Additional Remarks en Galvanic EkBricity. 163 



quantity of gas was thus obtained, it was examined, and found to confift of oxygen 

 eleven parts, and hydrogen twenty-five parts •, and four meafures of it being exploded 

 by the ele£lric fpark, lefs than half a meafure remained, or about one-ninth 6f the, whole. 

 From hence it is evident that the filver was but very little a(^ed upon in this experi- 

 ment, for we obtained nearly the fame quantity of oxygen as if gold or platina wires had 

 been employed. The bottle was next filled with diftilled water, and the fame procefs 

 repeated. In this cafe the filver was much corroded, and very little gas efcap?d from 

 the zinc fide ; a fufficient quantity of gas being, however, obtained, it was examined, 

 and found to confift of oxygen one part, and hydrogen fix parts. This mixture did 

 not explode without the addition of more oxygen. The caufe of thefe different refults 

 is readily explained on the fuppofition of an acid. For in "the firft experiment the 

 generated acid would immediately unite with the alkali in preference to the filver, and by 

 this means the principal agent in the oxydatlon would be removed. Similar experiments 

 were made with copper wires, and with exaftly the fame refults : in this Caft, when the 

 bottle was filled with the alkali, "no green fubftance was produced at the zinc wire; indeedj 

 the copper was fcarcely, if at all, a£ted upon. 



3dly, The corroded fubftances generated by this influenfce at the extremities of the zinc 

 wires are not pure oxydes, which, upon the fuppofition of fimple oxydation they ought 

 to be, when nothing but diftilled water is employed. We have remarkable examples of 

 this in the blueifh green fubfl:ance obtained from copper, and the dirty greeiiifli ycllowr 

 one from mercury, the laft of which exactly refembles what has been called nitrous 

 turbeth when too much waflied with water, and if pure ammonia be added to it, it in- 

 ftantly becomes black, a proof that it contains fome acid, for ammonia has no effefl: upon 

 the pure oxyde of mercury, but a confiderable one upon all the impure, rendering them 

 black, as turpeth mineral, &c. With regard to the green fubftance from copper, it is very- 

 certain that we have no pure oxyde of this colour, for all the green oxydes, as they have 

 been improperly called; contain acids of fome kind, as the carbonic, arfenical, acetous, 

 &c. and it is well known that the precipitates by the carbonated alkalis, &c. are all of this 

 kind. Indeed, there is but one pure oxyde of copper, viz. the dark red, or deep, brown. 

 Now, as thefe impure oxydes cannot be generated without an acid, aad as there can be 

 none in diftilled or lime water, it muft follow, that an acid is fomehow generated in the 

 procefs ; and as this acid a£l:s both upon mercury and filver, it is moft probably the 

 nitrous. The quantity, however, is certainly fmall, owing, in a great meafure, to the 

 weaknefs and imperfettion of our machines j and it is this circumftance which fenders it 

 fo difficult to dete£t it with caijj^inty. 



It may be afked, how can this acid be formed ? If azote were a compound fubftance, as 



has been lately affirmed, this queftion could be very rfeadily anfwered } but if not, we 



muft then fuppofe that a fmall quantity of aaote is always prefetit in Water, hoivevef long 



boiled, or repeatedly diftilled, and that it is with this the oxygen in its nafcent ftate 



3^ unites. 



