pile, cxpufed for nearly the fame time to y^atejr in contadl with the atmofphere, had de- 

 pofited much white oxide, and given out fome gas> and the zinc plates were whitened 

 both internally and externally *. 



b. No influence can be communicated from an elaftic atmofphere, enabling the zinc of 

 the galvanic pile to decompofe pure water ; for piles were introduced into hydrogen, 

 pitrogen, nitrous oxide, and hydro-carbonate, and fuffered to remain in them for different 

 lengths of time ; but in none of thefe gafes was the zinc more oxidated than if the pile 

 had been immerfed in pure water- 



c. A galvanic pile was fuffered to remain in vacuo for fourteen hours, the gage 

 being about -/-o, the zinc plates were flightly tarnifhed, but no white oxide had formed 

 upon them. 



2. Tke Oxidation of the Zinc Plates of the Galvanic Pile takes place "whenever the Water in 

 contaEl with them holds Atmofpheric Air^ or Oxygen, or Nitrous Gas, or Nitrous Acid, or 

 Afarine Acid, i^c. in Solution. 



a. The oxidation of the zinc of the pile in the atmofphere, and the protufion of 

 carbonate of foda, has been accurately defcribed by MefTrs. Nicholfon and Carlifle. I have 

 found that the phenomena of oxidation takes place much more rapidly in pure oxygen than 

 in the atmofphere. I have likewifc found that it takes place more flowly in nitrous gas 

 than in the atmofphere. That zinc is oxidated in folutions of nitrous and marine acids, 

 is a well known faft. . 



3, TFhett the Zinc in contall with Water, holding in folution Subjlances containing loofe Oxygen, 



or Acids, is oxidated, thefe Subjlances are altered, or they exert fame Chemical Affinities. 



a. A fmall galvanic pile, expofed to about twenty-one cubic inches of oxygen gas for 

 fix hours, effefted a diminution of it which might have equalled one-fourth. 



b. A fimilar pile, expofed to an equal quantity of atmofpheric air for two days, dimi- 

 nifhed it one-fixth : the refiduum being fuffered to pafs into the atmofphere, gave a fmell 

 which ftrongly refembled that of ammoniac ; and the pile held over marine acid produced 

 denfe white clouds. 



In another experiment, an equal quantity of air, expofed to the pile for three days, gave 

 but a very flight diminution with nitrous gas, and could not be inflamed with atmof- 

 pheric air. 



c. I have noticed, Ref. Chem. £3* Phil, that wetted ainc, placed in contact with nItrouS 

 gas over mercury, flowly converts it into nitrous oxide and ammoniac. A fmall pile, ex- 



* Tlie temperature in thefe experiments was from 54° to 6i*. It is impoffible to free water of a// its 

 diffblved air by boiling 1 it is likewife impoffible to prevent a few globules of air from paffing through the 

 cement whilfl it is cooling : the very flight tarni(h of zinc kept in boiled water may be owing to the 

 minute quantities of coniir.on air exifting in the water from bpth thefe caufes. 



X X 2 pofed 



