CMC

　　Other name: carmellose; croscarmellose; Carboxymethyl Cellulose; Cellulose Carboxymethyl Ether; Cellulose-CM 23; cmc; Carboxy Methyl Cellulose; carboxy methyl cellulose; cm cellulose cation exchanger fast flow fibrous F; Carboxyl Methyl Cellulose

　　CAS No:000-11-7

　　Chemical name: Sodium salt of the carboxymethyl ether of cellulose

　　Chemical formula:

　　The polymers contain substituted anhydroglucose units with the

　　following general formula: C6H7O2(OR1)(OR2)(OR3), where R1, R2 R3 each may be one of the following:

　　H

　　CH2COONa

　　CH2COOH

　　Molecular weight:

　　Higher than approximately 17 000 (degree of polymerisation approximately 100)

　　Definition: Carboxy methyl cellulose is the partial sodium salt of a carboxymethyl ether of cellulose, the cellulose being obtained directly from natural strains of fibrous plant material

　　Description: Slightly hygroscopic white or slightly yellowish or greyish odourless and tasteless, granular or fibrous powder.

　　Identification:

　　A. Solubility Yields a viscous colloidal solution with water. Insoluble in ethanol.

　　B. Foam test A 0,1 % solution of the sample is shaken vigorously. No layer of foam appears. (This test permits the distinction of sodium carboxymethyl cellulose from other cellulose ethers)

　　C. Precipitate formation To 5 ml of a 0,5 % solution of the sample, add 5 ml of 5 % solution of copper sulphate or of aluminium sulphate. A precipitate appears. (This test permits the distinction of sodium carboxymethyl cellulose from other cellulose ethers and from gelatine, locust bean gum and tragacanth).

　　D. Colour reaction Add 0,5 g powdered carboxy methyl cellulose sodium to 50 ml of water, while stirring to produce an uniform dispersion. Continue the stirring until a clear solution is produced, and use the solution for the following test:

　　To 1 mg of the sample, diluted with an equal volume of water, in a small test tube, add 5 drops of 1-naphthol solution. Incline the test tube, and carefully introduce down the side of the tube 2 ml of sulphuric acid so that it forms a lower layer. A red-purple colour develops at the interface.

　　Purity:

　　Assay: Content on the anhydrous basis not less than 99,5 %

　　Degree of substitution Not less than 0,2 and not more than 1,5 carboxymethyl groups (CH2COOH) per anhydroglucose unit

　　Loss on drying: Not more than 12 % (105°C to constant weight)

　　pH of a 1 % colloidal solution: Not less than 5,0 and not more than 8,5

　　Arsenic: Not more than 3 mg/kg

　　Lead: Not more than 5 mg/kg

　　Mercury: Not more than 1 mg/kg

　　Cadmium: Not more than 1 mg/kg

　　Heavy metals (as Pb): Not more than 20 mg/kg

　　Total glycolate: Not more than 0,4 %, calculated as sodium glycolate on the anhydrous basis

　　Sodium: Not more than 12,4 % on the anhydrous basis