1、BRITISH STANDARD BS 6829-4.6: 1988 ISO 4326:1980 Analysis of surface active agents (raw materials) Part 4: Ethylene oxide adducts Section 4.6 Method for determination of hydroxyl value ISO title: Non-ionic surface active agents Polyethoxylated derivatives Determination of hydroxyl value Acetic anhyd
2、ride method UDC 661.185.1:543.2 112BS6829-4.6:1988 This British Standard, having been prepared under the directionof the Chemicals Standards Committee, was published under the authority ofthe Board of BSI and comes intoeffect on 31August1988 BSI 12-1999 The following BSI references relate to the wor
3、k on this standard: Committee reference CIC/34 Draft for comment 87/53365 DC ISBN 0 580 16690 2 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Chemicals Standards Committee (CIC/-) to Technical Committee CIC/34, upon which the following
4、 bodies were represented: Chemical Industries Association Consumer Policy Committee of BSI Department of the Environment Department of Trade and Industry (Laboratory of the Government Chemist) London Regional Transport Ministry of Defence Royal Society of Chemistry Soap and Detergent Industry Associ
5、ation Society of Dyers and Colourists Society of Occupational Medicine Textile Institute Textile Research Council Amendments issued since publication Amd. No. Date of issue CommentsBS6829-4.6:1988 BSI 12-1999 i Contents Page Committees responsible Inside front cover National foreword ii 0 Introducti
6、on 1 1 Scope 1 2 Field of application 1 3 References 1 4 Definition 1 5 Principle 2 6 Reactions 2 7 Reagents 2 8 Apparatus 2 9 Sampling 2 10 Procedure 2 11 Expression of results 3 12 Test report 4 Publications referred to Inside back coverBS6829-4.6:1988 ii BSI 12-1999 National foreword This Section
7、 of BS6829 has been prepared under the direction of the Chemicals Standards Committee. It is identical with ISO 4326:1980 “Non-ionic surface active agents Polyethoxylated derivatives Determination of hydroxyl value Acetic anhydride method”, published by the International Organization for Standardiza
8、tion (ISO). Terminology and conventions. The text of the International Standard has been approved as suitable for publication as a British Standard without deviation. Some terminology and certain conventions are not identical with those used in British Standards; attention is drawn especially to the
9、 following. The comma has been used as a decimal marker. In British Standards it is current practice to use a full point on the baseline as the decimal marker. The symbol “l” has been used to denote litre (and in its submultiples). In British Standards it is current practice to use the symbol “L”. W
10、herever the words “International Standard” appear, referring to this standard, they should be read as “Section of BS6829”. There are no British Standards corresponding to ISO4317:1977 and ISO4327:1979. The Technical Committee has reviewed the provisions of these standards, and of ISO648, and has dec
11、ided that they are acceptable for use in conjunction with this standard. With reference to8.1, ISO/R 385 has been revised as ISO385-1:1984, ISO 385-2:1984 and ISO 385-3:1984, the relevant requirements of which are technically equivalent to those in BS846:1985 “Specification for burettes”. With refer
12、ence to8.4, a related British Standard to ISO648:1977 is BS1583:1986 “Specification for one-mark pipettes”. Additional information. With reference to clause5, water complying with grade 3of BS3978 “Specification for water for laboratory use” is suitable. With reference to7.3, the concentration of th
13、e sodium hydroxide standard volumetric solution, expressed as an amount-of-substance concentration, is c (NaOH)=5mol/L. In the definition of T in11.1, “normality” should be read as “amount-of-substance concentration (mol/L)”. Cross-references International Standard Corresponding British Standard ISO
14、 607:1980 BS 3762 Analysis of formulated detergents Part 1:1983 Methods of sample division (Identical) ISO 2211:1973 BS 5339:1976 Method of measurement of colour in Hazen units (platinum-cobalt scale) of liquid chemical products (Identical) ISO 4314:1977 BS 6829 Analysis of surface active agents (ra
15、w materials) Section 1.2:1988 Method for determination of free alkalinity or free acidity (Identical)BS6829-4.6:1988 BSI 12-1999 iii This Section describes a method of test only and should not be used or quoted as a specification defining limits of purity. Reference to this Section should indicate t
16、hat the method of test used is in accordance with BS6829-4.6. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity fro
17、m legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i to iv, pages1to 4, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment
18、table on the inside front cover.iv blankBS6829-4.6:1988 BSI 12-1999 1 0 Introduction The classical method for the determination of the hydroxyl value described in this International Standard requires, because of the toxic effects of pyridine and acetic anhydride, that all handling and the titration
19、be conducted under a well ventilated fume hood. However, for information, it is pointed out that Annex C of ISO4327 provides a procedure using a special apparatus which reduces the danger due to pyridine and acetic anhydride. 1 Scope This International Standard specifies a method for the determinati
20、on of the hydroxyl value of polyethoxylated condensates by esterification of the hydroxyl groups with acetic anhydride. 2 Field of application This method is applicable to the determination of the hydroxyl groups of polyethoxylated condensates of aliphatic and alicyclic compounds (in particular, of
21、ethylene oxide adducts of primary fatty alcohols, of alkylphenols and of fatty acids) and can be used for the determination of hydroxyl values from10 to1000. However, certain substances present in these materials may react with the acetic anhydride or with the standard volumetric sodium hydroxide so
22、lution used and consequently falsify the results. The possible interferences are detailed below: Primary and secondary amines, amides, tertiary alcohols, thiols and epoxides undergo side reactions which affect the accuracy of the method. Long-chain fatty acids and esters may interfere by forming anh
23、ydrides which are more stable than acetic anhydride and are not completely decomposed at the end of the method. Other free acids interfere by reacting with the standard volumetric sodium hydroxide solution; bases, including some tertiary amines, interfere by reacting with the acetic acid produced. I
24、n these cases a correction may be made for the acidity or alkalinity (see ISO4314). Epoxides are known to interfere, but the method can still be used if it is possible to eliminate them, by cold vacuum distillation, without affecting the hydroxyl value. By this means, free ethylene oxide, which inte
25、rferes at levels above0,5% (m/m), can be eliminated. The presence of water in the sample is revealed by reaction with the acetic anhydride, but the method may nevertheless be used without risk if the precautions described in the procedure are followed. This method is not applicable to propoxylated p
26、roducts. 3 References ISO 607, Surface active agents and detergents Methods of sample division. ISO 2211, Liquid chemical products Measurement of colour in Hazen units (platinum-cobalt scale). ISO 4314, Surface active agents Determination of free alkalinity or free acidity Titrimetric method. ISO 43
27、17, Surface active agents Determination of water content Karl Fischer method. ISO 4327, Non-ionic surface active agents Polyalkoxylated derivatives Determination of hydroxyl value Phthalic anhydride method. 4 Definition hydroxyl value I(OH) the number of milligrams of potassium hydroxide needed to n
28、eutralize the acetic acid required to acetylate the hydroxyl groups in1g of the material, or the number of milligrams of potassium hydroxide corresponding to the hydroxyl groups in1g of the material NOTEThe number of moles of potassium hydroxide corresponding to the hydroxyl value is equal to the nu
29、mber of hydroxyl groups present in1kg of the material.BS6829-4.6:1988 2 BSI 12-1999 5 Principle Esterification of the hydroxyl group by acetic anhydride in pyridine solution. Hydrolysis of the excess of acetic anhydride with water. Neutralization of the acidity which appears during the esterificatio
30、n, and of the acetic acid formed during the hydrolysis, by sodium hydroxide solution in the presence of phenolphthalein as indicator. Calculation of the hydroxyl value from the difference between the volumes of sodium hydroxide solution used for the titration of the blank and of the test solution. 6
31、 Reactions The reactions occurring are as follows: a) Esterification b) Hydrolysis of the excess acetic anhydride c) Neutralization of the acetic acid formed CH 3 COOH + NaOH F CH 3 COONa + H 2 O 7 Reagents During the analysis, use only reagents of recognized analytical grade, and only distilled wat
32、er or water of equivalent purity. 7.1 Pyridine, boiling temperature between114,5and 115,5 C. 7.2 Acetic anhydride solution in pyridine (acetylation reagent). Mix carefully1 volume of acetic anhydride, of minimum purity 97%, and10 volumes of the pyridine (7.1), avoiding overheating. Store in a dark g
33、lass bottle fitted with a ground glass stopper. Do not use this solution if its colour exceeds200Hazen units on the platinum-cobalt scale (determined by ISO2211). 7.3 Sodium hydroxide, 0,5N standard volumetric solution. 7.4 Phenolphthalein, 10g/lsolution in pyridine. Dissolve1g of phenolphthalein 3,
34、3-bis(4-hydroxyphenyl) phthalide in 100ml of the pyridine (7.1). 8 Apparatus Ordinary laboratory apparatus and: 8.1 Burette, capacity50ml, complying with the requirements of classA ofISO/R385. 8.2 Flat-bottomed flasks, capacity250ml, with conical ground glass sockets. 8.3 Air condensers, of effectiv
