SECONDARY ENRICHMENT OF SILVER ORES 19 
cause of the increase of K,, an increase of the acidity of the solution 
by addition of sulphuric acid should bring K, back to its true value, 
by decreasing the hydrolysis of the ferric sulphate. This, however, 
has not yet been experimentally verified. 
This constant is given with some hesitation; it should be verified 
by further experimental work before final acceptance. Moreover, 
as it stands it expresses a relation merely between the concentra- 
tions of the various salts involved, not between the concentrations 
of their ions; but in the absence of accurate determinations of the 
extent of ionization of these salts, this is unavoidable. 
REACTION OF SILVER CHLORIDE WITH SODIUM CHLORIDE 
The question of the secondary enrichment of silver deposits 
through the agency of chloride solutions has long been discussed. 
Silver chloride has a solubility in water of 0.0016 gm. per liter at 
20 C.t It has often been stated that the presence of sodium chlor- 
ide in the water increases the solubility. The information already 
at hand in regard to this question is comprised in the following 
table: 
NaCl in Solution AgCl in Solution Temperature 
gm. per liter gm. per liter 
BARS 0.0018 207C.** 
46.0 .0025 20, C. 
We 5 .0047 ae) (Cr 
76.7 -O125 Nore (Cp 
II5.0 .031 201.G. 
26) .090 200 C. 
230.0 5313 207 Ce 
100.0 .025 Lo Cai 
142.9 1070 ing” (Ci 
181.8 . 182 r5. GC: 
219.8 439 my (Ce 
23513 . 706 ines (Ge 
256.4 1.03 rye. 
263.1 19027 nse (Cy 
** Barlow, Jour. Am. Chem. Soc., XXVIII (1906), 1446. 
7 Schierholtz, Sitzungsberichte der Kaiserlichen Akademie der Wissenschaften zu Wien, 101, 2b (1890), 8- 
Thus it requires the presence in solution of 34.3 gm. of sodium 
chloride per liter, or 34,300 parts per million, to raise the solubility 
of the silver chloride to its value in pure water. In all sodium 
* Kohlrausch, Zeit. phys. Chem., L, 356. 
