CHLOROPHYLL 



317 



Chlorophyll a. 



Sinters and forms a 

 viscous mass at 117- 

 121°. 



Very sparingly soluble 

 in light petroleum, 

 but dissolves very 

 easily in most or- 

 ganic solvents. 



Phase Test. 

 Transient pure yellow 

 colour. 



Chlorophyll b. 



Sinters at 86-92°, and 

 becomes viscous at 

 120-130°. 



Quite insoluble in light 

 petroleum, and is 

 generally somewhat 

 less soluble than 

 chlorophyll a. 



Phase Test. 

 Transient brilliant red 

 colour. 



Chlorophyll {a and b). 

 No definite m.p. 



Practically insoluble in 

 cold light petroleum, 

 but dissolves readily 

 on addition of a few 

 drops of methyl or 

 ethyl alcohol. 



Phase Test 



(i.e. hydrolysis in 

 ethereal solution, with 

 methyl alcoholic pot- 

 ash), gives a transient 

 brown coloration (cf. 



P- 327)- 



ACTION OF ACID AND ALKALI UPON CHLOROPHYLL. 



The recognition of magnesium as an essential constituent 

 of chlorophyll, which is due to Willstatter,* has proved of 

 immense value in the study of the degradation products of 

 chlorophyll. 



By the action of alkalis and acids respectively upon the two 

 chlorophylls, it has been found possible to divide the degrada- 

 tion products of chlorophyll into two groups : — 



1. Those that retain magnesium, known as Phyllins. 



2. Those that are free from magnesium, known as Por- 

 phyrins. 



The Action of Alkalis. 



Chlorophyll a and b are compounds of a tricarboxyllic 

 acid, two of whose carboxyl groups are esterified by methyl 

 and phytyl alcohol respectively, while the third is present in 

 the form of a lactam grouping. 



When the two chlorophylls are treated with cold concen- 

 trated methyl alcoholic potash, their ester groups are hydro- 

 lysed and at the same time a molecular rearrangement takes 

 place accompanied by a colour change known as the Phase Test 

 (see p. 327). This colour change is supposed to be due to a 

 breaking open of the lactam grouping — NHCO — by the alkali 

 which is then followed by a closing of the ring by means of 

 one of the other carboxyl groups ; such an assumption would 



* Willstatter ; " Annalen," 1906, 350, 48. 



