THE ALUMINUM ELECTROLYTIC CONDENSER 



55 



the electrodes is of importance. Because of the delicate nature of 

 the film and the desirability of keeping it clean, the electrodes are 

 designed so that in the manufacture, packing and installation of the 

 condenser it is unnecessary to touch either the positive or the negative 

 plate surfaces after the film is formed. 



The fluid in which the condensers operate is shipped in sealed 

 glass containers to prevent contamination, and the routine to be 

 followed in the installation of the condensers emphasizes the need 

 for cleanliness on the part of the installer. However, the design 



o 



(J 400 



5 

 O300 



1-200 



200 400 600 800 1000 1200 



BORIC ACID CONTENT-GRAMS IN 19 LITERS OF WATER 



Fig. 10 — Specific resistance chart of ammonium borate electrolyte 



of the condenser and the method of supplying the condenser fluid 

 have been arranged so that satisfactory installations can be made 

 with ordinary skill and simple precautions. 



The Composition of the Electrolyte 



The electrolyte or condenser fluid as the solution is called is a 

 mixture of ammonia, boric acid and water. A chart showing the 

 specific resistance of different ammonium borate electrolytes is shown 

 in Fig. 10. Two curves on this chart illustrate an interesting charac- 

 teristic of these solutions. The heavy solid curve shows the neutral 

 ammonium borate solutions, that is, those having a hydrogen ion 

 concentration of 10~^ mols per liter. 



This curve was determined colorimetrically with suitable indicators 

 against standard solutions, and was checked by measurements with 



