—————————— LS 
7 7 eg 
Voltaic Electricity on Alcohol, &c. 343 
A moderately strong solution of recently prepared and colour- 
less hydriodic acid was placed in A, and connected with the ne- 
gative side of fifty pairs of two-inch plates. Distilled water was 
placed in B, and connected with the positive side ; and the con- 
nexion was made by asbestus, moistened with distilled water. A 
slight effervescence ensued from both poles. During the first ten 
minutes, there was no appearance of discoloration of the liquid 
in either tube. A slight yellow tint then appeared in the positive 
liquid, and no change in the negative, and shortly after, a just 
perceptible acid reaction on test-paper was observed in the posi- 
tive liquid. In a quarter of an hour, the battery was reversed in 
the manner already described as to muriatic acid. Instantly, not- 
withstanding the diminished action of the battery, the hydriodic 
solution which had been previously colourless, acquired a brown- 
ish colour round the positive pole, and not a bubble of gas ap- 
peared from that pole, whilst gas rose from the positive foil. The 
brown colour gradually diffused itself through the liquid. 
This experiment was now repeated with the difference that 
the level of the distilled water was made about a line higher than 
that of the hydriodic solution, which was perhaps a little weaker 
than in the preceding experiment. A slight evolution of gas 
soon arose from both poles, and in a quarter of an hour there was 
not the slightest discoloration of the liquid in either tube, nor 
did the water shew any acid reaction. The battery was then re- 
versed. The hydriodic solution was immediately discoloured 
round the positive foil as before, without any liberation of elastic 
fluid, whilst there was a slight effervescence from the negative 
foil. 
This last experiment was repeated with a power of thirty-six 
pairs of four-inch plates, with precisely the same result. 
The explanation of these experiments seems very apparent. 
When the hydriodic acid solution is in connexion with the nega- 
tive side, and the water with the positive, water is resolved into 
2 
