Double fortified salt composition containing iron and iodine and process for the preparation thereof

Abstract

The present invention relates to stable and white iron fortification and iron+iodine double fortification agents, their preparation and use in fortification of salt. These agents help overcome the normal difficulties encountered in iron and iodine fortification such as low iodine stability on storage, development of colour and odour, and use of unwanted additives to impart stability. In one of the invented products, both iron and iodine coexist in stable manner in the same matrix which allow for a more uniform distribution of iodine. The process of preparation is demonstrated to be scalable and utilizes commonly available raw materials which would enable the products to be synthesized in affordable manner.

Claims

1. A fortifying agent, for edible salt wherein the fortifying agent is of compound of formula (1a) or formula (1b):
[Mg.sub.4.30.4Fe(III)(OH).sub.10.60.8][CO.sub.3].sub.0.5.3H.sub.2O(1a),
or
[Mg.sub.4.30.4Fe(III)(OH).sub.10.60.8](CO.sub.3).sub.0.486(IO.sub.3).sub.0.0160.002.3H.sub.2O(1b) wherein the compound of formula (1a) has a magnetic moment of 1.49 B.M., and 13-15% low spin Fe(III) (w/w); and the compound of formula (1b) has a magnetic moment of 1.339 B.M., 13-15% low spin Fe(III) (w/w) and 0.4-0.6% (w/w) I.

2. A process for preparing the fortifying agent as claimed in claim 1 comprising the steps of: (i) preparing a slurry by mixing aqueous FeCl.sub.3 solution into aqueous Na.sub.2CO.sub.3 solution at a temperature of 25 to 35 C.; (ii) adding the slurry obtained in step (i) into an aqueous Mg(OH).sub.2 slurry to obtain a [Mg]:[Fe]ratio of 3.95 to 4.75 at a temperature of 25 to 35 C.; (iii) adjusting a pH of the slurry obtained in step (ii) with additional amounts of Na.sub.2CO.sub.3 to keep the pH of 9.0-10 to give a pH-adjusted slurry; (iv) charging the pH-adjusted slurry from step (iii) into a pressure reactor for hydrothermal treatment at a temperature of 140 to 150 C. for a period of 4to 5 hours followed by cooling at a temperature of 50 to 60 C., filtering and washing a white solid cake obtained with water to remove electrolytes to give it washed white solid cake, and ensuring a pH of wash water <10; (v) drying the washed white solid cake obtained in step (iv) at a temperature of 105-115C. to form a dry product; and (vi-a) pulverizing the dry product from step (v) to give a pulverized product, and passing the pulverized product through 30 to +72 BSS mesh to obtain the compound of formula (1a)
[Mg.sub.4.30.4Fe(III)(OH).sub.10.60.8][CO.sub.3].sub.0.5.3H2O(1a); or (vi-b) calcining the dry product obtained in step (v) at a temperature of 440-460 C. for a period of 1 to 2 hr, cooling at temperature of 50 to 60 C. and contacting with 1 mM aqueous KIO.sub.3 solution under stirring for a period of 4 to 5 min, leaving to stand thereafter for a period of 12 to 16 hours followed by separating a solid and washing the solid free of adhering iodate, drying at a temperature of 100 to 110 C. to obtain the compound of formula (1b)
[Mg.sub.4.30.4Fe(III)(OH).sub.1060.8](CO.sub.3).sub.0.486(IO.sub.3).sub.0.0160.002.3H.sub.2O(1b).

3. The process as claimed in claim 2, wherein the pH of the slurry in step (iii) is adjusted to 9.0-9.5.

4. The process as claimed in claim 2, wherein sea or sub-soil bittern is utilized as a magnesium source.

5. An iron fortified salt, fortified with the compound of formula (1a) of claim 1.

6. A double fortified salt, fortified with the compound of formula (1b) of claim 1, having an Fe content of 1000-1200 ppm and an I content of 30-40 ppm.

