136 



MICRO-SPECTROSCOPE AND POLARISCOPE [CH. VI 



position of the different colors may be determined by placing some ground glass 

 or some of the lens-paper near the prism and observing with the eye at the 

 distance of distinct vision.* 



3-trmaa. 



Fig. 121. Various Spectrums. — All except that of sodium were obtained by 

 diffused 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. 123. 



Sodium Spectrum. — The tine spectrum (\ic)i) 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 192). 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 characterised by the presence of 

 five absorption bands in the middle of the spectrum and is best shown by using a T \y 

 per cent, solution of permanganate in water in a watch-glass as in Fig. 123. 



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

 by a considerable darkening of the blue end of the spectrum and of four absorption 

 bands, one in the red near the line C and two between D and E nearly in the place 

 of the two bands of oxy-hcinoglobin ; finally there is a somewhat faint, wide, band 

 near F. Such a met-hemoglobin spectrum is best obtained by making a solution of 

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

 together (\ 2/1), and then adding three or four drops of a -jL per cent, aqueous 

 solution of permanganate of potash or a few drops of hydrogen dioxid (H 2 2 ). 

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



*The author wishes to acknowledge the aid rendered by Professor E. L. 

 Nichols in giving the explanation offered in this section. 



