426 SCIENCE PROGRESS 



Valuable additions to the knowledge of chlorophyll were 

 made later by Fremy, Timiriazeff, Kraus, Tschirsch, Hansen, and 

 others, but the principal advances are due to the labours of 

 Hoppe-Seyler, Schunck and Marchlewski, and to Willstatter 

 and his pupils. The three series of researches by these in- 

 vestigators require some detailed consideration, during the 

 course of which the influence of the discoveries of the earlier 

 observers will be discussed. 



Investigations by Hoppe-Seyler 



In 1879, Hoppe-Seyler isolated from grass a crystalline sub- 

 stance which he regarded as a derivative of the original green 

 pigment of plants, and to which he gave the name of chlorophyllan. 

 He obtained this product in the following way : The grass was 

 first extracted with ether several times with the object of 

 separating the fats, and then with boiling alcohol ; the extract 

 thus obtained was then employed for the extraction of a second 

 portion of grass, which had also been previously treated with 

 ether. The concentrated extract thereby obtained, deposited 

 crystals on standing. The filtrate from these crystals was then 

 evaporated, the residue washed with water, and the part 

 insoluble in water extracted with ether. This ethereal solution 

 deposited on standing crystals of chlorophyllan, which could, 

 after washing with the cold solvent, be purified by recrystallisa- 

 tion -from hot alcohol. The product analysed was purified by 

 repeated alternate recrystallisations from ether and alcohol, and 

 was found to contain both magnesium and phosphorus. 



By treatment of chlorophyllan with a potassium hydroxide 

 at 290 , an acid was obtained, to which Hoppe-Seyler gave the 

 name of chromatinic acid, and from which he prepared a barium 

 salt, the composition of which corresponded with the formula 

 (C2iH 35 3 )2 Ba. By treating the salts or the acid itself with excess 

 of mineral acids, a decomposition product of chromatinic acid 

 was obtained, which dissolved in acid water with a blue-purple 

 colour; on account of the similarity of the light-absorption of 

 the solution thereby obtained, to that of the blood-pigment 

 derivative described but a short time before, and prepared by 

 Hoppe-Seyler by the action of acids or reducing reagents 

 on haemin, and called by him haematoporphyrin, the new 

 substance from chlorophyll was designated phylloporphyrin. 

 The intimate chemical relationship between phylloporphyrin 



