EUSricity, Chemical ASion, Caloric? i»5 



that the hydrogen of the water fliould be in a ftate of quartation, or overcharged with 

 oxigen, in the fame manner as gold with filvcr, in order that the folution or parting may 

 take place. The contadl of the atmofphere is therefore neceflary to the water in the goblet, 

 in order that it may re-aflume the neceflary ftate of quartation, by abfoibing oxigen gas 

 from the atmofphere, in proportion as the oxidajtion of the metal feizes the radical of 

 that principle. 



If the experiment be made in a calm air, a kind of pellicle may be obferved at the fur- 

 face of the water, immediately over, and of the fame figure and fize as the metal, beneath 

 which ftreams even indicate the points of the furface and columns of the water, through 

 which the atmofpheric oxigen has been tranfmitted. This re-abforption is fo true, that if 

 in fome cafes a metallic oxide, well charged with oxigen, be fubftituted inftead of the con- 

 taft of the atmofphere, the combuftion of the metal under experiment is efFe£led with 

 facility. It is known that iron decompofes water without addition, though very flowly ; 

 but if the red oxide of lead be added at the bottom of the water, the iron becomes changed 

 into the black oxide without decompofition of the water. 



I have obtained, though after a very long time, the oxidation of tin in water in conta£l 

 with filver, in a bottle of flint glafs filled with water, and almoft hermetically clofed. But ' 

 I have remarked, that the lead which enters into this kind of glafs, yielded its oxigen to 

 the tin, and became changed into a black opaque oxide, in the fame manner as happe^ns 

 when a bottle of flint glafs, filled with hydrogen gas, is made red hot in the midft of 

 charcoal. The hydrogen is burned, and feizes the oxigen of the lead, which it revives, 

 as the tin operated in the cafe before-mentioned. 



It appears evident, therefore, that the experiment of Sultzer is nothing more than a 

 combuftion or chemical operation, as is proved not only by its refult, but its duration. For 

 electricity a6ts always inftantaneoufly, whereas the efi"e£l:s of the chemical affinities con- 

 tinue as long as the re-agents are not faturated. I left for a very long time in water, pieces 

 of filver wrapped in feveral folds of tin foil. I took out fome of them at different periods, 

 and found the progrefs of the combuftion exactly proportional to the time. In thofe which 

 I took out the laft the tin was corroded, and pierced through all its folds, as if it had been ' 

 plunged in an acid. But if other proofs be required, to flisw that eleftrlclty has no part 

 in the phenomenon in queftion, we might vary the experiments, fo as not to hinder the 

 eftefts of the ele£tric fluid, and evidently to prove by the eyes, that the_ combuftion which 

 happens depends on the difpofition of the metals, and their chemical affinity. 



For example, if a piece of tin of confiderable thicknefs be placed on the eye, and 

 touched at its oppofite furface with a bar of filver, there is no decompofition of water, nor 

 combuftion, nor light, and yet the contaft of the two metals ought to produce thefe fen- 

 fible effefts, if they depended on the communication of their eledlricity. 2. If a piece of 

 tin be held upon the eye, and another piece in the mouth, and a communication he made 

 between them by a bar of filver, there is no more appearance of light than in the former 

 experiment. 3. If a piece of gold be applied on the eye, one of filver on the tongue, and 



a com- 



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