Molecular formula. NaCl

Relative molecular mass. 58.44

Chemical name. Sodium chloride; CAS Reg. No. 7647-14-5.

Description. Colourless crystals or a white, crystalline powder; odourless.

Solubility. Freely soluble in water; slightly soluble in ethanol (~750 g/l) TS.

Category. Ionic equilibration agent.

Storage. Sodium chloride should be kept in a well-closed container.

Additional information. Sodium chloride has a saline taste.

Requirements

Definition. Sodium chloride contains not less than 99.0% and not more than 100.5% of NaCl, calculated with reference to the dried substance.

Identity tests

A. When tested for sodium as described under 2.1 General identification tests, yields the characteristic reactions. If reaction B is to be used, prepare a 20 mg/mL solution.

B. A 20 mg/mL solution yields reaction A described under 2.1 General identification tests as characteristic of chlorides.

Heavy metals. Use 1.0 g for the preparation of the test solution as described under 2.2.3 Limit test for heavy metals. Procedure 1; determine the heavy metals content according to Method A; not more than 10 μg/g.

Arsenic. Use a solution of 2.5 g in 35 mL of water and proceed as described under 2.2.5 Limit test for arsenic; not more than 4 μg/g.

Barium. Dissolve 4 g in 20 mL of water, filter if necessary, divide the solution into 2 portions and place them in two separate matched tubes. To 1 portion add 2 mL of sulfuric acid (~100 g/l) TS and to the other, 2 mL of water; the solutions remain equally clear for not less than 30 minutes when viewed down the vertical axis of the tube in diffused light against a black background.

Calcium and magnesium. To 20 mL of a 10 mg/mL solution add 2 mL each of ammonia (~100 g/l) TS, ammonium oxalate (25 g/l) TS, and disodium hydrogen phosphate (40 g/l) TS; no turbidity is produced within 5 minutes.

Iodides and bromides. Digest 2 g of finely powdered test substance for 3 hours with 25 mL of warm ethanol (~750 g/l) TS, cool, and filter. Evaporate the filtrate to dryness, dissolve the residue in 5 mL of water, add 1 mL of chloroform R, and cautiously add, drop by drop, with constant agitation, 5 drops of chlorine TS, previously diluted with twice their volume of water; the chloroform does not acquire a violet, yellow or orange colour.

Iron and sodium ferrocyanides. To 0.5 g add 5 drops of sulfuric acid (~100 g/L) TS and carefully heat until dry. Dissolve the residue in 6 mL of water, add 1 mL of hydrochloric acid (~70 g/L) TS, 1 drop of hydrogen peroxide (~60 g/L) TS, and 2 mL of ammonium thiocyanate (~75 g/L) TS; this constitutes solution A. Prepare in a similar manner solution B using 0.40 mL of iron standard FeTS instead of the residue obtained from the test substance. Solution A is not more intensely coloured than solution B when compared as described under 1.11.1 Colour of liquids (16 μg/g of total Fe).

Sulfates. Dissolve 1.7 g in 20 mL of water and proceed as described under 2.2.2 Limit test for sulfates; the sulfate content is not more than 0.3 mg/g.

Clarity and colour of solution. A solution of 1.0 g in 10 mL of carbon-dioxide-free water R is clear and colourless.

Loss on drying. Dry to constant weight at 130°C; it loses not more than 10 mg/g.

Acidity or alkalinity. Dissolve 2 g in 20 mL of carbon-dioxide-free water R and add 2 drops of bromothymol blue/ethanol TS; not more than 0.1 mL of sodium hydroxide (0.02 mol/l) VS or 0.2 mL of hydrochloric acid (0.02 mol/l) VS is required to attain the midpoint of the indicator (green).

Assay. Dissolve about 0.25 g, accurately weighed, in 50 mL of water and titrate with silver nitrate (0.1 mol/l) VS, using potassium chromate (100 g/l) TS as indicator. Each mL of silver nitrate (0.1 mol/l) VS is equivalent to 5.844 mg of NaCl.

Additional requirements for sodium chloride for parenteral use

Complies with the monograph for "Parenteral preparations".

Bacterial endotoxins. Carry out the test as described under 3.4 Test for bacterial endotoxins; contains not more than 5.0 IU of endotoxin RS per g.