318 



PIGMENTS 



account for the formation of four isomeric compounds, chloro- 

 phyllin and isochlorophyllin derived from chlorophylls a and h, 

 as indicated by the following formulae : — 



Chlorophyllin a when heated w4th alkali loses carbon- 

 dioxide, and yields two isomeric dibasic acids, glaucophyllin 

 and rhodophyllin, C3iH32N4Mg(COOH)2, and at a higher tem- 

 perature it loses two molecules of carbon dioxide, yielding 

 a monocarboxylic acid, pyrrophyllin, C3iH33N4Mg(COOH). 

 By heating with soda lime the third molecule of carbon 

 dioxide may be removed with the formation of aetiophyllin, a 

 substance containing no carboxyl group at all, and to which 

 the following formula is assigned : — 



CH = CH 



CHo 



C CH 



\ 



G 



N 



N 



X 



C.H;,- C C 



\ 



C 



X 



c 



CH 



Co He' C 



CH. 



^N Mg' 



■:N-r 



c 

 I 



CH, 



C Co He 



CCH: 



CH, 



Aetiophyllin, C3iH34N4Mg 



Chlorophyllin h when heated with alkali yields the same 

 pyrrophyllin, C3iH33N4MgCOOH, as chlorophyll h. 



* Willstatter, in his papers, does not represent chlorophyll h as having 

 a lactam grouping, but from its behaviour in the phase test there is every 

 reason to suppose that it possesses one. 



