Arizona republican., 1901-08-09
ACID..1Y OF ORES
An Important Problem Which Con.
 fronts tte Cyanider.

A correspondent of the Los Angeles
 Mining Review treats of the subJec: 9f tests made in cyaniding in this way:
 CT all the tests required of a cyanid- , CT, ;he 6etsrmination of acidity Is the
 most important On the proper exe1u- ton of this test. anl the application of alkai in right proportion depend largely | ly the success or failure of cyanide plant-the extraction oe the values, consumption of cyanide, ct :, This was
 most forcibly brought to mir.i in a ease where only two Lnuu1s Ci ;'l1e ger .On of ore had previously beer iarpIiei
 when by thorough prein!nry test
 snG the results thereof proved tiic :3d- visibility and necessity c; using at least seven pounds of lime instead Of two.
 In the first Instance, on account of lhe large consumption of cyanide, a 4-l0 DOT cent or stronger solution was necesSa- ry, and the result was poor extraction
 Of the gold with a considerable in ! crease of the time required. In tl,e sec
 ond instance, the lime requirel the consumption of cyanide and the strength of solution required, were ma terially reduced. with a much greater extraction of the gold
 The acidity of an ore or other ma. terial consists generally of various
 acid salts of iron, magnesia, etc. or O: free sulphuric acid, resulting from the decomposition of sulphurets which have destructive effect upon aka line cydnides with a prevention. more or less, of the extraction of the gold. | These may be neutrahzed to a large ex- tent by the proper application of an al- kiH-lime or soda. Various methods are in use for determining the proper amount of alkali to be applied.
 turman recommends that ten grams
 of ore be covered with water and s
 measured quantity of decinormal caus-
 ti2 soda stirred in, and the excess of so-
 da titrated with decinormal acid. The
 loss is the equivalent of theacidityof the ore.
 Feldtmann's method, given by Park,
 Is that the ore be shaken up with water
 ir tall glass jar or glass cylinder. and
 the solution titrated with standard soda ur'til the reaction is neutral to litmus paper.
 Bosqui. in commenting on this meth
 od, says that these tests, however, will frequently reveal no acidity. while sub sequent operations prove the necessity i of using an alkili. This accords with
 our own experience.
 Another method is to stir in weighed
 small quantities of solid lime instead of a solution of soda, until neutral or al- Kline to litmus paper. These methods
 are generally edious, and their failure
 to give the proper or full amount of ac- | iG.ty may be due to the following caus- es:
 The coarseness of the material treat ed, or the in sufficient time for the test. There are two general functions in d chemical reaction. viz: one of time and one of the intimacy of contact, which
 latter depends upon the dgree of fine
 ness of disintegration of the substances
 entering into the reaction. The finer
 an ore Is pulverized the more intimate
 the contact with the alkali, and hence the quicker and more complete the chemical reaction uetween the alkaIi
 and the acids of the ore Time may ov-
 ercome the lack of sufficient finenese, but a material may be so coarse thai
 such would not ha he case. In applying
 solid lime 1t should be very fine O., :n
 solution.