4 H. C. COOKE 
tion to compounds of silver with a single acid element, many double 
compounds, ‘particularly with arsenic, antimony, and tellurium. 
Argentiferous galena and tetrahedrite are likewise very common 
sources of silver. Since a description of the secondary enrichment 
of any metal must account fully for the processes of its solution in 
meteoric waters, its transportation by, and its precipitation from, 
them, a complete study of the processes of the secondary enrich- 
ment of silver must involve also an explanation of the migration of 
the sulphides of lead, copper, arsenic, and antimony, in the same 
ground-waters that carry silver. 
PREVIOUS WORK— EXPERIMENTAL 
Experimental data bearing on this problem are few, since those 
who have touched the question in the laboratory have rarely worked 
under the conditions which commonly obtain in secondarily enriched 
ore deposits; i.e., low temperatures, small concentrations, low 
pressures, and a somewhat narrow range of possibilities in the way 
of chemical composition. Johnston™ showed that silver carbonate 
will dissolve in water saturated with carbon dioxide at 15° C. to 
the extent of 0.846 gm. per liter. Senarmont? and Rickard3 
have demonstrated that native silver may be precipitated from 
silver solutions by organic or carbonaceous matter. Van Hise4 
states that silver sulphide is soluble in solutions of alkaline carbon- 
ates, but the writer has been unable to find reference to any experi- 
mental confirmation of this statement. 
A few experiments have also been made under conditions within 
the range of possibility as to composition, though not as to temper- 
ature and pressure. Spring’ showed that at pressures of 6,500 
atmospheres silver sulphide was formed from its elements. Moesta® 
obtained metallic silver by passing steam at 100 C. over silver sul- 
*G. S. Johnston, Chem. N., LIV (1886), 75. 
 Senarmont, Annales Chim. Phys., 3d ser., XXXII (1851), 140. 
3 Rickard, Trans. A.I.M.E., XXVI (1896), 978. 
4 Van Hise, U.S.G.S. Monograph 47 (1904), 1099. 
Ss Spring, Ber. Deutsch. Chem. Gesell., XVI, 324, 1002; XVII, 1218. 
6 Moesta, F. A., Uber das Vorkommen der Chlor-, Brom-, und Jodverbindungen des 
Silvers in der Natur; ein Beitrag zur Kenntn. d. geol. u. bergbaulichen Verhaltnisse von 
Nord-Chile. Marburg, 1870. 
