Freely soluble in ethanol (95%), in ether and in Methanol; very slightly soluble in water.
3.
Identification
Test A may be omitted if tests B, C &D are carried out. Tests B, C and D may be omitted if tests A are carried out. A. The infrared absorption spectrum is concordant with the reference spectrum of methyl paraben or with the spectrum obtained from methyl paraben RS.
B. The light absorption in the range 230 to 360 nm of a 0.0005% w/v in ethanol (95%) exhibits a maximum at about 258 nm, absorbance at about 258 nm, 0.52 to
0.56.
C. Boil 10 mg with 10 ml of water, cool and add 0.05 ml of ferric chloride solution; a reddish violet colour is produced.
D. Dissolve 0.1g in 2 ml of ethanol (95%) boil and add 0.5 ml of mercuric nitrate solution; a precipitate is formed and the supernatant liquid becomes red.
4.
Acidity
Dissolve 1.0 g in sufficient ethanol (95%) to produce 10 ml. To 2 ml of the solution add 3 ml of ethanol (95%), 5 ml of carbon dioxide-free water and 0.1 ml of bromocresol green solution. Not more than 0.1 ml of 0.1M sodium hydroxide is
required to change the colour of the solution.
5.
Appearance of solution
A 10% w/v solution in ethanol (95%) is clear or not more opalescence than Opalescence standard OS1 prepared by 5.0 ml of Opalescence standard & 95 ml of water .and not more intensely coloured than reference solution prepared by
mixing 1.5 ml ferric chloride colorimetric solution, 0.8 ml cobaltous chloride colorimetric solution, 0.2 ml cupric sulphate colorimetric solution and 97.5 ml of 1% w/v HCl solution.
6.
Chloride
Not more than 500 ppm.
7.
Sulphate
Heat 2 g with 100 ml of water, cool, add sufficient water to restore the original volume and filter. To 10 ml of the filtrate add 0.15 ml of dilute hydrochloric acid and 0.1 ml of barium chloride solution; no turbidity is produced within 10 minutes.
