Absorption of Light by Chlorophyll Solutions

In a previous paper (l), studies were made of chlorophyll degradation products frequently to be found in leaf extracts. The solation of spectroscopically pure chlorophylls a and b was then considered (2). The logical outcome of these studies is the application of the data to the determination of chlorophyll in extracts. It is complicated by the suggestion that chlorophyll as known to Willstatter and Stoll is an artifact. Meyer (3) states that Stall’s chlorophyll preparations cannot account for the absorption of crude leaf extracts, except on the basis of an abnormal 9 : I ratio of chlorophyll a to 6, and even then a discrepancy occurs in the green at about 5400 8. This paper deals with the estimation of chlorophyll in plant extracts by application of absorption coefficients of the isolated solid chlorophyll components. The question of artifacts is thereby automatically clarified. A secondary problem arises in the substantial effect of solvent on the coefficients, and this will be dealt with first. Effect of Solvent on Absorption CoefJicients of Chlorophylls a and b -Absorption coefficients have been reported (2) for the chlorophylls in anhydrous acetone in some detail. For certain comparisons, a few values were also given for benzene and anhydrous et’her ((2) Table III).’ Through the courtesy of Dr. F. I’. Zscheile,