434 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. 



parts of sodic siilpliide in the pi-eseuce of caustic soda are required to pi*o- 

 duce the same eft'ect. Cuprlc sulphide is alsosohible at 20^ in the sohition 

 of sodium carbonate to which sulphydric acid has been added. Over two 

 thousand parts of neutral sodium carbonate which had been semi-saturated 

 with hydrogen sulphide were required to dissolve one part of cupric sul- 

 phide at this temperature. Cupric sulphide is also soluble in each of tliese 

 solutions when hot. 



Solubility of zns. — TIic experiments on zinc sulphide were made in the same 

 manner as on cupric sulphide. Zinc sulphide is more soluble in a mixture 

 of sodic sulphide and caustic soda than in sodic sulphydrate. A solu- 

 tion containing a little l6*5s than a thousand parts of Na'S and about one 

 hundred parts of NaHO dissolved one part of ZnS at 20°. The sulphydrate 

 dissolves only a very small (juantit}' of zinc sulphide. Sodic carbonate par- 

 tially saturated with sulphydric acid also dissolves zinc sulphide. Over one 

 thousand parts of neutral sodium carbonate which had been semi-saturated 

 with hydrogen sulphide were found necessary to dissolve one part of zinc 

 sulphide at 20^. 



Solubility oi As's' and sb's\ — It IS, of course, perfectly well known that tlie 

 sulphides of arsenic and antimony dissolve freely in .sodic sulphide without 

 evolution of gas and in sodic suljohydrate with the e\'olution of hydrogen 

 sulphide. In cold solutions of sodic carbonate partially saturated with 

 sulphydric acid they dissolve freely without liberation of gas, because the 

 Indrosulphuric acid set free immediately combines with sodic carbonate. 



Insolubility of pbs and Ag-s. — The sulpliidcs of lead and silver seem to be en- 

 tirely insoluble in solutions of sodic sulphide, of sodic sulphydrate, or in 

 solutions of sodic carbonate partially saturated with hydrosulphuric acid. 

 We have obtained no evidence of solution with these sulphides even when 

 heated above 100° with the reagents in closed tubes. Gtilena is rarely 

 found in quicksilver mines and distinct silver minerals are still more seldom 

 found associated with cinnabar. Very little galena occurs in the gold mines 

 of California, and lead deposits usually differ widely in character and mode 

 of occurrence from either quicksilver or gold deposits. These fects seem to 

 indicate that the best natural solvent for lead is different from that which is 

 most effectual in dissolving cinnabar and gold. Mr. de Senarinont^ produced 



' .\nn:ilesilr,liiiiii.-. P.iris, vol. :!•>, isr.r. mi. 1(W. 171. 



