262 USING THE MICRO-SPECTROSCOPE [Ch. VIII 



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. 



§ 416. Carmine solution. — Make a solution of carmine by put- 

 ting o.i gram of carmine in ioo 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 oxyhemoglobin or carbon- 

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

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

 eral 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 is decidedly 

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

 if any can be seen, is markedly different. Carmine and O-hemoglobin 

 can be distinguished by the use of ammonium sulphide, the carmine 

 remaining practically unchanged while the blood shows the single 

 band of hemoglobin (§ 413). The acetic acid serves to differentiate 

 the CO-hemoglobin as well as the O-hemoglobin. 



§ 417. Colored bodies not giving banded spectra. — 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 microscope 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 unabsorbed waves, as occurs 

 with other colored objects. In this case, however, not all the light of 

 a given wave length is absorbed; consequently 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. 



§ 418. Nearly colorless bodies with clearly marked absorption 

 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 of the 



