Anhydrous Sodium Carbonate
(Ph. Eur. monograph 0773)
Na2CO3 106.0 497-19-8
DEFINITION
Content
99.5 per cent to 100.5 per cent (dried substance).
CHARACTERS
Appearance
White or almost white, slightly granular powder, hygroscopic.
Solubility
Freely soluble in water, practically insoluble in ethanol (96 per cent).
IDENTIFICATION
A. Dissolve 1 g in water R and dilute to 10 mL with the same solvent. The solution is strongly alkaline (2.2.4).
B. The solution prepared for identification test A gives the reaction of carbonates (2.3.1).
C. The solution prepared for identification test A gives reaction (a) of sodium (2.3.1).
D. Loss on drying (see Tests).
TESTS
Solution S
Dissolve 2.0 g in portions in a mixture of 5 mL of hydrochloric acid R and 25 mL of distilled water R. Heat to boiling and cool. Add dilute sodium hydroxide solution R until the solution is neutral and dilute to 50 mL with distilled water R.
Appearance of solution
The solution is clear (2.2.1) and not more intensely coloured than reference solution Y6 (2.2.2, Method I).
Dissolve 2.0 g in 10 mL of water R.
Alkali hydroxides and bicarbonates
Dissolve 0.4 g in 20 mL of water R. Add 20 mL of barium chloride solution R1 and filter. To 10 mL of the filtrate add 0.1 mL of phenolphthalein solution R. The solution does not become red. Boil the remainder of the filtrate for 2 min. The solution
remains clear (2.2.1).
Chlorides (2.4.4)
Maximum 125 ppm.
Dissolve 0.4 g in water R, add 4 mL of dilute nitric acid R and dilute to 15 mL with water R.
Sulfates (2.4.13)
Maximum 250 ppm, determined on solution S.
Iron (2.4.9)
Maximum 50 ppm.
Dilute 5 mL of solution S to 10 mL with water R.
Loss on drying (2.2.32)
Maximum 1.0 per cent, determined on 1.000 g by drying in an oven at 300 ± 15 °C.
ASSAY
Dissolve 0.400 g in 50 mL of carbon dioxide-free water R. Titrate with 1 M hydrochloric acid, determining the end-point potentiometrically (2.2.20). Read the volume added at the 2 point of inflection.
1 mL of 1 M hydrochloric acid is equivalent to 52.99 mg of Na2CO3.
STORAGE
In an airtight container.
