Carbon electrodes for an ultraviolet arc lamp for use in a light-fastness tester

Carbon electrodes for an ultraviolet arc lamp used for light-fastness testing, said electrodes comprising:

• an upper electrode in the shape of an elongated cylinder about 23 mm. in diameter, the cross-section of which has an exterior annular portion consisting of a carbonaceous material and an interior core portion consisting of a mixture of a carbonaceous material and potassium sulfate, the upper electrode having dispersed therethrough potassium chloride as a stabilizing agent;
• and
• a lower electrode in the shape of an elongated cylindrical tube about 18.5 mm. in diameter and having a hollow interior about 1-2 mm. in diameter and being of a carbonaceous material having a high electrical conductivity and having dispersed therethrough potassium chloride as a stabilizing agent;
• whereby when the upper and lower electrodes are placed with their ends opposed to each other and an alternating current at 135V and 16A is discharged thereacross, the discharge can be maintained stably for more than 50 hours and a stable light is continuously produced.