Mr Purvis, The absorption spectra, etc. 85 



The absorption spectra of concentrated and diluted solutions 

 of chlorophyll. By J. E. PuRVis, M.A., St John's College. 



[Read 8 February 1909.] 

 (Plates I— III.) 



The general phenomena of the absorption spectra of solutions 

 of chlorophyll have been described by various observers, and refer- 

 ences to such work up to 1908 are included in Kayser's Handbuch 

 der Spectroscopie, vol. IV. But, so far as the author knows, there 

 are no recorded observations on the comparative spectra of equiva- 

 lent quantities of chlorophyll in strong and dilute solutions : and 

 the aim of this paper is to describe a series of observations which 

 have been made in this direction. 



The well-dried leaves of fresh parsley were ground to a powder, 

 and the chlorophyll extracted with rectified spirit, filtering the 

 insoluble portions. A portion of the strong solution was diluted 

 7 19 "8 times with rectified spirit, and the strong solution was 

 placed in a glass cell of 5 mm. internal width, whilst the diluted 

 solution was introduced into a glass tube, with glass ends, 3599 mm. 

 long. The ratio of the dilutions was, therefore, as 1 : 719*8, and 

 there was as much chlorophyll in the one solution as in the other. 

 The two solutions were exposed to the same source of light for 

 equal periods of time. The only alteration in the conditions was 

 that made necessary by the change of the small cell with the 

 strong solution for the long tube with the dilute solution; with 

 this exception, all the conditions were fixed and exactly the same 

 throughout the whole series of observations. The apparatus and 

 photographic spectroscope used for the observations have been 

 fully described in the Proc. Camb. Phil. Soc. vol. xii. pt. III. p. 206, 

 in some experiments by the author on the absorption spectra of 

 concentrated and diluted solutions of didymium and erbium salts. 



Description of photographic plates. 



Unfortunately, it has not been found possible to reproduce the 

 phenomena observed on the original photographs with any close 

 degree of precision. The fault is particularly noticeable in the 

 weak band \ 565, which is unmistakeably clear on the original 

 photographs. The gradual changes, however, can be traced fairly 

 closely by comparing the changes of the bands X 538 and A, 508 

 in the reproductions 1 to 9, and which are described in the cor- 

 responding paragraphs 1 to 9. 



