G. FF. Becker—Solutions of Cinnabar, Gold, ete. — 207 
I found that pyrite, marcasite or precipitated ferrous sulphide 
when warmed with a solution of sodic sulphide diminished in 
quantity, while the solution changed color. The filtrates gave 
strong reactions for iron. 
Pyrite dissolves in cold solutions of sodium sulphide without 
any evolution of gas. The solvent power seems to increase 
with the temperature. Pyrite like cinnabar appears totally in- 
soluble in cold sodium sulphydrate, and, like cinnabar, pyrite 
dissolves to some extent in hot solutions of the sulphydrate. - 
Pyrite is also soluble in solutions of sodium carbonate partially 
saturated with sulphydric acid, both hot and cold. Quantita- 
tive determinations have been made, but are omitted here for 
the sake of brevity. 
Marcasite is more easily soluble than pyrite, and the simple 
precipitated sulphide goes into solution most readily of all. 
I think there can be no doubt that pyrite and marcasite form 
double salts with sodium sulphide entirely analogous to the 
soluble compounds of mercuric sulphide. Marcasite is more 
easily attacked than pyrite, Just as metacinnabarite is more 
susceptible to the action of reagents than cinnabar. 
Solubility of gold.-The association of gold and pyrite is 
world wide. According to Gahn* there is no pyrite which 
does not yield traces of gold when carefully tested. This in- 
deed does not accord with my experience, for extremely careful 
tests of some pyrite in my laboratory have failed to reveal any 
indication of gold. Gold is associated with quicksilver, how- 
ever, at Steamboat Springs, at some points on the gold belt of 
California, at the Manzanita mine, at the Reddington mine, and 
some other localities both in California and in foreign countries. 
From these facts I concluded that gold should be soluble in sodic 
sulphide. On warming chemically pure, precipitated gold-dust 
with a solution of sodic sulphide, the glittering scales of gold 
gradually disappeared. The filtrate after proper manipulation 
yielded a purple precipitate with phosphorous acid. 
A solution containing 843 parts of Na’S (by weight) dis- 
solves one part of gold at the ordinary temperature of the 
atmosphere. Gold also dissolves at ordinary temperatures in 
sodic sulphydrate, and in solutions of sodic carbonate partially 
saturated with sulphydric acid. The solubility appears to be 
increased and facilitated by heat. 
Solubility of other sulphides.—Cupric sulphide dissolves less 
readily than pyrite in sodic sulphide and in mixtures of the 
sodic carbonates and sodic sulphydrate. Unlike pyrite, it 
also dissolves in thoroughly saturated sodic sulphydrate. Zine 
sulphide is also soluble and behaves much as pyrite does. 
Quantitative determinations of the solubility of these substan- 
* Bischof’s Chem. Geol., vol. iii, p. 939. 
