FERROCYANIDES of CALCIUM, POTASSIUM and SODIUM
Prepared at the 17th JECFA (1973), published in FNP 4 (1978) and in FNP
52 (1992). Metals and arsenic specifications revised at the 57th JECFA
(2001). An ADI of 0-0.025 mg/kg bw was established at the 18th JECFA
(1974)
SYNONYMS Yellow prussiate of lime, potash or soda; hexacyanoferrate of calcium,
potassium or sodium; INS No. Calcium salt 538, Potassium salt 536,
Sodium salt 535
DEFINITION
Chemical names Calcium (or Potassium or Sodium) ferrocyanide,
Calcium (or Potassium or Sodium) hexacyanoferrate (II)
C.A.S. number 1327-39-5, Calcium salt
13943-58-3, Potassium salt
13601-19-9, Sodium salt
Chemical formula Ca2Fe(CN)6 · 12H2O
K4Fe(CN)6 · 3H2O
Na4Fe(CN)6 · 10H2O
Formula weight Calcium salt 508.3
Potassium salt 422.4
Sodium salt 484.1
Assay Not less than 99.0% of the respective ferrocyanide
DESCRIPTION Yellow crystals or crystalline powder
FUNCTIONAL USES Anticaking agent
CHARACTERISTICS
IDENTIFICATION
Solubility (Vol. 4)
Soluble in water; potassium and sodium salts are insoluble in ethanol
Test for ferrocyanide To 10 ml of a 1% solution of the sample add 1 ml of ferric chloride TS. A
dark blue precipitate is formed. (Retain the mixture for the Test for calcium).
Test for calcium (Vol. 4)
Passes test
Test the mixture from the Test for ferrocyanide
Test for potassium
(Vol. 4)
Passes test
Test for sodium (Vol. 4)
Passes test
PURITY
Cyanide Not detectable
Dissolve 10 mg of copper sulfate in a mixture of 8 ml of water and 2 ml of
ammonia TS. Wet a strip of filter paper with this solution, and place the wet
paper in a stream of hydrogen sulfide. When one drop of a 1% solution of
the sample is placed on the brown reagent paper, a white circle should not
be produced.
Ferricyanide Not detectable
Dissolve about 10 mg of the sample in 10 ml of water and place one drop of
this solution on a spot plate. Add one drop of a 1% solution of lead nitrate,
followed by a few drops of a solution prepared by saturating cold 2 N acetic
acid with benzidine. No blue precipitate or blue coloration should appear.
Arsenic (Vol. 4) Not more than 3 mg/kg (Method II)
Lead (Vol. 4) Not more than 5mg/kg
Determine using an atomic absorption technique appropriate to the
specified level. The selection of sample size and method of sample
preparation may be based on the principles of the method described in
Volume 4, “Instrumental Methods.”
METHOD OF
ASSAY
Weigh 3 g of the sample to the nearest 0.1 mg and transfer into a 400-ml
beaker. Dissolve in 225 ml of water, and add cautiously about 25 ml of
sulfuric acid TS. Add, with stirring, 1 drop of orthophenanthroline TS, and
titrate with 0.1 N ceric sulfate until the colour changes sharply from orange
to pure yellow. Each ml of 0.1 N ceric sulfate is equivalent to 50.83 mg of
Ca2Fe(CN)6 · 12H2O; 42.24 mg of K4Fe(CN)6 · 3H2O or 48.41 mg of
Na4Fe(CN)6 · 10H2O.
FERROCYANIDES of CALCIUM, POTASSIUM and SODIUM
SYNONYMS
DEFINITION
Chemical names
C.A.S. number
Chemical formula
Formula weight
Assay
DESCRIPTION
FUNCTIONAL USES
CHARACTERISTICS
IDENTIFICATION
Test for ferrocyanide
PURITY
Cyanide
Ferricyanide
Arsenic (Vol. 4)
Lead (Vol. 4)
METHOD OF ASSAY