234 



PIGMENTS 



Chlorophyll {a and b). 

 Analysis agrees with for- 

 mula C5BH,AN4Mg. 

 Bluish-black glistening 

 powder, with metallic 

 lustre. 

 Appears crystalline under 



the microscope. 

 No definite M.P. 



Practically insoluble in 

 cold light petroleum, 

 but dissolves readily on 

 addition of a few drops 

 of methyl or ethyl alco- 

 hol. 



Phase Test. 



Chlorophvll a. 

 C,,H„0,N,Mg. 



Bluish-black powder. 



Bluish-black powder. 



Sinters and forms a vis- 

 cous mass at 117-121° 



Very sparingly soluble in 

 light petroleum, but 

 dissolves very easily in 

 most organic solvents. 



Phase Test. 

 Transient pure yellov 



Chlorophvll b. 

 C,,H,oO,N,Mg. 



Dark green or greenish- 

 black glistening powder. 



Dark green or greenish- 

 black glistening powder. 



Sinters at 86-92°, and be- 

 comes viscous at 120 

 130°. 



Quite insoluble in light 

 petroleum, and is gener- 

 ally somewhat less 

 soluble than chloro- 

 phyll a. 



Phase Test. 

 Transient brilliant red 

 colour. 



(i.e. hydrolysis in ethereal 

 solution, with methyl 

 alcoholic potash), gives 

 a transient brown 

 coloration (cf. p. 240). 



From the above data it will be seen that neither ordinary 

 chlorophyll (a and d) nor either of the constituents of this 

 mixture show any marked tendency to crystallize which at 

 first sight would appear to be in contradiction with the well- 

 known fact first observed by Borodin * that when green leaves 

 are moistened with alcohol, and allowed to evaporate slowly 

 under a coverslip, crystals of chlorophyll may be observed 

 under the microscope. Willstatter and Benzf described a 

 method of obtaining this substance in quantity from Galeopsis 

 tetrahit, and later Willstatter and StoU \ showed that this 

 so-called crystalline chlorophyll was not present as such in the 

 plant, but was a secondary product produced by the action 

 of the alcohol upon the chlorophyll under the action of 

 an enzyme chlorophyllase. The phytyl group is thereby re- 

 placed by the ethyl group as illustrated by the equation : — 



/COOCH3 

 CsiHaNgMg^COOC^oHg 

 /CO 

 NH 



+ C^H.OH 



Amorphous Chlorophyll a 



/COOCH3 



i> 



xNH 



Crystalline Chlorophyll a 



* Borodin : " Bot. Ztg.," 1882, 40, 608. 



+ Willstatter and Benz : «' Annalen," 1907, 358, 267. 



X Willstatter and Stoll : id., igio, 378, 18. 



