 C1 or AmCl. 

 Two compounds having the composition of 



ammonium oxide, 2NH 3 +H 2 O = (NH 4 ) 2 O or Am 2 O and 

 ammonium hydroxide, NH 3 + H 2 O = (NH 4 )OH or AmOH, 



were actually isolated in 1909 (Annual Reports, 6, 14) ; it is 

 remarkable that both compounds, like ammonia itself, melt at 

 - 78 C. 



Daniell, in 1840, proposed to regard all salts as binary com- 

 pounds of two radicals. In the halogen salts of the metals both 

 radicals are simple or elementary. In the ammonium salts the 

 <' metallic " radical is compound. In the cyanides, sulphates, 

 nitrates, etc. the " non-metal" is replaced by a compound radical, 

 cyanogen CN, sulphate SO 4 , nitrate NO 3 , etc. These radicals are 

 the first products of the action of an electric current on the 

 salts. ' 



B. DECOMPOSITION OF THE ALKALIS 



Volta, in 1790, discovered that electric charges appeared on 

 insulated discs of zinc and copper if brought into contact and 

 then separated ; in 1800, he devised a Voltaic pile in which the 

 charges were constantly renewed and .a continuous electric 

 current was produced. The pile was soon developed into the 

 Voltaic battery and very large batteries were constructed in 

 England for Davy and in France for Gay-Lussac and 

 Thenard. 



Nicholson and Carlisle, in 1801, showed that water was 

 decomposed by the electric current into oxygen and hydrogen 



2H 2 -> 2H 2 + 2 



Berzelius and Hisinger, in 1803, showed that dissolved salts 

 were decomposed into alkali and acid by the electric 

 current, e.g. : 



Na 2 SO 4 + 2H 2 O -> 2NaOH + H 2 SO 4 



(Sodium (Caustic (Sulphuric 



sulphate.) soda.) acid.) 



