188 Remarks on ih Galvmiic lldtio-j. 



Tin formation of Sulphate of Zxna — As soon as the poles 

 of the battery are joined . z. is formed in the cell contain- 

 ing the zinc, and metallic copper is deposited on the 

 copper plate. A long series of experiments were insti- 

 tuted to determine the rate of formation of the s. z. during 

 the various conditions of the battery. A Hill's element 

 was put on a closed circuit through the galvanometer, 

 without any external resistance, and the specific gravity 

 of the 5. z. was measured daily, by means of a Baurne 

 hydrometer. The indications of the galvanometer needle 

 and the temperature, was also ascertained at the same 

 time. The jar containing the liquid was 7 inches high 

 and 6 inches in diameter. The zinc and copper plates 

 each presented a surface of 28 square inches. The dis- 

 tance between the plates was 5| inches. The battery was 

 started with s. z. at 21° B. specific gravity. This element 

 was on a closed circuit for 30 days ; at the end of that 

 time the s. z. was nearly saturated 43° B., temperature 50°, 

 and q. had decreased to only one-seventh of its normal 

 value. For the first 23 days, or while the specific gravity 

 of the s. z. was less 40° B., q. was sensibly the same from 

 day to day. 



It is a fundamental principle that the formation of 5. z. is 

 directly proportioual to the quantity of electricity passing 

 in the circuit. This would be strictly true, provided there 

 was no local action; but actual experience demonstrates 

 that this condition is never fulfilled. On laving down the 

 daily results in the form of a curve, having the specific 

 gravity of the s. z. for one ordinate, and the time for the 

 other, it was found that the observations could be well 

 represented by an equation of the second degree in which 

 a j = + 1-46° and a 2 =—0-08°. For this element, the 

 amount of liquid saturated with 8. z. between the limits 

 12° to 40° B., was 3-6 cubic inches daily. A second 

 element of the same size in which the distance between 



