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Pollution-free method for the determination of iron in iron ore
Tolanm, Vol. 29, pp. 700 to 702, 1982
0039-914oj82/080700-02sO3.00/0 Copyright 0 1982 Pergamon Press Ltd
Printedin Great Britain. All rights reserved
POLLUTION-FREE DETERMINATION
METHOD FOR THE OF IRON IN IRON ORE
S. KALLMANNand E. KOIUARKOVA Ledoux & Company, Teaneck, NJ 07666, U.S.A.
(Received 8 December
1981. Accepted 9 February 1982)
Summary-A method for the determination of total iron in iron ores and concentrates is described which avoids the use of mercuric chloride. The sample is decomposed either by an acid attack or by fusion with sodium peroxide. The hot sample solution in about 6M hydrochloric acid is treated with hot 10% stannous chloride solution till pale yellow, followed by addition of a slight excess of 2% titanous chloride solution; the excess is then oxidized with perchloric acid (1 + 1). The solution is rapidly cooled in ice-water, and the iron (11) is titrated with potassium dichromate (sodium diphenylsulphonate as indicator). The results show the same degree of precision, accuracy, and degree of interference as those obtained by the standard stannous chloride-mercuric chloride method.
Iron ore ranks second only to crude oil as a commodity in commerce and industrial use. A shipment of iron ore may weigh as much as 100,000 tons and its evaluation may be based on just a few analytical samples. The accurate determination of iron in iron ore is therefore of considerable economic importance. No instrumental method has been found accurate enough for the determination of iron in iron ores, although many routine iron determinations are carried out by XRF. Two titrimetric methods have been recommended by ASTM and IS0 for the determination of total iron in iron ores and concentrates.‘-’ They differ only in minor details. The ASTM methods are based on a dry sample, and the IS0 methods prescribe an “as received” sample and a separate moisture determination. One of the methods recommended by both ASTM and IS0 uses hydrogen sulphide as reductant, the other uses stannous chloride. In the latter case, a solution of mercuric chloride is used to oxidize the excess of stannous chloride. Both methods therefore involve reagents which in many countries are increasingly rejected for environmental reasons. The search for pollution-free methods has led IS0 Committee TC-102/SC-2 to form two task forces. One of these4 is considerine the use of silver as the reducing agent.’ Some obJ\ctions that have been made have prevented this method from being more widely used. One is of a practical nature; the reductor must be prepared, cared for and regenerated, a fact which makes the method less attractive for large-scale routine determinations. The second obiection involves the possible formation of hydrogen peroxide. There is also uncertainty regarding possible interference from copper. 700
The other task force is investigating of most of the iron(II1) with stannous
the reduction chloride, fol-
lowed by addition of a slight excess of titaneous chloride. The excess of titanium(II1) is removed by a delicate procedure requiring a precise titration (with Indigo Carmine solution as indicator) prior to the titration of the iron(U) with potassium dichromate.6 The procedure proposed here avoids the titration of the excess of titanium (III); instead the titanium(II1) is oxidized in boiling solution with perchloric acid (which is reduced to chloride). This reaction has been previously used for the determination of perchlorate,’ but not, to our knowledge, for the oxidation of titanium(II1). Under the conditions described in the procedure,
the iron(H) is not oxidized.
EXPERIMENTAL Reagents Ferrous ammonium sulphate solution (approx. O.lN). Dissolve 40 g of Fe(NH4)2(S04)2.6H20 in 400 ml of sulphuric acid (5 + 95). Transfer to a lOOO-mlstandard flask, dilute to volume with the same acid, and mix. Perchloric acid, 70% diluted 1:l. Phosphoric acid-sulphuric acid mixture. Pour 150 ml of
concentrated Dhosuhoric acid into 4OOml of water. with stirring. Add i50 AI of concentrated sulphuric acid; with stirring. Cool and dilute to 1000 ml with water. Potassium dichromate solution O.lN. Pulverize about 6 g of standard-grade reagent in an agate mortar, dry in an oven at 105” for 3-4 hr. and cool to room temperature in a desiccator. Dissolve 4.904 g of the dry reagent in 300 ml of water, transfer to a lOOO-ml standard flask, dilute to volume, and mix. Porassium permanganare solution, 25 g/l. Sodium diphenylaminesulphonate indicator solution. Dis-
solve 0.2 g of the reagent in water and dilute to 100 ml.
