1、BRITISH STANDARD BS 1715-2.8: 1989 ISO1066:1975 Analysis of soaps Part2: Quantitative test methods Section2.8 Method for determination of glycerol content ISO title: Analysis of soapsDetermination of glycerol contentTitrimetric method UDC 661.18:543BS1715-2.8:1989 This British Standard, having been
2、prepared under the directionof the Chemicals Standards Policy Committee, waspublished under the authorityof the Board of BSIand comes intoeffect on 31July1989 BSI 09-1999 The following BSI references relate to the work on this standard: Committee reference CIC/34 Draft for comment88/53274DC ISBN 0 5
3、80 17324 0 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Chemicals Standards Policy Committee (CIC/-) to Technical Committee CIC/34, upon which the following bodies were represented: Chemical Industries Association Consumer Policy Comm
4、ittee of BSI Department of the Environment Department of Trade and Industry (Laboratory of the Government Chemist) Ministry of Defence Royal Society of Chemistry Soap and Detergent Industry Association Society of Dyers and Colourists Amendments issued since publication Amd. No. Date of issue Comment
5、sBS1715-2.8:1989 BSI 09-1999 i Contents Page Committees responsible Inside front cover National foreword ii 1 Scope 1 2 Field of application 1 3 References 1 4 Principle 1 5 Reagents 1 6 Apparatus 1 7 Sampling 1 8 Procedure 1 9 Expression of results 2 10 Test report 3 Publications referred to Inside
6、 back coverBS1715-2.8:1989 ii BSI 09-1999 National foreword This Section of BS1715 has been prepared under the direction of the Chemicals Standards Policy Committee. It is identical with ISO1066:1975 “Analysis of soaps Determination of glycerol content Titrimetric method” published by the Internatio
7、nal Organization for Standardization (ISO). This method supersedes the methods “Determination of glycerol” given in BS1715:1963, which are deleted by amendment. Terminology and conventions. The text of the International Standard has been approved as suitable for publication as a British Standard wit
8、hout deviation. Some terminology and certain conventions are not identical with those used in British Standards; attention is drawn especially to the 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
9、 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”. Wherever the words “International Standard” appear, referring to this standard, they should be read as “Section of BS1715”. With reference to6.4 and6.6,
10、 British Standards related to ISO/R385 (now revised as ISO385-1:1984, ISO385-2:1984 and ISO385-3:1984) and ISO/R648 (now revised as ISO648:1977) are BS846:1985 “Specification for burettes” and BS1583:1986 “Specification for one-mark pipettes”, respectively. There is no British Standard corresponding
11、 to ISO2272 but, as this reference is supplied only for information, the validity of this British Standard is not affected. The International Standard for sampling of soaps (see clause3 and clause7) is not yet published. Relevant information is included in BS1715 “Analysis of soaps”, Part1:1989 “Gen
12、eral introduction, sampling, and test for presence of synthetic anionic-active surface active agents”. Additional information. With reference to clause5, water complying with grade3 of BS3978 “Specification for water for laboratory use” is suitable. With reference to5.4, the sulphuric acid solution,
13、 expressed as an amount-of-substance concentration, is c(H 2 SO 4 )=3.5mol/L. With referenceto5.5, 5.6 and5.7, the sodium hydroxide solutions, expressed asamount-of-substance concentrations, are c(NaOH)=2mol/L, c(NaOH)=0.05mol/L and c(NaOH)=0.125mol/L respectively. With reference to5.8, the sulphuri
14、c acid solution, expressed as an amount-of-substance concentration, is c(H 2 SO 4 )=0.05mol/L. Also, in the UK it is considered that sodium periodate having a minimum purity of99.0%(m/m) is adequate. In the definition of T in9.1, “normality” should be read as “amount-of-substance concentration (mol/
15、L)”. 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 that the method of test used is in accordance with BS1715-2.8. Cross references International Standard Corresponding British Sta
16、ndard ISO1042:1983 (replacing ISO/R1042) BS1792:1982 Specification for one-mark volumetric flasks (Identical) ISO1773:1976 (replacing ISO/R1773) BS 2734:1984 Specification for boiling flasks (narrow-necked), conical, flat bottom and round bottom (Identical)BS1715-2.8:1989 BSI 09-1999 iii A British S
