A Dichromate-Ferrous Sulfate Method for Antimony R. B. NEILL, St. Joseph Lead Co., Ronne Terre, Mo.
I
Solutions 1 CC. = 0.001 gram of antimony and 1 cc. = 0.005 gram are convenient. It is standardized against pure antimony metal treated the same as the sample. Ferrous ammonium sulfate solution, 1 cc. = 1 cc. of dichromate solution for convenience.
N ESTIMATING iron b y oxidation with potassium dichromate in hydrochloric acid solution, i t is necessary to
remove antimony. This suggested the possibility of a useful method for the determination of this metal. Accordingly, experiments were made on several materials containing known amounts of antimony in combination with copper, iron, tin, lead, zinc, manganese, arsenic, etc., TABLE11. RESULTSOF OUTLINEDPROCEDURES ON VARIOUS and two general methods of analysis were TYPES OF ANTIMONIAL MATERIAL devised. Element Present Sb Material
Suggested Procedure
Sb-Pb metal
Sb
Pb
Cu
%
%
%
2.70
..
.. ..
As %
Sn %
Fe
%
. . . . .. .. .. .. .. ..
97.2 0.06
.
Ni-Co
Zn
S
%
%
%
... ... ... ... ... ... ...
Found
% 2.70 2.72 2.70 0.93 0.96 0.96 4.85 4.85 4.90
FORTIPIT-BASE ALLOYS. Treat a 0.5- to 1.0. . . . . . . . . . gram sample in a 300-cc. Erlenmeyer flask Sb-Pb metal 0.95 98.9 ....... . . . . . . . . with 10 cc. of sulfuric acid (specific gravity 1.84), heat on a hot plate or over a flame until .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. solution or decomposition is complete and cool. Bearing metal 4.84a 0.14 2.45 0.05 92.2 . . . . . . . . . Add 40 cc. of water and boil a minute to remove sulfur dioxide. (If arsenic is present it .... .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. may be removed by volatilization a t the point Bearing metal 12.98a 0.10 3.00 0.05 82.8 .. . . . . . . . 12.95 where sulfur dioxide is boiled out by adding .. . . . . . . . . . . 50 cc. of hydrochloric acid, no water, and boil. . . . . . . . . . .. .. .. .. .. .. .. 13.05 13.0 ing gently to 20 to 30 cc.) Add 20 cc. of hyBearing p e t a l 14.27a 17.8 1.70 0.05 66.0 .. . . . . . . 14.25 .. .. .. .. .. .. .. .. .. .. .. . . . .. .. .. .. 14.2 drochloric acid (specific gravity 1.18) and when 14.2 solution is clear dilute to 150 cc. with cold water (cool if necessary to 40" C., as too hot Bearing metal 8.88a 90.6 0.10 0.04 . . . . . . . 8.9 . . . . solutions impair the indicator), and titrate as .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 8.95 8.95 follows: Matte 1.53 19.6 17.7 0.77 .. 29.0 3.8; .9 9.1 17.5 1.54 From a buret add standard dichromate solution .. . . . . . . . . . . .. .. .. .. .. .. .. 1.52 with thorough mixing until the orange color of 1.54 an excess can be seen through the green of the 4 An&& of bearing metals shown is average of results obtained in laboratories of five chromous chloride. Now add 2 to 3 drops of didifferent companies. phenylamine sulfonic acid indicator and 5 cc. of phosphoric acid (HsPOd, 85 per cent), and backtitrate with ferroussulfate solution, using 0.2 to 0.3 cc. in excess, and finish the titration with dichromate. The dichromate equivalent of the ferrous solution used is best determined a t this point by adding to Indicator, 1 gram of barium diphenylamine sulfonate dissolved in 100 CC. of concentrated sulfuric acid. Make fresh the solution just titrated the number of cubic centimeters used in the determination and titrating this jwith dichromate. This about every 3 months. FORLEAD-BASE ALLOYS, MATTES,AND CONCEKTRATES. Many volume of dichromate is subtracted from the original titration. The indicator color is violet when oxidized, green when reduced. antimony-lead alloys are difficult to decompose with sulThe dichromate solution may be of any desired strength. furic acid to produce a white lead sulfate. Dissolve a 0.5to 1-gram sample in a 300-cc. Erlenmeyer flask with 15 cc. of dilute nitric acid (1 to 1) and 0.5 gram of tartaric acid on a warm plate. When solution is complete, cool, add 10 cc. of concentrated sulfuric acid and 10 grams of poSYKTHETIC SOLUTIOKS TABLEI. ANALYSISOF EXPERIMEKTAL tassium sulfate, and take to a melt, starting on (Containing elements commonly associated with antimony, using FeSO1-KzCrz03 the hot plate where the charred tartaric acid No. of Found may be artially burned off, if it rises too high DeterminaElement Present in the task, by addin nitric acid dropwise. tions Sb Pb Cu -4s Sn Fe Si Zn Sb Gram Gram Gram Gram Gram Gram Gram Gram Gram When sulfur trioxide fumes appear, transfer the flask to a ring stand over a free flame and 3 0.150 . . . . . . . . . 0.850 . . . .. . . . 0.149 boil until the charred mass has become a light ... . . . . . . . . . . . . . . . . ... 0.150 ... ...... . . . . . . . . . .... ... 0.150 brown. Now lay the flask on its side and finish 3 0.150 0.200 . . . . . . 0.650 ... *. 0.149 boiling out the excess sulfuric acid (catching the ... ...... . . . . . . . . . ... 0.149 drip in a beaker). Cool the melt (add 50 cc. ... . . . . . . . . . . . . . . . .. .. ... 0.151 of hydrochloric acid and boil down to 20 cc. if 3 0.150 0.850 . . . . . . . . . .. ... 0.150 arsenic is present), add 25 cc. of water, 20 cc. .... .. .. .. .. .. ... .. .. .. ... of hydrochloric acid, and 10 grams of ammonium .. .. .. .. .. .. .. .. .. .. ... 0.149 0.149 chloride, and warm until solution is complete. ...... .. ... 0.0247 Dilute with cold water to 40" C. or less and 3 o:Oi50 o:iOo o:iOo o:Oio . . . . . . .. ... 0.0250 titrate as above. ... ...... . . . . . . . . . .. ... 0.0250 For the decomposition of mattes and con...... 0.0251 centrates, use concentrated nitric acid and add 3 o:oi50 0:iiIo 1:: . . . . . . o:ioo o:O4 o:iOo 0.0252 . . . . . . . . . . . . . . . . . . . .. . . . 0.0250 about 0.2 gram of tartaric acid or a bit of filter 3 0.0150 0.200 0.200 0.010 . . . 0.200 .. 0.100 0.0152 paper with the sulfuric acid. With this type ... ...... . . . . . . . . . .. ... 0.0150 of material (high iron) the phosphoric acid is ... . . . . . . . . . . . . . . . .. ... 0.0150 added before the dichromate in order to decolorize the yellow ferric ions.
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