1914] Clarence J. West 231 



Chlorophyll shows certain peculiarities in solubility. Water- 

 free acetone does not extract a trace after standing half an hour, 

 but becomes intensely green upon the addition of a little water. 

 Eighty percent acetone is the most suitable for extraction pur- 

 poses. Absolute alcohol behaves in the same way, but 90 percent 

 is the most suitable concentration. Ether and benzene become 

 colored only after the addition of a few drops of water. Methyl 

 alcohol is an exception, Chlorophyll being nearly insoluble in 80 

 percent methyl alcohol and readily soluble in the anhydrous sol- 

 vent. The efifect of the water is probably due to the fact that it 

 dissolves some of the mineral salt (potassium nitrate) of the leaf, 

 the resulting salt Solution changing the colloidal condition of the 

 Chlorophyll in the leaf and rendering it easily soluble. 



Three methods of extraction have been used, the last men- 

 tioned (below) being the most rapid and giving as pure products 

 as the first two. 



The first method used was by extraction in a flask. One kilo 

 of leaf meal was shaken with 2 liters of alcohol on a shaking 

 machine for 24 hours, the extract filtered off and the residue washed 

 with alcohol until the filtrate measured 2 liters. This liquid was 

 used to extract a second lot of meal, thus obtaining a so-called 

 double extract.^ 



The second method consisted in percolation.^*^ In this the meal 

 was moistened with alcohol (0.3 liter per kilo) and allowed to 

 stand three or four hours, sifted and placed in the percolator, care 

 being taken that the material was properly packed, not too tight 

 and without Channels. This was then percolated with 2 liters of 

 alcohol per kilo of meal, the Operation requiring about 24 hours. 



These two methods are open to two objections : The long action 

 of the solvent in contact with the leaf meal is favorable ( i ) to the 

 action of the chlorophyllase contained in the leaf, which more or 

 less completely decomposes the Chlorophyll and (2) it brings about 

 allomerization (see page 235), which is recognized by a change in 

 the decomposition products of the Chlorophyll with alkalis. 



These objections are overcome or avoided by the third method, 

 which consisted in extraction of the pigment on a porcelain funnel 



^ Willstätter : Ann. d. Chem., 350, 65 (1906). 

 10 Willstätter and Oppe : Ibid., 378, 5 (1910). 



