184 



Mr. E. Schunck. 



" Contributions to the Chemistry of Chlorophyll. No. 11." By 

 Edward Schunck, F.R.S, Received November 25, — Read 

 December 16, 1886. 



[Plate 1.] 



Considering the intimate though as yet little understood con- 

 nexion between chlorophyll and the carbon dioxide of the atmo- 

 sphere, it seemed to me that it might be of interest to ascertain 

 whether compounds of phyllocyanin, similar to those previously 

 described, could be obtaiued, in which the organic or other acid should 

 be replaced by carbonic acid. 



On passing a current of carbon dioxide through a solution of 

 phyllocyanin in absolute alcohol holding a quantity of freshly 

 precipitated hydrated ferrous oxide in suspension, no combination 

 took place, the phyllocyanin remaining unchanged, though the 

 current of gas was passed through the liquid for a considerable time. 



On substituting freshly precipitated cupric oxide for the ferrous 

 oxide there were slight indications of some reaction taking place, but 

 the phyllocyanin remained for the most part uncombined. 



A much more decided effect is produced when zinc oxide is 

 employed. On passing a current of carbon dioxide for several hours 

 through an alcoholic solution of phyllocyanin holding hydrated zinc 

 oxide in suspension, the colour of the liquid changes by degrees, the 

 dull phyllocyanin tint disappearing. On being filtered from the 

 excess of zinc oxide (which retains a pale-green tint, not removable 

 by washing with alcohol) it appears of a fine bluish-green ; it fluoresces 

 strongly, and shows absorption-bands which coincide with those of 

 the alcoholic solution of phyllocyanin zinc acetate. The liquid leaves 

 on evaporation a dark-green semi- crystalline residue, which may be 

 heated to 150° without undergoing any change, but is decomposed at 

 a temperature of 160 — 170°. It is, however, very easily decomposed 

 by the action of strong acids. On adding a little hydrochloric acid 

 to its alcoholic solution and heating, bubbles of gas are seen to 

 escape, the colour of the solution changes to blue, and on now adding 

 water there is a dull flocculent precipitate, which dissolves easily on 

 shaking up with ether, the solution showing the colour and absorp- 

 tion-bands peculiar to phyllocyanin solutions. There can be no 

 doubt, therefore, that the compound formed is a phyllocyanin zinc 

 carbonate, which by the action of strong acids is decomposed, yielding 

 phyllocyanin and carbon dioxide. An alcoholic solution of the com- 

 pound exposed in an open test-tube to sunlight soon loses its bright- 

 green colour and becomes yellow, the absorption-bands at the same 

 time disappearing. 



