348 Prof. Helmholtz on Galvanic Currents 



zero, and went up to 2 or 3 U.S., making irregular vibrations. 

 The weight was replaced and additional shot poured in very 

 slowly. The deflection almost instantaneously changed to 

 about 2 S.U., which increased slightly until the wire broke. 



Experiment!!, — A copper wire *24 millim. diameter. © = 15°, 

 Initial deflection 1 S.U. 



M. D. 



1 



3 1 



6 3 



9 3 



12 3 



15 4 



18 4 



21 2-5 



24 2-5 



27 2 



30 1-5 



33 1-5 



36 1-5 



39 1-5 



42 1-5 



The direction of the current was S.U. Several small weights 

 were added to the can ; but the deflection remained steady at 

 1*5. In copper wire, no fall in the deflection was observed 

 when the weight was left suspended for some time. 



The Physical Laboratory, 

 University College, London. 



XLVIII. On Galvanic Currents occasioned by Differences of 

 Concentration — Inferences from the Mechanical Theory of 

 Heat. By Professor Helmholtz*. 



WE will regard as the electro-chemical equivalent of an 

 ion that amount of it which is separated at the corre- 

 sponding electrode, in the unit of time, by the chosen unit of 

 current. 



The transport-number n, referred to the cation (Hittorf 's -), 



gives, as with Wiedemann, that fraction of the equivalent of 

 the cation in question which is carried by the unit of current, 

 during the unit of time, through each cross section of the cur- 

 rent's path in the solution, to the cathode. On the other hand, 

 the quantity (1 — n) of the anion goes in the opposite direction, 



* Translated from the Monatsbericht der konigUch preussischen Aka- 

 demie der Wismischaften zu Berlin, Nov. 1877, pp. 713-726. 



