(Ph. Eur. monograph 0003)
DEFINITION
Content
9.5 per cent m/m to 10.5 per cent m/m of HCl (Mr 36.46).
PREPARATION
To 726 g of water R add 274 g of concentrated hydrochloric acid and mix.
IDENTIFICATION
A. It is strongly acid (2.2.4).
B. It gives reaction (a) of chlorides (2.3.1).
C. It complies with the limits of the assay.
TESTS
Appearance
It is clear (2.2.1) and colourless (2.2.2, Method II).
Free chlorine
Maximum 1 ppm.
To 60 mL add 50 mL of carbon dioxide-free water R, 1 mL of a 100 g/L solution of potassium iodide R and 0.5 mL of iodide- free starch solution R. Allow to stand in the dark for 2 min. Any blue colour disappears on the addition of 0.2 mL of 0.01 M sodium thiosulfate.
Sulfates (2.4.13)
Maximum 5 ppm.
To 26 mL add 10 mg of sodium hydrogen carbonate R and evaporate to dryness on a water-bath. Dissolve the residue in 15 mL of distilled water R.
Residue on evaporation
Maximum 0.01 per cent.
Evaporate 100.0 g to dryness on a water-bath or using a rotary evaporator and dry the residue at 100-105 °C. The residue weighs a maximum of 10 mg.
ASSAY
To 6.00 g add 30 mL of water R. Titrate with 1 M sodium hydroxide, determining the end-point potentiometrically (2.2.20).
1 mL of 1 M sodium hydroxide is equivalent to 36.46 mg of HCl.
