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BELL SYSTEM TECHNICAL JOURNAL 



cathode polarization. The role of metallic impurities of lower over- 

 voltage in discharging hydrogen has already been considered. Oxygen, 

 it is obvious, aids corrosion by depolarizing cathodic areas on the 

 surface of the sheath. That the effect of oxygen is proportional to its 

 partial pressure in the atmosphere has been found in a laboratory 

 study, the results of which are given in Fig. 2. In this experiment six 

 specimens of extruded chemical lead, each of an area of one square 

 decimeter, were prepared for test by degreasing with carbon tetra- 



d 120 



5 



40 



10 20 30 40 50 60 70 80 90 



OXYGEN IN ATMOSPHERE ABOVE WATER IN PER CENT 



Fig. 2 — Effect of oxygen on corrosion of lead submerged in distilled water. 



chloride, and the tarnish film removed by dipping in dilute acetic acid 

 (one part of acid to five parts of water). These specimens washed 

 and dried, and weighed to the nearest milligram, were submerged in 

 large jars of distilled water which had been previously saturated with 

 purified nitrogen, oxygen or various mixtures of the two. The corre- 

 sponding atmospheres were maintained above the surface to the water 

 during the test. After a period of 18 hours the specimens were re- 

 moved, washed and the losses of weight determined. 