701
SHORT COMMUNICATIONS
Stannous chloride solution, ZO%. Dissolve 20 g of SnCI,.2H20 in 40 ml of concentrated hydrochloric acid by warming. Dilute to 200 ml with water. Prepare fresh as needed. Titanium(ll1) chloride solution, 2%. On a steam-bath warm 1 g of titanium sponge with about 30 ml of concentrated hydrochloric acid until dissolved. Dilute to 50 ml with water. Prepare fresh as needed. If preferred, dilute 1 volume of commercial titanous chloride solution (about 15% w/v) with 7 volumes of hydrochloric acid (1 + 1). Preparation (a) Acid
of sample
Calculation of iron content FeO/JV+BI-B2)S 0
where Vml is the volume ofj x 0.1 N dichromate required for titration of the iron in m g of sample.
solution
of iron (III)
Add to the sample solution 1 ml of potassium permanganate solution and boil for about a minute. To the hot solution add 10% stannous chloride solution dropwise until only a light yellow colour remains. It is essential that some iron(II1) is left unreduced. If all the iron is inadvertently reduced, reoxidize a little with a drop of permanganate solution. Reduce the remaining iron(II1) by adding 2% titanous chloride solution dropwise until the solution is colourless, then add an additional 3-5 drops. Rinse the walls of the beaker with water and heat to near boiling. Remove from the source of heat and immediately add-all at once-5 ml of perchloric acid (1 + 1). Mix well by swirling for 5 sec. Cool rapidly in ice-water. Rinse the cover and the walls of the beaker. Add 25 ml of phosphoric acid-sulphuric acid mixture and 0.25 ml of sodium diphenylaminesulphonate solution. The volume at this stage should be between 100 and 125 ml. Titrate with 0.1 N potassium dichromate to a deep violet. Determine the blank, using the same procedure and the same amounts of all reagents used in analysis of the sample, but in the reduction step use only 3-5 drops of the titanous chloride solution. To the cold solution thus prepared add 1.0 ml of O.lN iron(I1) solution. Titrate with the O.lN dichromate solution (B, ml). In another 400-ml beaker place the same volume of hydrochloric acid (1 + 9) as the volume of the blank solution. Add 1.0 ml of O.lN iron(I1) solution, 25 ml of the acid mixture and 0.25 ml of indicator solution. Titrate with the 0.1 N dichromate sol-
x 0.005585 x 100
m
DISCUSSION
decomposition.
Transfer 0.4 g of dried lOO-mesh sample (weighed to 0.1 mg) to a 400-ml beaker and decompose with hydrochloric acid with addition of a small amount of stannous chloride solution. Filter off and wash the residue, ignite it, then treat the cooled product with hvdrofluoric and sulohuric acids. Take up the residue with hydrochloric acid and add to the filtrate, which is then ready for reduction and titration. For details of the acid decomposition step see references 1 and 2. If preferred, analyse the sample on an “as received” basis and determine the -hygroscopic water on a separate portion of the sample, This method is limited to samples containing less than 0.1% vanadium or molybdenum. _ (b) Fusion decomposition. Fuse 0.4 g of sample in a zirconium or vitreous carbon crucible with 1.3 g of sodium carbonate and 2.7 g of sodium peroxide, in a muffle furnace at 700” until decomposed. Place the cold crucible in a 400 ml beaker, add about 20 ml of water to the crucible and cover the beaker with a watch-glass. After the reaction has ceased, wash the contents of the crucible into the beaker. If the sample contains more than 0.1% of vanadium and/or molybdenum, filter the alkaline solution and dissolve the iron hydroxide off the filter with hydrochloric acid. If the sample contains less than 0.1% vanadium and/or molybdenum, carefully add 20 ml of concentrated hydrochloric acid to the beaker and mix to dissolve the ferric hydroxide. Rinse the crucible with hot hydrochloric acid and add the washings to the beaker. Evaporate the solution to about 50 ml. For more details see reference 6. Reduction
ution (B, ml). The difference between B, and B, is the blank value for the reagents.
