122 



MICRO SPECTROSCOPE AND POLARISCOPE. {CH. VI. 



X 3 C 



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Fig. i 15. Various Spectrums —All except that of Sodium were obtained bv dif- 

 fused day light with the slit of such a width as gave the most distinct Fraunhofer 

 lines. 



It frequently occurs that with a substance giving several absorption bands (e. 

 g., chlorophyll) the density or thickness of the solution must be varied to show all 

 the different bands clearly. 



Solar Spectrum.— With diffused day-light and a narrow slit the spectrum is not 

 visible much beyond the fixed line B. In order to extend the visible spectrum in 

 the red to the line A, one should use direct sunlight and a piece of ruby glass in 

 place of the watch glass in Fig. iry. 



Sodium Spectrum.— The line spectrum (§ 182) of sodium obtained by lighting 

 the microscope with an alcohol flame in which some salt of sodium is glowing. 

 With the micro-spectroscope the sodium line seen in the solar spectrum and with 

 the incandescent sodium appears single, except under very favorable circumstances 

 (i 193). By using a comparison spectrum of day-light with the sodium spectrum 

 the light and dark D-lines will be seen to be continuous as here shown. 



Permanganate of Potash.— This spectrum is characterized by the presence of five 

 absorption bands in the middle of the spectrum and is best shown by using a T V per 

 cent, solution of permanganate in water in a watch glass as in Fig. 117. 



Met-hemoglobin.—The absorption spectrum of met-hemoglobin is characterized 

 by a considerable darkening of the blue end of the spectrum and of four absorp- 

 tion bands, one in the red near the line C and two between D and £ nearly in the 

 place of the two bands of oxy-hemoglobin ; finally there is a somewhat faint wide 

 band near F Such a met-hemoglobin spectrum is best obtained by making a solu- 

 tion of blood in water of such a concentration that the two oxy-hemoglobin bands 

 run together (J 202), and then adding three or four drops of a T \ percent, aqueous 

 solution of permanganate of potash or a few drops of hydrogen dioxid (HO) 

 Soon the bright red will change to a brownish color, when it may be examined. ° 



VARIOUS KINDS OF SPECTRA. 



By a spectrum is meant the colored bands appearing when light traverses a dis- 

 perses prism or a diffraction grating, or is affected in any way to separate the dif- 

 ferent wave lengths of light into groups. When daylight or some good artificial 

 light is thus dispersed one gets the appearance so familiar in the rainbow 



