hj the Galvamc Decompos'itlon of JVater. 245 



hydrogen in the tube A. Allow the apparatus to work, and 

 a few hours will furnish unequivocal marks of the existence 

 of the muriatic acid in the tube B, which had allowed oxv- 

 gen to escape, and of soda in the tube A, which retained it. 

 At the end of ten or twelve hours, nitrate of silver, poured 

 into B drop by drop, precipitates itself abundantly. If the 

 water of the two tubes is mixed together and evaporated, a 

 sensible quantity of muriate of soda is obtained. If the ex- 

 periment is made in the dark, the acid obtained in the tube B 

 is oxygenated. The citron yellow colour is very striking; 

 the smell of the acid cannot be mistaken ; light decomposes 

 it. The tubes must not be too narrow ; they ought to be 

 six or eight lines in diameter: without this precaution the 

 experiment will not succeed ; because the current, in order 

 to pass from B to A by the inferior orifice of the two tubes 

 plunged into a bad conductor, which is water, requires a cy- 

 linder of a great enough diameter in order to carry, in a given 

 time, a sufficient quantity of electricity into the tubes. The 

 latter must not be too far from one another ; they will be at 

 a convenient distance in aflat-bottomed drinking-glass. The 

 oxygenated acid soon attacks the gold. If evaporated, we 

 ought to have a fine purple of Cassius* for a residue. Has 

 any thing been discovered for a long time more perplexing 

 or more remarkable ? The discovery of soda belongs to Mas- 

 cagny, of Siennaf. I have the honour to be, &c. 



Leopold dk Buch, 



* The autl;or is hjere in an error. There can be no precipitate of Cassius 

 formed without the presence of tin. — Enjr. 



f The production of soda by the Galvanic action is a new fact ; but that of 

 an acid (then supposed to be the nitrous acid) belongs to Cruickshank : he 

 announced it very learnedly in a memoir entitled " Additional Remarks on 

 Galvanic Electricity," published in Nicholson's Journal for 1800. What 

 M> de Buch has here said relative to certain conditions of manipulation, with- 

 put which the experiment did not succeed, will peihaps explain the reason 

 why Messrs, Biot and 'I'henard met wilij no success in their attempts to repeat. 



PiCTKT, 



The production of soda by tjie Galvanic decomposition of water, was an- 

 nounced in 'I'he Philosophical Map^^zine so far back as the month of April 

 last; that is, exactly a year ago. M. de Buch's letter given above is dated in 

 October; and the number of M. Pictet's Journal, from which we have copied 

 it, i« that for November last. The first discovery, therefore, belongs to Mr. 

 Peel. See our xxist volume, p. 'J79. — Edit. 



0^3 XL\^ Tu'cntij' 



