Removal of Manganese in Determinations of the Zinc, Calcium, and Magnesium of Manganese Ores and Products
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ROBERT L. EVANS, W h i t e Rear Lake, M i n n . T.kSDARD treatises give procedures for the precipitation of manganese from concentrated nitric acid solutions by POtassium chlorate as a “separation” method in its determination (1, 2 ) . The author has found this precipitation an excellent manganese “removal” method in determining zinc, calcium, and magnesium contents of high-manganese ores and products. This method does not, require the double precipitation necessary in basic ammoniacal precipitations using bromine, ammonium persulfate, hydrogen peroxide, or a combination of ammonium persulfate and hydrogen peroxide, which has proved to be the best ammoniacal precipitation for these samples. The standard procedure is modified as follows:
The combined filtrate has a low enough concentration of nitrate ion for direct determination of zinc, calcium, and magnesium, which obviates the need of another evaporation to dryness, With good filtration this method removes up to 1 gram of manganese and leaves a clear solution with the manganese equivalent of not more than 1 or 2 drops of 0.1 A- potassium permanganate, as shown by bismuthate oxidation. Reprecipitation of the manganese from the combined residues precipitated in the routine determination of calcium and magnesium in six samples gave a filtrate that, contained less than 1 mg. of either calcium or magnesium.
After t,he addition of potassium chlorate the whole mixture of solution and suspended precipitate is very cautiously evaporated (slow overnight evaporation below the boiling point precludes bumping) to dryness on a lo\v-teniperaturehot Plate or steam bath. It is then moistened with a few milliliters of nitric acid and digested in 50 to 100 ml. of cold water for filtration, with or without suction, and the residue and precipitation b a k e r arc washed with an equal amount of watt^.
LITERATURE CITED
IT,F., Lundell, G. E. F.,“++plied ~~~~~~~i~ Analysis,” pp. 340-3, New York, John Wiley & Sons, 1929. (2) “Scott’s Standard Methods of Chemical Analysis,” ed. b,- N. H. Furman, 5th ed., 5’01. I. pp. 558-60, 571, New York, D. Van Nostrand Co., 1939.
(1) Hiliebrand,
R E C E I I - June ~ D 30, 1947.
Turbidimetric Method for Determination of Potassium Sulfate in Propellent Powders CARL BOYARS t 7 .S. .Vaz.al Powder Factory, Indian Head, M d .
FIE incorporation of potassium sulfate in colloided nitrorrcellulose propellants required a method for the control determination of this ingredient. At first, the new additive was determined gravimetrically by precipitation as barium sulfate. By modifying the method of Rudy ( 3 ) for the determination of sulfuric anhydride in cements, a satisfactory and rapid turbidinietric procedure has been developed.
filters. The scale can be read with reasonable precision in that region. The average deviation of calibration points from the straight line was under *2% for all calibration curves. Control laboratory, nontechnical personnel were rapidly trained in the anal\ tical operations, after which they obtained data comparing the turbidimetric method a ith gravimetric determinations on p o der ~ ~ lots. Thirty-five trial determinations showed that the turbidimetric procedure gave results that agreed with those obtained gravimetrically, within the precision of the calibration cuive. \I here a more rapid separation of the potassium sulfate is desired, the pondel may be taken up in combinations of organic solvents-e.g., acetone-acetic acid (4)-the insoluble potassium sulfate filteied off, and potassium sulfate determined turbidimetrically. Certain n-ater-soluble compounds, such a5 nitroguanidine ( I ) , interfere 1% ith the turbidimetric determination by crystallizing out as the solution cools.
A Lumetron photoelectric colorimeter, Model 4OO-.i, equipped \vith a Sola constant-voltage transformer, was used for the determination of optical density (in terms of the optical density of the blank as zero) of barium sulfate suspensions in matched test tubes. Calibrating solut,ionswere prepared by dilution to 100 nil. of portions of a standard potassium sulfate solution containing 1 gram of drird, reagent grade potassium sulfate per liter. The solutions, controlled a t a temperature of 25” * 2 ” C.,, were poured into 250-ml. beakers, 0.5 ml. of 6 -V hydrochloric acid was added to each, and a suspension of barium sulfate was produced by adding barium chloride crystals to t,he mechanically, stirred solution, as specified by Rudy ( 3 ) . Part of t,he suspension was pourcd into a clean, dry test tube, and the optical density was determined 90 seconds after addition of the barium chloride. Before each reading, the colorimeter was set a t zero optical density against distilled water as the reference standard. The straight-line calibration curve obtained was used by the control laboratory in the analysis of pon-ders. The powder, freed by extraction from ether soluble components, was taken up i n a solvent (ether-alcohol or acetone) and the nitrocellulose precipitated in the usual manner (a,5 ) by the addition of water. hfter the solvent had been evaporated, the wet nitrocellulose was washed into a sintered-glass crucible on a suction bell jar, using hot water to leach out the potassium sulfate. About five 10ml. portions were drawn through under vacuum. A 100-ml. volumetric flask was used as receiver for the filtrate, and after cooling and adjusting to volume, the potassium sulfate was estimated turbidimetrically.
ACKh OW’LEDGMEhT
The author wishes t o thank W.C. Cagle, who supervised this work, for his aid and suggestions in the course of this investigation. LITERATURE CITED
(1) Davis, T. L.. “Chemistry of Powder and Explosives,” pp. 4, 299, 324, Nen York, John Wiley & Sons, 1943. ( 2 ) Furman, K.H., “Scott’s Standard Methods of Chemical Anal>sis,” 5th ed., p. 1695, New York, D. Van Nostrand Co.. 1939. (3) Rudy, R. B., J . Research Satl. Bur. Standards, 16, 556 (1936). (4) U. S. Army Specification No. 50-12-18, Powder, Propellent, ’
M12, p. 9 (30 July, 1945). (5) War Dept., Tech. Manual TM 9-2900, “Military Explosives,” p. 70,1940.
Variations in response between different Lumetrons made it impractical to select a light filter or test tube size which would be universally applicable. I n general, it was found that a straight line was obtained over the 0.2 to 0.5 optical density region for all
RECEIVED M a y 31, 1947.
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