Oxidation
of excess
of
TiCIs with perchloric ucid
Six iron solutions were prepared by decomposition of 0.4000-g portions of NBS No. 690 (66.85% Fe), three by acid decomposition and three by fusion, as outlined in the procedure. The iron(III) was partially reduced with stannous chloride, then titanous chloride solution was added in slight excess. To test the rate and completeness of the oxidation of titanium(II1) by perchloric acid, the excess of titanous chloride solution added was varied from 1 drop to 2 ml. In all six cases, the volume of O.lN potassium dichromate solution required to oxidize the iron was identical (within +O.l ml) with that needed for control titrations of solutions obtained by using stannous chloride as sole reductant and mercuric chloride as oxidant for the excess of stannous chloride.* This indicates that titanium(II1) is efficiently oxidized by 5 ml of perchloric acid (1 + 1). It was further found that this oxidation is almost instantaneous if the perchloric acid is added to the solution at or near the boiling point. At 75” the oxidation is more sluggish. Rapid oxidation of the titanium(II1) is important, since the subsequent titration of the iron(H) with potassium dichromate should be carried out expeditiously. Stability of the iron
solufion
After the oxidation of the titanium(III) with perchloric acid, the hot solution containing the iron(I1) is rapidly cooled. During initial tests, the solutions were cooled under a blanket of carbon dioxide generated by the addition of a saturated sodium bicarbonate solution. When the cooling and standing period was varied from 4 to 25 min, no change in the volume of titrant needed was noted, thus indicating that the iron(I1) was stable under the experimental conditions used. When the addition of bicarbonate was omitted, a slight degree of aerial oxidation of the iron(I1) was noted after half an hour of standing, amounting to about 0.05-0.1 ml (total titration -47 ml) of O.lN potassium dichromate solution. Verification of procedure
The proposed method was applied to the determination of iron in a variety of iron ores of known composition. The results, along with those obtained by the conventional stannous chloride-mercuric chloride method, are presented in Table 1. The results
702
SHORT COMMUNICATIONS
Table 1. Determination of iron in standard iron ore samples Iron found, % Sample
Certified Fe value, %
SnC12-H&l2 procedure
SnC12-TiClsHClO., procedure
66.85 59.58
66.79 66,76 59.57
65.11
65.16
59.58
59.53 59.56 65.11 65.00 68.07 68.03 66.93 67.10
66.80 66.83 59.58 59.65 65.17 65.07 59.53 59.51 64.98 64.94 67.91 68.06 66.95 67.12
NBS-690’ (Canada) NBS-692* (Labrador) NBS-693’ (Nimba) NBS-692t NBS-693t
65.11
NBS-27bt (Sibley) Savage River?
68.23 67.26
*Acid decomposition. tFusion. $Suggested value. Table 2. Results obtained by U.S. Steel Corp.
Sample
Certificate Fe value %
U.S.S. Q.C.M. No. 8 NBS-690
66.11 66.85
NBS-270
64.96
NBS-27E
66.58
NBS-27C
65.00
German Std. 629-l German Std. 632-l BSC-301
36.21 60.78
NBS-692
59.58
Canadian Std. being certified (Bottle 402)
24.70
By IS0 Method 65.73 66.00 66.15
Iron found %
65.96 66.23 66.73 66.73 64.86 65.18 66.31 66.31 64.96 64.95 36.21 36.03 60.90 60.72 24.71 24.82 59.61 59.58 59.35 65.83 65.95 65.87 65.84
of a previous
round-robin testing programme’ indicated that the relative standard deviation of the stan-
nous chloride procedure is approximately 0.15%. The method was applied by U.S. Steel, Monroeville, Pa., to the determination of iron in a number of iron ore samples, with use of the fusion technique. Mr. J. Selvaggio of U.S. Steel obtained the results in Table 2.
