OP ARTS AND SCIENCES. 



159 



Experiments with Black Oxide of Copper (CuO). 



The experiments with platinum having shown the curve of radiation 

 to be independent of the temperature, it became desirable to see how 

 it might be affected by using different substances as sources of radia- 

 tion, and whether it is also true of other substances, that the form of 

 the curve is independent of the temperature. Accordingly, the spectra 

 iromjive different substances, varying widely in physical and chemical 

 properties, have been measured, each at several different temperatures. 

 The first of these was the black oxide of copper, CuO. 



In order to obtain a long and narrow radiating source of this sub- 

 stance, the platinum wire was coated with a saturated solution of the 

 nitrate of copper, applied by means of a camel's-hair brush, and then 

 a current sent through the wire. The red fumes of nitric peroxide 

 were driven off, leaving a coating of the black oxide, which became 

 incandescent on further heating. Quite a thick coating was applied in 

 order to make sure that the radiation came from the oxide, and not 

 from the platinum. 



These curves, the results of eighteen series of measurements, are 

 given in Plate III. and Table II. 



TABLE II. 



B line 11.15 



D line 12.45 



E line 14.35 



The lower curve represents the distribution at a low red heat, the 

 second at a low white, and the third at a full white heat. In this last 

 curve the radiating substance had melted and formed a black viscous 



