CHLOROPHYLL 325 



solution is no longer effected by the solvent alone but by the 

 solvent together with the accessory substances. 



If dry solvents are used, the extract is much less pure, since 

 it contains a larger proportion of carotinoids, lecithins, etc., 

 whose solubilities are very similar to those of chlorophyll. 



The following methods of extracting dried or fresh leaves 

 respectively are described by Willstatter : — 



1. Half a kilo of dried material is spread on a porcelain 

 Buchner funnel in a layer of not more that 4 to 5 cms. thick, 

 and 1-5 litres of solvent are drawn through this layer by means 

 of a filter pump in the course of half an hour. This filtrate, 

 measuring about 0-9 litre, contains from 4-25 to 4-5 grams of 

 chlorophyll. 



The solvent employed may be either 90 per cent (aqueous) 

 alcohol or 80 per cent (aqueous) acetone. The former filters 

 rather more rapidly, but acetone has the advantage over 

 alcohol in preventing the chlorophyll from undergoing what 

 is known as allomerization, a peculiar change which interferes 

 with its power of crystaUization, and prevents it giving the 

 phase test. 



2. Two and a half kilos of fresh leaves are ground up in 

 a mill and shaken in a bottle with 1-5 htres of acetone to 

 remove water and mucilage and to stop enzyme action. The 

 acetone is then filtered off on a pump ; it contains no chloro- 

 phyll. The residue is then freed from acetone by filtering on 

 a pump under a pressure of 200 atmospheres, and the resulting 

 hard mass, weighing 0-8 kg., is broken up and ground again. 

 On adding 1-5 Htres of acetone the latter becomes diluted to 

 80 per cent by the water still remaining in the residue ; the 

 mixture is shaken for five minutes and a further quantity of 

 I Htre of 80 per cent acetone is now added. The liquid is 

 filtered off on a pump and the residue treated three times with 

 half a litre of 80 per cent acetone. The total filtrate should 

 measure 37 litres and contain 47 grams chlorophyll. 



In order to ascertain what proportion of the total chloro- 

 phyll present has been removed in any particular extraction, 

 another quantity of dried material, say from 100 to 200 grams, 

 may be subjected to an exhaustive percolation with an excess 