Table 3. Results obtained by Andrew S. McCreath & Sons, Inc. Fe % TiCl, SnCl, procedure procedure 66.16 64.63 66.20 64.66 68.52 65.96 65.99 64.66 65.96 68.99
66.03 64.63 66.21 64.62 68.55 65.97 65.97 64.62 65.91 68.92
Fe % TiCl, SnCl* procedure procedure 63.88 61.87 65.96 67.37 64.90 64.58 65.99 13.15 2.95 3.27
63.85 61.93 66.03 67.36 64.77 64.61 65.96 13.17 2.91 3.35
The method was also examined by Andrew S. McCreath & Sons, Inc., Harrisburg, Pa. Mr. F. A. Pennington, Jr. submitted the set of averages of duplicate results in Table 3 for a variety of iron ores (the acid-decomposition procedure was used). REFERENCES 1. American
Society for Testing and Materials, 1978 Annual Book of Standards, Part 12, Method E-246, Hydrogen Sulfide Reduction Method. 2.. Idem, ibid., E-277, Stannous Chloride Reduction Method. q International Standard Oreanization. Standard IS0 3. 2597 (E) 1973. 4. Idem, Standard ISO/TC-102/X-2 (WG-17), N-571E. 5. 0. P. Bharaava. A. Alexion and W. G. Hines. Talanta. 1978,25,357. 6. Idem, Standard ISO/TC-102/X-2 (WG-16). 7. I. M. Kolthoff and P. J. Elving (eds.), Treatise on Analytical Chemistry, 1st Ed., Part II, Vol. 7, p. 374. Interscience, New York, 1962.
0039-914oj82/080700-02sO3.00/0 Copyright 0 1982 Pergamon Press Ltd
Printedin Great Britain. All rights reserved
POLLUTION-FREE DETERMINATION
METHOD FOR THE OF IRON IN IRON ORE
S. KALLMANNand E. KOIUARKOVA Ledoux & Company, Teaneck, NJ 07666, U.S.A.
(Received 8 December
1981. Accepted 9 February 1982)
Summary-A method for the determination of total iron in iron ores and concentrates is described which avoids the use of mercuric chloride. The sample is decomposed either by an acid attack or by fusion with sodium peroxide. The hot sample solution in about 6M hydrochloric acid is treated with hot 10% stannous chloride solution till pale yellow, followed by addition of a slight excess of 2% titanous chloride solution; the excess is then oxidized with perchloric acid (1 + 1). The solution is rapidly cooled in ice-water, and the iron (11) is titrated with potassium dichromate (sodium diphenylsulphonate as indicator). The results show the same degree of precision, accuracy, and degree of interference as those obtained by the standard stannous chloride-mercuric chloride method.