7. The double fortified salt of claim 6, which is white in appearance and remains so after 12 months of storage with negligible loss of iodine.

8. The double fortified salt of claim 6, wherein both Fe and I have a uniformity of distribution in the double fortified salt wherein an amount of iron and iodine in a kg of the double fortified salt is spread over 8 g of the fortifying agent.

9. The fortifying agent as claimed in claim 1, wherein the fortifying agent disintegrates spontaneously in 5-10 minutes in a solution of 0.068M HCl.

10. A double fortified sat, fortified with the compound of formula (1a) of claim 1 and iodate exchanged synthetic hydrotalcite with 5-6% w/w iodine loading.

11. The double fortified salt of claim 10, which has 1000-1200 ppm Fe and 38-40 ppm I, and is white in colour.

12. The double fortified salt of claim 10, wherein the iron is spread over 8-9 g and the iodine is spread over 0.5-0.6 g of the fortifying, agent.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 represents XRD pattern of the product as obtained in example 1.

(2) FIG. 2 represents XRD pattern of the product as obtained in example 2.

(3) FIG. 3 represents XRD pattern of the product as obtained in example 3.

(4) FIG. 4 represents XRD pattern of the product as obtained in example 4.

(5) FIG. 5 represents XRD pattern of the product as obtained in example 5.

(6) FIG. 6 represents XRD pattern of the product as obtained in example 6.

(7) FIG. 7 represents XRD pattern of the product as obtained in example 7.

(8) FIG. 8 represents XRD pattern of the product as obtained in example 8.

DETAIL DESCRIPTION OF THE INVENTION

(9) The present invention pertains to the development of white hydrotalcite type products which serve the purpose of iron fortification or iron and iodine double fortification of common salt. Precise control of a combination of process parameters during preparation of the materials together yield the beneficial effect of the white crystalline products exhibiting hydrotalcite-type powder XRD pattern, while containing high amounts of Fe(III) and even Fe(III) and IO.sub.3.sup. within the same matrix. The compounds thus prepared can be approximately represented as
[Mg.sub.4.30.4Fe(III)(OH).sub.10.60.8][CO.sub.3].sub.0.53H.sub.2O

(10) exhibiting magnetic moment of 1.49 B.M., and having 13-15% low spin Fe(III) (w/w) and
[Mg.sub.4.30.4Fe(III)(OH).sub.10.60.8](CO.sub.3).sub.0.486(IO.sub.3).sub.0.0160.002.yH.sub.2O
exhibiting magnetic moment of 1.339 B.M., and having 13-15% low spin Fe(III) (w/w) and 0.4-0.6% (w/w) iodine.

(11) The compounds so prepared are white in colour, exhibit excellent stability towards retention of both iron and iodine, and dissolve completely in acidic condition of pH 2-3 that prevails in the stomach. Where [Mg.sub.4.30.4Fe(III)(OH).sub.10.60.8][CO.sub.3].sub.0.5.3H.sub.2O is used for iron fortification, iodate-exchanged synthetic hydrotalcite as disclosed in the prior was co-mixed with the above to supply iodine. Where [Mg.sub.4.30.4Fe(III)(OH).sub.10.60.8](CO.sub.3).sub.0.486(IO.sub.3).sub.0.0160.002.yH.sub.2O is used, ca. 8 g of the product added into 1 kg of salt gives 1000-1200 ppm Fe and 30-40 ppm I uniformly distributed throughout the salt.

(12) SHT containing IO.sub.3.sup. is prepared following the method of U.S. Pat. No. 7,695,707 dated 13 Apr. 2010. SHT-Fe and SHT-IO.sub.3 are mixed in the required proportion in edible salt to contain about 1000 ppm of Fe and 30 ppm of iodine.

