The Extraction of Pure Pigments from the Leaf. 2 1 



the pump. Then 250 c.c. of solvent is added and slowly sucked 

 through with the pump. After five minutes another 250 c.c. of 

 solvent is added and sucked by the pump for ten minutes. This 

 operation is repeated with two further additions of 250 c.c. of solvent, 

 and finally the pump is allowed to work as strongly as possible and the 

 powder is sucked dry. The 1,500 c.c. of solvent used gives 800 to 

 900 c.c. of extract. It will be noticed that the solvent only passes 

 once through the powder, and that the extraction is rather rapid. 



In order to obtain good results with small quantities of solvents 

 in so short a time, a good deal of care is necessary. It is essential 

 to have the powder dry and to get it sucked into a coherent mass 

 on the Buchner funnel before commencing the extraction. The 

 layer of powder on the funnel must not be too high : not more than 

 5 cms. 



The amount of solvent required and the time necessary for 

 extraction depend on the chlorophyll content and on the fineness 

 of the powder, but at the end of the extraction the powder should 

 remain colourless or coloured only slightly yellow. 



(5) The Separation and Purification of Chlorophyll. Various 

 methods for the separation of the green pigments have been worked 

 out by Willstatter and his co-workers. The most successful of 

 these, of which we give a rdsume below, is that of Willstatter and 

 Stoll. 



The essentials of this method are, firstly, the transference of 

 the pigment from acetone to petrol ether and the removal from the 

 petrol ether solution of accompanying substances by washing with 

 watery acetone. The xanthophyll is then removed by means of 

 methyl alcohol. By washing the petrol ether solution with water, 

 the last traces of acetone and methyl alcohol are removed. As 

 chlorophyll is insoluble in pure petrol ether, it is precipitated, and 

 so is filtered from the carotin which remains in solution. 



The details of the method are as follows. The extract from 

 2 kilos of nettle powder is obtained as indicated in the preceding 

 section. Four litres of petrol ether (S.G. -64 to -66) are put in a 

 7-litre separating funnel and the extract added to this in two 

 successive portions. With each of these additions is also added 

 i-litre of water, and the funnel is gently rotated at the same time. 

 The liquid separates into an upper deep green layer and a lower 

 weak yellow green layer. The latter is run off. The remaining 

 petrol ether layer is mixed with two successive litres of 80% acetone 

 which removes impurities but very little chlorophyll. The acetone 



