The Black range. (Robinson, Socorro County, N.M.) 1882-1897, 1886-09-17
Lixiviation of Silver Ores--Ef-
feet OF Caustic Lime.


C. A. Stetefeldt. OF New York City,
read tue following before the Ameri-
can Institute of mining Engineers.
In my paper on Russell's process
( Transactions, vol. xiii. p. 54). men,
ton under Sec. 10 the deleterious In
tiuence OF caustic alkalies In llxiviation.
Mr.. Russell's recent experiments have
thrown more light upon this subject.
and fully explain why. In many cases,
the extraction of silver by hyposulhite
solutions has hitherto been failure
IL a silver ore that contains calcium
carbonate is subjected to chlorizing
roas ting. part OF the lime is convert
ed into caustic lime, It's quantity de.
pending Outside of the percentage of
calcium carbonate) upon the char
acter OF the ore. With an increase OF
sulphurets of the base metals In the ore
the formation of caustic lime win be
lessened. This caustIc lime reacts
upon the silver In the ore In two ways:
1. IL caustlc lime comes In contact
with silver chloride ut red heat. metal
ic silver Is formed. AS this reaction.
necessitates a close juxtaposition of
the particles concerned. IL will vary
materially in degree, according TO cir
cumstances, and may effect. especially
with lowgrade ores, only small per-
centage Of silver. Besides. In case the
metallic silver Is not actually melted. II
will be readily dissolved by the extra
solution. Hence, the damage done by
the roasting process itself may be very
slight.
On moistening the roasted ore. On
the cooling,hoor. and then teaching 1t
with water, aud subsequently with a
solution of sodium hyposulphite. cal
cium hydroxlde is dissolved, and reacts
on silver chloride with formation OF
silver oxide, If the ore on the cooling
floor is sprinlled with water While still
red hot, IL Is reasonable TO suppose that
SILVER oxide will be convented into met.
talie silver. In teaching with water.
calcium hydroxide is only In part re-
moved (lO9 parts of water at 10 degrees
c. dissolved 0,l86s parts. and at 1909 C..
0,O752 parts. OF calcium hydruxide),
That the caussic solution will decom.
pose chlorides and sulphates of the
heavy base metals, 1t Is hardly aeces
sary to mention.
In applying the sodium hyposulphite
solution, the remainder Of the calcium
hydroxide is quickly dissolved. calcium
hyposulphide and caustic soda deing
formed. The latter now reacts much
more energetically on account of great
er concentration. and seems to do the
principal damage In the final result of
the lixiviation process.
With our knowledge OF chemistry.
the above is the only statement of re-
actions am able TO give for this case.
If we now take into consideration that
silver oxide is easily dissolved by So
dium hyposulphide solution (for one
equivalent of silver dissolved, one
equivalent Of caustic soda is set free)
and that metallic silver yields to Rus
sells extra-solution, the question may
well be asked: How can caustIc lime
seriously effects the final result of lix
ivation. even taking II for granted that
u caustic hyposulphite solution is an in
ferior solvent for silver combinations
The facts. however. remains; and since
Mr.. Russell has found at Lake Valley
New Mexico. simple remedy to over
come this serious difficulty, it Is doubt