148 Analyses of Books. 



not closed, the entire action is local — in one of the ordinary con- 

 struction, much is in circulation — and, in the perfect one, all the 

 chemical power circulates and becomes electricity. By estimating 

 the quantity of zinc dissolved, and the quantity of decomposition 

 effected in the volta-electrometer, these proportions can be appre- 

 ciated. If a voltaic battery were formed of zinc and platinum, the 

 latter metal, surrounding the former, as in the double copper arrange- 

 ment, and the whole being excited by dilute sulphuric acid, then no 

 insulating divisions of glass, porcelain, or air, would be required be- 

 tween the contiguous platinum plates, and provided these did not 

 touch metallically the same acid, which being between the zinc and 

 platinum, would excite the battery into powerful action, would be- 

 tween the two surfaces of platinum, produce no discharge of the 

 electricity, nor cause any diminution of the power of the trough. 

 This is a necessary consequence of the resistance to the passage of the 

 current, which occurs at the place of decomposition, for that resistance 

 is fully able to stop the current, and, therefore, act as insulation to 

 the electricity of the contiguous plates, as the current which tends 

 to pass between them, never has a higher intensity than that due to 

 the action of a single pair. If the metal surrounding the zinc be 

 copper, and if the acid be nitio-sulphuric acid, then a slight discharge 

 between the two contiguous coppers does take place, provided there 

 be no other channel open, by which the forces may circulate, but 

 when such a channel is permitted, the return discharge is much 

 diminished. Upon these principles, the author was led to construct 

 a trough, in which, the coppers passing round both surfaces of the 

 zincs, were only separated from each other by paper. He soon 

 found, that this was exactly Hare's trough. It is very convenient, 

 for when composed of 40 pairs of 3 inch plates, it can be unpacked 

 in five minutes, and re-packed in half an hour. Its effect on plati- 

 num wire, in the shock, Ike, was equal to 40 pairs of 4 inch plates 

 with double coppers, in porcelain troughs. With 20 pairs of 4 inch 

 plates arranged in Hare's trough, and 20 pairs of 4 inch plates in 

 porcelain troughs, there was a consumption by the former, of 3-7 

 atoms zinc, and 5"5 for the latter. Hence, no doubt can exist, of the 

 great superiority of Hare's method of arrangement. This plan will, 

 therefore, soon supersede the old method, as 100 pairs of plates need 

 not occupy a trough of more than 3 feet in length ; and, by making 

 it turn upon a pivot, the acid may be poured off when required. The 

 author recommends troughs of porcelain, because it is difficult to 

 make a wooden one constantly water tight. 



Under distinct heads, the author describes some important practi- 

 cal points. 



Nature and strength of the acid. — Of all the acids singly, nitric 

 acid answers best. It improves the action of sulphuric acid. The 

 proportions employed by Dr. Faraday for ordinary purposes were 

 200 water, 4^ sulphuric acid, and 4 nitric acid. The quantity which 

 each zinc plate lost in these circumstances was 2*16 atoms; with 

 double the quantity of acids and the same proportion of water, the 

 loss was 2*20 atoms. No copper is dissolved during the regular action 

 of the trough, but much ammonia is disengaged when nitric acid is 

 present. 



