288 
Ingvar Jorgensen and Walter Stiles. 
Willstatter first dried his leaves and powdered them before 
extracting the pigment. The advantages and disadvantages of 
using fresh and dried leaves may be summarised as follows. 
Preparations from fresh leaves are important (i) for analytical 
purposes when small quantities only are necessary; (ii) when it 
is necessary to find the true proportions of the various pigments; 
(iii) when the action of chlorophyllase on chlorophyll is utilised for 
the preparation of crystalline chlorophyll. On the other hand 
fresh leaves have the disadvantages that (i) they are more difficult 
to divide finely; (ii) it is more difficult to prevent the alteration of 
the chlorophyll in fresh leaves than in the dry powd&r. However, 
this difficulty may be overcome by treating with a watery solution 
of methyl or ethyl alcohol of such concentration that no chlorophyll 
is extracted while at the same time the enzymes are destroyed. 
Willstatter himself used the dried powder of leaves for all 
ordinary extractions. The use of the dried powder has these 
advantages, (i) To obtain the same quantity of pigment a much 
smaller quantity of material is required than if fresh material is 
used. This allows of the use of small vessels for the extraction 
operations, a very important advantage when the small quantity of 
chlorophyll present in the crude material is considered, (ii) A 
saving in the solvents is effected. These are not diluted by the 
water content of the leaves which constitutes about 75% of the 
fresh leaves, (iii) As a leaf can be chosen the dried powder of 
which keeps well, the preparation of the pigments can be made 
independent of the season and growing place of the plants. 
The disadvantages of using the dried material are as follows : 
(i) Loss of chlorophyll owing to drying. If the drying is done 
properly this loss is very small. Thus Willstatter found in alcoholic 
extracts of dried nettle and of Galeopsis 95 to 96% of the chlorophyll 
in fresh leaves, (ii) Again, if the leaves are not properly dried, 
alteration of the pigments may take place. Some dried leaves are 
spoilt by being kept (e.g., Grass), others (e.g., Elder and Conifer 
leaves) are even spoilt by drying. But even in such cases the 
chlorophyll may be preserved unchanged if the leaves are dried in 
a vacuum desiccator over sulphuric acid. 
It should be mentioned that Willstatter has compared the 
pigments extracted from fresh leaves and dried leaf powder and 
has found them identical. 
(3) The Solvents. For the various reasons given above 
Willstatter used the dried powder of nettle leaves for all ordinary 