(13) The iodine content in DFS is analyzed by procedure given in Indian J Med Res 123, April 2006, pp 531-540 with slightly modifications i.e. 1 ml of 5% KI was added to 10 g sample and to it 50 ml of 0.2 M H.sub.3PO.sub.4 was added and liberated iodine was tritrated with 0.005 N sodium thio sulphate. Iron content of DFS was measured by spectrophotometric method using o-phenanthroline i.e. 2.5 g DFS was dissolved in 100 ml 0.2 N HCl and 5 ml of the filtrate was used with hydroxyl ammonium chloride (HAC). Iron in DFS was also checked using ICP-OES instrument. 2.5 gm of DFS was dissolved in 100 ml 0.2 N HCl and 25 ml of this solution was diluted to 400 ml. This solution was analyzed with ICP-OES instrument shown 1.582 ppm of iron. (i.e. 1012 ppm of total iron in DFS). Magnetic moment data were recorded at the Indian Association for the Cultivation of Science, Jadavpur.

(14) The present invention is directed to provide a process for the preparation of double fortified salt (DFS) that exhibits greater stability for iron in form of low spin Fe.sup.3+ and iodine in form of IO.sub.3.sup. as fortifying agents. Accordingly the present invention outlines the process of preparation of DFS comprising the following steps: (i) Taking Mg.sup.2+ containing salt or bittern, (ii) diluting to required level, (iii) clarifying the solution, (iv) adding into it sodium hydroxide solution in two stages, i.e., a small amount in the first stage for precipitation of unwanted hydroxides which are then removed and thereafter, adding more sodium hydroxide to obtain a pure form of magnesium hydroxide, (v) Filtering the slurry of magnesium precursor and washing with water (vi) Slurrying the Mg precursor into DM water (vii) Preparing the solution of Fe.sup.3+ salt in water, (vii) Adding it into soda ash solution, (ix) mixing the Fe precursor so prepared into Mg precursor slurry prepared in step (vi) above, (x) Allowing the solids in mixed slurry to settle, (xi) removing the supernatant solution, (xii) adding the solution of soda ash into the decanted solids, (xiii) heating the slurry prepared in step (xii) in an autoclave upto 150 C. for 1-5 hours, (xiv) Cooling the slurry, (xv) filtering the slurry, (xvi) washing the cake, (xvii) drying the cake, (xviii) pulverizing the dried solids, (xix) sieving the product, (xx) using the product as is along with SHT-iodate to formulate double fortified salt, (xxi) optionally, calcining the product obtained in (xix) above and contacting with an aqueous solution of potassium iodate to incorporate 0.4-0.6% iodine (w/w) so as to provide iron and iodine in the same matix, (xxii) formulating double fortified salts using the compositions of (xx) and (xxi) above such that the final salt thus prepared contains up to 1200 ppm of iron and up to 40 ppm of iodine.

(15) Inventive Steps

(16) The main inventive steps are:

(17) i. Discovering that by control of the Mg.sup.2+:Fe.sup.3+ ratio and the pH during crystallization of Fe, Mg-hydrotalcite, a white Fe.sup.3+-exchanged SHT-carbonate can be obtained which, in combination with iodate-exchanged synthetic hydrotalcite as disclosed in the prior art, would give a double fortification agent that is also white in colour. ii. Recognizing that it is feasible to incorporate iodate within the Fe, Mg-hydrotalcite matrix itself and thereafter computing the amount that would be required so that the same matrix delivers Fe and I in the required proportions when mixed into edible salt. iii. Discovering that such iodate incorporation into Fe, Mg-hydrotalcite alters the crystallinity of the sample but without adverse effect on whiteness and stability of the product under use. iv. Recognising further that incorporation of both micronutrients in the same matrix makes it much easier to ensure uniform distribution of these micronutrients in the salt, particularly iodine which otherwise would be more difficult to distribute uniformly. v. Thereafter demonstrating excellent stability of the resultant salts on long storage and also through boiling water test. vi. Recognising that Mg.sup.2+ too is an important micronutrient which can be provided by the above composition. vii. Dispensing with undesirable additives such as sodium hexametaphosphate used in some commercial formulations of DFS.

