Hydro- Electrical Currents. 3M 



an electro-nibtive force, which, added Id th6 affinity ot tlie irbii for oxy- 

 gen at these points, is sufficient to effect the decomposition. Henc^ 

 it follows, that the feeblest electrical currents with which we are ac- 

 quainted, may be made to decompose water when assisted by the affi- 

 nity of the metals forming the poles for the nascent oxygen, eliminated 

 by platinum and a more powerful current. 



13. Although I have never succeeded with any decomposition by 

 platina poles, and a thermo-current at the highest temperature, I could 

 command, with oxydizable metals, as performed by Mr Watldns,* the 

 battery, figures 2, 3, oxydizes and deposits metallic copper in a volta- 

 meter at 200° Fahrenheit, at the rate of 21 grains per day, the difference 

 in weight betwixt 2 equal copper wires after 24 hours' action being 42 

 grains J so that, in 164 days, a quantity of copper equal to the whole weight 

 of the battery can be deposited, while, to all external appearance, the 

 bars which developed the force essential for this powerful chemical ac- 

 tion have undergone little change. 



14. The metallic salts, when placed in a voltameter with poles of the 

 sxme metal as their base, yield readily to a thermo-current ; under such 

 circumstances, there are a great number of metallic compounds decom- 

 posable by this force, where the difference of temperature betwixt the 

 two ends of the battery might serve to measure the relative power of 

 the afiinities which unite the elements of the electrolice. 



14. The cyanuret of silver in solution, now so much used in electro- 

 plating, undergoes electrolization with a thermo-current, derived from 

 a single pair of antimony and bismuth bars, excited by radiating to a 

 clear sky. The silver appears in the usual frosted form on the negative 

 pole, and I believe this metallic deposit can be obtained at lower tempe- 

 ratures and with feebler currents than any other metal. Copper poles, 

 and iron poles in a solution of water acidulated with sulphuric acid, give 

 as distinct evidence of decomposition of water by feeble currents, as we 

 obtain with the cyanuret of silver and pure silver poles ; with copper 

 poles, the black oxide of copper is obtained, then the fluid is slightly 

 tinged by the formation of the sulphate of copper ; with iron poles, the 

 green tinge from the sulphate of iron appears. But for all of tliera, it ia 

 essential thoroughly to exclude the atmosphere, otherwise a more active 

 source of chemical action will be present, which will render it impossible 

 to watch the effect of the thermo-electrical current. For these minute 

 indications, I have found it necessary to keep the bars in action from three 

 to six months before the evidence of the decomposition could be relied 

 on. At their commencement, the galvanometer, when applied to form 

 part of the circuit, shewed that minute quantities of electricity passed; 

 but as Dr Faraday had found that fluids were capable of conducting 

 electricity to a small extent without decomposition, this did not appear 



* Fhilosophiotd Magazine, voL xii. p. 51U 