Iron ore ranks second only to crude oil as a commodity in commerce and industrial use. A shipment of iron ore may weigh as much as 100,000 tons and its evaluation may be based on just a few analytical samples. The accurate determination of iron in iron ore is therefore of considerable economic importance. No instrumental method has been found accurate enough for the determination of iron in iron ores, although many routine iron determinations are carried out by XRF. Two titrimetric methods have been recommended by ASTM and IS0 for the determination of total iron in iron ores and concentrates.‘-’ They differ only in minor details. The ASTM methods are based on a dry sample, and the IS0 methods prescribe an “as received” sample and a separate moisture determination. One of the methods recommended by both ASTM and IS0 uses hydrogen sulphide as reductant, the other uses stannous chloride. In the latter case, a solution of mercuric chloride is used to oxidize the excess of stannous chloride. Both methods therefore involve reagents which in many countries are increasingly rejected for environmental reasons. The search for pollution-free methods has led IS0 Committee TC-102/SC-2 to form two task forces. One of these4 is considerine the use of silver as the reducing agent.’ Some obJ\ctions that have been made have prevented this method from being more widely used. One is of a practical nature; the reductor must be prepared, cared for and regenerated, a fact which makes the method less attractive for large-scale routine determinations. The second obiection involves the possible formation of hydrogen peroxide. There is also uncertainty regarding possible interference from copper. 700
The other task force is investigating of most of the iron(II1) with stannous
the reduction chloride, fol-
lowed by addition of a slight excess of titaneous chloride. The excess of titanium(II1) is removed by a delicate procedure requiring a precise titration (with Indigo Carmine solution as indicator) prior to the titration of the iron(U) with potassium dichromate.6 The procedure proposed here avoids the titration of the excess of titanium (III); instead the titanium(II1) is oxidized in boiling solution with perchloric acid (which is reduced to chloride). This reaction has been previously used for the determination of perchlorate,’ but not, to our knowledge, for the oxidation of titanium(II1). Under the conditions described in the procedure,
the iron(H) is not oxidized.
EXPERIMENTAL Reagents Ferrous ammonium sulphate solution (approx. O.lN). Dissolve 40 g of Fe(NH4)2(S04)2.6H20 in 400 ml of sulphuric acid (5 + 95). Transfer to a lOOO-mlstandard flask, dilute to volume with the same acid, and mix. Perchloric acid, 70% diluted 1:l. Phosphoric acid-sulphuric acid mixture. Pour 150 ml of
concentrated Dhosuhoric acid into 4OOml of water. with stirring. Add i50 AI of concentrated sulphuric acid; with stirring. Cool and dilute to 1000 ml with water. Potassium dichromate solution O.lN. Pulverize about 6 g of standard-grade reagent in an agate mortar, dry in an oven at 105” for 3-4 hr. and cool to room temperature in a desiccator. Dissolve 4.904 g of the dry reagent in 300 ml of water, transfer to a lOOO-ml standard flask, dilute to volume, and mix. Porassium permanganare solution, 25 g/l. Sodium diphenylaminesulphonate indicator solution. Dis-
solve 0.2 g of the reagent in water and dilute to 100 ml.
701
SHORT COMMUNICATIONS
Stannous chloride solution, ZO%. Dissolve 20 g of SnCI,.2H20 in 40 ml of concentrated hydrochloric acid by warming. Dilute to 200 ml with water. Prepare fresh as needed. Titanium(ll1) chloride solution, 2%. On a steam-bath warm 1 g of titanium sponge with about 30 ml of concentrated hydrochloric acid until dissolved. Dilute to 50 ml with water. Prepare fresh as needed. If preferred, dilute 1 volume of commercial titanous chloride solution (about 15% w/v) with 7 volumes of hydrochloric acid (1 + 1). Preparation (a) Acid
of sample
Calculation of iron content FeO/JV+BI-B2)S 0
where Vml is the volume ofj x 0.1 N dichromate required for titration of the iron in m g of sample.
