THE CHEMISTRY OF CHLOROPHYLL 



By S. B. SCHRYVER 



In spite of the large amount of labour devoted to the subject, 

 both by botanists and chemists, but little progress has been 

 made until very recent times, in the elucidation of the true 

 chemical nature and constitution of the green colouring matters 

 of plants. This is due to the many technical difficulties in 

 which the experimental investigation abounds ; the small yield 

 obtainable, their labile nature, and the difficulty of separating 

 the green pigments from fats and other colouring matters by 

 which they are always accompanied, may be considered as the 

 chief causes which have impeded the knowledge of the chemistry 

 of chlorophyll. 



The fact that green leaves yield up their pigment to fats 

 and oils was discovered in 1682 by Nehemiah Grew, and the 

 solutions thus obtained were the subject of several investiga- 

 tions during the course of the eighteenth century and the earlier 

 years of the nineteenth century, notably by Rouelle, Meyer, 

 Fourcroy, Berthollet, Senebier, Proust, and Vauquelin. Their 

 discoveries were, however, of subsidiary importance, and require 

 no detailed consideration in this place. 



The name " chlorophyll " was first given to the green 

 pigment by Pelletier and Caventou in the year 1817; these 

 investigators recognised that the alcoholic extract was not of 

 homogeneous nature, but consisted of a mixture of several 

 substances. Berzelius attempted to separate the constituents of 

 the mixture, and obtained, by treating the alcoholic extract of 

 plants with alkali, a water soluble constituent, which is to-day 

 known as alkachlorophyll. 



The physical properties of chlorophyll solutions were also 

 the subject of numerous investigations during the earlier half 

 of the nineteenth century, notably by Brewster and Stokes, who 

 examined and plotted the absorption spectra, and made various 

 observations on the phenomenon and fluorescence of the 

 solutions. 



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