(18) The following examples are given by way of illustration and therefore should not be construed to limit the scope of the invention.

EXAMPLE 1

(19) 700 ml of 0.9N sodium hydroxide solution was added over 45 minutes under stirring into 100 ml of 0.374 M MgCl.sub.2 solution (7.6 gm Mg.sup.2+) and further stirred for 15 minutes at ambient temperature.

(20) The slurry was filtered using single filtration unit and the cake was washed with water till Cl.sup. content of filtrate reached a value of around 0.1% (w/v). Wet cake of Mg(OH).sub.2 was well dispersed in demineralised water and made up to 1000 ml slurry (hereinafter also referred to as Mg precursor).

(21) 200 ml FeCl.sub.3 solution containing 2.83% Fe.sup.3+ (w/v) (0.101 mol) was added over 30 minutes into 660 ml of 0.28 M sodium carbonate (0.185 mol) at ambient temperature. It was further stirred for 15 minutes at ambient temperature to obtain a slurry (hereinafter referred to as Fe.sup.3+ precursor).

(22) Slurry of Fe.sup.3+ precursor so prepared was added into slurry of magnesium precursor in 20 minutes at ambient temperature and the resultant slurry was kept for settling for 1 hour. 800 ml of supernatant was decanted and 800 ml of solution containing 5 gm of sodium carbonate prepared in DM water was added and maintained pH of the slurry at 9. The slurry having [Mg]:[Fe] mole ratio of 3.14 was then charged in an autoclave and heated up to 145 C. and corresponding pressure. The slurry was subjected to this condition for 1 hr. The slurry was allowed to cool down to 60 C. and product was then filtered and washed till free from adhering electrolytes. The end of washing was indicated by measurement of pH of the wash water to be <10. The cake was dried in dryer at 110 C. 25 gm of product was obtained which was pulverized to pass through 30+72 BSS mesh. The product was characterized by XRD, IR and particle size distribution. XRD pattern exhibited all the six major diffraction bands of hydrotalcite like material, specifically bands at 7.92, 3.95, 2.62, 2.34, 1.55 and 1.52 (FIG. 1). The product was, however, unacceptable as it had a brown red colour.

EXAMPLE 2

(23) 3150 ml of 0.9N sodium hydroxide solution was added over 45 minutes under stirring to 1950 ml clarified bittern prepared in Example 4 containing 37.4 gm of magnesium ions (1.558 mol) with continuous stirring at ambient temperature.

(24) The slurry is filtered using single filtration unit and the cake is washed with water till content of filtrate reached a value of around 0.1% (w/v). Wet cake of magnesium precursor was well dispersed in demineralised water and made up to 5000 ml slurry.

(25) 760 ml FeCl.sub.3 solution containing 2.83% Fe.sup.3+ (w/v) (0.304 mol) was added over 30 minutes into 2500 ml solution of 0.28 M sodium carbonate (0.7 mol) at ambient temperature. It was further stirred for 15 minutes at ambient temperature to obtain a slurry.

(26) Slurry of Fe.sup.3+ precursor so prepared was added to slurry of magnesium precursor in 20 minutes at ambient temperature and mixed slurry was kept for 1 hour. 3000 ml of supernatant liquid was decanted and solution containing 40 gm of sodium carbonate prepared in DM water was added and maintained pH of the slurry at 11.5. The slurry having [Mg]:[Fe] mole ratio of 4.11 was then charged in a pressure reactor and heated up to 145 C. and corresponding pressure. The slurry was subjected to this condition for 2 hr. The slurry was allowed to cool down to 60 C. and product was then filtered and washed till free from adhering electrolytes. The end of washing was indicated by measurement of pH of the wash water to be <10. The cake was dried in dryer at 110 C. 125 gm of product was obtained which was pulverized to pass through 30+72 BSS mesh. The product was characterized by XRD, IR and particle size. XRD pattern exhibited all the six major diffraction bands at around 7.84, 3.92, 2.62, 2.34, 1.55 and 1.45 (FIG. 2) The diffraction pattern is shown in FIG. 2. The product was, however, unacceptable as it had a brown red colour.

