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STATE BOARD OF AGJIICULTURE. 



led US to introduce a still further change in the apparatus. The two 

 systems differ radically in the type of detector used. We used the alter- 

 nating current galvanometer, while Washburn and Bell still made use of 

 the telephone, which they have, however, greatly improved. 



The conductivity of a solution of any electrolyte is simply tlie recipro- 

 cal of its resistivity. The resistivity of that solution is usually measured 

 by balancing it against a known standard resistance. The apparatus 

 used is the well known Wheatstone Bridge. This is a network of six con- 

 ductors represented in one of the following three forms all of which are 

 equivalent. See Fig. 1. Like letters designate the same conductors and 

 the same points of connections in all. In the text books of physical 

 chemistry the sketches are more diagramatic usually taking the form 

 represented in Fig. 2. The parts referring to the six conductors are 



Fig. 1. 

 Conventional diagrams of tlie six conductors in a Wheatstone Bridge Network. 



e> 



v.- 



Fig. 2. 

 Conventional drawing of the parts of the Kohlrausch Setup. 

 ceU ; Y, resistance ; K, induction coil. 



T, telephone; Z, electrolytic 



