426 QUICKSILVER DEPOSITS OP THE PACIFIC SLOPE. 



sum of all the errors of experiment and analysis,' the variation is not 

 i;'reat. 



In another anal3'sis of this solution, devised for the purpose of deter- 

 mining separately the sulphur combined with the hydrogen and that directly 

 united with sodium (an attempt which was only approximate!}- successful), 

 the total sulphur also actually came out somewhat higher than in that cited. 



These analyses, which formed the conclusion of a tedious series of 

 experiments, appear to me to show beyond an}' reasonable doubt that 

 there is a compound HgS, 4Na-S which is soluble in the presence of Na-S, 

 H-S and which is decomposed by hydrogen sulphide in the presence of 

 sulphydrate by the reaction HgS, 4Na=S + 411-8 zzHg8-f4Na=S, H-S. 



Conclusions from the experiments. — It appcars froHi the above that tlicre are at 

 least three double salts of the form HgS, «Na-S where n may be 1, 2, 

 or 4, and, judging from the analogy of the potassium compounds, there is 

 probably also a compound of this group where ii is .}. The possibility of a 

 case in which n is 3 has also been adverted to. Thus mercuric sulphide 

 readily enters into combination with sodic sulphide in various proportions, 

 while all the best known soluble compounds of mercuric sulphide and sodium 

 have the same general formula. The presence of carbonates of the alkalis 

 is also known, especially from Mchu's results, to be compatible with the ex- 

 istence of these compounds. The question therefore arises whether such 

 double sulphides may not exist in natural waters. 



Possible existence of Na-S in natural waters.— This qUeStioU rCSolvCS ItSclf iutO tWO. 



It is to be considered whether sodic sulphide 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 the compounds Na-S and HgS is sufficient to overcome 

 the obstacles to the formation of sodic sulphide and that this compound will 

 form when mercuric sulphide is present. The latter possibility is the more 

 important, but the former is uianifestly one of interest to chemical geology. 

 It seems commonly to be assumed that only the acid carbonate of sodium 

 exists in natural waters. I know of no warrant for this assumption. The 



' Among other sources of error in \rorking witli these compounds is the absorption of carbonic acid 

 and the liberation of H'S. The solutions never cease to smell of the latter. 



