The Chemistry of Chlorophyll. 1 5 



from an ether solution by an equal volume of 25% hydrochloric acid, 

 while with 32% it is almost entirely extracted: again only traces of 

 phytochlorin e are extracted by 0-5% acid, but it is almost entirely 

 extracted with 4 to 5% acid. The " hydrochloric acid number " is 

 the percentage content of that acid which by shaking removes 

 approximately two-thirds of the dissolved substance from an equal 

 volume of an ethereal solution. 



It was thus possible to separate the decomposition products of 

 phaeophytin by fractionating the mixture of them in ether with 

 hydrochloric acid of different concentration. 



The formation of the large number of decomposition products 

 of phaeophytin is due to the instability of chlorophyll in alcoholic 

 solution. By uniform treatment of material, however, Willstatter 

 has been able to ensure obtaining only two, but never fewer, 

 decomposition products from phaeophytin : phytochlorin e, 

 C3jH^,ONJCOOH)a,andphytorhoding,C32H3o02N«(COOH)2. 

 As the molecular weight of phaeophytin is of the same order 

 of magnitude as that of phytochlorin e and phytorhodin g, and as 

 these cannot be converted into one another, and as moreover they 

 are formed in definite proportions by weight, it follows that they 

 are formed from two different phaeophytins and ultimately from 

 two different chlorophylls." 



The summary on the next page may serve to make clear the 

 action of different reagents on the chlorophyll molecule. In each 

 case we have represented the actions with chlorophyll a. Similar 

 reactions take place with chlorophyll b. 



Description of Chlorophyll. Chlorophylls a and b as precipitated 

 out by petrol ether are microcrystalline. Chlorophyll a forms a 

 blue black powder which makes a green mark. Chlorophyll b 

 forms a green to green black powder. 



Chlorophyll a is easily soluble in ethyl alcohol, acetone, chloro- 

 form, ether and carbon-disulphide, pyridin and benzene, moderately 

 soluble in methyl alcohol and soluble with difficulty in 80% ethyl 

 alcohol, 90% methyl alcohol (even warm) and petrol ether (even 

 warm). It is practically insoluble in 80% methyl alcohol. 



Chlorophyll b has much the same solubility properties as 

 chlorophyll a, except that the solubility is generally slightly less. 

 It is completely insoluble in petrol ether and practically insoluble 

 in 90% methyl alcohol. 



' For further information on the chemistry of chlorophyll see Willstatter 

 and Stoll (1913). A short account of the chemistry of chlorophyll has also 

 recently been published by Willstatter in English ; see Willstatter (1915a). 



