120 



INFRA-RED EMISSION SPECTRA. 



oxides, it emits a continuous spectrum. The depression at 3.2 p. is small. 

 The transmission bands in cassiterite, Sn0 2 , were found to be small. 



12 3 4 5 6 7 



Fig. 88. Iron oxide, (a) (6); Copper oxide. 



8/1 



0/234567 8/J. 



Fig. 89. Cobalt uxiue {a)\ Chromium oxide (b), (c); Stannic oxide. 



Nickel Oxide (NiO); Calcium Sulphate (CaS0 4 +2H 2 0). 

 (Curves a, b, c = NiO; curve <f = CaS0 4 ; fig. 90. Temperature about 900 . Trans- 

 mission, Carnegie Publication No. 65, p. 18; curve b, fig. 2.) 



The nickel-oxide surface was rougher than for the other oxides, 

 hence not so uniformly heated. At the highest temperature the de- 



