544 M. PoggendorfF on Galvanic Circuits composed of 
trated acid with 4 vol. water^ or in weight 1 and 2 parts). In 
this case there was no indication of 5 > i ; the first deflexion 
occurred even with the first immersion of the platina in favour 
of s <i, and indeed very violently = 90°. All the succeeding 
effects were likewise powerful^ and in the same direction. The 
deflexion w^as^ with slight vibrations^ 80°, '](f, 60°, and so on, 
till at last about 20°, from whence, remarkably enough, it again 
increased. The amplitude of the last observed vibration went 
from 70° + 30°. 
The violent action of the acid on the zinc obliged me to ter- 
minate the experiment ; but it was immediately recommenced 
with amalgamated zinc and the same acid. At present the cur- 
rent was nearly zero; only a slight deflexion of about 4° be- 
trayed an inclination to 5 c i. 
I now heated the platina, and indeed only that plate which 
was to stand in the acid. On contemporaneous immersion of 
both plates (of which the one heated had naturally, as in all 
similar experiments, perfectly cooled) a deflexion of 90° in the 
direction s^i first resulted, immediately succeeded by one like- 
wise of 90° in the direction 5 c i, and the needle now vibrated 
on the same side of the meridian, successively about the points 
85°, 80°, 75°, 70°, 60°, 50°, 40°, till at last, after some minutes, 
it merely indicated a permanent deflexion of 2°, but still always 
in the direction s^i. 
The heating of the platina was at present performed on the 
other plate, which was to be placed in the iodide of potassium. 
The result on immersion w^as of the same kind, but considerably 
less in strength than the previous one. The first deflexion 
in favour of 5 > i amounted only to 5°, and the one immediately 
succeeding, in the direction s to 22° only, upon which the 
needle then soon came to rest. A second heating of the plate 
to be placed in the acid, produced again the same result in its 
whole force. The first deflexion, in the direction s i, was 90°; 
the second, in the direction 5 < i, likewise 90°, and the current 
now^ retained this direction wdth great energy, which diminished 
but very slowly*. 
* This phsenomenon also appeared when dilute hydrochloric acid was em- 
ployed, and to a far greater extent. If, after the effect has decreased to zero, 
the plate standing in the acid be taken out, washed, heated, and, after cooling, 
re-immersed, a movement of 90°, in the direction s c i, is immediately ob- 
tained, succeeded by a highly permanent deflexion in the same direction. If 
after the deflexion has again descended to nearly zero, we perform the same 
operation with the plate inserted in the iodide of potassium, this has but a very 
weak, in most cases, no result. Heating of both plates acted as when this was 
performed solely with the first. I likewise observed on this occasion that 
heated plates of platina almost wholly lose their remarkable effect by being 
suspended for some hours in the atmosphere. 
