19, 20. CHLOROPHYLL. 19 



or by agitation with ether. In examining these acids attention 

 must bo paid to the possible presence of members of the oleic-acid 

 series ( 130, 131) and of the allied ridnoleic acid. (See also 12.) 

 As a preliminary "operation an ultimate analysis may be made ; 

 and if this, as well as the reactions of the oil already observed, 

 does not point directly to a particular acid, an attempt must be 

 made to accomplish a separation either by treating the plaster 

 obtained by heating the fat-acid with oxide of lead, with ether 

 (which dissolves oleate of lead) or absolute alcohol ; or by frac- 

 tionally precipitating an alcoholic solution of a soda-soap with 

 acetate of barium, or acetate or chloride of calcium ( 130, 131). 



CHLOROPHYLL AND ALKALOIDS EXTRACTED SIMULTANEOUSLY 

 WITH THE FIXED OIL. 



20. Chlorophyll. The petroleum- spirit extract of vegetable 

 substances often shows a green colour by transmitted light. 

 'This is generally due to chlorophyll. Such solutions are usually 

 fluorescent, and appear blood-red by reflected light. Pure chloro- 

 phyll is only slightly soluble in petroleum spirit, and its presence 

 in this extract is accounted for by the influence exercised 

 tupon its solubility by the fixed oil. That the green colour is 

 really due to chlorophyll may easily be shown by spectroscopic 

 -examination. White light, on passing through a solution of this 

 substance, undergoes a change in various of its constituent 

 colours, as shown by the absorption bands in the spectrum. If 

 the Fraunhofer line A correspond to 17 on the scale, B to 28, 

 C to 34, D to 50, and F to 90, there are observable in the 

 spectrum (compare Table I. to 148, Nos. 13 and 14) 1 four 

 absorption bands situated between B and F, the darkest of which 

 extends from 30 to 42, and the remaining three from 44 to 50, 52 

 to 56, and 58 to 60 respectively. From 80 to the end the spectrum 

 gradually darkens. Of these absorption bands only the first two 

 can be observed in dilute solutions, and the relative amount of 

 chlorophyll dissolved may be judged from the presence or absence 

 of the others. It would be scarcely possible to obtain absolute 

 values for the amount of chlorophyll present, as liquids containing 

 but very small quantities of that body are comparatively deeply 

 coloured. Moreover, no method has hitherto been found available 



1 In examining a fresh leaf, only the most marked line between B and C i* 

 seen. Compare Vogel, Ber. d. d. chem. Ges. B. xi. pp. 623, 1367 (1878). 



9 9 



