Schunck . — The Chemistry of Chlorophyll. 95 
that may be present, and then redissolved in boiling glacial 
acetic acid. The solution on cooling deposits the compound 
in crystalline plates, which are elongated, pointed at the ends, 
of a pale greenish-blue by transmitted, and of a brilliant 
purple, with a semi-metallic lustre, by reflected light. A 
solution of this compound in acetic acid imparts very pleasing 
shades of green to white leather and to wool, silk, or cotton 
prepared with albumen ; it acts as a so-called substantive 
dye, i.e. one that requires no mordant for its fixation. When 
the reprehensible practice of adding copper to the vinegar 
used for pickling vegetables is followed, it is this compound 
which is formed, imparting to the vegetables the lively green 
colour which some people admire; vinegar alone turns the 
colour of vegetables to a greenish-brown in consequence of the 
formation of phyllocyanin or phylloxanthin. A commercial 
preparation has lately been introduced to which the name 
chlorophyll has been given. It consists essentially of one 
of the cupric compounds just described, as may be seen on 
comparing the absorption-spectrum of its ethereal solution 
with that of phyllocyanin cupric acetate. 
If it be thought desirable by the collector of plants to pre- 
serve the green colour of his specimens he may do so by 
immersing them for some time in vinegar holding acetate of 
copper in solution, then taking them out, washing well, and 
drying as usual. The effect with some plants is extremely 
pleasing, the green tint of the living leaves being retained ; the 
process, I have no doubt, would tend to preserve the speci- 
mens, though the time it would require would probably render 
it inapplicable in most cases. 
The phyllocyanin compounds containing iron yield solutions 
of a pure green tint like that of chlorophyll, but they are not 
strikingly fluorescent, and when exposed to sunlight in open 
vessels they retain their colour for a long time. The ferrous 
group may be divided into two sub-groups ; the first sub- 
group comprising compounds into which one of the fatty 
acids — acetic, palmitic, or oleic acid — enters as a constituent ; 
the other sub-group consists of such as are formed by the 
