Contributions to the Chemistry of Chlorophyll. 



359 



acid. These reactions make it somewhat doubtful whether these 

 compounds are to be considered as double salts in the ordinary accep- 

 tation, and whether the metallic constituents may not rather be con- 

 tained in them somewhat in the same way as the iron in hamiatin. 



I have still a few remarks to make on the distinctive properties 

 characterising the three principal groups of these compounds, the 

 cupric, zinc, and ferrous groups. 



Of 'these, the cupric compounds are the most beautiful, and, at the 

 ■same time, the most stable. Their solutions show a brilliant colour, 

 inclining more to blue^than green, and spectra with four absorption 

 bands, the position of which varies somewhat according to the acid 

 employed. They are not decomposed by treatment with strong acids. 

 If an alcoholic solution of any one of them be mixed with a large 

 quantity of hydrochloric acid and boiled, the colour is not changed, 

 and on adding water, and then shaking up with ether, the ethereal 

 liquid which rises to the surface shows the same colour and the same 

 spectrum as the original alcoholic solution. The phyllocyanin cupric 

 acetate is the most beautiful of the series. It is best prepared by 

 adding cupric acetate to absolution of phyllocyanin in boiling acetic 

 acid. The crystalline mass which separates out on standing is 

 filtered off, treated with dilute hydrochloric acid to remove any 

 excess of cupric acetate that may be present, and then redissolved in 

 glacial acetic acid boiling. The solution on cooling deposits the 

 compound in crystalline scales, which are elongated, pointed at the 

 ends, of a pale greenish-blue by transmitted light, and of a brilliant 

 purple, with a semi-metallic lustre, by reflected light ; it much 

 resembles crystallised indigo-blue. The other cupric compounds 

 yield only microscopic crystals. 



The zincic group of compounds yield solutions of a brilliant green, 

 -showing spectra of five bands. These compounds are distinguished 

 from the preceding by their instability in the presence of strong acids. 

 If an alcoholic solution of any one of the zinc compounds be mixed 

 with hydrochloric acid.and boiled, its colour changes to blue. On now 

 adding water, the blue colour disappears, and a precipitate is formed 

 which on shaking up with ether dissolves. The ethereal solution 

 has the colour and shows the absorption spectrum of phyllocyanin 

 solutions. The zinc compounds are therefore decomposed by hydro- 

 chloric acid, yielding phyllocyanin again as one of the products of 

 decomposition. 



The behaviour of phyllocyanin towards zinc oxide in the pre- 

 sence of organic acids may serve to explain a peculiar phenomenon 

 first observed by Church* and subsequently described by Tschirch. 

 The former took chlorophyll that had become olive-brown on standing, 

 and, acting on it with zinc powder in the water-oven, obtained a body 

 * " Chemical News," xxxviii, 168. 



