1、BRITISH STANDARD BS 6392-7: 1983 Incorporating Amendment No.1 Testing of ethanol for industrial use Part 7: Method for determination ofmethanol content 0.10% (V/V) to1.50% (V/V) (visual colorimetric method) NOTEIt is recommended that this Part be read in conjunction with the information given in the
2、 “General introduction” published separately asBS6392-0. UDC 661.722:543.432.062:547.261BS6392-7:1983 This British Standard, having been prepared under the directionof the Chemicals Standards Committee, was published under the authority ofthe Board of BSI and comes into effect on 31August1983 BSI 12
3、-1999 The Committees responsible for this British Standard are shown inPart0. The following BSI references relate to the work on this standard: Committee referenceCIC/4 Draft for comment80/51209DC ISBN 0 580 13373 7 Foreword This Part of BS6392 is technically equivalent to ISO1388, “Ethanol for indu
4、strial use Methods of test” Part8 “Determination of methanol content methanol contents between0,10 and1,50% (V/V) Visual colorimetric method”, published in1981 by the International Organization for Standardization (ISO). For ease of production, the text of ISO1388-8:1981, with the omission of the An
5、nex, has been used for this British Standard. 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
6、on the baseline as the decimal marker. This standard describes a method only and should not be used as a specification defining limits of purity. Reference to the standard should indicate that the method of test used is in accordance withBS6392-7. A British Standard does not purport to include all t
7、he 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 cover, an inside front cover, pagesi andii,
8、pages1 and2 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. Amendments issued since publication Amd. No. Date of issue Comments 4943 March1986 Indicated by a sidel
9、ine in the marginBS6392-7:1983 BSI 12-1999 i Contents Page Foreword Inside front cover 1 Scope and field of application 1 2 Principle 1 3 Reagents 1 4 Apparatus 1 5 Procedure 1 6 Expression of results 2ii blankBS6392-7:1983 BSI 12-1999 1 1 Scope and field of application This Part of BS6392 describes
10、 a visual colorimetric method for the determination of the methanol content of ethanol for industrial use. The method is applicable to products having methanol contents between0,10 and1,50% (V/V). 2 Principle Conversion of the methanol present in a test portion to formaldehyde by oxidation with a so
11、lution of potassium permanganate in phosphoric acid. Reaction of the formaldehyde formed with Schiff reagent. Visual comparison of the colour obtained with the colours of standard colorimetric solutions containing known quantities of formaldehyde. 3 Reagents During the analysis, use only reagents of
12、 recognized analytical grade, and distilled water or water of equivalent purity. 3.1 Potassium permanganate, 30g/l solution in phosphoric acid. Dissolve3g of potassium permanganate in a little water, add15,5ml of orthophosphoric acid solution, 1,69g/ml, dilute to100ml with water and mix. 3.2 Oxalic
13、acid, 50g/l solution in sulphuric acid. WARNING Harmful in contact with skin and if swallowed. Avoid contact with skin and eyes. Dissolve5g of oxalic acid in100ml of50% (V/V) sulphuric acid solution, prepared by diluting sulphuric acid, approximately1,84g/ml, about98% (m/m) solution,1+1 (V/V) with w
14、ater. 3.3 Schiff reagent WARNING Basic fuchsin is carcinogenic. Avoid skin contact with basic fuchsin and its solutions and inhalation of its dust. 3.3.1 Preparation Place 1500ml of water in a3000ml conical flask, add4,500 0,005g of p-rosaniline hydrochloride (basic fuchsin) and swirl to dissolve. A
15、dd9,6 0,05g of disodium disulphite sodium metabisulphite (Na 2 S 2 O 5 ), mix, and allow to stand for5 to10min. Add40ml of approximately295g/l sulphuric acid solution, mix thoroughly, stopper the flask and allow to stand for about12h. Decolorize the solution, if necessary, by treatment with activate
16、d carbon. 3.3.2 Determination and adjustment of free sulphur dioxide content Transfer10ml of the colourless reagent(3.3.1) to a250ml conical flask. Add20ml of water and5ml of freshly prepared starch solution and titrate the solution with standard volumetric iodine solution, c(1/2I 2 )=0,1mol/l, unti
17、l the characteristic dark blue colour is just obtained. NOTE1ml of iodine solution, c(1/2I 2 )=0,1mol/l, corresponds to0,0032g ofSO 2 . If the free sulphur dioxide content does not fall within the optimum range (0,18to0,31g per100ml of reagent), adjust as appropriate, increasing the level by adding
18、a calculated quantity of disodium disulphite or decreasing it by bubbling air through the reagent solution. 3.4 Methanol, standard solution corresponding to0,2% (V/V) of methanol. Place2,00ml of absolute methanol in a1000ml one-mark volumetric flask, add a quantity of methanol-free ethanol correspon
19、ding to98ml of anhydrous ethanol, dilute to the mark with water and mix. 1ml of this standard solution contains0,002ml of absolute methanol. NOTEIndustrial methylated spirits95% (V/V) is not suitable for use in place of the methanol-free ethanol used in the preparation of this reagent. 4 Apparatus O
20、rdinary laboratory apparatus, and 4.1 Colorimetric tubes, of capacity approximately20ml, fitted with ground glass stoppers. 4.2 Water bath, capable of being controlled at20 1 C. 5 Procedure 5.1 Test portion and preparation of the test solution Take as the test portion a volume (V 1 ) of the laborato
21、ry sample, corresponding to10,0ml of anhydrous ethanol, and place it in a100ml one-mark volumetric flask. Prepare the test portion by diluting to the mark with water and mixing. Transfer5,0ml of this solution to one of the colorimetric tubes(4.1). 5.2 Preparation of standard solutions, used for the
22、preparation of standard colorimetric solutions NOTEIndustrial methylated spirits95%(V/V) is not suitable for use in place of the methanol-free ethanol used in the preparation of the standard solutions.BS6392-7:1983 2 BSI 12-1999 Into a series of five100ml one-mark volumetric flasks, place the volume
23、s of the standard methanol solution(3.4) indicated in the following table, dilute to the mark with10%(V/V) solution of methanol-free ethanol in water and mix. 5.3 Preparation of standard colorimetric solutions Into a series of five of the colorimetric tubes(4.1), place5,0ml of each of the standard m
24、ethanol solutions(5.2). Treat the contents of each of the tubes, including the tube containing5,0ml of the test solution(5.1), as follows. Add 2,0ml of the potassium permanganate solution(3.1), mix and allow to stand for10min in the water bath(4.2), controlled at20 1 C. Then add2,0ml of the oxalic a
25、cid solution(3.2) and mix. At this stage, the solutions should be colourless and free from precipitated manganese. Add5ml of the Schiff reagent(3.3), mix and allow to stand for1h. 5.4 Determination Examine the tubes vertically and note the standard colorimetric solution having a colour matching most
26、 closely that developed in the test solution. NOTEIn cases of doubt, choose the standard colorimetric solution having the lower concentration. 6 Expression of results The methanol content, expressed as methanol as a percentage by volume, is given by the formula where V 0 is the volume, in millilitre
27、s, of methanol in the dilute standard solution(see5.2) from which was prepared the standard colorimetric solution having a colour matching most closely that developed in the test solution; V 1 is the volume, in millilitres, of the test portion. Standard methanol solution(3.4) Corresponding volume of
28、 methanol ml ml 5,00 10,0 25,0 50,0 75,0 0,010 0,020 0,050 0,100 0,150 V 0 100 V 1 -blankBS 6392-7: 1983 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 Eu
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