35、e length800mm, with conical ground glass joints. 8.4 One-mark pipettes, capacities15 and25ml, complying with the requirements of ISO648. 9 Sampling Laboratory samples of polyethoxylated surface active agents shall be prepared and stored according to the instructions given in ISO 607. 10 Procedure Al
36、l the necessary apparatus shall be absolutely clean and dry.BS6829-4.6:1988 BSI 12-1999 3 10.1 Test portion It is essential that the approximate water content of the test portion be known; if necessary, determine the water content of the sample by the method specified in ISO4317. Weigh, to the neare
37、st0,001g, into a dry and previously tared flask (8.2), a mass of the laboratory sample as specified in the table below: NOTEFor water contents between0,25 and1% (m/m), the mass (m 0 ), in grams, of the test portion shall not exceed: where V 0 is the volume, in millilitres, of the standard volumetric
38、 sodium hydroxide solution (7.3) used for the blank test (seeclause11); I(OH)is the estimated hydroxyl value, in milligrams of potassium hydroxide per gram; H 2 Ois the percentage, by mass, of water in the test sample. WARNING All the operations specified below shall be conducted under a well ventil
39、ated fume hood. 10.2 Determination 10.2.1 Acetylation Using a pipette, add, as carefully as possible, exactly15ml of the acetylation reagent (7.2) to the flask. Moisten the condenser joint with the pyridine (7.1) and attach the condenser (8.3) to the flask. Swirl to mix the contents. Heat the flask
40、for1h in a boiling water bath, the contents of the flask being below the level of the water. Swirl to mix after about10min in the bath. 10.2.2 Hydrolysis and titration of excess reagent Add2 ml of water, through the condenser, to the flask and swirl. Heat the flask in the boiling water bath for5min.
41、 Cool the flask and contents to below30 C. Add70ml of water through the condenser. Remove the condenser and rinse the ground glass joint with water. Using a pipette (8.4), add25ml of the standard volumetric sodium hydroxide solution (7.3). Add 0,2ml of the phenolphthalein indicator solution (7.4) an
42、d titrate with the standard volumetric sodium hydroxide solution (7.3) with vigorous stirring, until the solution remains pink for15s. 10.3 Blank test Carry out a blank test at the same time as the determination, using the same reagents, but replacing the test portion with2 or3 drops of water. 11 Ex
43、pression of results 11.1 Method of calculation The hydroxyl value, I(OH), corresponding to the test portion, is given by the formula where V 0 is the volume, in millilitres, of the standard volumetric sodium hydroxide solution (7.3) used for the blank test; V 1 is the volume, in millilitres, of the
44、standard volumetric sodium hydroxide solution (7.3) used for the determination; Hydroxyl value I(OH) Mass of test portion, m 0 g Lower than 40 8 to 10 40 to 200 Over 200 380 I OH () - 0,5 380 100 I OH () -BS6829-4.6:1988 4 BSI 12-1999 T is the exact normality of the standard volumetric sodium hydrox
45、ide solution (7.3); m 0 is the mass, in grams, of the test portion; C is the positive acid value, or the negative alkali value, of the material (see ISO4314); this value shall be ignored if it is0,3 or less. 11.2 Precision For compounds having hydroxyl values of40or more, comparative analyses have g
46、iven the following statistical results: 11.2.1 Repeatability The difference found between the results of two determinations carried out on the same sample simultaneously or in rapid succession by the same analyst using the same apparatus should not exceed1,1% of the mean value. 11.2.2 Reproducibilit
47、y The difference between the results obtained on the same sample in two different laboratories should not exceed2,8% of the mean value. 12 Test report The test report shall include the following particulars: a) all information necessary for the complete identification of the sample; b) the reference
48、 of the method used (reference to this International Standard); c) the results and the method of expression used; d) the test conditions; e) any operational details not specified in this International Standard, or regarded as optional, as well as any incidents likely to have affected the results.BS6
49、829-4.6:1988 BSI 12-1999 Publications referred to See national foreword.BS 6829-4.6: 1988 ISO4326:1980 BSI 389 Chiswick High Road London W4 4AL BSIBritishStandardsInstitution BSI is the independent national body responsible for preparing BritishStandards. It presents the UK view on standards in Europe and at the international level. It is incorporated by Royal Charter. Revisions BritishStandards are updated by amendment or revision. Users of BritishStandards should make sure th