solution
of iron (III)
Add to the sample solution 1 ml of potassium permanganate solution and boil for about a minute. To the hot solution add 10% stannous chloride solution dropwise until only a light yellow colour remains. It is essential that some iron(II1) is left unreduced. If all the iron is inadvertently reduced, reoxidize a little with a drop of permanganate solution. Reduce the remaining iron(II1) by adding 2% titanous chloride solution dropwise until the solution is colourless, then add an additional 3-5 drops. Rinse the walls of the beaker with water and heat to near boiling. Remove from the source of heat and immediately add-all at once-5 ml of perchloric acid (1 + 1). Mix well by swirling for 5 sec. Cool rapidly in ice-water. Rinse the cover and the walls of the beaker. Add 25 ml of phosphoric acid-sulphuric acid mixture and 0.25 ml of sodium diphenylaminesulphonate solution. The volume at this stage should be between 100 and 125 ml. Titrate with 0.1 N potassium dichromate to a deep violet. Determine the blank, using the same procedure and the same amounts of all reagents used in analysis of the sample, but in the reduction step use only 3-5 drops of the titanous chloride solution. To the cold solution thus prepared add 1.0 ml of O.lN iron(I1) solution. Titrate with the O.lN dichromate solution (B, ml). In another 400-ml beaker place the same volume of hydrochloric acid (1 + 9) as the volume of the blank solution. Add 1.0 ml of O.lN iron(I1) solution, 25 ml of the acid mixture and 0.25 ml of indicator solution. Titrate with the 0.1 N dichromate sol-
x 0.005585 x 100
m
DISCUSSION
decomposition.
Transfer 0.4 g of dried lOO-mesh sample (weighed to 0.1 mg) to a 400-ml beaker and decompose with hydrochloric acid with addition of a small amount of stannous chloride solution. Filter off and wash the residue, ignite it, then treat the cooled product with hvdrofluoric and sulohuric acids. Take up the residue with hydrochloric acid and add to the filtrate, which is then ready for reduction and titration. For details of the acid decomposition step see references 1 and 2. If preferred, analyse the sample on an “as received” basis and determine the -hygroscopic water on a separate portion of the sample, This method is limited to samples containing less than 0.1% vanadium or molybdenum. _ (b) Fusion decomposition. Fuse 0.4 g of sample in a zirconium or vitreous carbon crucible with 1.3 g of sodium carbonate and 2.7 g of sodium peroxide, in a muffle furnace at 700” until decomposed. Place the cold crucible in a 400 ml beaker, add about 20 ml of water to the crucible and cover the beaker with a watch-glass. After the reaction has ceased, wash the contents of the crucible into the beaker. If the sample contains more than 0.1% of vanadium and/or molybdenum, filter the alkaline solution and dissolve the iron hydroxide off the filter with hydrochloric acid. If the sample contains less than 0.1% vanadium and/or molybdenum, carefully add 20 ml of concentrated hydrochloric acid to the beaker and mix to dissolve the ferric hydroxide. Rinse the crucible with hot hydrochloric acid and add the washings to the beaker. Evaporate the solution to about 50 ml. For more details see reference 6. Reduction
ution (B, ml). The difference between B, and B, is the blank value for the reagents.
Oxidation
of excess
of
TiCIs with perchloric ucid
Six iron solutions were prepared by decomposition of 0.4000-g portions of NBS No. 690 (66.85% Fe), three by acid decomposition and three by fusion, as outlined in the procedure. The iron(III) was partially reduced with stannous chloride, then titanous chloride solution was added in slight excess. To test the rate and completeness of the oxidation of titanium(II1) by perchloric acid, the excess of titanous chloride solution added was varied from 1 drop to 2 ml. In all six cases, the volume of O.lN potassium dichromate solution required to oxidize the iron was identical (within +O.l ml) with that needed for control titrations of solutions obtained by using stannous chloride as sole reductant and mercuric chloride as oxidant for the excess of stannous chloride.* This indicates that titanium(II1) is efficiently oxidized by 5 ml of perchloric acid (1 + 1). It was further found that this oxidation is almost instantaneous if the perchloric acid is added to the solution at or near the boiling point. At 75” the oxidation is more sluggish. Rapid oxidation of the titanium(II1) is important, since the subsequent titration of the iron(H) with potassium dichromate should be carried out expeditiously. Stability of the iron
