94 Schunck . — The Chemistry of Chlorophyll. 
the solution showing the colour and absorption-bands peculiar 
to phyllocyanin-solutions. It is evident that the compound 
is decomposed, the hydrochloric acid combining with the zinc 
oxide and the phyllocyanin, while the carbonic acid escapes, 
the phyllocyanin hydrochloride being decomposed on the 
addition of water. I have already mentioned the fact that 
Filhol observed a green coloration on adding zinc acetate to 
a solution of his ‘ matiere noire crystallisable.’ The same re- 
action was obtained by Tschirch on treating chlorophyllan in 
solution with zinc powder. Both observers must have been 
working, I imagine, either with phyllocyanin or some closely 
allied substance. The acid, the presence of which is in my 
opinion an essential condition of the reaction, consisted in 
Tschirch’s experiment, I rather think, of some fatty acid. 
The cupric class of compounds is almost as interesting as 
the zincic. These compounds give solutions of a brilliant 
colour inclining more to blue than to green, and showing spectra 
with four absorption-bands, the position of which varies some- 
what according to the acid employed. They are compounds 
of remarkable stability. If an alcoholic solution of any one of 
them be mixed with a large quantity of hydrochloric acid and 
boiled, the colour remains unchanged, 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. Such an alcoholic solution 
may be exposed in a loosely stoppered bottle to alternate sun- 
light and diffused daylight for weeks and even months without 
undergoing any perceptible change, being more stable under 
these circumstances even than phyllocyanin solutions. That 
these compounds should exhibit such remarkable stability as 
compared with the corresponding compounds of zinc is a 
singular and unaccountable fact. The most beautiful of the 
cupric series of compounds is the phyllocyanin cupric acetate. 
It is best prepared by adding cupric acetate to a solution 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 
