4 M. W. Beetz on the Excitation of Electricity 



trated solution of sulphate of zinc. The two fluids were con- 

 nected with one another by means of a siphon filled with 

 dilute sulphuric acid and closed at both ends by clay cells. 

 A Daniell element in the form previously employed by me 

 served as unit, its zinc-cell being filled with solution of sul- 

 phate of zinc. If d denote electromotive force of such an 

 element, and D that of a Daniell element the zinc-cell of 

 which contains dilute sulphuric acid, then ^=0'95D. As the 

 force D is generally taken for the unit force, I have reduced 

 all the following data to the same. In like manner I cite 

 from previous memoirs the values of the electromotive forces 

 in terms of the unit D = l. I also regard always as the point 

 of issue, i. e. the positive part of the element in question, the 

 amalgamated zinc in dilute sulphuric acid ; so that, for ex- 

 ample, the electromotive force of zinc in dilute sulphuric 

 acid | Platinum in dilute sulphuric acid (or, abbreviated, 

 Zn | Pt) = l*61D; Zinc in dilute sulphuric acid | Platinum 

 coated with hydrogen in dilute sulphuric acid (or Zn | Pt, H) 

 = 0'80D, &c. Thus I found the force Zn | Pd, when I had 

 only mechanically rubbed the oxidized plate, always very 

 great, varying between 1'90 and 2*03 D, evidently because 

 there were always some remains of oxide still adhering. But 

 if the brown oxide was removed by diluted hydrochloric acid, 

 the electromotive force was found to be constant within tolerably 

 narrow limits — namely, 



1-24, 1-26, 1-24, 1-29, 1'32, 1-31, 1-28. 

 Mean ... Zn | Pd = P28D. 



If we may regard as actually pure the palladium thus 

 cleaned, its position in the electromotive series is considerably 

 nearer to zinc than that of platinum. Still it is not advisable, 

 in measuring-experiments, to refer the position of a palladium 

 plate polarized by any gas to that of pure palladium ; it can 

 be much more certainly ascertained if under all circumstances 

 the amalgamated zinc plate in a concentrated solution of sul- 

 phate of zinc be united with the plate to be examined by the 

 siphon to form a series, or if two plates polarized by different 

 gases be placed immediately opposite one another. 



Two strips cut from the same sheet of palladium were 

 passed through corks which closed the upper ends of two 

 glass tubes. The tubes were filled with diluted sulphuric 

 acid and plunged upside down into a glass containing the 

 same fluid. Oxygen was then introduced into one of the 

 tubes, and hydrogen into the other. Both the gases had been 

 evolved by electrolysis and kept in small gasometers, from 

 which they could be taken as required. 



