148 MICRO-SPECTROSCOPE AND POLARISCOPE [CH. VI 



spectrum is nearly like that of oxy-hemoglobin, but the bands are 

 farther toward the blue. Add several drops of ammonium sulphide and 

 allow the blood to stand some time. No reduction will take place, 

 thus forming a marked contrast to solutions of oxy-hemoglobin. By 

 the addition of a few drops of glacial acetic acid a dark brownish red 

 color is produced. 



213. Carmine Solution. Make a solution of carmine by put- 

 ting y^th gram of carmine in 100 cc. of water and adding 10 drops of 

 strong ammonia. Put some of this in a watch-glass or in a small vial 

 and compare the spectrum with that of oxy-hemoglobin or carbon 

 monoxide hemoglobin. It has two bands in nearly the same position, 

 thus giving the spectrum a striking similarity to blood. If now several 

 drops, 15 or 20, of glacial acetic acid are added to the carmine, the 

 bands remain and the color is not markedly changed, while with 

 either oxy-hemoglobin or CO-hemoglobin the color would be de- 

 cidedly changed from the bright red to a dull reddish brown, and 

 the spectrum, if any could be seen, would be markedly different. 

 Carmine and O- hemoglobin can be distinguished by the use of ammo- 

 nium sulphide, the carmine remaining practically unchanged while the 

 blood shows the single band of hemoglobin ( 210). The acetic acid 

 serves to differentiate the CO-hemoglobin as well as the O-hemoglobin. 



214. Colored Bodies not giving Distinctly Banded Absorp- 

 tion Specftra. Some quite brilliantly colored objects, like the skin of 

 a red apple, do not give a banded spectrum. Take the skin of a red 

 apple, mount it on a slide, put on a cover-glass and add a drop of 

 water at the edge of the cover. Put the preparation under the micro- 

 scope and observe the spectrum. Although no bands will appear, in 

 some cases at least, yet the ends of the spectrum will be restricted and 

 various regions of the spectrum will not be so bright as the comparison 

 spectrum. Here the red color arises from the mixture of the unab- 

 sorbed waves, as occurs with other colored objects. In this case, 

 however, not all the light of a given wave length is absorbed, conse- 

 quently there are no clearly defined dark bands, the light is simply 

 less brilliant in certain regions and the red rays so predominate that 

 they give the prevailing color. 



215. Nearly Colorless Bodies with Clearly Marked Ab- 

 sorption Spectra. In contradistinction to the brightly colored 

 objects with no distinct absorption bands are those nearly colorless 

 bodies and solutions which give as sharply defined absorption bands as 

 could be desired. The best examples of this are afforded by solutions 



