i50 Mr R. Adie's Experments with Thermo- and 



fcliange In tlie affinities of the substances electrolized ; consequently, they 

 become a delicate measure of variations in affinities* 



10. Where copper poles immersed in a sulphate of copper solution are 

 used, for an electrical current to oxydize and deposit the metal, the affi- 

 nity of the copper for oxygen rises with the temperature, while, at the 

 opposite pole^ it appears not to retain it more jfirmly ; but in working 

 with my feeble currents, I have found that a lower intensity will suffice 

 to oxydize copper at the positive pole, than is necessary to precipitate it 

 as a metal on the negative pole. 



11. As the thermo-electrical current from the battery, figures 2, 3, 

 Could be relied on for regular action during a period of steady weather, 

 I made experiments of two days* duration each, to ascertain the changes 

 in the quantity of copper oxydized at the positive, and precipitated at the 

 hegative pole, at different temperatures, by a constant electro-motive 

 force. 



The mean of two experiments each for 55, &5, 130, and 200 degrees of 

 Fahrenheit, gave quantities corresponding to the numbers 9, 16, 110, 320, 

 the effect increasing in an accelerated ratio. In the experiments con- 

 ducted in a voltameter at 55°, there is no copper precipitated on the ne-r 

 gative pole, but the quantity oxydized at the positive pole measures the 

 extent to which water has been electrohzed. 



Hence, in manipulating with electrical currents of low intensity, it is 

 essential to attend to the temperature of the decomposing cell, for the 

 force which separates the particles of oxygen from hydrogen is made 

 up of the electrical power and the affinity of the metal of the pole (in 

 the above cases copper), for oxygen in its nascent state, platinum poles, 

 used with the same electro-motive force, are unable to effect any decom- 

 position in acidulated water at temperatures within our command. 



Where the temperature of the voltameter was allowed to change with 

 the season, the same cause which exalted the intensity of the thermo- 

 current removed a force acting in conjunction with it, producing a rapid 

 diminution in the extent of the decomposition ; therefore, the loss of affi- 

 nity of copper for oxygen proceeds in a more rapid ratio than the gain 

 to the intensity of the current, from a greater difference of temperature 

 betwixt the two extremities of the pole. 



Hence the apparent loss of power in the thermo-battery, figures 2, 3, 

 during the 4 months* action, and on restoring the decomposing cell, to 

 its former temperature, electrolysis assumed the activity given at the 

 commencement. 



12. It must be evident that, in pushing decompositions by thermo-cur- 

 rents to their highest point, assistance may be derived from a high 

 temperature in the voltametre. Iron, for example, decomposes water 

 without any aid from electricity at a red heat ; at 60° Fahrenheit it re- 

 quires the assistance of a powerful thermo-electric current to disunite 

 the elements of water; betwixt these two temperatures there is an ex-. 

 tensive range of affinity^ requiring, at the different points of the scale, 



