290 
Ingvar Jorgensen and Walter Stiles. 
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 resume 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 
