204 3 G. Fl. Becker—Solutions of Cinnabar, Gold, ete. 
tions, while all the best known soluble compounds of mercuric 
sulphide and sodium have the same general formula. The pres- 
ence of carbonates of thealkalies is also known, especially from 
Méhu’s results, to be compatible with the existence of these com- 
pounds. The question therefore arises whether such double 
sulphides may not exist in natural waters. 
Possible existence of Na’S in natural waters._-This question 
resolves itself into two. It is to be considered whether Na’S 
may exist in natural waters as such, In that case such waters 
must dissolve mercuric sulphide. It is also possible that 
alkaline monosulphides cannot exist as such in these waters, 
but that the affinity of sodic sulphide and mercuric sulphide is 
sufficient to overcome the obstacles to the formation of sodic 
sulphide, and that this compound willform when mercuric sul- 
phide is present. The latter possibility is the more important 
one, but the former is manifestly one of interest to chemical 
geology. 
A train of thermochemical reasoning, upon which it is not 
necessary to enter here, makes it extremely probable that, at 
temperatures exceeding 80°, a certain amount of sodic sulphide 
may form by the decomposition of neutral sodium carbonate and 
sodium sulphydrate in the presence of acid sodium carbonate.. 
The behavior of such mixtures to mercuric sulphide at the 
temperature indicated is also such as it would beif the sodic 
sulphide actually formed ; but a full and sufficient proof of the 
reaction which theory indicates as probable seems very difficult: 
and has not yet been accomplished. It is certain, however, that 
a tendency exists to the formation of sodium sulphide under 
these conditions. When in addition to this tendency, the 
affinity of mercuric sulphide for sodic sulphide is brought into 
play, it can be proved experimentally that sodic sulphide is 
formed. We found that at a temperature of about 90° a mix- 
ture of the two carbonates and the sulphydrate dissolves mer- 
curic sulphide freely without a sensible evolution of gas. If 
the solvent does not contain sodic sulphide, it must contain the 
sulphydrate. Hence it becomes important to ascertain the 
behavior of mercuric sulphide to sodic sulphydrate at mod- 
erately elevated temperatures. 
While sodic sulphydrate will not dissolve a trace of mercuri¢ 
sulphide at ordinary temperatures, if mercuric sulphide is added 
to a solution of sodium sulphydrate which stands upon the 
water-bath, hydrogen sulphide is evolved and mercuric sul- 
phide goes into solution. The fact that hydrogen sulphide is 
evolved demonstrates that sodic sulphide must be formed. 
Cooling does not reprecipitate the mercuric sulphide, and the 
compound dissolved is therefore of the form HgS, nNa,S. 
Though the solubility of mercuric sulphide in warm solutions 
