216 CYANOGENETIC GLUCOSIDES CHLOKOPHYLL 



Phaseolus lunatus), occurs also in young flax plants. Its composition 

 and hydrolysis are indicated by the following equation : 



C 10 H 1T O fi N + H 2 = C fi H 12 6 + HCN + (CH 3 ),CO 



Phaseolunatin. d-glucose. Acetone. 



It is thought probable that the hydrocyanic acid yielded by Cassava 

 root (from which tapioca is obtained), the Ceara rubber plant and the 

 Para rubber plant is derived from the same compound. 



Many other plants are known to yield small quantities of hydro- 

 cyanic acid. Thus, the leaves and stems of the sweet potato, Ipomcea 

 batatas, which have often been noticed, in Queensland, to be poisonous, 

 have been found to yield from 0*014 to 0'019 per cent of their weight 

 of prussic acid. 



The young shoots of oats, wheat and barley and many of the 

 graminece have been carefully examined but found to be free from any 

 cyanogenetic compounds. 



The functions of the cyanogenetic compounds in plants are not 

 known, though some investigators consider it probable that they are 

 transitional products, produced perhaps by the action of formaldehyde 

 upon nitrates, from which, first, amino-acids are derived, and that these 

 latter in turn, serve as materials from which the proteids are built up. 



VII. CHLOKOPHYLL. 



This substance is the essential constituent of all the green-coloured 

 portions of plants and is the medium by which the assimilation of 

 carbon compounds from carbon dioxide and water, by the aid of energy 

 derived from light, takes place. 



Its nature and constitution have formed the subject of many re- 

 searches. In many plants it occurs associated with other colouring 

 substances, of which carrotene, C 40 H 5G , and xanthophyll, C 40 H r)f( O.,, are 

 the most important. The former can be obtained in copper-coloured 

 leaflets, which appear red by transmitted light ; the latter is similar in 

 appearance to carrotene but transmits yellow light. Both readily ab- 

 sorb oxygen (up to 34 or 36 per cent of their weight) and are con- 

 verted into colourless substances. 1 



Pure chlorophyll, obtained from plants by Willstatter and Hug, a 

 is a bluish-black, lustrous, glistening powder which melts somewhat 

 indefinitely between 93 and 106. It is soluble in ether, giving a 

 greenish-blue fluorescent liquid ; soluble also in alcohol or in benzene 

 and pyridine. 



Its composition is C 55 H 7 oO 6 N 4 Mg and its ash consists of pure 

 magnesia. 



Willstatter regards as the fundamental constituent a compound 

 which he calls chlorophyllin and which has the composition, C. U H, 9 N 4 

 Mg(COOH) 3 . 



1 Willstatter & Mirg, Ann., 1907, 355, 1 ; Jour. Chem. Hoc., 1907, Abstracts, i. 865. 

 2 Ann., 1910, 378, 18; 1911, 380, 177; 1911, 382,129; Jour. Chem. Soc., 

 1911, Abstracts, i. 140, 393 and 659. 



