IV] CARBON ASSIMILATION 31 



destroyed. If then water is added after saponification with hot alkali, 

 and the solution is shaken up with ether, the ether will remain colourless. 



When chlorophyll is treated with acids, a different reaction takes 

 place. The chlorophyll changes in colour to olive-green and loses most 

 of its fluorescence. The magnesium of the molecule is removed, being 

 replaced by hydrogen, and the resulting jjroduct is termed phaeophytin 

 (see Scheme 1, p. 34). 



From phaeophytin a series of decomposition products have been 

 obtained, which fall into two groups, the phytochlorins and the phyto- 

 rhodins. The phytochlorins are olive-green in colour, and are derived 

 from chlorophyll a; the phytorhodins are red, and are derived from 

 chlorophyll b. The phaeophytins from the two chlorophylls are indis- 

 tinguishable until the above decomposition products are obtained. 

 (The original discovery of two kinds of chlorophyll was brought about 

 by the differentiation of these decomposition products.) 



A number of phytochlorins and phytorhodins have been identified 

 and are designated by letters a, b, etc. By employing a uniform method 

 of treatment, however, two of these products, phytochlorin e and phyto- 

 rhodin g, can be secured. 



The phytochlorins and the phytorhodins are of course magnesium-free 

 compounds and can be obtained by the action of acid on the chlorophyllins 

 and isochlorophyllins. Phytochlorin e and phytorhodin g, in particular 

 are obtained by the action of acid on isochlorophyllins, i.e. they are ' 

 magne.sium-free isochlorophyllins. They are formed by the addition of 

 acid to the products of saponification with hot alkali. 



The separation of the various phytochlorins and phytorhodins can be 

 brought about by means of their different distribution between ether 

 and hydrochloric acid : each compound can be extracted from ether 

 according to the concentration of the acid used. 



Expt. 24. T/te formation of phytochlorin and phytorhodin. 5 c.c. of an ether 

 solution containing both chlorophylls a and h are evaporated to dryness in a te.st- 

 tube in a water-bath, and the residue treated with 3 c.c. of boiling 30 % potash 

 solution in methyl alcchol, and boiled gently for half a minute. A liquid with a red 

 fluorescence is produced which consists of a solution of the potassium salts of 

 isochlorophyllins. The solution is diluted with double its volume of water, and 

 concentrated hydrochloric acid is added until the solution is just acid. The liquid i.s 

 then shaken with ether in a separating funnel : the dissociation products produced 

 by the previous treatment pass into the ether solution which thus acquires an 

 olive-brown colour. 



The ether solution is shaken twice, each time with 10 c.c. of 4% hydrochloric 

 acid (sp. gr. 1-02 i.e. 12-9 c.c. strong acid: 87-1 c.c. water), and the green-blue acid . 

 layer is separated and neutralized with ammonia and shaken with more ether, which 