17、tandard 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 from legal obligations. Summary of pages This document comprises a front cov
18、er, an inside front cover, pagesi toiv, pages1 to4, 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 table on the inside front cover.iv blankBS1715-2.8:1989 BSI 09-1999 1 1 Sco
19、pe This International Standard specifies a titrimetric method for the determination of the glycerol content of commercial soaps, excluding compounded products. 2 Field of application This method is applicable to soaps with glycerol contents equal to or greater than0,5%(m/m) 1) .This method is not ap
20、plicable in the presence of organic compounds containing more than two hydroxyl groups on adjacent carbon atoms. 3 References ISO 2272, Surface active agents Analysis of soaps Determination of low contents of free glycerol Spectrophotometric method. ISO., Soaps Sampling 2) . 4 Principle Decompositio
21、n of the soap with sulphuric acid, and extraction of the fatty acids with light petroleum. Oxidation of the glycerol by periodic acid to formic acid and formaldehyde, and titration of the formic acid produced, using a pH meter. 5 Reagents The reagents used shall be of recognized analytical purity an
22、d shall have the following properties. 5.1 Distilled water, from which carbon dioxide has been removed by boiling for15min and cooling in a vessel protected from atmospheric carbon dioxide. 5.2 Light petroleum, boiling range between40 and60 C. 5.3 1,2-Ethanediol,50%(V/V) aqueous solution. 5.4 Sulphu
23、ric acid, approximately7N solution. 5.5 Sodium hydroxide,2N solution. 5.6 Sodium hydroxide,0,05N solution. 5.7 Sodium hydroxide,0,125N standard volumetric solution, carbonate free. 5.8 Sodium periodate solution, prepared as follows: Dissolve, at room temperature,60 0,5g of sodium periodate (NaIO 4 )
24、, minimum purity99,8%, in distilled water containing120ml of approximately0,1N sulphuric acid solution. Dilute to1l. If the solution is turbid, filter it through a glass filter of porosity16 to40m, and place it in a brown glass bottle, which should be kept stoppered and in the dark. 6 Apparatus Ordi
25、nary laboratory apparatus, and in particular: 6.1 Beakers, capacity250 and600ml. 6.2 Separating funnels, capacity250ml. 6.3 One-mark volumetric flasks, capacity250ml, complying with the requirements of class A of ISO/R1042. 6.4 Burette, capacity50ml, complying with the requirements of class A of ISO
26、/R385. The drainage time shall be not less than90s for50ml. 6.5 Flat-bottomed or round-bottomed flask, capacity500ml, complying with the requirements of ISO/R1773. 6.6 Pipette, capacity50ml, complying with the requirements of class A of ISO/R648, with a stated drainage time in order to ensure delive
27、ry of a constant volume. 6.7 Variable-speed stirrer (preferably magnetic) with glass paddles. 6.8 pH meter fitted with a glass electrode. The pH meter shall be calibrated by means of two standard buffer solutions: potassium hydrogen phthalate C 6 H 4 (COOK) (COOH),0,05M solution, pH4,00 at20 C; diso
28、dium tetraborate decahydrate Na 2 B 4 O 7 10H 2 O,0,01M solution, pH9,22 at20 C. 7 Sampling Laboratory samples shall be prepared and stored according to the procedures specified in ISO. 8 Procedure 8.1 Test portion Weigh, to the nearest0,01g, about10g of the laboratory sample into a250ml beaker(6.1)
29、. 8.2 Blank test Carry out a blank test under the same conditions as the test itself, without adding soap, with100ml of the water(5.1). Adjust the pH to8,1 0,1, as specified in8.5, but carry out the final titration to pH6,5 0,1. 1) For a glycerol content of less than0,5%(m/m), the method specified i
30、n ISO2272 should be used. 2) In preparation.BS1715-2.8:1989 2 BSI 09-1999 8.3 Decomposition of soap and removal of fatty acids Dissolve the test portion in100ml of the hot water(5.1). When dissolution is complete, transfer quantitatively into a separating funnel(6.2), rinsing the beaker with a littl
31、e of the water. Add about10ml of the sulphuric acid solution(5.4), shake, and allow to cool. After cooling, add about100ml of the light petroleum(5.2), shake, and allow the layers to separate. Draw off the aqueous layer into a second separating funnel, extract it again with about50ml of the light pe
