400 TENTH ANNUAL REPORT OF 



galvanometer by platinum wires, a current is obtained wliicli passes 

 from the hydrogen solution to the other liquid. The former acts 

 relative to the latter as zinc to copper. When gold or silver wires 

 were used in this experiment, no current was obtained. 



2. The experiment having been made under exactly the same cir- 

 cumstances, excepting that the liquid in the tube contained oxygen 

 in solution instead of hydrogen, there was no current with connecting 

 wi-res of i)latinum, gokl, or silver. 



3. When the liquid in the tube contained a small quantity of 

 chlorine or bromine instead of hydrogen, a current was obtained, 

 which passed from the wide vessel into the tube, whether the experi- 

 ment was made with platinum, gold, or silver wire. 



4. If the current of a battery be passed through water containing 

 sulphuric acid placed in a U-shaped tube, this liquid will yield a 

 secondary current only in case the connexion with the galvanometer 

 be made with a platinum wire. By using gold or silver wire the 

 needle of the multiplier does not show the least deflection. 



5. If the experiment be made as in 4, using, however, dilute hy- 

 drochloric acid instead of dilute sulphuric acid, a secondary current 

 will be obtained even when the closing has been made with gold or 

 silver wire. 



The experiments under 1, 3, and 5 indicate that the course of the 

 polarization is to be found in the gases which are dissolved in the 

 water. 



The cases in which the liquids treated with gases yield no current 

 from polarization, (Nos. 2 and 4,) exactly correspond with tlie cases 

 above described, where metallic wires or plates immersed in gases 

 produced no such current, (Nos. 6 and 7.) In order to prove that the 

 stratum of gas adhering to the metallic plates or the gases dissolved 

 in the liquids are the cause of galvanic polarization, it must be ex- 

 plained why the same effect is not also produced in these cases. The 

 view of Schonbein on this subject we give in the following paragraph : 



§ 41. Schonbein' s theory of galvcmic polarization. — If two like me- 

 tallic plates be immersed in a liquid, one clean and the other coated 

 with a stratum of gas ; or if two such plates be placed in the two 

 branches of a U-shaped tube filled with the same liquid, except that 

 in the liquid in one of the branches a gas is held in solution, and not 

 in the other, the dissimilarity between the two parts is a sufficient 

 cause for the appearance of electrical tension. This tension will 

 cause an electrical current as soon as a metallic connexion is made 

 between the two plates. But in order that such a current may tra- 

 verse the wire of a multiplier, it must pass through the liquid, which 

 cannot transmit the feeblest current without electrolysis. Tlie ap- 

 pearance of the polarization current therefore is inseparably connected 

 with the beginning of the electrolysis of the liquid ; the current can- 

 not exist in any case when the electrical difference in the two surfaces 

 in contact is not sufficient to bring about electrolysis. 



For example, if the water acidified by sulphuric acid on one side 

 be terminated by a pure gold or silver plate, and on the other side by 

 one coated with a stratum of hydrogen, no current appears on con- 



