Preparation of Mixed Derivatives of Carboxymethyl Starch and Determination of Substitution Degree by a New Colorimetric Method

Carboxymethyl starch (CMS) and mixed CMS‐benzoate derivatives were prepared and some physical properties were estimated. A new colorimetric method for determination of the substitution degree (D. S.) of CMS derivatives by using I‐acid was developed. The factors affecting the color development and stability of I‐acid method were studied and the most suitable conditions for color reaction were found. The substitution degrees of prepared CMS and its mixed derivatives were determined by the I‐acid method and the results were compared with those of classical methods.