260 Muriatic Acid produced hj means of Galvanism. 



On exposing to the sand bath a mixture of bruised indigo 

 and muriatic solution of tin with excess of acid, and oxidated 

 at the minimum, the colouring substance is decomposed, 

 liberating a gas of an insupportable and pernicious smell, 

 which ought to be examined. 



If indigo, treated with the muriatic solution of tin ox- 

 idated at the minimum, without the assistance of a caustic 

 alkali, is of no use in dyeing, this is not the case with sul- 

 phate of indigo treated or mixed in different proportions 

 with the same solution of tin, after having previously ab- 

 sorbed the sulphuric acid ; the latter being made use of in 

 printing-houses for producing all sorts of blue and green 

 shades. 



XLIV. Letter of M. Veau de Launay, M.B. to M. De- 

 LAMETHERiK, xipou the Production of the Muriatic Acid 

 ly means of Galvanism '■^. 



OiNCE my note, inserted in your journal for July last, the 

 experimental class of the Galvanic Society has repeated se- 

 veral times the experiment of Messrs. Pacchjani and Brug- 

 natellif relative to the formation of the muriatic acid, and 

 always with success ; i. e. with the formation of muriatic 

 acid at the zinc pile in a manner more or less perceptible j 

 sometimes even the acid was of a very strong smell, and co- 

 loured yellow J. I also obtained it several times in my own 

 ]aboratory with a pile d'alizeau of seventy pairs only. It is 

 more than a year ago since I was convinced of the truth of 

 this interesting experiment, which would not be called in 

 question at present, but that every chemist or natural philo- 

 sopher endeavours to explain it by a theory of his own, more 

 or less ingenious. For my own part, I am contented with 

 knowing the facc fo be true from personal observation. In 

 the last experiments made at the arsenal at M. Riffault's, one 

 of the members of the experimental class of the Galvaniq 



* From Jnnrvr.l dc Phynqiie, August 180R, p. 165. 

 •|- See Philosophical Magazine, vol. xxv. p. 260. 

 \ We operated with a gold wire. 



Society, 



