ISO 11216 pdf download

ISO 11216 pdf download.Modified starch — Determination of content of carboxymethyl groups in carboxymethyl starch 1 Scope This International Standard specifies a method for the determination of the content of carboxymethyl groups in carboxymethyl starch. The method is suitable for determining carboxymethyl group contents between 1 ,6 % ( m / m ) and 1 0,0 % ( m / m ). 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this International Standard. At the time of the publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on the International Standard are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain registers of currently valid International Standards. ISO 1 666:1 996, Starch — Determination of moisture content — Oven-drying method. ISO 3696:1 987, Water for analytical laboratory use — Specification and test methods. 3 Definition For the purposes of this International Standard, the following definition applies. 3.1 carboxymethyl group content mass of carboxymethyl groups in the acid form divided by the mass of the test portion of carboxymethyl starch in the acid form NOTE The carboxymethyl group content is expressed as a percentage by mass. 4 Principle The carboxymethyl groups are converted into the acid form by acidifying a solution or a suspension of the starch with hydrochloric acid. After the starch is precipitated with methanol, it is allowed to settle before being filtered off on a sintered glass crucible. The excess acid is completely removed by washing with methanol. The starch is dried and a weighed portion is treated with a measured excess of sodium hydroxide solution. The sodium hydroxide not used by the sample is back-titrated with hydrochloric acid. 5 Reagents and materials Use only reagents of recognized analytical grade. 5.1 Water, complying with at least grade 3 in accordance with ISO 3696. The water shall be free from carbon dioxide. 5.2 Methanol, 1 00 %. 5.3 Hydrochloric acid, c (HCl) = 4 mol/l. 5.4 Sodium hydroxide solution, c (NaOH) = 0,1 mol/l, free from carbon dioxide. 5.5 Phenolphthalein solution, in ethanol 90 % ( V/V ), r(phenolphthalein) = 1 0 g/l. 5.6 Dilute hydrochloric acid, c (HCl) = 0,1 mol/l. 5.7 Sodium chloride. 6 Apparatus Usual laboratory apparatus and, in particular, the following. 6.1 Beakers, of capacity...