1、BRITISH STANDARD BS2068:1970 Incorporating Amendment No.1 Specification for Acetic anhydrideBS2068:1970 This BritishStandard, having been approved by the ChemicalsIndustry Standards Committee, was published underthe authority of the Executive Board on 20January1970 BSI 12-1999 First published Decemb
2、er1953 First revision January1970 The following BSI references relate to the work on this standard: Committee referencesCIC/4 andCIC/4/5 Draft for comment68/5637 ISBN 580 05784 4 Co-operating organizations The Chemicals Industry Standards Committee, under whose supervision this BritishStandard was p
3、repared, consists of representatives from the following Government departments and industrial organizations: Board of Trade British Steel Industry Chemical Industries Association* Department of Health and Social Security Fertilizer Manufacturers Association Gas Council Institution of Gas Engineers M
4、inistry of Agriculture, Fisheries and Food Ministry of Technology Laboratory of the Government Chemist National Sulphuric Acid Association Royal Institute of Public Health see the back cover of this standard. A British Standard does not purport to include all the necessary provisions of a contract.
5、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, pages1 to6 and a back cover. This stand
6、ard 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. 1) ISO/R754, “Acetic anhydride for industrial use. Methods of test.”BS2068:1970 BSI 12-1999 1 1 Scope This BritishStandard specifies requiremen
7、ts for acetic anhydride suitable for industrial purposes. 2 Description BritishStandard acetic anhydride shall be clear and free from matter in suspension, and shall consist essentially of acetic anhydride, (CH 3 CO) 2 O. 3 Colour The colour of the material shall not exceed15 Hazen units when measur
8、ed by the method described inAppendix A or by a suitable instrumental method. 4 Distillation range When the material is distilled by the method described inAppendix B, the initial boiling point at1013mbar 2) (760mmHg) pressure shall not be below138.0 C and the dry point at1013mbar(760mmHg) pressure
9、shall not be above141.5 C. 5 Ash The material shall not leave more than100 parts per million by mass of ash when tested by the method described inAppendix C. 6 Inorganic chlorides The material shall not contain more than50 parts per million by mass of inorganic chlorides, expressed as Cl and determi
10、ned by the method described inAppendix D. 7 Inorganic sulphates The material shall not contain more than50 parts per million by mass of inorganic sulphates, expressed as SO 4and determined by the method described inAppendix E. 8 Anhydride content The material shall show an anhydride content of not l
11、ess than98.0% by mass, calculated as acetic anhydride, (CH 3 CO) 2 O, and determined by the method described inAppendix F. 9 Sample A representative sample of the material measuring at least1 litre shall be taken from the bulk for the purpose of examination in accordance with this standard. The samp
12、le shall be placed in a clean, dry and airtight glass-stoppered glass bottle of such a size that it is nearly filled by the sample. 2) 1mbar=100N/m 2 =0.750mmHg.BS2068:1970 2 BSI 12-1999 NOTEBecause of the toxic nature of acetic anhydride the tests described in the appendices should always be carrie
13、d out under conditions of good ventilation. Appendix A Limit test for colour A.1 Apparatus 1) Two matched Nessler cylinders 3) , 100ml capacity. 2) One-mark volumetric flask 4) , 500ml capacity. 3) One-mark volumetric flask 4) , 250ml capacity. A.2 Reagents The reagents used shall be of a recognized
14、 analytical reagent quality. Water complying with BS3978 5)shall be used throughout. 1) Cobaltous chloride, hexahydrate. 2) Hydrochloric acid, concentrated, 36,5% (m/m)(11N). 3) Chloroplatinic acid reagent. Dissolve250mg of platinum in a small quantity of aqua regia contained in a glass or porcelain
15、 basin by heating on a water bath. When the metal has dissolved evaporate the solution to dryness. Add1ml of the hydrochloric acid and again evaporate to dryness. Repeat this operation twice more. A.3 Preparation of colour standard Dissolve0.50g of the cobaltous chloride hexahydrate and the whole of
16、 the chloroplatinic acid (prepared as described above) in50ml of the hydrochloric acid. Warm, if necessary, to obtain a clear solution and after cooling, pour into the500ml volumetric flask. Dilute with water to the mark. Pipette7.5ml of this solution into the250ml volumetric flask. Dilute with wate
