Chemical Science. 181 



U. CHEMICAL SCIENCE. 



1. ON THE ELECTRO-MAGNETIC EFFECTS OF METALLIC PLATES 



HAVING VARIOUS POSITIONS, INTERVALS, &C. &C. (By M. BiglOU.) 



M. Bigiou has made experiments to determine the relation of 

 electro-magnetic effects, which take place when equal discs of zinc 

 and copper are immersed, under different circumstances, in the same 

 fluid. He obtained the following results: i. Voltaic electricity is 

 transmitted through a metallic plate, having its surface grooved or 

 roughened with sand-paper, more easily than through a plate of the 

 same metal with a polished surface *. ii. In placing one of the 

 plates inclined to the other, the effect is diminished t- iii- The ex- 

 tent of the surface of copper, as M. Marianini has shown, has a 

 greater influence over the electro-magnetic effect than that of the 

 zinc. The author shows, however, that nothing would be gained in 

 the construction of a voltaic battery, by making the zinc much 

 smaller than the copper, as the greatest effect takes place when they 

 are nearly of the same size. iv. The author remarks that the effect 

 diminishes as the distance between the plates increases J. The most 

 valuable part of his paper, is that in which he gives the relative de- 

 flecting forces of the same plates with different acid solutions. This 

 was ascertained with the torsion galvanometer. 

 Water, with -fa of its bulk of sulph. acid . . 106 of torsion. 



Do. -j 1 ^ of muriatic acid 58 do. 



D' Tiff f nitric acid 106 do. 



Do. -fa of nitric acid, and -fa muriatic acid, 59 do. 



D' ^V f nitric, and T ^ sulphuric acid 96 do. 



Do. -fa of nitric, and -fa sulphuric acid 120 do. 



From this it appears, that equal volumes of nitric and sulphuric 

 acids produce the greatest electro-magnetic effects. 



2. HARE'S DELICATE GALVANOMETER. 



Dr. Hare, of Philadelphia, has constructed a galvanometer, with a 

 riband of tin-foil thirty-four feet long, with a slip of paper inter- 

 vening, which he says is more sensitive than those made with cop- 

 per-wire, covered with silk, when the copper-wire was eighty feet 

 long. He finds pure mercury, obtained by precipitating the proto- 

 nitrate by copper, is negative to copper and the other metals, whereas 

 impure mercury is positive, unless the amalgam be formed with the 



* According to the experiments of Mr. Leslie, the same thing takes place with 

 heat. 



f This is also the case with radiant heat. 



J He does not seem to be aware of the law, experimentally proved by Mr. 

 Ritchie, (Journal of the Royal Institution, No. I., page 35,) that the effect 

 diminishes inversely as the square root of the distance oi' the plates. 



