353 



GALVANISM. 



the base with which il was united and the vessel in 

 which it was, and pass by the amianthus wholly into 

 the water, the base remaining in the first cup : and if, 

 after tin's change be effected, the wires are reversed, 

 the acid will immediately begin to quit the cup into 

 which it liad passed in the former experiment, and to 

 return to the first cup, while the base will move in 

 an opposite direction, till all of it is collected in the 

 vessel in which the negative wire was placed. 



Phenomena still more extraordinary present them- 

 selves in connexion with these most interesting 

 researches. The elements of compound bodies are 

 actually conveyed by the influence of the electric 

 current through solutions of substances, on which, 

 under other circumstances, they would have exerted 

 an immediate and powerful chemical action, without 

 any such effect being produced. Acids, for example, 

 may be transmitted from one cup, connected with the 

 negative pole, to another cup on the opposite or posi- 

 tive side, through a portion of fluid in an intermediate 

 cup tinged with any of the vegetable coloured infu- 

 sions, which are instantly reddened by the presence 

 of an acid, without occasioning the slightest change 

 of colour. The same happens also with alkalies. 

 Sir H. Davy found that when three vessels were 

 connected with each other by moistened amianthus, 

 and there was placed in the first a solution of sulphate 

 of potash, with a wire from the negative side, in the 

 middle a vessel with a solution of ammonia (a substance 

 having a strong attraction for sulphuric acid), and in 

 the third, water, with a wire from the positive side of 

 the galvanic battery ,. in five minutes (a battery of 

 150 pairs of plates being employed) acid was found 

 collecting around the wire in the water. It had, 

 therefore, passed through the ammonia, without the 

 affinity of this being sufficient to arrest it. When 

 the disposition was reversed, and the saline solution 

 connected with the positive side, the water with the 

 negative, and an acid placed in the middle, the alka- 

 line base was conveyed through the interposed acid, 

 and collected in the pure water. The same results 

 were obtained in operating on a number of other 

 salts, alkaline, earthy, and metallic. Where a strong 

 force of cohesion, however, interfered, the substance 

 was intercepted : thus sulphuric acid could not be 

 transmitted through a solution of barytes or stronti- 

 tes ; nor these earths through sulphuric acid : when 

 it was attempted, these earths fell down in insoluble 

 precipitates. Not only liquids, but solid substances 

 are decomposed by means of the galvanic energy, and 

 their elements transferred to the opposite wires. And 

 such is the force of this agent, that the most minute 

 portion of a substance thus acted on by either of the 

 wires is collected around it. Portions of muriatic 

 acid, of soda, and of other alkalies and acids, appear 

 at the opposite poles, even when distilled water alone 

 is employed, proving that these substances, in the 

 condition of neutral salts, exist in all waters, how- 

 ever purified they may be by art. 



From these researches, the general law is estab- 

 lished, that when compounds are placed in the 

 galvanic circuit, their elements are separated from 

 the state of combination in which they exist, and, 

 according to their peculiar nature, are collected, 

 some around the positive, others around the negative 

 pole. How this is effected, whether by attractions 

 alone exerted at each pole, or by repulsions, or by 

 both, the element attracted to the one oeing repelled 

 from the other, is not so apparent. 



Grotthus, in explaining the galvanic decomposi- 

 tion of water, advanced the conjecture, that as, in 

 the voltaic pile, each pair of plates has its negative 

 and positive poles, it may establish a similar polarity 

 among the elementary particles of the portion of 

 water interposed between its principal poles. One 



element of the water may thus acquire the positive, 

 the other the negative state ; and if this happens, 

 then, according to the laws of electricity, that which 

 has become negative (the oxygen in the case of 

 water) will be repelled from the negative and 

 attracted to the positive pole ; and that which lias 

 become positive (the hydrogen) will be repelled from 

 the positive and attracted to the negative side. 

 This explanation is extremely probable. With 

 regard to the mode of conveyance, it may be by suc- 

 cessive decompositions and recompositions of the. 

 compound between the two poles ; in water, for 

 instance, the particle at each wire may be decom- 

 posed ; the one element maybe disengaged, and the 

 residual element may attract a corresponding por 

 tion of the other from the next particle, and thus, bj 

 a series of successive decompositions and recomposi- 

 tions, each may be brought to the wire to which it 

 is attracted and evolved ; or, what is equally pos- 

 sible, the decomposition may be confined to the 

 particles at each pole, and the element receiving the 

 opposite electricity may be repelled from it, and, by 

 this repulsion and the corresponding attraction at 

 the opposite wire, be brought to that other pole ; 

 and analogy is in favour of this supposition. In 

 atmospheric air, bodies rendered positively or nega- 

 tively electrical, are attracted and repelled at con- 

 siderable distances. From the degree in which 

 electricity exists in galvanic arrangements, water is 

 a medium, with regard to it, nearly as atmospheric 

 air is to electricity evolved in the common electrical 

 machine j and it may therefore allow electric 

 attractions and repulsions to operate in a similar 

 manner. 



A different theory has been proposed by Sir H. 

 Davy, and which has received the appellation of 

 the electro-chemical theory. It has been adopted by 

 some eminent philosophers, and among others by Ber- 

 zelius. He conceived that bodies possess natural elec- 

 tric energies, which are inherent in them, whether 

 they are in a state of combination or not. Oxygen, 

 chlorine, iodine, and acids, according to the theory, 

 are naturally negative ; while inflammables, as 

 hydrogen, sulphur, &c., and metals, are naturally 

 positive. Hence, when the combinations of these 

 substances are subverted by the galvanic influence, 

 the substances are evolved in the electric state 

 natural to them ; and as it is a law of electricity, 

 that bodies in opposite states attract each other, the 

 oxygen, being negative, is immediately attracted by 

 the positive wire, while the inflammable or metallic 

 base, being naturally positive, is attracted by the 

 negative wire. In this way, the uniform appearances 

 of these bodies at their particular poles, is accounted 

 for. To explain how combination is subverted by 

 the electric influence, a further hypothesis is sug- 

 gested by the author of the theory, viz., that chemi- 

 cal attraction may itself be a modification of electri- 

 city ; that the same power which communicates 

 attractive and repulsive properties to masses of 

 matter, may, when acting upon the ultimate particles 

 of different bodies, induce them either to separate or 

 unite, as their natural electrical states are the same 

 or different. Thus, if hydrogen is naturally positive, 

 and oxygen naturally negative, according to the 

 laws of electricity, they must attract each other ; 

 and if these opposite states are sufficiently exalted to 

 give them an attractive force, superior to the power 

 of aggregation, they may be expected to combine ; 

 and in like manner, other bodies, whose particles are 

 in different states, may from this cause be united toge- 

 ther. If a body also, whose electrical energy exceeds 

 that of one of the substances combined, be brought 

 to act upon these, it may expel that ingredient, and 

 take its place ; and this may be the cause of what is 



