C6H6O2 110.11
1,3-Benzenediol
Resorcinol [108-46-3].
Resorcinol contains not less than 99.0 percent and not more than 100.5 percent of C6H6O2, calculated on the dried basis.
Identification:
A: Infrared Absorption 197K NOTE—If necessary to recrystallize, dissolve in dehydrated alcohol.]
B: Dissolve 100 mg in 2 mL of 1 N sodium hydroxide, add 1 drop of chloroform, and heat the mixture: an intense crimson color is produced. Then add a slight excess of hydrochloric acid: the color changes to pale yellow.
C: To 10 mL of a solution (1 in 100) add 1 drop of ferric chloride: a blue-violet color is produced, and it fades slowly.
Melting range: between 109 and 111 .
Loss on drying: Dry it over silica gel for 4 hours: it loses not more than 1.0% of its weight.
Residue on ignition: not more than 0.05%.
Phenol: Heat gently a solution (1 in 20): the odor of phenol is not perceptible.
Catechol: To 10 mL of a solution (1 in 20) previously mixed with 2 drops of 1 N acetic acid add 0.5 mL of lead acetate: no turbidity is produced.
Ordinary impurities: To pass the test.
Assay: Dissolve about 1.5 g of Resorcinol, accurately weighed, in water to make 500.0 mL. Transfer to an iodine flask 25.0 mL of the resulting solution, add 50.0 mL of 0.1 N bromine VS, dilute with 50 mL of water, add 5 mL of hydrochloric acid, and at once insert the stopper in the flask. Shake for 1 minute, allow to stand for 2 minutes, and add 10 mL of potassium iodide TS while slightly loosening the stopper. Shake thoroughly, allow to stand for 5 minutes, remove the stopper, and rinse it and the neck of the flask with 20 mL of water into the flask. Titrate the liberated iodine with 0.1 N sodium thiosulfate, adding starch as the endpoint is approached. Perform a blank determination. From the volume of 0.1 N sodium thiosulfate used, calculate the volume, in mL, of 0.1 N bromine consumed by the resorcinol. Each mL of 0.1 N bromine is equivalent to 1.835 mg of C6H6O2.
Ph Eur
C6H6O2 --- 110.1 --- 108-46-3
Action and use: Keratolytic.
DEFINITION
Resorcinol contains not less than 98.5 per cent and not more than the equivalent of 101.0 per cent of benzene-1,3-diol, calculated with reference to the dried substance.
CHARACTERS
A colourless or slightly pinkish-grey, crystalline powder or crystals, turning red on exposure to light and air, very soluble in water and in alcohol.
IDENTIFICATION
A. Melting point:109C to 112C.
B. Dissolve 0.1 g in 1 ml of water add 1 ml of strong sodium hydroxide solution and 0.1 ml of chloroform, heat and allow to cool. An intense, deep-red colour develops which becomes pale yellow on the addition of a slight excess of hydrochloric acid.
C. Thoroughly mix about 10 mg with about 10 mg of potassium hydrogen phthalate, both finely powdered. Heat over a naked flame until an orange-yellow colour is obtained. Cool and add 1 ml of dilute sodium hydroxide solution and 10 ml of water and shake to dissolve. The solution shows an intense green fluorescence.
TESTS
Solution S: Dissolve 2.5 g in carbon dioxide-free water R and dilute to 25 ml with the same solvent.
Appearance of solution: Solution S is clear and not more intensely coloured than reference solution and remains so when heated in a water-bath for 5 min.
Acidity or alkalinity: To 10 ml of solution S add 0.05 ml of bromophenol blue solution. Not more than 0.05 ml of 0.1 M hydrochloric acid or 0.1 M sodium hydroxide is required to change the colour of the indicator.
Related substances: To pass the test
Pyrocatechol: To 2 ml of solution S add 1 ml of ammonium molybdate solution and mix. Any yellow colour in the solution is not more intense than that in a standard prepared at the same time in the same manner using 2 ml of a 0.1 g/l solution of pyrocatechol.
Loss on drying: Not more than 1.0 per cent, determined on 1.00 g of powdered substance by drying in a desiccator for 4 h.
Sulphated ash: Not more than 0.1 per cent, determined on 1.0 g.
ASSAY
Dissolve 0.500 g in water and dilute to 250.0 ml with the same solvent. To 25.0 ml of the solution in a ground-glass-stoppered flask add 1.0 g of potassium bromide, 50.0 ml of 0.0167 M potassium bromate, 15 ml of chloroform and 15.0 ml of hydrochloric acid. Stopper the flask, shake and allow to stand in the dark for 15 min, shaking occasionally. Add 10 ml of a 100 g/l solution of potassium iodide, shake thoroughly, allow to stand for 5 min and titrate with 0.1 M sodium thiosulphate, using 1 ml of starch solution R as indicator.
1 ml of 0.0167 M potassium bromate is equivalent to 1.835 mg of C6H6O2.
1,3-C6H4(OH)2
Formula Wt 110.11
CAS Number 108-46-3
REQUIREMENTS
Assay: 99.0-100.5% C6H4(OH)2
Melting point: 110-112C.