EXAMPLE 3

(27) 350 ml of 0.9N sodium hydroxide solution was added over 45 minutes under stirring into 50 ml of 0.354 M MgCl.sub.2 solution (3.6 gm Mg.sup.2+) and further stirred for 15 minutes at ambient temperature.

(28) The slurry was filtered using single filtration unit and the cake was washed with water till Cl.sup. content of filtrate reached a value of around 0.1% (w/v). Wet cake of Mg(OH).sub.2 was well dispersed in demineralised water and made up to 500 ml slurry.

(29) 75 ml FeCl.sub.3 solution containing 2.83% Fe.sup.3+ (w/v) (0.038 mol) was added over 30 minutes into 250 ml solution of 0.28 M sodium carbonate (0.07 mol) at ambient temperature. It was further stirred for 15 minutes at ambient temperature to obtain a slurry.

(30) Slurry of Fe.sup.3+ precursor so prepared was added into slurry of magnesium precursor in 20 minutes at ambient temperature and the resultant slurry was kept for settling for 1 hour. 350 ml of supernatant was decanted and 350 ml of solution containing 2 gm of sodium carbonate prepared in DM water was added and maintained pH of the slurry at 9. The slurry having [Mg]:[Fe] mole ratio of 3.95 was then charged in an autoclave and heated up to 145 C. and corresponding pressure. The slurry was subjected to this condition for 2 hr. The slurry was allowed to cool down to 60 C. and product was then filtered and washed till free from adhering electrolytes. The end of washing was indicated by measurement of pH of the wash water to be 10. The cake was dried in dryer at 110 C. 13.5 gm of product was obtained which was pulverized to pass through 30+72 BSS mesh. The product was characterized by XRD, IR and particle size distribution. XRD pattern exhibited all the six major diffraction bands of hydrotalcite like material, specifically bands at 7.83, 3.92, 2.62, 2.33, 1.55 and 1.50 . (FIG. 3). Although in all the Examples 1-3 a hydrotalcite-like material was obtained, the product in the present example was white in colour unlike the red brown colour of the products obtained in Examples 1 and 2.

(31) Examples 1-3 teach us the critical importance of the [Mg]:[Fe] mole ratio and pH of slurry taken for hydrothermal treatment for the objective of obtaining a white product.

EXAMPLE 4

(32) Bittern with a density of 29 Be containing 20% NaCl, 8.4% MgCl.sub.2, 5.4% MgSO.sub.4 and 1.8% KCl (w/v) was diluted with water to get magnesium ions concentration of about 2% (w/v). The diluted bittern was then treated with a solution of non-ferric aluminium sulphate containing 1.02% (w/v) Al.sub.2O.sub.3 and a solution of 1N caustic soda to precipitate 100 ppm aluminium hydroxide and 300 ppm of magnesium hydroxide. These precipitates were removed by settling to refine the bittern. The clarified bittern containing 1.92% (w/v) magnesium ions was obtained.

(33) 350 ml of 0.9N sodium hydroxide solution was added over 45 minutes under stirring to 190 ml clarified bittern containing 3.6 gm of magnesium ions (0.15 mol) with continuous stirring at ambient temperature.

(34) The slurry is filtered using single filtration unit and the cake is washed with water till Cl.sup. and SO.sub.4.sup.2 content of filtrate reached a value of around 0.1% (w/v). Wet cake of magnesium precursor was well dispersed in demineralised water and made up to 500 ml slurry.

