12 



PROCEEDINGS OP THE AMERICAN ACADEMY. 



electrolyte was wide in order to allow of measurement through the 

 small conductivity of the dilute solutions. The accompanying sketch 

 will give a better idea of the arrangement. The Peltier eifect above 

 mentioned was neglected by Gockel, because it usually amounted to 

 less than one per cent of the whole potential to be measured ; but in the 

 present series I thought the safer course was to eliminate it. 



Ear* 



Diagram of Apparatus. 



The glass part at the left of the diagram is drawn about one third of tlie actual 

 size. The remainder of tlie apparatus is not drawn to scale, being annexed 

 merely to show the connections. For tliose familiar with the Ostwald-Poggen- 

 dorff metiiod no explanation is necessary.* 



The potentials were measured as before by the Poggeudorff compen- 

 sation method, a sensitive galvanometer as well as a very sensitive Lipp- 

 mann electrometer being used for the normal and decinormal solution, and 

 the electrometer alone for the centinormal. In order to secure greater 

 accuracy, the Ostwald potential box * of 1 ,000 ohms was connected with 

 a Daniell " gravity " cell, and 9,700± ohras external resistance, so that 



* Hand- und Hilfsbuch pliys. chem. Mess., pp. 252, 253. 