solufion
After the oxidation of the titanium(III) with perchloric acid, the hot solution containing the iron(I1) is rapidly cooled. During initial tests, the solutions were cooled under a blanket of carbon dioxide generated by the addition of a saturated sodium bicarbonate solution. When the cooling and standing period was varied from 4 to 25 min, no change in the volume of titrant needed was noted, thus indicating that the iron(I1) was stable under the experimental conditions used. When the addition of bicarbonate was omitted, a slight degree of aerial oxidation of the iron(I1) was noted after half an hour of standing, amounting to about 0.05-0.1 ml (total titration -47 ml) of O.lN potassium dichromate solution. Verification of procedure
The proposed method was applied to the determination of iron in a variety of iron ores of known composition. The results, along with those obtained by the conventional stannous chloride-mercuric chloride method, are presented in Table 1. The results
702
SHORT COMMUNICATIONS
Table 1. Determination of iron in standard iron ore samples Iron found, % Sample
Certified Fe value, %
SnC12-H&l2 procedure
SnC12-TiClsHClO., procedure
66.85 59.58
66.79 66,76 59.57
65.11
65.16
59.58
59.53 59.56 65.11 65.00 68.07 68.03 66.93 67.10
66.80 66.83 59.58 59.65 65.17 65.07 59.53 59.51 64.98 64.94 67.91 68.06 66.95 67.12
NBS-690’ (Canada) NBS-692* (Labrador) NBS-693’ (Nimba) NBS-692t NBS-693t
65.11
NBS-27bt (Sibley) Savage River?
68.23 67.26
*Acid decomposition. tFusion. $Suggested value. Table 2. Results obtained by U.S. Steel Corp.
Sample
Certificate Fe value %
U.S.S. Q.C.M. No. 8 NBS-690
66.11 66.85
NBS-270
64.96
NBS-27E
66.58
NBS-27C
65.00
German Std. 629-l German Std. 632-l BSC-301
36.21 60.78
NBS-692
59.58
Canadian Std. being certified (Bottle 402)
24.70
By IS0 Method 65.73 66.00 66.15
Iron found %
65.96 66.23 66.73 66.73 64.86 65.18 66.31 66.31 64.96 64.95 36.21 36.03 60.90 60.72 24.71 24.82 59.61 59.58 59.35 65.83 65.95 65.87 65.84
of a previous
round-robin testing programme’ indicated that the relative standard deviation of the stan-
nous chloride procedure is approximately 0.15%. The method was applied by U.S. Steel, Monroeville, Pa., to the determination of iron in a number of iron ore samples, with use of the fusion technique. Mr. J. Selvaggio of U.S. Steel obtained the results in Table 2.
Table 3. Results obtained by Andrew S. McCreath & Sons, Inc. Fe % TiCl, SnCl, procedure procedure 66.16 64.63 66.20 64.66 68.52 65.96 65.99 64.66 65.96 68.99
66.03 64.63 66.21 64.62 68.55 65.97 65.97 64.62 65.91 68.92
Fe % TiCl, SnCl* procedure procedure 63.88 61.87 65.96 67.37 64.90 64.58 65.99 13.15 2.95 3.27
63.85 61.93 66.03 67.36 64.77 64.61 65.96 13.17 2.91 3.35
The method was also examined by Andrew S. McCreath & Sons, Inc., Harrisburg, Pa. Mr. F. A. Pennington, Jr. submitted the set of averages of duplicate results in Table 3 for a variety of iron ores (the acid-decomposition procedure was used). REFERENCES 1. American
Society for Testing and Materials, 1978 Annual Book of Standards, Part 12, Method E-246, Hydrogen Sulfide Reduction Method. 2.. Idem, ibid., E-277, Stannous Chloride Reduction Method. q International Standard Oreanization. Standard IS0 3. 2597 (E) 1973. 4. Idem, Standard ISO/TC-102/X-2 (WG-17), N-571E. 5. 0. P. Bharaava. A. Alexion and W. G. Hines. Talanta. 1978,25,357. 6. Idem, Standard ISO/TC-102/X-2 (WG-16). 7. I. M. Kolthoff and P. J. Elving (eds.), Treatise on Analytical Chemistry, 1st Ed., Part II, Vol. 7, p. 374. Interscience, New York, 1962.