Chromic Chloride or Chromium Chloride contains not less than 98.0 percent and not more than 101.0 percent of CrCl3·6H2O.
Insoluble matter—0.01%).
Substances not precipitated by ammonium hydroxide— (0.20% as sulfate).
Sulfate— (0.01%).
Iron— The limit is 0.01%.
Chromic Chloride - Chromium Chloride
CrCl3-6H2O 266.45
Chromium chloride (CrCl3) hexahydrate
Chromium(3+) chloride hexahydrate [10060-12-5]
Anhydrous 158.36 [10025-73-7]
Chromium Chloride - Chromic Chloride or Chromium Chloride contains not less than 98.0 percent and not more than 101.0 percent of CrCl3-6H2O
Identification—
A: To 5 mL of a solution (1 in 250) in a test tube add 1 mL of 5 N sodium hydroxide and 10 drops of 30 percent hydrogen peroxide, and heat gently for about 2 minutes:
a yellow color develops.
B: To 5 mL of a solution (1 in 250) in a test tube add 5 drops of silver nitrate TS: a white, curd like precipitate is formed, and it is insoluble in nitric acid.
Insoluble matter— Transfer 10 g to a 250-mL beaker, add 100 mL of water, cover the beaker, and heat to boiling. Digest the hot solution on a steam bath for 30
minutes, and filter through a tarred filtering crucible of fine porosity. Rinse the beaker with hot water, passing the rinsing through the filter, and wash the filter
with hot water until the last washing is colorless. Dry the filter at 105oC the weight of the residue does not exceed 1 mg (0.01%).
Substances not precipitated by ammonium hydroxide— Dissolve 2.0 g of Chromic Chloride or Chromium Chloride in 80 mL of water, heat the solution to boiling, and
add a slight excess of ammonium hydroxide. Continue heating to remove the excess ammonia, cool, dilute with water to 100.0 mL, and mix. Pass through a retentive filter,
and transfer 50.0 mL of the clear filtrate to an evaporating dish that previously has been ignited and tarred. Add 0.5 mL of sulfuric acid to the filtrate, evaporate on
a steam bath to dryness, heat gently to remove the excess acid, and ignite gently: the weight of the residue does not exceed 2.0 mg (0.20% as sulfate).
Sulfate— Prepare a test solution by dissolving 2.0 g in 10 mL of water. Add 1 mL of 3 N hydrochloric acid, filter if necessary to obtain a clear solution, wash
the filter with two 5-mL portions of water, and dilute with water to 40 mL. Prepare a control solution in a similar manner, but use 1.0 g of the substance under test,
and after the filtration step add 0.10 mL of 0.020 N sulfuric acid. To each solution add 3 mL of barium chloride TS, mix, and allow to stand overnight. Decant most of
the supernatants, without disturbing the precipitates, but leaving twice the volume of liquid in the control solution as in the test solution. Dilute each solution with
water to 25 mL, and sonicate for 1 minute: any turbidity in the test solution does not exceed that in the control solution (0.01%).
Iron— Dissolve 1.0 g of Chromic Chloride or Chromium Chloride in 100 mL of water, and mix. Transfer 10 mL of this solution to a 100-mL color comparison tube,
dilute with water to 45 mL, add 2 mL of hydrochloric acid, and mix (Test Preparation). Proceed as directed for Procedure, except to add 15 mL of butyl alcohol to the
Test Preparation and the Standard Preparation at the same time that the Ammonium Thiocyanate Solution is added. Shake for 30 seconds, and allow the layers to separate:
the color in the upper butyl alcohol layer from the Test Preparation is not darker than that from the Standard Preparation. The limit is 0.01%.
