VOLT A ISM. 



It will be proper to obferve here, tlut the intcrpofed 

 fluid does not afford a quantity of eleftricity proportionate 

 to the rapidity of the oxydation, or at leall the quantity ot 

 galvanic energy cannot be appreciated beyond a certain 

 limit. If the quantity of the concentrated acid be much 

 more than from V„ to ^V the weight of the water, the power 

 of the battery will not be found to increafe but from another 

 caufe, which we (hall hereafter explain ; the power is much 

 fooner exhaufted than when a fmaller dofe is ufed. The 

 zinc is oxvdated fo flowly by faline bodies, that they may 

 be ufed in faturated folutions. Potafh, in a cauilic Hate, 

 even when much diluted with water, might be ufed to great 

 advantage. At the fame time that it fcarcely appears to 

 oxydate the zinc, when a fingle pair of wires of copper and 

 zinc are ufed, the copper wire affords as much hydrogen 

 durincr the contaft, as could be expeded from tlie agency 

 of an°acid. It is, therefore, highly probable, that potadi 

 or foda will be fubftituted for acids in galvanic experiments, 

 as well for the fake of economy as from its being lefs offeu- 

 five to the operator. It poffeffes another advantage ftill 

 greater, in not deftroying the zinc plates like acid 



folutions. , • r J n J 



From what has been faid regarding the interpoled tluid, 

 it will be eafy to infer that the greateft part of the galvanic 

 energy, which is eleftricity excited by chemical aftion, de- 

 pends upon the prcfence of the water, and fomc fubftance 

 which can difTolve the zinc, and at the fame time give a 

 to the water. The effeft is 



vanic battery are made to terminate in a veffel of pure water 

 the water will be obferved to be decompofed, the oxygen 

 being given out at the pofitive wire, or that com:ng from 

 the zinc lide of the battery, and the hydrogen from the ne- 

 gative or oppofite wire. If the fmailell quantity of an 

 acid, a ialt, or an alkali, be added to the water, the rapidity 

 of the decompoiition will be increafed very confpicuoufly. 



As it is of fome importance to know the relative con- 

 dufting power of water, and its different compounds, the 

 following apparatus has been contrived for this purpofe, re- 

 prefented in Jig- 7. Let c ^ be a fniall cup of wood var- 

 niihed, or, what is much better, glafs ; and z, c two wires of 

 platina diftinftly inferted in the bottoni of the cup, fo as to 

 be water tight. A glafs tube, op, filled with the fluid, is 

 inverted in the cup to receive the gas which arifes from the 

 wires z c, while the fluid defcends, and is contained in the 

 cup. If the cup f ^ be made larger, and of an oval fliape, 

 two glafs tubes may be inverted over each wire, and the gafes 

 may be obtained feparately. Fig. 8. A B C D, is a frame 

 fupporting one of the cups. The parts G and F are of 

 glafs or variiilhed dry wood, cemented into the parts 

 A B C D, which are of brafs, fo that the two lides H and I of 

 the frame are detached. The apparatus,_/ff. 7. with four 

 others firailar, are to be placed in the frame, the wires 

 being inferted into one fide of the frame, and the other, c, 

 rcfting upon the other fide. When the glafs tubes of each 

 are filled with different fluids, the (!,de H is connected with 



greater condufting power to the water. 1 tie eneCt is one end of the battery, and that of I with the other. Since 

 not as fir Humphrey Davy has fuppofed, produced by the the galvanic current muff neceffarily take the bed condudor, 

 opp'ofite eleftrical ilatcs of the elements of the compounds the action will commence through that fluid having the 



