350 



GALVANISM. 



a Mr. Peel, of Cambridge, containing an account of an experiment in which > 

 the water that remained, after a large portion had been decomposed by the pile, I 

 yielded on evaporation muriate of soda, although the water used in the experi- 

 ment had been distilled with every precaution necessary to free it from impu- 

 rities. On inquiry being made at Cambridge, no person corresponding with 

 the name and address of the professed author cou>d be found ; and the state- 

 ment was concluded to be a mere attempt to practise on the credulity of the 

 scientific world, when the surprise was revived by the publication of experi- 

 ments actually made by Professor Pacchiomf of Pisa, in which the same re- 

 sult was attained as was stated in the pretended Cambridge experiment. Syl- 

 vester being led to the same conclusion, ascribed the supposed effects, in 

 common with Pacchioni, to the oxydation of hydrogen, on the one hand in a 

 higher, and on the other in a lower degree than that which forms water. 



Such were the confusion and obscurity in which the community of science 

 was involved on the subject of the Voltaic decomposition of water, when the 

 question was taken up by Davy. In common with others, he had observed at 

 an early period the presence of an acid and alkali in water under the process 

 of decomposition ; but states, that, so early as 1800, he concluded from his ex- 

 periments that the acid proceeded from the animal and vegetable substances 

 which he employed, and that the alkali arose from the corrosion of the glass 

 vessels in which the experiment was conducted. Similar inferences were 

 made by the Galvanic Society of Paris, by MM. Biot and Thenard, and by Dr. 

 Wollaston ; the last of whom removed one of the sources of these disturbing 

 elements by the happy expedient of connecting the positive and negative por- 

 tions of water by a piece of well-washed asbestos. 



The investigation now undertaken by Davy was commenced by decompo- 

 sing distilled water in two small cups of agate, P N (fig. 3), connected by a 



Pig. 3. 



piece of white transparent amianthus, A. The wires of the Voltaic battery of 

 160 pairs of four-inch plates were connected with the water, the positive wiie 

 being immersed in the cup P, and the negative wire in N. After the process 

 had been continued for forty-eight hours, the water in the cup P was found to 

 redden litmus paper, and turmeric paper was affected by the water in N. It 

 appeared, therefore, and further experiment confirmed the indication, that acid 

 was present in the positive water, and alkali in the negative. 



t Vol. xxii., p. 179. 



J 



