234 PIGMENTS 



PhzEophorbide is the name given to the magnesium free 

 analogue of chlorophyllide, and is, therefore, the monomethyl 

 ester of phaeophorbin and has the formula — 



yCOOH 

 CsiHjiN^-COOH 



\cOOCH3 



By similar methods it is possible to obtain from each of 

 the phyllins corresponding magnesium free compounds which 

 are known as Porphyrins. Thus glauco- and rhodo-phyllin 

 give rise to glauco- and rhodo-porphyrin, while phyllo- and 

 pyrro-phyllin yield phyllo- and pyrro -porphyrin. 



If the magnesium free compound phytylphaeophorbide is 

 heated for half an hour with 24 per cent methyl alcoholic 

 potash, two compounds, phytochlorin e and phytorhodin g, are 

 obtained.* These same two substances are formed from any 

 other phaeophorbides as well as from phytylphaeophorbide, 

 and from whatever source prepared the ratio of phytorhodin 

 g to phytochlorin e is always i : 2'5.f 



The fact that these two compounds may be obtained in 

 this way is explained by assuming that natural chlorophyll is 

 in reality a mixture of two substances, an idea long ago sug- 

 gested by Stokes and also by Schunk and Marchlewski. It 

 has in fact been shown that ethyl phaeophorbide obtained 

 from crystalline chlorophyll by the removal of the magnesium 

 may be resolved into two modifications known as a and b 

 ethylphaeophorbides ; the former of these when hydrolysed 

 yields phytochlorin e, while the latter gives phytorhodin g^ 

 thus yielding a striking chemical confirmation of conclusions 

 drawn by Stokes from spectroscopic observation. 



With a view to the further elucidation of the constitution 

 of the chlorophyll molecule, especially in regard to the com- 

 plex to which the three carboxyl groups are attached, the 

 oxidation of the porphyrins by means of chromic acid in the pre- 

 sence of sulphuric acid has been studied by Marchlewski \ and 

 by Willstatter and Asahina.§ These investigations point to 



* Willstatter and Hocheder : id., 1907, 354, 232. 



t Willstatter and Isler : id., 1911, 380, 154; Willstatter and Utzinger: id., 

 191 1, 382, 129. 



:t Marchlewski : " Chem. Zentralbl.," IQ02, i, 1017. 



§ Willst itter and Asahina : " Annalen," 1910, 373, 227. 



