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 XLV. Intelligence and Miscellaneous Articles. 



ON GALVANIC CURRENTS BETWEEN SOLUTIONS OF DIFFERENT 

 DEGREES OF CONCENTRATION OF THE SAME SUBSTANCE, AND 

 THEIR SERIES OF TENSIONS. BY DR. JAMES MOSER. 

 rpHE electromotive force of liquid galvanic series is influenced by 

 ■*- the concentration of the liquids. In order to determine the 

 nature of this influence, I have investigated, in the laboratory of 

 Professor Helmholtz, liquids with which it is possible to isolate 

 this influence of the concentration. All chemical processes were 

 to be excluded ; therefore only differences of concentration might 

 exist or changes in it occur during the passage of the current. 

 Likewise, for the elimination of all chemical actions, it was neces- 

 sary that the electrodes should consist of that metal which was 

 contained in the solution. 



Two glasses with differently concentrated solutions of the same 

 salt were connected by a siphon ; and the circuit was closed by a 

 metallic conduction with the electrodes just mentioned. I then 

 observed, in all the cases investigated, that a current arises ivhich 

 proceeds from the more dilute to the more concentrated solution. It 

 may be represented thus : — 



Zn, dilute Zn S0 4 , concentrated ZnS0 4 , Zn. 



This current appeared regularly in a series of solutions of sulphate, 

 nitrate, chloride, and acetate of zinc, sulphate and nitrate of copper, 

 chloride of iron, acetate and nitrate of silver, &c. 



I observed the electromotive forces of these series by Poggen- 

 dorff's method of compensation, modified by Du Bois-Reyniond, 

 from a few thousandths up to one fifth of a Daniell, the latter force 

 between very dilute and highly concentrated solutions of zinc 

 chloride. 



I give, in the following Table, the ten electromotive forces, be- 

 tween the combinations of two, of five solutions of sulphate of 

 zinc, the unit being nearly 0*001 of a Daniell : — 



100 parts of solution contain of 

 ZnS0 4 + 7H 2 



15 per 

 cent. 



30 per 



cent. 



45 per 

 cent. 



60 per 



cent. 



1 per cent. 

 15 „ 

 30 „ 

 45 



18 



22 

 5 



28 

 13 



7 



36 

 21 



17 

 9 



These numbers indicate a series of tensions ; for e. g. the electro- 

 motive force between 



15- and 30-per-cent. solution is 5, 



30- and 60-per-cent. solution . . 17, 

 15- and 60-per-cent. solution . . 21, 



I then confirmed the existence of a series of tensions by con- 

 necting with each other, by four siphons, five glasses, of which the 

 1st, 3rd, and 5th contained solutions of equal strength (45-per- 

 cent.), the 2nd contained stronger solution (60-per-cent.), the 