32、troleum, shake and allow to settle. Draw off the aqueous layer into a third separating funnel, extract it a third time with50ml of the light petroleum, shake, and allow to settle. Draw off the aqueous layer into a250ml one-mark volumetric flask(6.3). Combine the ethereal extracts and wash them twice
33、, each time with about50ml of the water. Combine the washings with the acid solution in the250ml one-mark volumetric flask and dilute to the mark with the water(5.1). 8.4 Aliquot portion to be taken for determination The best conditions for the determination of glycerol using50ml of the sodium perio
34、date solution(5.8) are obtained when the aliquot portion on which the test is to be carried out contains between0,3 and0,5g of glycerol. The volume of the aliquot portion be taken for the determination is shown in the following table: If the amount taken for determination is less than recommended, t
35、he results obtained will be too high and lack precision. If the amount taken for determination is greater than that recommended, the results obtained will be low. If the result obtained does not fall within the expected range, as set out in the table, repeat the determination on another aliquot port
36、ion. For glycerol contents less than2,5%(m/m), reduce the volume of the sodium periodate solution to25ml. 8.5 Determination Introduce the aliquot portion to be tested into the500ml flask(6.5). Boil 3)the solution gently for5min to expel any carbon dioxide and light petroleum that may be present. All
37、ow to cool with a carbon dioxide trap in the neck of the flask. Transfer the aliquot portion quantitatively into a600ml beaker(6.1). If the volume of liquid in the beaker is too small to permit adequate stirring, add a sufficient quantity of the water(5.1). If the pH of the solution is less than3, i
38、nsert the glass electrode(6.8) and start the stirrer(6.7). Add, drop by drop, the2N sodium hydroxide solution(5.5) until the pH is3, then add, drop by drop, the0,05N sodium hydroxide solution(5.6) until the pH is8,1 0,1. Pipette exactly50ml (or25ml, as appropriate) of the sodium periodate solution(5
39、.8) into the solution. Mix the solution thoroughly with the aid of the stirrer, cover the flask with a watch-glass and leave for30min in the dark at room temperature (below35 C). When30min have elapsed, add10ml of the1,2-ethanediol solution(5.3) and mix well. Cover again with the watch-glass and lea
40、ve for20min in the dark at room temperature (below35 C). Then titrate, using the pH meter(6.8), with the0,125N sodium hydroxide solution(5.7) until a pH of8,1 0,1 is reached. Note the volume used, to the nearest0,05ml. 9 Expression of results 9.1 Method of calculation The glycerol content, is given,
41、 as a percentage by mass, by the formula Expected glycerol content in laboratory sample Volume of acid solution to be taken for determination (from the250ml flask) % (m/m) ml 16to20 12to16 8to12 6to8 4to6 less than4 50 75 100 150 200 250 3) A naked flame must not be used for heating because of the r
42、isk of combustion of flammable gases. where V 0 is the volume, in millilitres, of the aliquot portion taken for the determination; V 1 is the volume, in millilitres, of the0,125N sodium hydroxide solution(5.7) used for the determination; V 2 is the volume, in millilitres, of the0,125N sodium hydroxi
43、de solution(5.7) used in the blank test; T is the exact normality of the0,125N sodium hydroxide solution(5.7); m is the mass, in grams, of the test portion. 0092 1 , V 1 V 2 ()T 250 V 0 - 100 m - = 2 302T V 1 V 2 () V 0 m -BS1715-2.8:1989 BSI 09-1999 3 9.2 Repeatability The maximum difference betwee
44、n the results of two determinations carried out simultaneously or in rapid succession by the same analyst, in tests carried out by23 laboratories on a sample containing2,7%(m/m) of glycerol, was0,04%. 9.3 Reproducibility The maximum difference between the results of two tests in different laboratori
45、es on the sample containing2,7%(m/m) of glycerol, in tests carried out by23 laboratories, was0,2%. 10 Test report The test report shall include the following particulars: a) all information necessary for the complete identification of the sample; b) the method used; c) the results obtained; d) the t
46、est conditions; e) any operational details not specified in this International Standard or optional, as well as all incidents likely to have influenced the results.4 blankBS1715-2.8:1989 BSI 09-1999 Publications referred to See national foreword.BS 1715-2.8: 1989 ISO1066:1975 BSI 389 Chiswick High R
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