THE SMITHSONIAN INSTITUTION. 317 



inagnitiule of the difFCTcnce wliicli exists between the degrees of ox- 

 idability of the metals composing the circuit." * * . * 



"Now, if the oxidability of a metal is actually related to its vol- 

 taic action as stated, it is very evident that the place which a metallic 

 body has in the tension series of the contactists denotes the degree 

 which belongs to the same metal in the scale of oxidability of metallic 

 bodies. Comparing the tension series of the metals obtained by 

 water and the galvanoscope, with the scale of oxidability of the same 

 bodies determined by ordinary chemical methods, it is impossible not 

 to see the great accordance between the two series." * * * 



"Now, since we have a number of electrolytes in which other 

 metaloids than oxygen, such as the haloids, sulphur, and seleneum, 

 play the part of anions in their combination with hydrogen, it follows 

 from what has been said, that the electrical tension series of metals 

 determined with different electrolytes, cannot accord with each other 

 perfectly. This want of accordance has been placed beyond doubt by 

 various experiments, and the number of cases is not very small in 

 which tlie same two metals manifest a different voltaic relation for 

 each other when they are placed in diiferent electrolytic liquids ; so 

 that the same metal which in one liquid is positive towards the second 

 metal, manifests the opposite in another liquid. 



" The case of a reversal of voltaic action which the same two 

 metals exhibit in two diiferent liquids must, in accordance with the 

 above statements, always appear when the chemical relation of these 

 metals to the anions of the electrolytes used is not the same ; that is, 

 when the afiinity of one and the same metal for the two anions of 

 the electrolyte does not exceed the affinity of the other metal for the 

 same anions, or shows the opposite relations." 



" Experience above all teaches that in general the proportions of 

 affinity w-hich §xist between the metals and oxygen are similar to 

 those which take place between those bodies and the haloids, sulphur, 

 seleneum, &g. ; hence the voltaic relations which the metals manifest 

 in electrolytic liquids not containing oxygen, accord so frequently 

 with those which are observed in the same bodies in water." * * * 



"Let us now consider those batteries which consist of one metal 

 and two electrolytic liquids. 



" The most interesting example -is that composed of water, muriatic 

 acid, and gold. 



" This battery yields a current which ])asses from the gold to the 

 acid, and from this to the water. This current is very weak, and by 

 reason of the rapid positive polarization of the gold immersed in the 

 water, it soon ceases to have a measurable strength. 



" The origin of this current depends upon the simple fact, that 

 the gold possesses a greater chemical affinity for the chlorine of the 

 muriatic acid, than for the oxygen of the water." * * * * 



"It is easily inferred from the preceding explanation, that all 

 voltaic arrangements consisting of two different electrolytes and a 

 metal must form circuits, in case the metal used has a greater chemi- 

 cal affinity for the anion of one of the electrolytic bodies than for 

 the -anion of the other. It is likewise evident that the force of the 



