1、BRITISH STANDARD BS 6392-8: 1983 Incorporating Amendment No.1 Testing of ethanol for industrial use Part 8: Method for determination of esters content NOTEIt is recommended that this Part be read in conjunction with the information given in the “General introduction” published separately as BS 6392-
2、0. UDC 661.722:543.851.1BS6392-8:1983 This British Standard, having been prepared under the directionof the Chemicals Standards Committee, was published under the authority ofthe Board of BSI and comes intoeffect on 31August1983 BSI 12-1999 The Committees responsible for this British Standard are sh
3、own inPart0. The following BSI references relate to the work on this standard: Committee reference CIC/4 Draft for comment 80/51209 DC ISBN 0 580 13374 5 Foreword This Part of BS6392 is technically equivalent to ISO1388 “Ethanol for industrial use Methods of test” Part9 “Determination of esters cont
4、ent Titrimetric method after saponification”, published in 1981 by the International Organization for Standardization (ISO). For ease of production, the text ofISO 1388-9:1981, with the omission of the Annex, has been used for this British Standard. Some terminology and certain conventions are not i
5、dentical 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 marker. This standard describes a method only and should not be u
6、sed as a specification defining limits of purity. Reference to the standard should indicate that the method of test used is in accordance with BS6392-8. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their cor
7、rect 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, pages i and ii, pages 1 and 2, an inside back cover and a back cover. This standard has been updated (see cop
8、yright 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 4944 March 1986 Indicated by a sideline in the marginBS6392-8:1983 BSI 12-1999 i Contents Page Foreword
9、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 2 Publication referred to Inside back coverii blankBS6392-8:1983 BSI 12-1999 1 1 Scope and field of application This Part of BS6392 describes a titrimetric method, aft
10、er saponification, for the determination of the esters content of ethanol for industrial use. The method is applicable to products having esters contents, expressed as ethyl acetate, in the range0,005to0,15% (m/m). NOTEThe title of the publication referred to in this standard is given on the inside
11、back cover. 2 Principle Saponification of the esters present in a test portion by boiling with excess standard volumetric sodium hydroxide solution; determination of the residual sodium hydroxide, and hence the amount used for saponification, by titration with standard volumetric hydrochloric acid s
12、olution in the presence of phenolphthalein as indicator. 3 Reagents During the analysis, unless otherwise specified, use only reagents of recognized analytical grade, and distilled water or water of equivalent purity, carbon dioxide-free, recently prepared. 3.1 Water, carbon dioxide-free. Boil disti
13、lled water and allow it to cool in a flask fitted with a stopper carrying a soda-lime guard-tube. 3.2 Sodium hydroxide, standard volumetric solution, c(NaOH) = 0,1 mol/l. 3.3 Hydrochloric acid, standard volumetric solution, c(HCl) = 0,1 mol/l. 3.4 Phenolphthalein, 5g/l ethanolic solution. Dissolve 0
14、,5g of phenolphthalein in 100ml of95%(V/V) ethanol and add the sodium hydroxide solution (3.2) until a pale pink coloration is obtained. 4 Apparatus Ordinary laboratory apparatus, and 4.1 Conical flask, of borosilicate glass, of capacity500ml, and having a ground neck. 4.2 Reflux condenser, water-co
15、oled having a ground glass joint to fit the flask (4.1). NOTEClean the apparatus as follows. Place a mixture of ethanol and sodium hydroxide solution (the proportions are not critical) in the flask(4.1), attach the reflux condenser (4.2) and heat the mixture gently under reflux for several minutes.
16、Discard the mixture and clean the flask and the condenser, first by washing with tap water and then by rinsing several times with distilled water. 5 Procedure 5.1 Test portion Take50,0ml of the laboratory sample. If the esters content, expressed as ethyl acetate, is expected tobeless than or equal t
17、o0,01% (m/m), take100 0,1ml. 5.2 Determination Place the test portion (5.1) in the flask (4.1), and add20ml of water and0,5ml of the phenolphthalein solution (3.4). Neutralize the solution usually with the sodium hydroxide solution (3.2) until a pink coloration, persisting for about15s, appears. Add
18、10,0ml of the sodium hydroxide solution (3.2). Fit the condenser (4.2) and heat for1h on a boiling water bath. Fit a soda-lime guard-tube to the top of the condenser and cool the flask in water. Remove the soda-lime guard-tube and wash the inside of the condenser with two10ml portions of water, coll
19、ecting the washings in the flask. Disconnect the flask and wash the ground neck with10ml of water, again collecting the washings in the flask. Carefully titrate the solution with the standard volumetric hydrochloric acid solution (3.3) until the pink colour just disappears. 5.3 Blank test Carry out
20、a blank test on the neutral solution from the determination (5.2), using the procedure specified in5.2, paragraphs2 and3.BS6392-8:1983 2 BSI 12-1999 6 Expression of results The esters content, expressed as a percentage by mass of ethyl acetate (CH 3 COOC 2 H 5 ), is given by the formula where V 0 is
21、 the volume, in millilitres, of the test portion (5.1); V 1 is the volume, in millilitres, of the hydrochloric acid solution (3.3) used for the determination; V 2 is the volume, in millilitres, of the hydrochloric acid solution (3.3) used for the blank test; is the density, in grams per millilitre,
22、of the sample at20 C (see BS4522); 0,008 8is the mass, in grams, of esters, expressed as ethylacetate, corresponding to1mlof sodium hydroxide solution, c(NaOH) = 0,100 mol/l. NOTEIf the concentrations of the standard volumetric solutions used are not exactly as specified in the list of reagents, an
23、appropriate correction should be made.BS6392-8:1983 BSI 12-1999 Publication referred to BS 4522, Method for the determination of density of liquids at20 C. BS 6392-8: 1983 BSI 389 Chiswick High Road London W4 4AL BSIBritishStandardsInstitution BSI is the independent national body responsible for pre
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