474 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. 



mixtures of sodie .sulphide and sodic sulpliydrate are brouglit in contact with 

 mercuric sulpliide. The ])rosenee of sodic carbonates diminishes the solu- 

 bihtv of mercuric sidphide, but does not prevent sohition. Ammonium 

 carbonate completel}- prevents sohition at temperatures behiw the boiling- 

 point, but not at l-if)° C. 



These facts suffice to lead to important conclusions with reference 

 to spring waters, such as those mentioned above. When neutral sodic 

 carbonate is treated with sulphydric acid at ordinary temperatures, sodic 

 sulphydrate forms. At temperatures approaching the boiling-point, it is 

 probable that a certain quantity of sodic sulphide is also produced. At 

 these higher temperatures either of these sulphur compounds will dissolve 

 cinnabar, and the presence of sodic carbonates will not prevent solution. 

 These conclusions were amply verified by direct experiments. 



Mercuric sul])hide may be wholly or partly precipitated from solutions 

 of the sulphosalts in many ways : by excess of sulph}'dric acid or of other 

 acids, by borax and other mineral salts, by cooling (especially in the presence 

 of ammonia), and by dilution. In the last case a certain quantity of metallic 

 quicksilver, as well as mercuric sulphide, is formed, and this is very probably 

 one of the methods by which native quicksilver has been produced in nature. 



Metallic gold, iron pyrites, cupric sulphide, and zincblende were found 

 to be soluble in solutions of sodic sulphide ami in solutions of the carbonates 

 to which sulphydric acid had been added. All of them appear to form 

 sulphosalts with the alkaline compound. It has long been known that 

 sulphides of arsenic and antimony are soluble in sodic sulphide. They 

 also dissolve in mixtures of the carbonates and sulphides of sodium. 



Natural solutions of sodic carbonates and sulphides, which are conunon 

 components of hot spring waters, are thus capable of dissolving at least five 

 of the principal metals, as well as sulphur, arsenic, and antimony. Combi- 

 nations of these elements form a large part of the minerals found in mines. 

 There is little or no doubt that the cinnabar of the California deposits has 

 been dissolved and precipitated as indicated above and that at least a part 

 of the gold of that State has been produGed in a similar manner, but I by no 

 means assert that natural deposits of cinnabar and of gold have never been 

 produced in an}- other way. 



