CRYSTALLIZATION PRODUCED BY VOLTAIC ACTION. 439 
acids having a less affinity than itself towards the bases is owing solely 
to the small energy of action in the pile; for if the action were more 
powerful, all the acids would be indiscriminately transferred to the 
positive pole. ] 
The electric current employed by us in order to produce decomposi- 
tions, may arise from two causes; the chemical reaction which the two 
liquids in contact exercise on each other, and the chemical action of 
the liquid of the small tube on the metal immersed in it. In the first 
case, if the reaction be sufficiently energetic, the second cause may be 
dispensed with: in like manner, if the second cause be of sufficient in- 
tensity, the first becomes superfluous. But when both are feeble and 
the currents resulting from them have the same direction, their sum is 
then indispensable to the production of the electro-chemical effects. 
In general, whenever the two currents take the same course, their sum 
cannot but be favourable to the decompositions and the formation of 
the products. It often happens that these two currents are so weak 
that the reduction of the oxide in the great tube cannot take place. In 
that case there is no effect produced. If, therefore, after an interval of 
some days, we perceive no precipitation of copper on the plate of cop- 
per immersed in the solution of the nitrate or the sulphate, it is useless 
to continue the experiment longer, and the apparatus must be changed. 
In the experiment in which the great tube contains sulphate of copper, 
and the small one contains, in its lower part, potter’s clay moistened 
with a solution of nitrate of potash, and alcohol, the chemical re- 
action of the nitrate on the sulphate has had considerable influence in 
producing the current which has decomposed the sulphate of copper ; 
for the action of the alcohol on the lead must have been sufficiently 
feeble to give rise to a sensible electric current. It would be desirable 
to operate always on such solutions as would exercise on each other 
chemical actions sufficiently energetic to give out the requisite currents, 
when the plate immersed in the liquid is gold or platina, in order that 
we may be able to study the phenomena of decomposition and recom- 
position with facility, and independently of the reaction of the oxides, 
This would be the only course to be taken in order to discover what it 
is that takes place in the liquid organic compounds, when, by means of. 
electricity, we introduce into them such bodies as are capable of carry- 
ing off some of their constituent parts. This want of sufficient reac- 
tion in the liquids may be supplied by operating with the following 
apparatus, which enables us, when we wish, to avoid the action of the 
metallic oxides formed at the positive pole. As this apparatus enables us 
to operate in a great variety of cases, we shall more minutely describe 
its construction and use. 
We take three jars A, A’, A", (fig. 3.) placed in a line at a short 
distance from each other. The first is filled with a solution of sulphate 
or nitrate of copper; the second, with a solution of that substance 
