102 



INFRA-RED EMISSION SPECTRA. 



of the emission bands on the side of the spectrum toward the short wave- 

 lengths. Further examples will be found in figs. 77 and 78. In this and 

 in the preceding substance the emission bands are not so sharp as usual, 

 which may be due to the greater molecular weight of the base. 



Porcelain (Pyrometer Tubing). 

 (Hollow rod 15 by 2 mm. (hole 1 mm.). Energy supplied, 9.2 watts. Fig. 69.) 



The sample of pyrometer tubing examined was heated to a light-red 

 color (1400 ) to keep it conducting. The energy spectrum is marked for 



Fig. 69. Porcelain. 



its strong emission, with sharp maxima at 1.8, 2.1, 2.83, 3.7, 4.1, and 

 4.5 ft, and with indications of bands beyond 6 ft. 

 a hydrous aluminum silicate. 



Porcelain is made from 



Glass ("Soft Glass"). 



(Rod 3 by 2 mm., heated to dull red color. Curve a, fig. 70. Transmission, 



Carnegie Publication No. 65, p. 65.) 



The substance examined was a piece of ordinary "soft" white glass 



tubing, drawn into a solid rod. There are emission bands at 2, 2.86, 3.6, 



4.4, and 5.5 pt. 



Magnesia (Pyrometer Tubing). 



(Hollow rod, 12 by 1.5 mm. (hole 1 mm.). Energy supplied, 6.6 watts. Curve b, fig. 70.) 



This material is used to insulate thermo-couples, and conducts only at 

 high temperatures. It is probably a mixture of magnesium oxide (see 

 fig. 80) and silica. The temperature was probably 1200 to 1400 . The 



