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XLV. Intelligence and Miscellaneous Articles. 



ON THE HEAT PRODUCED BY AN ELECTRIC DISCHARGE. 

 BY R. CLAUSIUS. 



To the Editors of the Philosophical Magazine and Journal. 

 Gentlemen, 

 TN a paper by Prof. W. Thomson, in the March Number of the 

 -■■ Philosophical Magazine, p. 193, the following statement occurs 

 on the discoverj' of the important law, that the heat capable of being 

 ]5roduced by an electric discharge is not simply proportional to the 

 quantity of electricity employed, but to the square of the same, 

 " as was first demonstrated by Joule in a communication to the 

 Royal Society in 1840, although it had been announced by Sir W. 

 Snow Harris as an experimental result, to be simply proportional to 

 the quantity. Mr. Joule's result has been verified by independent 

 observers in France, Italy and Germany." I may be allowed to 

 observe on this subject, that the investigations of Riess, mentioned 

 by me in my paper on the mechanical equivalent of an electric dis- 

 charge, are of a much older date. The memoir in which Riess 

 refuted the statement of Snow Harris, and_proved to a certainty by 

 numerous experiments that the heat which is produced by the dis- 

 charge of a Leyden battery in any part of the connecting wire is 

 represented by the formula q" 



s 

 in which q denotes the quantity of electricity used, and s the surface 

 of the inner coating, is printed in PoggendorfF's Annalen for March, 

 1837. 



I am. Gentlemen, 



Yours faithfully, 

 BerUn, March 19, 1854. R. Clausius. 



ON SOME PECULIAR REDUCTIONS OF METALS IN THE HUMID 

 WAY. BY PROF. WOHLER. 



The following experiments were made for Prof. Wohler by Hiller. 

 Tiie observation first made by Bucholz, that long crystals of metallic 

 tin are formed when a rod of that metal is inserted in a solution of 

 protochloride of tin, and the latter carefully overlaid with water, was 

 first of all further tested. It appeared that, for the production of 

 large crystals, the solution of chloride of tin must be acid. Of the 

 tin immersed in the solution there was always more dissolved than 

 was made up by that which crystallized. In one experiment the 

 proportioDS were as 7 : 6. 



These crystals are formed at the point of contact between the two 

 fluids. If the solution be neutral, they appear below this in the 

 solution of the protochloride, and remain bright. 



Copper, inserted into a neutral solution of nitrate of copper, covers 

 Itself entirely with brownish-red crystals of protoxide of copper, and 

 afterwards with sharp crystals of metallic copper. The copper is 

 dissolved, especially at the point of contact of the fluids. The same 

 phaenomenon is produced, but in a less degree, with sulphate of 

 copper. In solution of perchloride of copper, the copper is covered 

 with crystals of the protochloride. 



Phil. May. S. 4. Vol. 7. No. 45. April 1854. X 



