ELECTROMOTIVE FORCES IN THE VOLTAIC CELL. 



507 



Numbers obtained from unsatisfactory oxides and hydrates, like those 

 of aluminium, arsenic, and bismuth, are not likely to be useful for our 

 present purpose. I know of no better data yet available however. 



It is now easy to write down a Volta series obtained by pure calculation 

 from heats of combustion. We can then see how far it agrees with tbo 

 results of direct experiment. The principle on which I determine which 

 of the preceding numbers to select is simply to choose Thomsen's when 

 it refers to the simplest oxide, and in other cases to take what one can get. 

 Metals about which there is obvious uncertainty, as for instance sodium, 

 aluminium, bismuth, &c. are omitted. I only take the common ones. 



Calculated Volta Series. 



1-32 

 115 

 •92 

 •81 

 •67 

 •5 

 •13 



To compare this series with those obtained by experiment, we may as 

 well take zinc as the metal of reference, and write down the Volta effect 

 between it and the other metals, first as abstracted from the above table, 

 and then as found by different observers. Strictly, one ought first to 



1 This number for sodic oxide agrees with Thomsen's value for the hydrated 

 oxide, whereas for K, Ba, Sr, Ca the oxide is distinctly below the hydrate. By 

 analogy, one would expect to have to subtract some 25,000 from the hydrated oxide 

 Na.„0,Aq, and this gives the 130,000 which I put down as a hypothetical number for 

 Na„0. 



