THE CHEMISTRY OF CHLOROPHYLL 427 



and haematoporphyrin was only completely demonstrated some 

 years later. 



By more gentle treatment of chlorophyllan with alcoholic 

 potassium hydroxide, another acid was obtained, which could 

 be readily separated from other products by taking advantage 

 of the fact that its potassium salt was soluble only with 

 difficulty in alcohol ; to prepare it chlorophyllan was boiled for 

 one hour with alcoholic potassium hydroxide ; carbon dioxide 

 was then passed through the solution, and a precipitate con- 

 sisting chiefly of the potassium salt of the new acid and of 

 potassium carbonate was obtained ; this was dissolved in water, 

 and the barium salt of the acid precipitated by means of barium 

 acetate ; from this salt the free acid was obtained by the 

 addition of acetic acid. It was called by Hoppe-Seyler 

 chlorophyllanic acid. In addition to the insoluble barium salt, 

 a soluble salt was also obtained, which was shown to be 

 barium glycerophosphate ; and Hoppe-Seyler concluded that 

 chlorophyllan was a derivative of lecithin, an opinion which 

 was generally held until quite recently, when it was shown to 

 be erroneous by the investigations of Willstatter, to be described 

 below. 



Chlorophyllan was held by Hoppe-Seyler himself to be 

 probably a changed product of the original pigment contained 

 in plants. That this view was correct was subsequently shown 

 by Tschirsch, who found that the plant acid caused a decom- 

 position of the original chlorophyll, leading to the production 

 of chlorophyllan. The actual natare of the change was demon- 

 strated afterwards by Willstatter (see below). 



The most important discovery due to Hoppe-Seyler is 

 perhaps that of phylloporphyrin ; it was not prepared by him 

 in a pure condition, but it was the first product obtained which 

 indicated a chemical relationship between the green pigments of 

 plants and the blood. 



Researches by Schunck and Marchlewski 



The investigations to be described under the above heading 

 were commenced by Schunck alone, who published a pre- 

 liminary account of his results in the Proceedings of the Royal 

 Society ; he was joined afterwards by Marchlewski, and the 

 results of the conjoint work appeared in Licbig's Annalen ; in 

 the latter publications the full experimental details are given. 



