230 Willstätter's Rcscarches on Chlorophyll [Jan. 



Chlorophyll of different plants. Earlier authors supposed 

 that different plants er varieties of plants, such as mono- and di- 

 cotyledonous plants, contained different kinds of Chlorophyll.^ 

 Etard^ claimed that one plant {Lolium perenne) contained no less 

 than six different varieties, each fraction of waxy material having 

 been considered a pure Chlorophyll. After a careful examination 

 of the Chlorophyll from over two hundred different kinds of plants, 

 Willstätter is fully justified in concluding that there is only one 

 Chlorophyll,^ though this exists in two forms. Certain difificulties 

 which were not understood before this conclusion was fully estab- 

 lished such as the effect of the enzyme, chlorophyllase, and the 

 effects of the solvent used, the time of extraction, and other condi- 

 tions, will be considered in detail below. 



Preparation of Chlorophyll. In the preparation of Chloro- 

 phyll either fresh leaves or dry leaf meal niay be used. For the 

 preparation of large quantities of Chlorophyll, dry material is pref- 

 erable, since the yield per kilo is much larger, the leaf containing 

 from 50 to 75 percent of water in the fresh state, depending upon 

 the season. The volume of solvents required is smaller, and the 

 solvents, after being used, are not diluted with the water originally 

 present in the leaf and there fore are more easily recovered. Fur- 

 thermore, the work may be carried out at any time of the year. The 

 two possible dangers in the use of the dry material are: loss of 

 Chlorophyll and chemical changes in the nature of the dyestuff dur- 

 ing the process of drying. It has been shown that both of these 

 may be avoided if the drying is care fully carried out. The dry 

 material is used in most of the work described below. In certain 

 cases fresh leaves are preferred — e. g., in the rapid preparation of 

 pure Chlorophyll from small amounts of leaves, in the quantitative 

 estimation of the green and yellow pigments, and where the action 

 of chlorophyllase is desired. 



The amount of Chlorophyll present in one kilo of fresh leaves 

 varies from 0.9 to 2.1 gin. The Chlorophyll content of the dry 

 substance varies from 0.5 to i.o percent. 



6 Gautier: Bull. soc. ehem. [4], 5, 319 (1909)- 

 ^Etard: La biochemie et les chlorophylles (1906). 



8 Willstätter, Hocheder and Hug: Ann. d. Chem., 371, i (1909) ; Willstätter 

 and Oppe, ibid., 378, i (1910); Willstätter and Isler, ibid., 380, 154 (1911). 