conftituting the fluid medium, fince the hypothefis is contra- 

 difted by experiment. If there wanted another experiment 

 to decide, that the galvanic effeft is as the chemical effeft, 

 the following would fuffice. Take two wine-glaffes, con- 

 taining dilute muriatic acid, and conneft them by an arc 

 made of two wires, one of zinc and the other of platina, fol- 

 dcred or tied together, the zinc being in one glafs and the 

 copper in the other. If the circuit be complicated between 

 the glaffes by an arc of platina wire, no appearance of bub- 

 bles will be obferved upon the platina wire of the compound 

 arc. If, however, a fmall quantity of nitric acid be poured 

 into the glafs containing this wire, hydrogen gas will be 

 immediately evolved from it, and at the fame time the other 

 platina wire in the fame glafs will become oxydated. This 

 effea is not caufed by the ekaHcal agency of the nitric 

 acid, which is decompofed ; becaufe when copper is ufed 

 inftead of platina, with the pure muriatic acid, the fame 

 effea takes place. It appears, therefore, that the increafcd 

 cffea would be attributed only to the oxydation of the wire 

 of the homogeneous arc, in the glafs containing the negative 

 wire of the compound arc. 



In every galvanic procefs, from a fingle combination to an 

 unhmited feries, no effea is obferved till the circuit is com- 

 plete ; and during this, a current of elearicity is efta- 

 blifiied from the zinc furface of one combination to the 

 copper of the fucceeding. While it is paffing through a 

 metal, whatever be its length, it obeys the laws of elec- 

 tricity very ftriaiy,but when it paffes through a humid con- 

 duaor, it appears to poffefs rather anomalous properties. 

 It is proper to obferve here, that conduaors of Galvanifm 

 are of two kinds ; the one we (hall call dry conduaors, and 

 the other humid. The firil clafs comprifes all the metals, 

 well burnt charcoal, plumbago, and the fulphurets of metals. 

 Water appears to be effential to the fecond kind, holding in 

 folution acids, alkahes, or neutral falts. Simple water has 

 its conduaing power increafed by the fmalleft quantity of any 

 acid, alkali, or fait. When the conduding wires of a gal- 



greateft. conduaing povixr. If a thin bit of baked wood or 

 glafs be put under the refting part c, in that where the 

 aaion commenced, the current will be transferred to the 

 next inferior conduaor, and fo on to all the rell. By this 

 means an accurate table, fhewing the relative conduaing 

 powers of fluids, may be eafily obtained. 



Since the quantity of gas is the tell of the conduaing 

 power, fome allowance mull be made when the muriates are 

 the fubjea of experiment. Almoft all the oxygen gas dif- 

 appears in converting the muriatic into oxymuriatic acid. 

 In a fimilar way the hydrogen does not appear when certain 

 metaUic folutions are employed, fince it combines with 

 the oxygen of the metallic oxyd, and the metal is re- 

 duced. When the battery is in full power, and of great 

 extent, the relative conduding power of the fluids may be 

 expreffed by the time required for the afcending gas to dif- 

 place the hquid in the glafs tube. In all thofe experiments 

 where the elements of bodies are transferred to different 

 fides, the transfer takes place through any of the moift con- 

 duaors, but not through any of the dry ones. No transfer 

 can therefore be made through folid bodies, except the body 

 be permeable to moifture. Sir Humphrey Davy, in his ex- 

 periments, made ufe of the fibrous afbeftus moiltened with 

 water. Where the fluids are required to be ftrittly fcpa- 

 rate, bladder anfwers very well as a feparating medium. 

 Animal and vegetable fubftances, however, abound with 

 fo many elements, that in nice experiments they would be 

 objeaionable. A veffel divided into a proper number of 

 ceils of earthenware, in the ftate of bifcuit, would be bell 

 calculated for thefe experiments. This veffel ihould be 

 made of pure filex and pure alumina. Should it ever be- 

 come an objed of manufaaure to feparate acids and alkalies 

 from neutral falts, a veffel of wood, with a feparation in the 

 middle, of unglazed earthenware, would aniwer very well. 



We fliall here mention fome curious faas conneaed with 

 the iiiterpofition of metals, in different conduding media. 

 When the wires, coming from the two ends of a galvanic 



battery. 



