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USAC has a comprehensive quality control program for the production of antimony oxide. The control program includes (1) carefully sourcing raw materials with low impurities, (2) the campaigning of single lots with no commingling of other lots, (3) the dedication of one production line for one product, (4) the removal of impurities, (5) the careful adjustment of production controls, (6) the detailed monitoring of product for color, size, impurities, content, and other physical, mineralogical, and chemical parameters, (7) careful labeling of all products, (8) packaging, and (9) a statistical product control system (SPC). Composite samples for each lot are kept in a library for
3 years.

A Fisher Sub-Sieve Sizer (FSSS) is used in the plant for the control of the median particle size. A Micromeritics Sedigraph is used for particle size distribution. Color determinations are made using a Data Color Microflash colorimeter. An X-Ray diffractometer (XRD) is used to determine valentinite. Higher valence antimony oxides are determined by ethylene glycol digestion. Trace elements are determined by inductively coupled argon plasma (ICP), and by X-ray diffraction (XRE) using a Niton XL3t with Golld technology. The XRF is calibrated for specific matgricies using the ICP.



11 October 2011-USAC METHOD

(Notice: this method also titrates iron and is unreliable for most low grade ores and mill tails where we use ICP and XRF)


1.    Weigh 1.0 gram for mill tails, leach residue; slag; 0.5 grams for wet or dry sodium antimonite, low-grade ore; 0.2 grams for hand sort, metal, and mill concentrates. THE SAMPLE SHOULD BE CRUSHED, SPLIT, PULVERIZED, AND HOMOGENIZED IN A CERAMIC MORTAR AND PISTIL SO THAT IT WILL ALL PASS A 100 MESH SCREEN.

2.    Place in wide mouth 500 ml Erlenmeyer flask with 25 mls of concentrated sulfuric acid.

3.    Set the flask on a hot plate adjusted to 100-105 degrees centigrade and digest for at least 45 minutes until the white fume reaches the top of flask. THE DIGESTION  IS EXTREMELY IMPORTANT. IT CAN PROCEED MORE THAN 45 MINUTES BUT SHOULD NOT BE TAKEN TO DRYNESS.

4.    Add 1 small spatula (approximately 200 mgs) of hydrazine sulfate 3 times at least at 5-minute intervals.  The hydrazine sulfate reduces all the antimony to the plus three valence.  It is important to fume for at least 20 minutes after the last addition of hydrazine sulfate to ensure that all the hydrazine sulfate (a strong reducing agent) has been used up.  If this does not happen, you will be titrating the hydrazine sulfate and you will not reach an end point.  Do not evaporate to dryness.

5.    Remove when refluxing reaches top of flask.  (When white smoke reaches top of flask and small rivulets of water run back down in flask).

6.    Cool.  Wash down sides of flask with 25 mls. of water and 40 mls. of concentrated hydrochloric acid.

7.    Boil 3 minutes.  This volatilizes the arsenic.

8.    Cool and wash down sides of flask with water diluting to 300 mls.

9.    Filter heads and tails before titration.

10. Add 20 mls. of concentrated hydrochloric acid and titrate. TITRATION SHOULD BE DONE WITH A MAGNETIC STIRRER.

11.  Calculations:

Titer X Factor                  X         100 = % Sb

Sample weight

Titer X Factor                  X         1,000 = g/l

Ml aliquot



1.    First all the antimony is reduced to the plus 3-valence state.  On titration, it is oxidized to the plus 5-valence state.

2.    To prepare the titer add 2 grams of potassium permanganate per liter of water.

(Approximately 0.004 grams of antimony/1 ml of titer)

3.    To standardize titrate 0.25 grams of antimony metal 3 times to determine the factor.



            1.  Fume hood.

            2.  500 ml wide mouth Erlenmeyer flasks.

            3.  Spatula

            4.  Triple beam balance.

            5.  Balance accurate to 1 mg.

            6.  Hot plate

            7.  Cooling tray.

            8.  1000 ml. volumetric flask.

            9.  100 ml graduated cylinder.

            10.  50 ml. burette.

            11.  Burette stand with white stand.

            12.  Wash bottle.

            13.  Weighing papers.

            14.  Filtering funnel and paper.

            15.  Filter stand.

            16.  Steel mortar and pestle.

            17.  Ceramic mortar and pestle.

            18.  Pulverizer.

            19.  Laboratory jaw crusher.

            20.  Sample splitter.

            21.  Sample journal.



            1.  Sulfuric acid.

            2.  Hydrochloric acid.

            3.  Hydrazine sulfate.

            4.  Potassium permanganate.

            5.  Boiling crystals.

            6.  CP antimony metal.


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