G. F. Becker—Solutions of Cinnabar, Gold, etc. 201 
the relative effect of the quantity of sodium sulphide and sodium 
hydrate on the quantity of mercuric sulphide which a given 
mixture of the solvents would take up. It is almost impos-~ 
sible to make experiments of this kind with the same accu- 
racy which can easily be attained in precipitations because, if 
one or more drops of either fluid reagent is added to a mass con- 
sisting of mercuric sulphide partially dissolvedin the men- 
struum, it is not practicable to say how long a time will elapse 
before the additional drop will have become saturated. Ap- 
proximate results are however readily obtained, and these ap- 
pear in the present case to be sufficient. 
It was found that, provided a small quantity of free hydrate 
exists in the mixture, the solubility of HgS depends solely 
upon the quantity of Na’S in the solution. The average of 
fourteen experiments made with varying proporsitions of sodic 
hydrate gives 1HgS to 2°03 Na’S. From the nature of the 
experiments a slight excess in the quantity of solvent employed 
is to be expected. One experiment was made by mixing mer- 
curic sulphide and sodic sulphide in the proportion of two 
molecules of the latter to one of the former, and adding a few 
drops of caustic soda. A mere trace of mercuric sulphide 
remained undissolved, and this completely disappeared on the 
addition of a single drop of a solution of sodic sulphide, so that 
less than one drop completed the solution. 
Chemists of course regard cases ofsolution such as that under 
discussion as due to the genesis of soluble double salts, which 
are formed according to ordinary laws of composition. The 
ner’s potassium compound. He found mercuric sulphide insoluble in sodic hydrate 
-er in the simple sulphide of sodium, but highly soluble in mixtures. 
Alkaline pentasulphides convert amorphous quicksilver sulphide digested with 
them into cinnabar (Gmelin-Kraut, Handbuch der Chemie, vol. iii, p. 756, where 
many references may be found), and this process implies a certain degree of solu- 
bility. Mr. Barfoed, however, found mercuric sulphide insoluble at ordinary 
pressures in sodium sulphydrate to which sulphur had been added, and the solubility, 
in the pentasulphide is probably slight. The conversion of the black sulphide into the 
red, does not appear to imply more than a mere trace of solubility, for Messrs. H. 
Sainte-Claire Devilleand Debray produced rhombic crystals of cinnabar by heating 
precipitated sulphide with chlorhydric acid to 100° C.in aclosed tube (Fouqué and 
Michael-Lévy, Syuthése des Min. et des Roches, p. 313). No statement is made in the 
account of this experiment of any means being employed to produce any great pres- 
sure. Mr.S. B. Christy (this Journal, vol. xvii, 1879, p. 453) found that at pressures of 
from 150 to 590 pounds per square inch and temperatures of from 180° to 250° various 
liquids heated with precipitated mercuric sulphide convert it into vermilion. He 
experimented with polysulphides of potassium, potassic sulphydrate, acid sodic 
carbonate charged with sulphydric acid, and a spring water containing acid sodic 
carbonate which he charged with sulphydrie acid. He reached no conclusion as 
to the state of combination of the mercury in solution. The fact that glass is 
greatly attacked at high pressures and temperatures by alkaline solutions of course 
leaves many possibilities open. Prof. R. Wagner (Journal fiir prakt. Chemie, vol. 
xcvili, 1866, p. 23), has shown that mercuric sulphide is soluble in barium sulphide, 
and Prof. Roth (Allgem. u. chem. Geol., vol. i, p. 264) thinks it probable that cal- 
cium sulphide possesses a similar power. 