(35) 75 ml FeCl.sub.3 solution containing 2.83% Fe.sup.3+ (w/v) (0.038 mol) was added over 30 minutes into 250 ml solution of 0.28 M sodium carbonate (0.07 mol) at ambient temperature. It was further stirred for 15 minutes at ambient temperature to obtain slurry.

(36) Slurry of Fe.sup.3+ precursor so prepared was added into slurry of magnesium precursor in 20 minutes at ambient temperature and the resultant slurry was kept for settling for 1 hour. 350 ml of supernatant was decanted and 350 ml of solution containing 2 gm of sodium carbonate prepared in DM water was added and maintained pH of the slurry at 9.0. The slurry having [Mg]:[Fe] mole ratio of 3.95 was then charged in an autoclave and heated up to 150 C. and corresponding pressure. The slurry was subjected to this condition for 2 hr. The slurry was allowed to cool down to 60 C. and product was then filtered and washed till free from adhering electrolytes. The end of washing was indicated by measurement of pH of the wash water to be 10. The cake was dried in dryer at 110 C. 11 gm of product was obtained which was pulverized to pass through 30+72 BSS mesh. The product was characterized by XRD, IR and particle size distribution. XRD pattern exhibited all the six major diffraction bands of hydrotalcite like material, specifically bands at 7.77, 3.89, 2.62, 2.33, 1.55 and 1.49 . (FIG. 4). The product obtained in the present example was white in colour as in Example 3.

(37) This example teaches the use of an inexpensive source of magnesium chloride, namely bittern.

EXAMPLE 5

(38) 3500 ml of 0.9N sodium hydroxide solution was added over 45 minutes under stirring to 1950 ml clarified bittern containing 37.5 gm of magnesium ions (1.562 mol) with continuous stirring at ambient temperature.

(39) The slurry is filtered using single filtration unit and the cake is washed with water till Cl.sup. and SO.sub.4.sup.2 content of filtrate reached a value of around 0.1% (w/v). Wet cake of magnesium precursor was well dispersed in demineralised water and made up to 5000 ml slurry.

(40) 760 ml FeCl.sub.3 solution containing 2.83% Fe.sup.3+ (w/v) (0.384 mol) was added over 30 minutes into 2500 ml solution of 0.28 M sodium carbonate (0.7 mol) at ambient temperature. It was further stirred for 15 minutes at ambient temperature to obtain a slurry.

(41) Slurry of Fe.sup.3+ precursor so prepared was added to slurry of magnesium precursor in 20 minutes at ambient temperature and mixed slurry was kept for 1 hour. 3000 ml of supernatant liquid was decanted and solution containing 20 gm of sodium carbonate prepared in DM water was added and maintained pH of the slurry at 9.5. The slurry having [Mg]:[Fe] mole ratio of 4.05 was then charged in a pressure reactor and heated up to 145 C. and corresponding pressure. The slurry was subjected to this condition for 1 hr. The slurry was allowed to cool down to 60 C. and product was then filtered and washed till free from adhering electrolytes. The end of washing was indicated by measurement of pH of the wash water to be 10. The cake was dried in dryer at 110 C. 135 gm of product was obtained which was pulverized to pass through 30+72 BSS mesh. The product was characterized by XRD, IR and particle size. XRD pattern exhibited all the six major diffraction bands at around 7.75, 3.93, 2.61, 2.33, 1.55 and 1.52 . (FIG. 5) The product obtained in the present example was white in colour.

(42) This example teaches scale up of the process of Example 4 by a factor of ca. 12.

EXAMPLE 6

(43) Carnallite end bittern with a density of 35 Be having 11.2% Mg.sup.2+, 0.15% K.sup.+, 0.27% Na.sup.+, 0.31% SO.sub.4.sup.2, 0.26% Ca.sup.2+, 32.28% (w/v) was diluted with water to get magnesium ions concentration of about 2.24% (w/v). The diluted bittern was then treated with a solution of non-ferric aluminium sulphate containing 1.02% (w/v) Al.sub.2O.sub.3 and a solution of 1N caustic soda to precipitate 100 ppm aluminium hydroxide and 300 ppm of magnesium hydroxide. These precipitates were removed by settling.

