372 C. A. Peters — Electrolysis of Sodium Chloride 



alont to "0887 grins, of chlorine was heated for 1^ hours at 

 about 390° and nearly 14 hours at about 530°, gained in all -0011 

 gnus. The same anode, after being relieved of most of its silver 

 chloride by solution in ammonia, was heated a total of 25^ 

 hours at about 390° (8 separate heatings) and gained '0055 

 grms. At 530° one heating of four hours caused an increase 

 of 1 mgrm. 



In the electric oven three heatings of an hour each at about 

 435° (varying from 390-480°) caused an increase of "0008 grms. 

 on an anode holding the chlorine from 50 cm3 of •IN sodium 

 chloride solution. 



The increase in weight, then, of a silver-plated platinum 

 electrode is apparent upon long heating at temperatures of 

 from 400° to 500°, but it is so small during short periods, say 

 15 minutes, that it may be neglected. 



The only explanation offered is the statement of Graham's* 

 that silver heated to redness will absorb the surrounding gases. 

 If this is the explanation for the phenomena observed, it is 

 evident that the absorptive power of silver is considerable 

 below red heat. 



Decrease in Weight upon Heating. — H. Rosef says silver 

 oxide begins to decompose at 250°. One might expect, there- 

 fore, that exposure of an anode to a temperature of 300° 

 would quickly decompose all the oxide on it. The action of 

 an anode, then, coated with silver chloride and silver oxide at 

 temperatures of 300° and over will be interesting. 



To observe such action a solution of 50 omS of '1~N sodium 

 chloride ("1773 of chlorine) was electrolyzed and the anode 

 heated 15 minutes in the electric oven at 305° and weighed. 

 It showed a gain of *1793 grams. The heating was continued 

 for 6 periods of about an hour each at temperatures of 300- 

 500° as shown in Table II. 







Table II. 









Successive 









Increase in 



loss in 









weight 



weight 



Time of 



App. av. 



Eange of 



of anode 



of anode 



heating 



temp. 



temperature 



grms. 



grms. 



min. 



C=. 



0°. 



•1793 







16 



305 



280-320 



•1789 



•0004 



60 



u 



230-335 



•1784 



•0005 



65 



a 



275-325 



•1782 



•0002 



60 



a 



280-325 



•1770 



•0012 



100 



a 



305-370 



•1767 



•0003 



65 



410 



400-465 



•1767 



•oooo 



60 



450 



415-480 



* Phil. Mag. (4), xxxii, 503. 



f Ann. Phys. [I], lxxxv, 317 (Pogg.). 



