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A. Synthetic Additives
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C. Mixture Additives
Standard and Specification > Synthetic Additives > Ferric Chloride
415. Ferric Chloride  
Chemical Formula FeCl3·6H2O 
Molecular Weight 270.30 
[Compositional Specifications of Ferric Chloride]
Content Ferric Chloride contains 98.5~102.0% of Ferric Chloride (FeCl3·6H2O).
Description Ferric Chloride occurs as yellowish brown crystals or lumps with hygroscopic properties.  
Identification Ferric Chloride responds to the tests for Chloride and Ferric salts.
Purity (1) Clarity of Solution: 1 g of Ferric Chloride is dissolved with 10 ml of hydrochloric acid (1→100) through heating. The turbidity of resulting solution should show slightly low level of turbid or better.

(2) Free acid: 2 g of Ferric Chloride is dissolve with 5 ml of water. There is no sign of vapor when glass rod dipped with ammonia is brought near to this solution.

(3) Nitrate: 5 g of Ferric Chloride is dissolve in 25 ml of water and heated to boil. Then 25 ml of ammonia is added. After cooling, mark this mixture to 100 ml with water and filter. Consider the filtrate as the test solution. Add 5ml of water, 0.1 ml of Indigocarmine, and 10ml of sulfuric acid to 5 ml of test solution. The solution should remain blue more than 5 minutes.

(4) Sulfate: Add 3ml of anhydrous sodium carbonate solution (1→8) to 20ml of test solution (3) and evaporate to dryness in the steam bath. Heat the content with a low flame of burner until there is no sign of the white vapor. After cooling, add 10ml of water and 3ml of hydrochloric acid (1→4) to the content and evaporate to dryness it in the steam bath. Dissolve the content with 0.3ml of hydrochloric acid (1->4) and water. Make 50ml of solution with water and tested for sulfate. Its content should not be more than the amount that corresponds to 0.4 ml of 0.01 N sulfuric acid.

(5) Heavy metal: 1 g of Ferric Chloride is dissolved in 3 ml of aqua regina in a porcelain crucible, which is evaporated to dryness in a water bath. The residues are dissolved in 5 ml of dilute hydrochloric acid (1→2), which is transferred into a separatory funnel with a stopcock. The porcelain crucible is washed twice with 5 ml of dilute hydrochloric acid (1→2) and the wash liquid is added to the separatory funnel. The aqueous solution is washed 3 times with 40 ml each of ether and the ether phase is discarded. In the aqueous phase, 0.05 g of hydroxylamine hydrochloride is dissolved, which is heated for 10 minutes in a water bath. After adding 1 drop of phenolphthalein solution, ammonia solution is added until it turns red. After cooling, dilute hydrochloric acid (1→2) is drop-wise added until the solution becomes colorless, where 4 ml of dilute acetic acid (1→20) is added and well mixed. The solution is diluted to 50 ml with water, which is then filtered, if necessary. This test solution is tested for heavy metals. Its content should not be more than 20ppm. A color standard is prepared by following the same procedure with 2 ml of lead standard solution mixed with 3 ml of aqua regina in a porcelain crucible.

(6) Zinc: 20 ml of the test solution prepared in (3) above is neutralized by hydrochloric acid and then make 30ml with water. Add 3 ml of diluted hydrochloric acid and 0.2 ml of potassium ferrocyanide (1→10), and allow to stand for 15 minutes. The solution should not be more turbid than the following reference solution. To prepare reference solution, measure 3ml of zinc standard solution, and add water to make 30ml. Add 3ml of diluted hydrochloric acid and 0.2 ml of potassium ferrocyanide (1→10) to this solution, and allow to stand 15 minutes. (not more than 30 ppm as Zinc)

(7) Arsenic: Prepare the test solution by dissolving 0.5g of Ferric Chloride to 20 ml of water then apply 0.2 g of L-ascorbic acid. The arsenic test result for the test solution should be adequate.
Separately, the standard solution is prepared with 2ml standard arsenic solution with additions of 20ml water and 0.2 g of L-Ascorbic acid. And then repeat the same testing procedure as mentioned above. (not more than 4ppm)

(8) Free chloride: 2g of Ferric Chloride is dissolved in 5 ml of water. After heating, the filter paper treated with the starch iodide zinc solution should not turn blue.
Assay 0.6 g of Ferric Chloride is precisely weighed and transferred into a flask with a ground-glass stopper along with 50 ml of water as a solvent. 3 ml of hydrochloric acid and 3g of potassium iodide are added. The stopper is placed on the flask, which is set-aside for 15 minutes in a dark place. Then the contents are titrated with 0.1N sodium thiosulfate solution (indicator: starch solution). Separately, a blank test is carried out by the same procedure.

1 ml of 0.1 N sodium thiosulfate = 27.030mg  FeCl3·6H2O