Assay— Dissolve about 0.4 g of Chromic Chloride or Chromium Chloride, accurately weighed, in 100 mL of water contained in a glass-stoppered, 500-mL conical flask,
add 5 mL of 5 N sodium hydroxide, and mix. Pipette, slowly, 4 mL of 30 percent hydrogen peroxide into the flask, and boil the solution for 5 minutes. Cool the solution
slightly, and add 5 mL of nickel sulfate solution (1 in 20). Boil the solution until no more oxygen is evolved, cool, and add 2 N sulfuric acid drop wise until the color
of the solution changes from yellow to orange. Add to the flask a freshly prepared solution of 4 g of potassium iodide and 2 g of sodium bicarbonate in 100 mL of water,
then add 6 mL of hydrochloric acid. Immediately insert the stopper in the flask, and allow to stand in the dark for 10 minutes. Rinse the stopper and the sides of the
flask with a few mL of water, and titrate the liberated iodine with 0.1 N sodium thiosulfate VS to an orange color. Add 3 mL of starch TS, and continue the titration to
a blue-green endpoint. Each mL of 0.1 N sodium thiosulfate is equivalent to 8.882 mg of CrCl3·6H2O.
DESCRIPTION
Chromic chloride hexahydrate occurs as very dark green to violet crystals or crystalline powder. It is hygroscopic, and freely soluble in water. It is soluble in ethanol and insoluble in ether and in acetone.
Function: Nutrient
Packaging and Storage: Store in tightly sealed containers in a cool, dry place, away from moisture.
IDENTIFICATION
A. Procedure
Sample solution: Dissolve 1 g of the sample in water to a final concentration of 4 mg/mL.
Analysis: In a test tube, add 1 mL of 5 N sodium hydroxide and 10 drops of 30% hydrogen peroxide to 5 mL of the Sample solution, and heat gently for about 2 min.
Acceptance criteria: A yellow color develops.
B. Chloride
Sample solution: 4 mg/mL
Acceptance criteria: Passes test for Chloride.
ASSAY
Analysis: In a glass-stoppered, 500-mL conical flask, dissolve 0.4 g of the sample in 100 mL of water. Then, add 5 mL of 5 N sodium hydroxide, and mix. Pipet slowly 4 mL of 30% hydrogen peroxide into the flask and boil the solution for 5 min. Cool the solution slightly and add 5 mL of nickel sulfate solution (50 mg/mL). Boil the solution until no more oxygen is evolved, cool and add 2 N sulfuric acid dropwise until the color of the solution changes from yellow to orange. Add to the flask a freshly prepared solution of 4 g of potassium iodide and 2 g of sodium bicarbonate in 100 mL of water, then add 6 mL of hydrochloric acid. Immediately insert the stopper in the flask and allow to stand in the dark for 10 min. Rinse the stopper and the sides of the flask with a few mL of water and titrate the liberated iodine with 0.1 N sodium thiosulfate to an orange color. Add 3 mL of
starch and continue the titration to a blue-green endpoint. Each mL of 0.1 N sodium thiosulfate is equivalent to 8.882 mg of Cr3Cl- 6H2O.
Acceptance criteria: 98% to 101%
IMPURITIES
Arsenic: 1 mg/kg maximum.
Cadmium: 1 mg/kg maximum.
Lead: 1 mg/kg maximum.
Mercury: maximum. NMT 1 mg/kg
Chromium (VI): To pass the test; Acceptance criteria: 250 microg/g maximum.
Water-Insoluble matter:
Analysis: Transfer 10 g of the sample to a 250-mL beaker, add 100 mL of water, cover the beaker and heat to boiling. Digest the hot solution on a steam bath for 30 min, and filter through a tared Gooch crucible. Rinse the beaker with hot water, passing the rinsings through the crucible, and wash the crucible with hot water until the last washing is colorless. Dry the crucible at 105C.
Acceptance criteria: The weight of the residue does not exceed 1 mg (0.01% maximum.).
Substances Not Precipitated by Ammonium Hydroxide:
Analysis: Dissolve 2.0 g of the sample in 80 mL of water, heat the solution to boiling, and add a slight excess of ammonium hydroxide to ensure the formation of a precipitate. Continue heating to remove the excess ammonia, cool, dilute with water to 100.0 mL, and mix. Pass through a retentive filter, and transfer 50.0 mL of the clear filtrate to an evaporating dish that previously has been ignited and tared. Add 0.5 mL of sulfuric acid to the filtrate, evaporate on a steam bath to dryness, heat gently to remove the excess acid, and ignite gently.
Acceptance criteria: The weight of the residue does not exceed 2 mg (NMT 0.20% as sulfate).
