SILICATES. 



97 



the data was obtained, a rough estimate is made of the temperature at 

 which a complete radiator would emit light of a color similar to that given 

 out by the substance under investigation. The fact that soot from the gas 

 flame was burned off the rods not emitting light would indicate that the 

 temperature was above 6oo C, and in all cases the estimated temperature 

 is greater than 8oo C. 



The length of the rods used depended upon the melting-point. For 

 example, the "soft glass" rod was very short on account of its softening 

 at the temperature necessary to keep it electrically conducting. The ends 

 of the rods were shielded from the spectrometer slit. All these curves are 

 reduced to the normal spectrum by dividing the observed galvanometer 

 deflections by the slit-width expressed in wave-lengths. In this work the 

 unsteadiness of the bolometer prevented an accurate mapping of small 

 emission bands occurring beyond 6 /*. 



Albite (NaAlSiaOs). 

 (Rod 8 mm. long, tapering from i.8 to 2.8 mm. in diameter. Energy supplied, 7.1 and 8.2 

 watts. Curves a and b, fig. 63. Temperature 8oo. Transmission given in Carnegie 

 Publication No. 65, p. 65.) 



The rod was translucent and seemed to emit no light except that re- 

 flected from the platinum terminals. The emission band at 2.88 /* is 



1 2 3 4 5 6 7 



Fig. 64. Emission spectrum of orthoclase (var. adularia). 



more intense than the one found in orthoclase, just as was found in the 

 absorption spectrum. Two other bands are noticeable at 4.1 and 4.5 /*, 

 respectively. 