(44) The clarified bittern containing 2.2% (w/v) magnesium ions is obtained.

(45) 63 L of 1.0 N sodium hydroxide solution was added over 45 minutes under stirring to 34 L clarified bittern prepared as above containing 748 gm of magnesium ions (31.17 mol) with continuous stirring at ambient temperature.

(46) The slurry is filtered using single filtration unit and the cake is washed with water till Cl.sup. content of filtrate reached a value of around 0.1% (w/v). Wet cake of magnesium precursor was well dispersed in demineralized water using colloidal mill to prepare 90 L slurry containing magnesium ions.

(47) 13 L FeCl.sub.3 solution containing 2.83% Fe.sup.3+ (w/v) (6.57 mol) was added over 30 minutes into 44 L solution of 0.28 M sodium carbonate (12.32 mol) at ambient temperature. It was further stirred for 15 minutes at ambient temperature to obtain a slurry.

(48) Slurry of Fe.sup.3+ precursor so prepared was added to slurry of magnesium precursor in 20 minutes at ambient temperature and mixed slurry was kept for settling for 1 hour. 50 L of supernatant liquid was decanted and solution containing 350 gm of sodium carbonate prepared in DM water was added and maintained pH of the slurry at 10. The slurry having [Mg]:[Fe] mole ratio of 4.74 was then charged in a pressure reactor and heated up to 145 C. and corresponding pressure. The slurry was subjected to this condition for 5 hr. The slurry was allowed to cool down to 60 C. and product was then filtered and washed till free from adhering electrolytes. The end of washing was indicated by measurement of pH of the wash water to be 10. The cake was dried in dryer at 110 C. 2.4 kg of product was obtained which was pulverized to pass through 30+72 BSS mesh. The product was characterized by XRD, IR and particle size. XRD pattern exhibited all the six major diffraction bands at around 7.87, 3.94, 2.62, 2.33, 1.55 and 1.52 . (FIG. 6) The product obtained in the present example was white in colour

(49) This example teaches the further scale up of the process taught in Examples 4 and 5 to kilogram scale.

(50) Thermo-gravimetric analysis of the product of the present example revealed that the loss on heating was ca. 11-12% up to 200 C. which is ascribed to loss of bound moisture while in the range of 200-400 C. the loss in weight was ca. 21% which is ascribed to decomposition of carbonate with concomitant release of CO.sub.2.

(51) Based on the above data and the absolute Mg and Fe contents in the products as obtained in Examples 3-6, the chemical formula of the white products obtained may be written as [Mg.sub.4.30.4Fe(III)(OH).sub.10.60.8][CO.sub.3].sub.0.50.3H.sub.2O. Further, the magnetic moment of the product of Example 6 was found to be 1.49 suggesting that Fe is present in the product as low spin Fe(III).

EXAMPLE 7

(52) DFS was prepared using iodizing agent and iron fortifying agent prepared in Example 6 above. 3.1 gm of iodizing agent SHT-IO.sub.3 (6% I.sub.2) (prepared by the process of U.S. Pat. No. 7,695,707) and 44 gm iron fortifying agent (13% Fe w/w) were added to 5 kg NaCl having purity >99%. The DFS prepared was stored in plastic jar with lid. The salt was analyzed for iodine and iron content periodically.

(53) Following table indicate the result of analysis.

