316 



PROTOPLASM 



becomes a hydrogen electrode, i.e., an electrode of hydrogen 

 gas sensitive to hydrogen. To keep the electrode saturated, a 



Fig. 146. — Connections for making pH determinations with a Leeds and 



Northrup Type-K potentiometer. 



stream of hydrogen gas must be constantly flowing through the 

 solution (the gas does not affect the pH of the solution). 



-BA. 



i_A o5G 



Fig. 147. — Interior connections of Leeds and Northrup Type-K potentiometer. 



It is not possible to measure the potential of a single electrode. 

 Two electrodes are necessary to give a measurable potential. 



