1388/7 International Standard (ISO INTERNATIONAL ORGANIZATION FOR STANDARDIZATION+MEXAYHAPOAHAA OPrAHW3ALWA IO CTAHAAPTW3AUWMORGANISATION INTERNATIONALE DE NORMALISATION ANl rexn o So Ethanol for industrial use - Methods of test - Part 7 : Determination of methanol content [methanol contents between 0,01 and 0,20 % (V/ V)l -- Photometric method Ethanol a usage industriel -- Methodes d'essai - Partie 7: Dosage du methanol [teneurs de 0,01 a 0,20 % (V/V)] -- Methode photometrique First edition 1981-11-01 011981 SO1388/7-1981 (E) UDC 661.722 : 543.42 : 547.261 Ref.No.ISO 1388/7-1981 (E) Descriptors:industrial products,ethanols,tests,determination of content,carbinols,spectrophotometric analysis Price based on 4 pages Foreword Iso (the International Organization for Standardization)is a worldwide federation of national standards institutes (iso member bodies). The work of developing Inter- national Standards is carried out through Iso technical committees. Every member bodyinterested ina subjectforwhichatechnical committeehasbeen set uphasthe right to be represented on that committee. International organizations, governmental andnon-governmental,in liaisonwithiso,also take partinthe work. Draft International Standards adopted by the technical committees are circulated to the member bodies for approval before their acceptance as International Standards by the Iso Council. International Standard ISo 1388/7 was developed by Technical Committee ISO/TC 47, Chemistry, and was circulated to the member bodies in February 1980. It has been approved by the member bodies of the following countries : Australia France Romania Austria Germany, F.R. South Africa, Rep. of Belgium Hungary Switzerland Brazil Italy Thailand Bulgaria Korea, Rep. of United Kingdom China Philippines USSR Czechoslovakia Poland The member body of the following country expressed disapproval of the document on technicalgrounds : Netherlands International Standards ISo 1388/1 to iSO 1388/12 cancel and replace ISO Recom- mendationR 1388-1970,of whichthey constitute a technical revision. @International Organization for Standardization, 1981 Printed in Switzerland ISO1388/7-1981 (E) INTERNATIONALSTANDARD Ethanol for industrial use Methods of test Part 7 : Determination of methanol content [methanol contents between 0,01 and 0,20 % (V/V)) -- Photometric method Scope and field of application 3.3 4,5-Dihydroxynaphthalene-2,7-disulphonic acid (chromotropic acid), solution in sulphuric acid. This part of ISo 1388 specifies a photometric method for the determination of themethanol content of ethanolfor industrial 3.3.1 Preparation of the solution use. Dissolve 0,1 g of chromotropic acid, or its disodium salt, in The method is applicable to products having methanol con- 10 ml of water. Add, while cooling, 90 ml of suiphuric acid, tentsbetween0,01and0,20%(v/V). Q approximately 1,81 g/ml,about90 % (m/ m) solution,and mix. This document should be read in conjunction with ISo 1388/1 Prepare this solution at the time of use. (see the annex) If the solution causes significant coloration during colour development of the compensation solution (5.3.1) or the blank 2 Principle test solution (5.2), purify the chromotropic acid, or its disodium salt, in accordance with the procedure specified in 3.3.2. Conversion of the methanol present in a test portion to for- maldehyde by oxidation with a solution of potassium per- 3.3.2 Purification of the chromotropic acid manganate inphosphoric acid.Reaction of theformaldehyde formed with chromotropic acid. Dissolve about 10 g of chromotropic acid, or its disodium salt, in 25 ml of water. If the disodium salt is used, add, while cool- Photometricmeasurementof thevioletcolorationobtainedata ing, 2 ml of sulphuric acid, Q approximately 1,84 g/ml, to con- wavelength of about 570 nm. vert it to the free acid. Add 50 ml of methanol, heat just to boil- ing and filter through a sintered glass filter funnel, porosity grade P 10*. 3 Reagents Add 100 ml of propan