GALVANISM. 



17 



ferred must have passed through the 

 fluid in the middle vessel, but without 

 affecting the coloured solution in its 

 passage. By reversing the connections 

 with the poles of the battery, a similar 

 transfer of the alkali will be made ; it 

 will be collected in the tinged water of 

 the negative cup, which it will render 

 green ; but the intermediate portion of 

 fluid will not, either in this or in the 

 former case, exhibit any trace of the 

 substance which is carried through it by 

 the influence of electricity. 



(52.) No union, under similar cir- 

 cumstances, is found to take place, be- 

 tween acids and alkalies, when either of 

 these active chemical principles is trans- 

 mitted by voltaic electricity through the 

 other, provided the compound which 

 they would form by their union remains 

 soluble ; for should the compound be in- 

 soluble, the union takes place, and the 

 product, on falling to the bottom of the 

 fluid by its superior gravity, is removed 

 from the line of the electric action. When, 

 for example, sulphuric acid is attempted 

 to be passed through a solution of bary- 

 tes, or vice versa, barytes through a solu- 

 tion of sulphuric"" acid, sulphate of ba- 

 rytes is formed, which being insoluble in 

 the fluid, falls down as a precipitate, 

 and being removed from the action of 

 the electric current, proceeds no further 

 in its course. If some basis of me- 

 chanical support be provided, whereby 

 this removal from the voltaic influence 

 can be prevented, the transfer may some- 

 times be continued, notwithstanding the 

 body has assumed a solid form ; thus 

 magnesia or lime will pass along moist 

 asbestos, from the positive to the nega- 

 tive sides ; but if a vessel of pure water 

 be interposed, they do not reach the 

 negative vessel, but sink to the bottom. 

 In like manner when nitrate of silver 

 was on the positive side, and distilled 

 water on the negative, the silver, as we 

 have already seen, passed along the 

 transmitting fibres of the asbestos, so as 

 to cover it with a thin metallic film. 



(.)3.) When the fluids placed in the 

 same voltaic circuit are connected, not 

 by fluids, but by pieces of metal, such 

 as wires, the changes above described 

 take place in each separate portion of 

 fluid, each alternate metallic surface 

 performing the functions of a positive 

 and negative polarity, according to its 

 place in the circuit of, the electric current. 

 Those parts into which the electricity is 

 entering possess properties corresponding 

 to those of the negative wires or poles of 



the battery ; and those which are giving 

 exit to the electricity, act as positive 

 wires. The former will collect around 

 them the several bases of neutral and me- 

 tallic salts, and the hydrogen of the de- 

 composed water ; the latter will collect 

 oxygen, and the compounds in which 

 oxygen predominates, such as the acids. 

 (54.) The decomposition of the alka- 

 lies and of the earths, which crowned 

 this brilliant career of discovery, is, in 

 point of theory, only a particular in- 

 stance of the general fact above stated, 

 namely, that combustible substances are 

 carried to the negative wire, and oxygen 

 evolved at the positive wire. Various 

 other applications have been made of the 

 voltaic battery to the purposes of che- 

 mical decomposition. Sulphuric acid 

 is resolved by its means into oxygen gas 

 and sulphur. Phosphoric acid, in like 

 manner, yields oxygen gas and phos- 

 phorus. Ammonia separates into hy- 

 drogen and azote, with a small propor- 

 tion of oxygen. Oils, alcohol, and ether, 

 when acted on by a powerful battery, 

 deposit charcoal, and give off hydrogen, 

 or carburetted hydrogen. But it would 

 be encroaching too far on the province 

 of chemistry to extend our illustrations 

 of this subject to any greater length. 



6. Physiological effects of Galvanism. 



(55.) The action of voltaic, as well as 

 of common electricity, on a living ani- 

 mal is chiefly exerted on the functions of 

 the nervous system. It is shown in the 

 production of sensation, in the excita- 

 tion of muscular contraction, and in al- 

 tering the products of secretion. 



(56.) If any considerable part of the 

 human body form part of the circuit of 

 a voltaic pile or battery, a separate 

 shock is experienced every time a con- 

 nection is made with the poles of the 

 apparatus ; provided the skin through 

 which the electric current is to pass be 

 sufficiently moist to allow of its being 

 transmitted : for in its usual dry state 

 the cuticle, or outer skin, is scarcely 

 pervious to electricity of such low inten- 

 sity as that afforded by galvanism. The 

 most effectual method of receiving the 

 whole force of the battery is to wet both 

 hands with water, or what answers still 

 better, with a solution of common salt, 

 and to grasp a silver spoon in each ; the 

 circuit is then to be completed by touch- 

 ing one pole of the battery with one 

 spoon, and the opposite pole with the 

 other spoon. Another mode is to plunge 



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