()i7 



2. Apparatus. In fig. 1 the appanitus used is represented 

 schematically. The liquid serving in the experiment runs from flask 

 Fi into flask F.^ through a doubly bent glass tube Kap, which is 

 partly drawn to a capillary. Into tlie three-necked Woulfp flask F^, 

 which is closed by means of rubbei- stoppers with copper wire 

 ligature, arrives also (1) a tube a through which air can be pressed 

 and (2) an electrode E^ . In the other flask F^ is found an electrode 

 E^ and a thermometer Th. The electrodes are Ag-AgCl electrodes. 

 A silver wire is fixed into a glass capillary by means of Cailletet- 

 wax. The protruding end is electrolytically covered with AgCl 

 according to the indications given by Jahn ^). 



A constant pressure above the liquid in flask Fj^ is obtained as 

 follows : by means of a cycle foot-pump mercury can be pressed from 

 the reservoir R^ into R^ ; the pressure thereby generated is read off 

 on the open mercury manometer. As owing to the transferring of the 

 liquid from F^ to F^ the pressure would diminish a little during 

 the experiment, it is kept constant by means of the arrangement 

 CD by turning the handle C\ 



The measurement of the potential differences between the electrodes 

 E^ and E^ was carried out by the compensation method ofPooGEN- 

 DORFF-Du Bois Reymond. A galvanometer could not be used as a zero 

 instrument because the strength of the current passing through the 

 instrument is exceeding!}^ small in consequence of the enormous 

 resistance^ in the battery F^F.^. Hence, a capillary electrometer 

 {KEM in fig. 1) was used, which was fixed to the object table of 

 an ordinary microscope; the axis of the microscope was, of course, 

 placed horizontally. The readings were made using of an ocular- 

 micrometer, objective 4c (Reichert) and Huygens ocular J. 



The following serves to further explain the figure. aS'j is a key 

 for cutting off the short circuit of the capillary electrometer; A in- 

 dicates that this is connected with the earth. As working element 

 are used one or more accumulators Ace whose tension was determ- 

 ined by comparison with a Weston standard-cell, which was placed 

 in a thermostat at 25° (WNE). By the different cuirent inter- 

 rupters are indicated ; by 0^ the electrodes E^ and E^ can be brought 

 into short circuit, which was always done during the time that no 

 observations were made. By 0^ the current of the working cell is 

 twitched in; 0^ annables to introduce at will one, two or four 

 accumulators as a compensation battery. 0^ renders it possible to 

 take up in the circuit either the standard cell or the battery F^F^. 



^) Zeitschrift f. physik. Ghem. 33, special page 556 (1900). 



