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Description
PROCEDURE:
Cobaltous chloride CS (Red solution)
(Mol. Formula: CoCl2.6H2O, Mol. Wt: 237.93)
Reagents:
(1) Hydrogen peroxide TS: Pipette 10 mL of 30% hydrogen peroxide solution into a 100 mL volumetricflask, dilute to volume with purified water.
(2) Sodium hydroxide solution (1 in 5) : Mix 10 g of sodium hydroxide with 50 mL of purified water.
(3) Dilute sulfuric acid (1 in 4) : Mix 10 mL of sulfuric acid with 40 mL of purified water.
(4) Hydrochloric acid andPurified water mixture (25 : 975) : Mix 25 mL of hydrochloric acid with 975 mL of purified water.
(5) Starch TS: Mix 1 g of soluble starch with 10 mg of red mercuric iodide and sufficient cold water to make a thin paste. Add 200 mL of boiling water and boil for 1 minute with continuous stirring. Cool,and use only the clear solution.
(6) 0.1N Sodium thiosulfate VS: Prepare and standardize as directed in the current version of General Test Procedure: Preparation and Standardization of 0.1N Sodium Thiosulfate VS (GTP029).
Preparation: Transferred about 16.25 g of cobaltous chloride, accurately weighed to a 250 mL volumetric flask, dissolved and diluted to volume with hydrochloric acid and purified water mixture (25:975).
Standardization:
(a) Pipette 5 mL of this solution into a 250 mL iodine flask, add 5 mL of hydrogen peroxide TS and 15 mL of sodium hydroxide solution (1 in 5), boil for 10 minutes on a hot plate, cool and add 2 g of potassium iodide and 20 mL of dilute sulfuric acid (1 in 4).
(b) When the precipitate has dissolved, add 3 mL of starch TS as the indicator, titrate the liberated iodine with 0.1N sodium thiosulfate VS.
(c) Perform the blank determination with the same quantities of the same reagents.
Calculations: (V2 ~ V1) x N x 23.79
Contents of CoCl2. 6H2O = -------------------------------
in mg per mL 0.1 x 5
Where,
V1 = Volume of 0.1N sodium thiosulfate consumed by the sample in mL,
V2 = Volume of 0.1N sodium thiosulfate consumed by the blank in mL,
N = Normality of 0.1N sodium thiosulfate VS.
Adjust the final volume of the solution by the addition of enough of the hydrochloric acid and purified water mixture (25:975) so that each mL contains 59.5 mg of CoCl2. 6H2O.
Cupric sulfate CS
(Mol. formula: CuSO4.5H2O, Mol. Wt. :249.69)
Reagents:
(1) Hydrochloric acid andPurified water mixture (25 : 975) : Mix 25 mL of hydrochloric acid with 975mL of purified water.
(2) Starch TS : Mix 1 g of soluble starch with 10 mg of red mercuric iodide and sufficient cold water to make a thin paste. Add 200 mL of boiling water and boil for 1 minute with continuous stirring. Cool, and use only the clear solution.
(3) 0.1N Sodium thiosulfate VS: Prepare and standardize as directed in the General Test Procedure; Preparation and Standardization of 0.1N Sodium Thiosulfate VS. lask, dissolved and diluted to volume with hydrochloric acid and purified water mixture (25:975)
Standardization :
(a) Pipet 10 mL of this solution into a 250-mL iodine flask, add 40 mL of purified water, 4 mL of acetic acid, 3 g of potassium iodide and 5 mL of hydrochloric acid.
(b) Titrate the liberated iodine with 0.1N sodium thiosulfate VS by adding 3 mL of starch TS as indicator.
(c) Perform the blank determination with the same quantities of the same reagents.
(V2 ~ V1) x N x 24.97
Contents of CuSO4.5H2O = ---------------------------------
in mg per mL 0.1 x 10
Where,
V1 = Volume of 0.1N sodium thiosulfate consumed by the sample in mL,
V2 = Volume of 0.1N sodium thiosulfate consumed by the blank in mL,
N = Normality of 0.1N sodium thiosulfate VS.
Adjust the final volume of the solution by the addition of enough of the hydrochloric acid and purified water mixture (25:975) so that each mL contains 62.4 mg of CuSO4.5H2O.
Ferric Chloride CS
(Mol. formula : FeCl3.6H2O, Mol. Wt. :270.3)
Reagents:
(1) Hydrochloric acid andPurified water mixture (25 : 975) : Mix 25 mL of hydrochloric acid with 975 mL of purified water.
(2) Starch TS : Mix 1 g of soluble starch with 10 mg of red mercuric iodide and sufficient cold water to make a thin paste. Add 200 mL of boiling water and boil for 1 minute with continuous stirring. Cool, and use only the clear solution.
(3) 0.1N Sodium thiosulfate VS: Prepare and standardize as directed in the General Test Procedure; Preparation and Standardization of 0.1N Sodium Thiosulfate VS.
Preparation: Transferred about 13.75g of ferric chloride, accurately weighed to 250 ml volumetric flask, dissolve in 6.25 ml of HCl and dilute to volume with purified water.
Standardization:
(a) Pipet 10 mL of this solution into a 250-mL iodine flask, add 15 mL of purified water, 3 g of potassium iodide and 5 mL of hydrochloric acid, allow the mixture to stand for 15 minutes and add 100 mL of purified water.
(b) Titrate the liberated iodine with 0.1N sodium thiosulfate VS by adding 3 mL of starch TS as indicator.
(c) Perform the blank determination with the same quantities of the same reagents.
Calculations:
(V2 ~ V1) x N x 27.03
Contents of FeCl3.6H2O = -----------------------------
in mg per mL 10
Where,
V1 = Volume of 0.1N sodium thiosulfate consumed by the sample in mL,
V2 = Volume of 0.1N sodium thiosulfate consumed by the blank in mL,
N = Normality of 0.1N sodium thiosulfate VS.
Adjust the final volume of the solution by the addition of enough of the hydrochloric acid and purified water mixture (25:975) so that each mL contains 45.0 mg of FeCl3.6H2O.
Tags
General testing procedure, colorimetric solutions, standardization
