1885.] The Chemistry of Chlorophyll 



339 



cnpric oxide or zinc oxide is added to a solution of phyllocyanin in 

 boiling alcohol no combination takes place. 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 uncombined phyllocyanin, for its 

 spectrum is different, and on standing it deposits lustrous crystals, 

 which doubtless consist of a compound containing phyllocyanin, 

 acetic acid, and copper. If zinc oxide be employed a similar effect is 

 observed, the liquid acquires an intense green colour like that of 

 a chlorophyll solution, and now contains the corresponding acetate of 

 phyllocyanin and zinc. The same phenomenon is seen when ferrous 

 oxide, manganese oxide, or silver oxide is taken, liquids of various 

 shades of green being obtained which contain phyllocyanin com- 

 pounds, but no similar compounds are formed when potassium, 

 sodium, barium, calcium, magnesium, or lead acetate is employed. 

 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. Oxalic acid, however, seems to 

 be without effect, and tartaric acid fails in some cases. 



The various compounds have a number of properties in common, 

 though the several classes differ, inter se, in some important particu- 

 lars. They all dissolve more or less readily in alcohol, ether, chloro- 

 form, benzol, and carbon disulphide, but are all insoluble in water 

 with the exception of the phyllocyanin manganese acetate, which 

 dissolves readily therein. The solutions have a green colour varying 

 from grass-green, like that of chlorophyll solutions, to a fine bluish- 

 green or blue, and they show peculiar spectra. The alcoholic solu- 

 tions remain unchanged when sulphuretted hydrogen is passed 

 through them, no precipitate is formed, and the solutions on evapora- 

 tion leave the various compounds with their original properties. It is 

 only on incineration that the presence of metallic constituents is 

 detected. Lastly, they are all soluble in dilute alkaline lyes, and are 

 reprecipitated unchanged on the addition of acetic acid. These 

 reactions make it somewhat doubtful whether these compounds are to 

 be considered as double salts in the ordinary acceptation, and whether 

 the metallic constituents may not rather be contained in them some- 

 what in the same way as the iron in hematin. Of the various 

 compounds those belonging to the cupric class are the most stable ; 

 they are not decomposed by boiling hydrochloric acid. The zinc 

 compounds, on the other hand, are very readily decomposed by 

 hydrochloric acid, yielding phyllocyanin. 



The behaviour of phyllocyanin towards zinc oxide in the presence 

 of acids may serve to explain a peculiar phenomenon first observed by 