(54) TABLE-US-00001 No. of Days Iodine, ppm Iron, ppm 0 38.3 1076 30 38.5 70 38.3 100 38.2 1053 130 38.1 156 38.6 174 38.4 1286 369 39.5 811 40.2 1153 1100 38.5

EXAMPLE 8

(55) Double Fortified salt prepared in Example-7 was measured for its whiteness index using Digital Reflectance meter made by Photo Electric Instruments Pvt Ltd, Rajasthan with respect to whiteness of magnesium carbonate taken as 100% whiteness. The following table indicates whiteness index of DFS along with those of common salt used for preparation of DFS designated as Solar Salt, one of the branded iodized salts available in Indian market designated as BR.-Salt.

(56) TABLE-US-00002 Designation of salt Whiteness index DFS 95 Branded salt 97

EXAMPLE 9

(57) 6 gm of Mg Fe hydrotalcite as prepared in Example-6 above and exhibiting XRD pattern having intensity peaks (A.sup.0) 7.81, 3.91, 2.62, 2.36, 1.55, shown FIG. 7 and sharp IR absorption peak of interlayer carbonate ions at 1380 cm.sup.1, was powdered to pass through 60 BSS mesh and calcined in a furnace at 450 C. for two hour. The calcined hydrotalcite was cooled to 70 C. This was added to 300 ml of 0.001M potassium iodate solution prepared in distilled water. The reacting mass was stirred for five minutes maintaining the said temperature and left to stand for 16 hours with. The resultant slurry was filtered. The solid separated was washed with distilled water till the wash filtrate does not show any silver iodate precipitate with silver nitrate. The solids were dried at 110 C. The product off white in colour was characterized by XRD, IR and particle size. The product was characterized by XRD, IR and particle size. XRD pattern exhibited major diffraction bands at around 7.97, 3.99, 2.66, 2.35, 1.55 . The compound was found to have peak characteristic of hydrotalcite like material and indicated absence of crystalline impurities. The diffraction pattern is shown in FIG. 8. Similarly absence of amorphous impurities was indicated by IR spectrum. The dry off white material was analyzed for its iodine content using classical method of iodometry employing sodium thiosulphate as titrant and found to contain 0.5% of iodine in it. The iron content of the product was analyzed with ICP-OES instrument shown 13.5% (w/w) of iron. The composite filtrate was analysed for its potassium iodate content and found to contain 7.69 mg of potassium iodate. The K.sup.+ content of the composite filtrate analysed by flame photometer was found to be 11 mg.

(58) The present example teaches that the Fe.sup.3+ and IO.sub.3.sup. can co-exist in the same hydrotalcite matrix while still imparting satisfactory whiteness. Based on the analytical data of constituents, the chemical formula of the nearly white product obtained may be written as [Mg.sub.4.30.4Fe(III)(OH).sub.10.60.8](CO.sub.3).sub.0.486 (IO.sub.3).sub.0.0160.002.yH.sub.2O.

EXAMPLE 10

(59) DFS was prepared using iodizing agent and iron fortifying agent prepared in Example 9 above. 8.0 gm of iron and iodizing agent having 0.5% (w/w) iodine and 13.5% (w/w) iron was mixed thoroughly and uniformly with 1 kg of solar salt, which is ground and sieved to obtain fraction of 32+72 BSS mesh. The DFS prepared was stored in plastic jar with lid. The salt was analyzed for iodine and iron content. One of the best brand iodized salt was obtained from the market and used as control salt sample, which was analyzed for its iodine content and found to contain 37 ppm of iodine. Iodine loss was determined after boiling 5% w/v solution of both the samples for 15 minutes. The salt containing iodine and iron in the form of hydrotalcite equivalent to 40 ppm of iodine retained all the iodine without any loss. The loss iodine was 13.5% in a similar test with a branded salt containing 37 ppm of iodine, initially.

(60) This example teaches that even when Fe and I are intercalated in the same matrix, a white salt having excellent stability of Fe and I can be achieved as judged by the boiling water test.

Advantages of the Invention

(61) Reaction is carried out at both gram scale and kilogram scale and similar products were obtained indicating that the process is readily scalable.