208 G. F. Becker—Solutions of Cinnabar, Gold, ete. 
ces have also been made. The solubility of the sulphides of 
arsenic and antimony in sodie sulphide and in the sulphydrate 
is of course well known. In the presence of neutral sodic car- 
bonate sulphides of arsenic and antimony dissolve in sodic 
sulphydrate without the evolution of gas, because the sulphy- 
dric acid set free reacts upon the carbonate. 
Natural solutions and precipitations.—The foregoing experi- 
ments show that there is a series of compounds of mercury of 
the form HeS, nNa’S one or the other of which is soluble in 
aqueous solutions of caustic soda, sodic sulphydrate or sodic 
sulphide, and apparently also in pure water, at various temper- 
atures. These solutions subsist, or subsist to some extent in 
the presence of sodic carbonates, borates and chlorides. There 
is the strongest evidence that the waters of Steamboat Springs 
contain mercury in this form, and that the waters of Sulphur 
Bank have contained mercury in the same form, if indeed they 
do not still carry it in solution. Bisulphide of iron, gold and 
zincblende form double sulphides with sodium, which appear 
to be analogous to those of mercury. Copper also forms a 
soluble double sulphide, but combines more readily with sodic 
sulphydrate than with the simple sulphide. All of these solu- 
ble sulphosalts may exist in the presence of sodic carbonates. 
Mercuric sulphide is readily precipitated from these solutions. 
Any substance is more soluble in hot solutions than in cold 
ones, provided that increase of temperature does not resolve 
the fluid molecules into others which are less soluble ; as happens 
with sodium chloride, neutral sodium carbonate, etc. Dimin- 
ishing temperature is thus a cause of precipitation, and dimin- 
ishing pressure appears to act in a similar way. There are also 
other methods of precipitation which may be carried out under 
natural conditions. If a natural solution of mercury comes in 
contact with strong solutions of borax, or with sulphydrie acid, 
or any stronger acid, it will lose a portion of the mercuric 
sulphide in solution. At Steamboat Springs and Sulphur 
Bank large quantities of sulphuric acid are formed near the 
surface and, percolating downward, must precipitate mercury 
in some form. The acid waters penetrate to a depth of at least 
20 or 80 feet and this explains the fact that the waters reaching 
the surface carry so little quicksilver. These same causes must 
also produce precipitation of the other ores and of gold from 
solutions. 
Another method by which mercuric sulphide may be precipi- 
tated, as has been seen, is mere dilution. Now, ascending 
solutions of quicksilver must sometimes meet with springs; 
and when they do so, metacinnabarite, or black sulphide will 
be precipitated, and with it alsoa small amount of quicksilver- 
In nearly all mines a small quantity of “ virgin” quicksilver 
