PRIMARY AND SECONDARY RESULTS OF ELECTROLYZATION. 97 



meter (707-)) the oxygen, whether from strong or weak acid, proved to be in the same 

 proportion as from water. When the acid was diluted to specific gravity 1*24, or 

 less, the hydrogen also proved to be the same in quantity as from water. Hence I 

 conclude that the nitric acid does not undergo electro-chemical decomposition, but the 

 water only ; that the oxygen at the anode is always a primary result, but that the pro- 

 ducts at the cathode are often secondary, and due to the reaction of the hydrogen 

 upon the nitric acid. 



753. Nitre. — A solution of this salt yields very variable results, according as one 

 or other form of tube is used, or as the electrodes are large or small. Sometimes the 

 whole of the hydrogen of the water decomposed may be obtained at the negative 

 electrode ; at other times, only a part of it, because of the ready formation of secondary 

 results. The solution is a very excellent conductor of electricity. 



754. Nitrate of ammonia^ in aqueous solution, gives rise to secondary results very 

 varied and uncertain in their proportions. 



755. Sulphurous acid. — Pure liquid sulphurous acid does not conduct nor suffer 

 decomposition by the voltaic current *, but, when dissolved in water, the solution 

 acquires conducting power, and is decomposed, yielding oxygen at the anode, and 

 hydrogen and sulphur at the cathode. 



756. A solution containing sulphuric acid in addition, was a better conductor. It 

 gave very little gas at either electrode : that at the anode was oxygen, that at the 

 cathode pure hydrogen. From the cathode also rose a white turbid stream, consisting 

 of diffused sulphur, which soon rendered the whole solution milky. The volumes of 

 gases were in no regular proportion to the quantities evolved from water in the volta- 

 electrometer. I conclude that the sulphurous acid was not at all affected by the 

 electric current in any of these cases, and that the water present was the only body 

 electro-chemically decomposed ; that, at the anode, the oxygen from the water con- 

 verted the sulphurous acid into sulphuric acid, and, at the cathode, the hydrogen elec- 

 trically evolved decomposed the sulphurous acid, combining with its oxygen, and 

 setting its sulphur free. I conclude that the sulphur at the negative electrode was only 

 a secondary result ; and, in fact, no part of it was found combined with the small por- 

 tion of hydrogen which escaped when weak solutions of sulphurous acid were used. 



757. Sulphuric acid. — I have already given my reasons for concluding that sul- 

 phuric acid is not electrolyzable, i. e. not decomposable directly by the electric current, 

 but occasionally suffering by a secondary action at the cathode from the hydrogen 

 evolved there (681.). In the year 1800, Davy considered the sulphur from sulphuric 

 acid as the result of the action of the nascent hydrogen -f. In 1804, Hisinger and 

 Berzelius stated that it was the direct result of the action of the voltaic pile X ; an 

 opinion which from that time Davy seems to have adopted, and which has since been 



* See also De la Rive, Biblioth^que UniverseUe, torn. xl. p. 205 ; or Quarterly Journal of Science, vol. xxvii. 

 p. 407. 



t Nicholson's Quarterly Journal, vol. iv. pp. 280, 281. J Annales de Chimie, 1804, torn. 11. p. 173. 



MDCCCXXXIV. O 



