80 Intelligence and Miscellaneous Articles. 



dilated to its true density. The corrected conductibility expresses 

 thus the conductibility which the solution would have on the double 

 hypothesis, — 1st, that the dissolved salt would not produce any in- 

 crease in volume of the solvent, water ; 2nd, that the conductibility 

 of water increases proportionally to its density, the temperature re- 

 maining constant, and that the same is true of the salt. 



3. I call the calculated conductibility the sum obtained by adding 

 to the proper conductibility of water a number proportional to the 

 quantity of salt dissolved in a gramme of water. 



4. If the double hypothesis of § 2 is true, the calculated and cor- 

 rected conductibilities ought to coincide ; and reciprocally, if coinci- 

 dence takes place, the double hypothesis is admissible. 



5. In operating on nine solutions of sulphate of copper in distilled 

 water, the true density of which varied from T018 to T177, the 

 agreement obtains as far as 1 to 2 per cent., except for the first, 

 which has a very feeble conducting power, and therefore difficult to 

 determine, and for the last, which is saturated. In the two last cases 

 the deviation is less than a tenth, and is in the same direction in 

 both cases. 



6. It may be admitted as a first approximation, — 1st, that the 

 conductibility of a solution of sulphate of copper is equal to the 

 sum of the conductibilities of water and the salt; 2nd, that the 

 latter are proportional to the respective densities of the two sub- 

 stances, the temperature remaining the same. 



7. The latter law supposes that the constitution of each of the 

 molecules, water and sulphate of copper, has not been modified by 

 the fact of solution ; but when we consider how a mere difference of 

 a few degrees in temperature modifies the conductibility of a liquid, 

 we are surprised at the small limits between the corrected and the 

 calculated conductibilities of solutions of sulphate of copper. 



8. In a solution of sulphate of copper the water and the salt act 

 separately as conductors ; each is traversed by its own peculiar 

 derived current ; each consequently is decomposed by the current, f 



9. The copper reduced by electricity in a solution of sulphate of 

 copper has a double origin : one part proceeds from the direct reduc- 

 tion effected by the current, the other is a secondary product of the 

 action of nascent hydrogen on the copper salt. The relation of 

 the weights of these two deposits varies with the concentration, and 

 probably with the temperature of the liquid. 



10. The presence of a free acid in a solution adds a third con- 

 ductor to the two others, and diminishes, so far, the proportion of 

 copper directly reduced. 



1 1 . As the properties of the deposit vary with its origin, they will 

 probably vary also with the concentration and degree of neutrality 

 of the solution. 



12. The work absorbed by the reduced metal, depends not only 

 on the nature of the metal, and of the acid with which it was com- 

 bined, but also on its molecular state ; the electromotive force of a 

 Daniell's battery varies with the concentration and neutrality of the 

 solution of sulphate of copper. This variation, however, is comprised 

 within very narrow limits.-— Comptes Rendvs, Oct, 21, 1861. 



