EXPERIMENT STATION BULLETINS. 



5S3 



Range of 3 scale divisions. Reading was made quickly. The switch was 

 closed for only an instant at a time. This precaution was necessary as 

 the thin film of solution between the electrodes was exposed to a heating 

 effect of the current. By allowing the current to pass for only an instant 

 the heating effect was found to be negligible. 



Experiment III. 



In D and E of the preceding experiment the range of scale divisions 

 is 1 in one case and 3 in the other. For solutions of high resistance these 



(Tom 



Fig. 14. 

 Arrangement and connection of parts when a D. C. galvanometer and rectifier are used. 



results may be considered very good. An experiment was made however 

 to see if the range could be shortened. 



It is a well known fact that a D. C. galvanometer is more sensitive than 

 an A. C. galvanometer, but the former cannot be used with alternating 

 currents. If, in some way, the alternating current can be rectified so 

 as to become unidirectional then a D. C. galvanometer can be used. Tliis 

 change in current can be brought about by cutting out one of the phases 



