404, Intelligence and Miscellaneous Articles. 
OBSERVATIONS ON THE USE OF INSOLUBLE COMPOUNDS 
IN VOLTAIC PILES. BY M. BECQUEREL. 
In the decompositions announced in 1837, effected on insoluble 
substances placed in contact with the negative pole of a couple or 
battery, I was able to reduce large quantities of different metallic 
substances, more especially chloride and sulphide of silver, and sul- 
phate and phosphate of lead. These effects are analogous to the 
decomposition of fused chloride of silver, which takes place when 
this substance is immersed in acidulated water in contact with a 
plate of zinc. 
Many years afterwards I recurred to the subject, and showed the 
advantage to be derived from the use of insoluble substances in the 
construction of voltaic couples. The couples might be composed of 
an oxidizable metal (zinc or iron), a single liquid, generally saline 
water, and a conductor of tin, surrounded by one of the substances 
mentioned—such as silver, lead, or copper minerals, and in particular 
sulphate of lead. 
One of the most important applications of these effects was the 
electro-chemical treatment of silver and lead ores*, using in this 
case the remarkable action produced by an oxidizable metal on 
sulphate of lead in presence of saline water. Since this time I have 
frequently used these sulphate of lead batteries in my electro-che- 
mical researches. They were piles with one liquid; the oxidizable 
metal was zinc placed in a sailcloth bag, or in a permeable vessel filled 
with saturated solution of salt. The second conductor consisted of 
a bar of charcoal, or a plate of copper, lead, or tin, in contact with 
brine saturated with sulphate of lead, or holding it in suspension. 
The contents of the vessel in which this latter solution was placed 
was often 3000 litres. Six such couples, united as a battery, gave 
pretty strong sparks. The intensity of their action depends on the 
depolarization of the negative plate by the sulphate of lead which 
is reduced, and by which the disengagement of hydrogen is pre- 
vented. Besides, the liquid contains sulphate of lead in solution as 
well as diffused; for it is soluble in about fifty parts of the saline 
solution. The permeable diaphragm serves to prevent the closing 
of the circuit and the destruction of the effect of the pile, by the 
precipitation of lead on the zinc when solution of salt is employed. 
It is to be observed that the electromotive force of the couple is 
the difference of the effect produced by the liquid on the zinc and 
on the reduced lead, and that hence it is sufficient to have a rod or 
plate of tinned iron or of lead, as negative conductor in contact with 
the sulphate of lead. For some years, masses of sulphate of lead, 
produced in the manufacture of sulphuric acid at Dieuze, and sold 
at alow price, have thus been reduced to the metallic state. In the 
fusion of the lead it is necessary to take suitable precautions, as it 
frequently contains a little sulphate.-—Comptes Rendus, April 2, 1860. 
* Comptes Rendus, vol. ii. p. 23; and Becquerel’s Traité d’Electricité, 
vol, ii. p. 355 et seq. 
