HEAT DISSIPATION AT ELECTRODES OF SHORT ELECTRIC ARC 



935 



direction) which would impossibly complicate interpretation of the data. 

 Experiments under conditions 3 were carried out with the limonene vapor 

 pressure maintained at about the lowest value at which activation can be 

 produced (0.06 mm Hg in most experiments). At this low pressure activa- 

 tion does not develop until the electrodes have been operating for some time, 

 but when it develops the open circuit potential after an arc is —5 volts 



10 12 14 

 TIME IN MINUTES 



Fig. 1 — Readings of the galvanometer in series with the thermocouples in the moving 

 electrode, when the electrode was positive and when it was negative. Electrodes activated 

 by vapor of (/-limonene at a pressure of 0,06 mm Hg with 60 closures per second and an 

 arc at every closure. Condenser of 0.01 mf charged to 40 volts, discharged on each closure 

 through an inductance of 10 X 10~^h. Galvanometer deflections in mm are transformed 

 into ergs per closure by multiplying by 0.510. The experimental points obtained from this 

 figure are marked by small arrows on Fig. 2. 



which is also the value reached after arcing in the inactive condition. The 

 observance of this open circuit voltage is proof that each arc is an arc in 

 platinum vapor, and not carbon. 



An example of data taken upon active (carbonized) electrodes with a 

 circuit inductance of 10 X 10"^ h (conditions 3), and an arc at every closure 

 ending in an open circuit potential of —5 volts as verified by continuous 

 observation of the oscilloscope recording the potential across the contacts, 



