Disodium Hydrogen Citrate
C6H6Na2O7,11⁄2H2O 263.1 144-33-2
Action and use
Anticoagulant.
DEFINITION
Sodium Acid Citrate contains not less than 98.0% and not more than 104.0% of C6H6Na2O7,11⁄2H2O.
CHARACTERISTICS
A white powder.
Freely soluble in water; practically insoluble in ethanol (96%).
IDENTIFICATION
Yields the reactions characteristic of sodium salts and of citrates, Appendix VI.
TESTS
Acidity
pH of a 3% w/v solution, 4.9 to 5.2, Appendix V L.
Arsenic
0.50 g dissolved in 25 mL of water complies with the limit test for arsenic, Appendix VII (2 ppm).
Chloride
Dissolve 1.0 g in 100 mL of water. 15 mL of the resulting solution complies with the limit test for chlorides, Appendix VII (330 ppm).
Oxalate
Dissolve 1.0 g in 4 mL of water, add 3 mL of hydrochloric acid and 1 g of granulated zinc and heat on a water bath for 1 minute. Allow to stand for 2 minutes, decant the liquid into a test tube containing 0.25 mL of a 1% w/v solution of phenylhydrazine hydrochloride and heat to boiling. Cool rapidly, transfer to a graduated measuring cylinder, add an equal volume of hydrochloric acid and 0.25 mL of potassium hexacyanoferrate(III) solution, shake and allow to stand for 30 minutes. Any red colour produced is not more intense than that produced by treating in the same manner 4 mL of a 0.005% w/v solution of oxalic acid (150 ppm, calculated as anhydrous oxalic acid).
Sulfate
Dissolve 0.50 g in 57 mL of water and add 3 mL of 2M hydrochloric acid. 15 mL of the resulting solution complies with the limit test for sulfates, Appendix VII (0.12%).
Readily carbonisable substances
Heat 1.0 g, in powder, with 10 mL of sulfuric acid for 30 minutes in a water bath protected from light. Not more than a pale brown colour is produced.
ASSAY
Heat 2 g until carbonised, cool and boil the residue with 50 mL each of water and 0.5M hydrochloric acid VS. Filter, wash the filter with water and titrate the excess of acid in the filtrate and washings with 0.5M sodium hydroxide VS using methyl orange solution as indicator. Each mL of 0.5M hydrochloric acid VS is equivalent to 65.78 mg of C6H6Na2O7, 11⁄2H2O.
