THE ACTION OF LIGHT 



561 



from it gave an imide of haematinic acid, together with methyl-ethyl-maleic imide. 

 Further, Nencki and Zaleski (1901) found that haemin, on reduction, gave 

 hcemo-pyrrol, which is, according to Kiister (1908) and Piloty (1909), a dimethyl- 

 ethyl-pyrrol. Willstatter obtains this substance from chlorophyll also, and finds 

 it to be a mixture in both cases of three isomeric dimethyl-ethyl-pyrrols. 



From information given me by Prof. Willstatter, I understand that he does 

 not regard the similarity in constitution between chlorophyll and haemoglobin 

 as being of any great significance. The mother substances were probably at hand, 

 and compounds with the properties of the two pigments respectively being 



4oo 



3 



i 



5 



Green [ Blue | Vi olet 



FIG. 178. ABSORPTION SPECTRA OF CHLOROPHYLL AND ASSOCIATED PIGMENTS. Scale 

 of wave lengths at top and bottom. Fraunhofer lines marked at the top. The 

 colours of the regions of the spectrum indicated at the bottom. 



1 Nettle leaf, living. Chlorophyll in colloidal state (Willstatter und Stoll, p. 62). 

 " a-chlorophyll in ether (do. , p. 170). 



6-chlorophyll in ether (do., p. 171). 



Carotin in alcohol (do. , p. 246). 



Xanthophyll in alcohol (do., p. 246). 



required, if one may use the expression, these pyrrol derivatives were made 

 use of. 



In the leaf, according to Willstatter, chlorophyll probably exists as an 

 adsorption compound with a colloid, but not combined with a lipoid, as some have 

 stated. 



The two yellow pigments are both unsaturated and autoxidisable, that is, they 

 spontaneously oxidise in the air. They are nitrogen-free. Both pigments have 

 two absorption bands in the blue and blue- violet (see Fig. 178). 



The one, carotin, is an unsaturated hydrocarbon (C 40 H 5C ). It is soluble in 

 petroleum ether and is identical with the " lutein " of the corpora lutea of mammals, 



36 



