EXPERIMENTS OF GALVANIC ELECTRICITY. ] 35 



which gives for the fpace between 55° and 212°, or 157°, How far they 

 the quantity 0. 327 inftead of 0. 321, as Mr. Dalton finds it. agree * 

 This difference of fomewhat lefs than one fiftieth part of the 

 expanfion, may perhaps have arifen from a difference in the 

 fcales of operation, of perhaps the difficulty of producing a 

 given temperature through the whole mafs of a fluid, &c. 



XII. 



Account ofjbme Experiments made in the Laboratory of the Royal 

 Iriflitution, relating to the Agencies of Galvanic Electricity, in 

 producing Heat, and in effecting Changes in different fluid Sub- 

 ftanees. By H. Davy, Prof. Chem. 



I. IT has been fhown, by a very interefting experiment madeDifcovery of 



in France, by Meflrs. Fourcroy, Vauquelin, and Thenard, ueH^andThe- 



that the power of galvanic batteries containing large plates, tonard, of the 



ignite metallic fubftances, is much greater than that of batte- f ea ; er >g nition 

 o ' o by large galva- 



ries compofed of an equal number of fmall plates ; though their nic plates. 



agencies upon water, and upon the human body, are nearly 



the fame. 



In examining the circumftances of the action of a galvanic The trough with 



apparatus, or trough, conftructed in the Royal Inflitution, and tfojFfanwHa io^n 



containing twenty feries of plates of copper and zinc, fquare,of chemical 



and thirteen inches in diameter, I obferved that the fame rela- agenC) l as r 



* 4 apparatus. 



tions between chemical agency and the production of galvanic 

 electricity exifted as in other cafes. When pure water was 

 ufed for filling the cells, the fparks, as well as the fliocks, 

 were extremely indiftinct ; and the battery was capable of ig- Water had little 



niting only about a line of iron wire of -,-ipr of an inch in diame- e ^^' J falts and 

 °„ T . , _ . _ . , ,', , ,. acid much more. 



ter. With lolution or muriate or loda it acted better ; and di- 

 luted nitric acid was fiill more efficacious. With this lait fub- 

 ftance, it became capable of rendering white-hot three inches 

 of the iron wire of T ^, and of caufing two inches to enter 

 into fulion. 



In comparing the effects produced by a folution of nitrous Nitrous acid did 

 acid, of the fpecific gravity of 1.4, in about fixty parts ofwa-"^J^ frg 

 ter, with thofe occafioned by a concentrated folution of carbo- For it h much 

 nate of potam, the acid was found to produce by much the* " P°^ erful 

 greatejt intenfity of action ; which can hardly be afcribed to potato, though it 



arj y conducts much 

 J left. 



