A Method of estimation of Fe(total) in sponge iron
Field of the invention:
This invention relates to a method of estimation of total iron content in sponge iron.
Sponge iron manufacture is primarily based on the principle of removal of oxygen from Iron ore as a result of which the obtained product becomes porous and hence named as sponge Iron produced by chemical reduction without fusion.
The ratio of metallic iron to total iron is the prime Indicator of the

quality of sponge iron. Hence estimation of Fe (total) accurately Is a prerequisite to ascertain the quality of sponge iron.
Total iron content in a sponge iron is the sum total of metallic iron and iron oxides in different forms, which is represented by
Fe(total) = Fe(met) + FeO + Fe2O3 + FeaO4
Background of the invention:
There are two existing methods which are commonly followed for the
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estimation of total iron in sponge iron, the potassium permanganate method and potassium dichromate method.
In the potassium permanganate method, 0.5 gm sample of sponge iron is added with 10 mith of conc. HC followed by heating to dryness and subsequent addition of dilute HCl Thereafter 6 gm of pure zinc to the dried sample with dilute HCI for reduction of ferric bn to ferrous ion. The resultant solution is then diluted to about 200 ml followed by addition of 5ml of conc. H2SO4. The solution is that filtered and to the filtrate 25 ml of Zimmerman Reinhardt reagent is added and titrated with std. 5/56 N KMnO4 to estimate Fe(total) of sponge iron.
In the potassium dichromate method .5 gm sample is added with 10
ml of conc. HCl followed by heating to dryness and subsequent

addition of dilute HCI. To this solution stannous chloride is added

drop by drop till the red color discharges completely. Then 10 ml of
HgCl2 is added to the resulted solution and diluted to 200 ml and the resulting salution is titrated with 5/56 N K2Cr2O to estimate Fe (totai) in sponge Iron.
The first method of existing art [suffers from the difficulties of availability of pure zinc.
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In the second existing method indicators are to be used which is not necessary while titrating with KMnO4 which acts as a self indicator thus consuming time and cost
The present invention aims to remove the said difficulties of the prior art by modifying existing methods with cost saving, time saving and improved efficiency of test result characteristics.
Description of the Invention:
According to one of the objectives of the invention Instead of zinc as employed in potassium permanganate method stannous chloride (Sncl2) Is used to change the ferric Ion to ferrous ion in the testing procedure.
According to another objective of the invention Potassium Permanganate is used as a tritration solution instead of Potassium dichromate method.
The present method of testing procedure is described as follows:

0.5 gm sample is taken in a dried 400 ml beaker to which 45 mi of 2:1 HCi is added and the contents are then warmed below the boiling point of the solution to get a clear solution. The reactions involved in the step result in the formation of a clear solution-
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followed by the following reaction Involved
Fe+2HCI = FeCl2 + H2 FeO + 2 HCI = FeCI2 + HsO
Fe2O3 + 6 HCI = 2 FeCl2 + H2O
Fe3O4+ 8 HCI = FeCI2 + 2 FeCl3 + 4 H2O
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Then stannous chloride solution (10 % in conc. HCI) is added till the solution becomes colorless by reduction of trlvalent iron and 2-3 drops of the stannous chloride solution is aided in excess.
The reaction involved in this step is represented by 2 FeCl3 + SnCl2 = 2 FeCl2 + SnCl4
The above solution is diluted with 50 ml of distilled water and cooled to room temperature Then 15 mi of mercuric chloride solution Is added to the cold solution to nullify the effect of excess stannous chloride which is a reducing agent and known to have an Interference in reactions with KMnO4
The reaction involved in this step is expressed as SnC!2 + HgCl2 = SnCl4, + Hg
The resulted entire contents are then transferred to a 1 liter conical
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flask after a period of about 10 minutes.
Then 35 ml of Zimmerman Reinhardt reagent is added to the flask for
suppressing the effect of HCI while titrating against KMnO4 and the
contents diluted to 500 ml with distilled! water.
The contents are then filtered through grade 40 and 41 filter paper and filtrate collected into a 250 ml conical flask. The solution is then titrated against standard KMnO4 solution to a faint pink end point.
The reaction involved In this step Is represented by
10 FeCl2 + 2 KMnO4 + 16 HCI =10 FeCl3 + 2 KCI + 2 MnCl2 + 8 H2O
Burette regarding shows directly the % Fe total on 0,5 gm sample basis.
In order to validate the method, similar samples have been tested for all the existing methods and the comparative results are given below in Table- 1.
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Table -1

The comparative results indicate clearly that the present invention is capable of estimation of Fe (total) content in sponge iron with improved performance marginally.
Though the invention is illustrated with a specific example some alterations of concentration of HCl, Sncl2 and Hgcl2 and holding time are possible to be employed In the defined steps of the method within the scope and limit of the invention as defined In the appended claims.
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We claim:
l. A method of estimation of total iron In sponge iron comprising the steps of taking a sample of sponge iron in a dried beaker, adding 2:1 hydrochloric acid into the beaker and the contents of the beaker then heated below the boiling point of the solution to get a clear solution of hydrochloric acid dissolving the total iron in it, stannous chloride solution in concentrated hydrochloric acid is then added to the solution In warm condition till the solution becomes colourless to reduce trivalent iron to ferrous iron, required amount of distilled water is that added to the resulted solution and the solution being allowed to cool to room temperature, proportionate amount of mercuric chbride solution is then added to the cold solution and the resultant contents of the beaker is transferred to a conical flask after a holding time, Zimmerman Reinhardt reagent is then added to the flask and the contents of flask is diluted with distilled water followed by filtration, the filtrate being collected into a conical flask and the said filtrate is titrated against standard potassium permanganate solution to a feint pink end point, the total % of the sample being read directly on the calibrated burette on the basis of total weight of iron of the sample used.
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2. A method of estimation of total iron in sponge iron as claimed in
claim 1 wherein stannous chloride used in a solution of
concentration of 10 % in concentrated HCI.
3. A method as claimed in claim 1 wherein after reaction with
mercuric chloride the resulted solution is held for about 10
minutes before transferring it to 1 liter conical flask.
4. A method as claimed in claim 1 wherein 0.5 gm of sponge iron as
sample is kept in a 400 ml beaker for estimation on of total Fe
content.
5. A method as claimed in claim 1 wherein mercuric chloride is
added to the cold solution containing stannous chloride to nuilyfy
the effect of access reducing agent stannous chioride to prevent
its interference in reactions with KMnO4.
6. A method as claimed in claim 1 wherein 30 mi of Zimmerman
Reinhardt is added to the conical flask for suppressing the effect
of HCI while titrating against KMnO4 and the contents diluted to
500 ml with distilled water before the step of filtration.
7. A method as claimed in claim 1 wherein Fe (total) of the sponge
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