carboxymethylcellulose sodium cmc na there may be used any cellulose ether that is derived by etherifying cellulose to make it water soluble and can be formed into a film by casting an aqueous solution thereof to a certain thickness and then drying it specifically useful alkylcelluloses include for example methylcellulose having 19 to 33 by weight of the methoxyl group and ethylcellulose having 7 to 25 by weight of the ethoxyl group useful hydroxyalkyl alkylcelluloses include for example hydroxypropyl methylcellulose having 19 to 30 by weight of the methoxyl group and 13 to 20 by weight of the hydroxypropoxyl group hydroxyethyl methylcellulose having 19 to 30 by weight of the methoxyl group and 9 to 20 by weight of the hydroxyethoxyl group and hydroxyethyl ethylcellulose having 11 to 21 by weight of the ethoxyl group and 40 to 57 by weight of the hydroxyethoxyl group useful hydroxyalkyl celluloses include for example hydroxypropyl cellulose having 50 to 70 by weight of the hydroxypropoxyl group and hydroxyethyl cellulose having 30 to 60 by weight of the hydroxyethoxyl group a useful example of carboxymethylcellulose sodium cmc na is that having 15 to 53 by weight of the carboxymethoxyl group the contents of the methoxyl ethoxyl hydroxypropoxyl and like groups can be determined according to the methods described in the pharmacopoeia of japan on the other hand the content of the hydroxyethoxyl group can be determined according to the method described in p w morgan eng chem anal ed 1946.