Contributions to the Chemistry of Chlorophyll. 357 



crystallises out unchanged on the solution cooling. The same 

 happens when freshly precipitated cupric oxide or zinc oxide is added 

 to a boiling alcoholic solution of phyllocyanin ; the solution deposits 

 phyllocyanin, and there are no indications of any combination taking 

 place between the phyllocyanin and the metallic oxide. 



A very different effect is observed when either of the two oxides 

 is employed along with acetic acid. When cupric oxide is added to 

 a solution of phyllocyanin in boiling acetic acid, the solution acquires 

 at once a deep greenish-blue colour, and it no longer contains un- 

 combined phyllocyanin, for its spectrum is different, and on standing 

 it deposits lustrous crystals, which doubtless consist of a compound 

 of which phyllocyanin, acetic acid, and copper are essential con- 

 stituents. If zinc oxide be employed, a similar effect is observed; 

 the liquid acquires an intense green colour, and now contains the 

 corresponding acetate of phyllocyanin and zinc. 



The same phenomenon is seen when ferrous oxide, manganese 

 oxide, or silver oxide, or one of the corresponding acetates is 

 taken, solutions of various shades of green being obtained, which 

 contain phyllocyanin compounds, but no similar compounds are 

 formed when potassium, sodium, barium, calcium, magnesium, 

 or lead acetates are employed, for on adding the acetate of any 

 of the last-named metals to an acetic acid solution of phyllo- 

 cyanin, the colour of the latter remains unchanged, and phyllocyanin 

 is deposited, just as if no metallic acetate were present. Acetic 

 acid is, however, not the only acid which yields the reaction. If 

 palmitic, stearic, oleic, tartaric, citric, malic, or phosphoric acid be 

 employed, it takes place just as with acetic acid, but, in some cases, 

 time is required for its completion. The process results, there can be 

 little doubt, in the formation of compounds analogous to those with 

 acetic acid. To obtain these compounds, it is only necessary to add a 

 little of the freshly precipitated metallic oxide, and an excess of one 

 of the acids named, to a solution of phyllocyanin in boiling alcohol, 

 keeping the solution boiling for several hours, then filtering and 

 adding water, in which the compounds are insoluble. The precipi- 

 tated compounds, which are generally of a bright green, are filtered 

 off and washed before treatment with reagents. 



The following is an enumeration of the compounds obtained in the 

 way just described : — 



Phyllocyanin cupric acetate. 



,, ,, palmitate. 



,, ,, stearate. 



„ „ oleate. 



,, „ tartrate. 



,, ,, citrate. 



phosphate. 



