543 
Two Fluids, and of Two Metals not in Contact, 
The first oscillation of the needle had the amplitude 80° — 45° 
{i. e, went from 80° on the one side of the meridian to 45° on 
the other). The deflexions^ however^ decreased rapidly, and 
when they had sunk to 12°— 0° the platina was removed. This 
washed, dried, and again inserted, produced a current in the 
direction s^L The first deflexions were 90° — 85 ; the fol- 
lowing, 85° — 80°; 80° — 75°, &c., till at last 6° — 3°, when 
they were again taken out. The third, fourth, fifth, &c., im- 
mersion gave all of them currents in the direction s ^i, only 
commencing with slighter deflexions. 
At the same time two remarkable circumstances occurred 
here. At the commencement, namely, the (distilled) zinc, as 
is always the case when its surfaces are very bright, was but 
very slightly attacked by the dilute sulphuric acid, which also 
in this case consisted of 1 vol. concentrated acid, and 9 vol. 
water ; but the longer it remained in it the stronger the action 
became, so that at last the disengagement of gas was very 
lively. At the commencement, the vibrations of the needle, 
although great, were nevertheless quite regular ; but in propor- 
tion as the evolution of gas increased, sudden convulsions were 
evident in the vibrations, which became greater and greater, and 
at last passed into actual starts of 30, 40, 50, 60, 70, &c. de- 
grees, and thus far exceeded the commencing deflexions which 
even on the fourth immersion did not amount to more than 
10°. All these starts took place’ in the direction 5 < Their 
progressive increase evidently pointed to an increasing ascend- 
ency of the iodide of potassium over the acid. — The second 
notable circumstance was, that with each taking out of the 
platina, although both plates were removed at the same time, 
a strong deflexion (of 90°) likewise in the direction s re- 
sulted. This phaenomenon was especially surprising at the 
close of the first immersions, as the needle then made but very 
small and quite regular vibrations*. 
I now repeated the same experiment (zinc filed bright, pla- 
tina not heated) with a stronger sulphuric acid (1 vol, concen- 
* I frequently observed similar starts, and especially when, on employing 
ordinary zinc, I endeavoured to find out whether sulphuric acid or hydrochloric 
acid (both of the degrees of dilution mentioned at p. 489.) would develope the 
greater electromotive force. With silver, as negative metal, the convulsions 
and starts of the needle were so powerful that I could not decide as to the di- 
rection of the current. With platina these disturbances did not occur, because 
it was first examined, and the acids did not then act so violently on the zinc. 
With copper and tin they vanished in comparison to the force of the main effect; 
for with copper, the sulphuric acid, and with tin, the hydrochloric acid, had in the 
highest degree the superiority. Subsequent experiments, partly with bright 
filed distilled zinc, partly with ordinary, but amalgamated, showed me that also 
with platina and silver the sulphuric acid has the ascendency, although in a 
far less degree. 
