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INDIANA UNIVERSITY 



The specific conductivities oi* ju^rchloric acid are the average of 

 several readings at different poiiiis on the bridge wire. The other 

 readings were taken as near the center of the bridge as possible. 

 The cell constant ranged from about 0.25 to 0.28, so that, in the case 

 of high conductivities, the bridge reading with one ohm in the box, 

 had to be taken some distance from the middle. 



The curves show that : 



1. A solution of perchloric acid containing 0.43 grams per cc. 

 is the best conducting solution. (Curve I.) 



2. The conductivity of mercurous perchlorate increases slowly 

 with increase in concentration, (Curve II.) 



3. The conductivity of solutions oi mercurous perchlorate in- 

 creases very rapidly with increasing amounts of free perchloric acid. 

 (Curve III.) 



Voltameter Experiments. The original intention of this re- 

 search was to use the form of apparatus described in the London 

 Electrician, merely substituting mercurous perchlorate for the po- 

 tassium mercuric iodide. However, several difficulties arose, chief 

 among which was the difficulty of securing an iridium cathode. Ef- 

 forts were made to substitute platinum, palladium and magnetic 

 oxide of iron, but with poor success, because the precipitated mer- 

 cury stuck to the cathode. The magnetic oxide of iron, with proper 

 precautions, might be successfully used as cathode material. A 

 large piece of the oxide-' was ground to the shape of a cone and the 

 surface was polished. Electrical connection was made by pushing a 

 platinum wire into a hole in the base of the cone. This connection 

 was covered with sealing wax. The precipitated mercury fell from 

 the cathode in a fine steady stream. The cathode soon began to dis- 

 integrate along some small cracks or imperfections in the mag- 

 netite. The small particles of the oxide which became detached in 

 this manner mixed with the precipitated mercury. Since this disin- 

 tegration of the magnetite could not be prevented, experiments with 

 it were abandoned. 



Mercury as cathode material was much more satisfactory, al- 

 though one great difficulty appeared — the mercury deposit consisted 

 in part of a black powder. Various substances were added to the 

 electrolyte to modify the deposit. Alcohol, glue, aluminum per- 

 chlorate and sodium perchlorate were tried. Alcohol was effective 

 temporarily, but had to be renewed at frequent intervals ; glue was 

 ineffective, as was the aluminum perchlorate. Sodium perchlorate 



^ Part of an anode which had been used ccmmercially in the electrolysis of 

 sodium chloride. 