17、r to the mark. This diluted solution has a colour of15 Hazen units and should always be freshly prepared. A.4 Procedure Fill one of the Nessler cylinders to the mark with the sample, and the other with the colour standard. Using a white background compare the colours. Appendix B Method for the deter
18、mination of distillation range B.1 Apparatus The apparatus required is described in BS658 6)and comprises: 1) Distillation flask, of130ml distillation capacity, complying with the requirements of BS658 6) . 2) Thermometer, No.F150C/100 complying with the requirements of BS593 7) . 3) Condenser, Type
19、1, complying with the requirements of BS658 8) . 4) Draught screen, type C, and non-asbestos heat-resistant flask support sheet with50mm diameter central hole, complying with the requirements of BS658 6) . B.2 Procedure Assemble the apparatus as described in BS658 6) . Measure100ml of the sample int
20、o the distillation flask from a graduated measuring cylinder and add a few small anti-bumping granules. Place the flask, thermometer and a suitable receiver in position and ensure that the condenser has a steady supply of water. Adjust the rate of heating so that the first drop of distillate falls f
21、rom the end of the condenser in12minutes to17 minutes. Read the temperature at the instant the first drop falls from the end of the condenser and record as the observed initial boiling point. Further adjust the rate of heating so that the distillate is collected at the rate of3ml to4ml per minute. R
22、ead the temperature indicated at the instant the last drop of liquid evaporates from the lowest point in the distillation flask and record as the observed dry point. Disregard any liquid on the side of the flask. 3) BS612, “Nessler cylinders”. 4) BS1792, “One-mark volumetric flasks”. 5) BS3978, “Wat
23、er for laboratory use”. 6) BS658, “Apparatus for the determination of distillation range”. 7) BS593, “Laboratory thermometers”. 8) BS658, “Apparatus for the determination of distillation range”.BS2068:1970 BSI 12-1999 3 B.3 Corrections to be applied to the observed temperatures 1) If the thermometer
24、 gives incorrect readings at the observed initial boiling point or observed dry point, correct the readings by subtracting the amount of error if the thermometer is reading high, or adding the amount of error if the thermometer is reading low. 2) Read the barometer and correct the reading as describ
25、ed in BS4591 9) . 3) When the corrected barometric pressure deviates from1013mbar 10)(760mmHg), apply further corrections to the observed temperatures by subtracting0.037 C for every millibar above1013mbar(0.050 C per millimetre of mercury) or adding0.037 C for every millibar below1013mbar(0.050 C p
26、er millimetre of mercury). NOTEThese last corrections are valid only for pressures above930mbar(700mmHg). Appendix C Method for the determination of ash C.1 Outline of method The mass of residue, if any, is determined after evaporation of the sample to dryness and ignition until no carbonaceous matt
27、er remains. C.2 Procedure Evaporate to dryness in small portions100g of the sample in a weighed platinum or silica dish of capacity50ml on a steam bath or electric hotplate in a fume cupboard, and gently ignite the residue until no carbonaceous matter remains. Cool the dish and contents to atmospher
28、ic temperature in a desiccator containing anhydrous calcium chloride, and weigh to the nearest0.2mg. C.3 Calculation Ash, parts per million by mass= Appendix D Limit test for inorganic chlorides D.1 Outline of method The turbidity produced when silver nitrate is added to a solution prepared from the
29、 sample in presence of nitric acid is compared with that similarly obtained from a standard chloride solution. D.2 Apparatus 1) Nessler cylinders, 100ml capacity, complying with BS612 11) . 2) One-mark volumetric flask 12) , 250ml capacity. D.3 Reagents The reagents used shall be of a recognized ana
30、lytical reagent quality. Water complying with BS3978 13)shall be used throughout. 1) Nitric acid, approximately5N solution. 2) Standard chloride solution, 1ml=0.0001gCl. Dilute28.2ml of0.1N hydrochloric acid solution to1000ml with water. 3) Silver nitrate, 50g/l solution. D.4 Procedure D.4.1 Weigh2g
31、 of the sample, and allow it to dissolve in95ml of water, cooling if necessary. 9) BS4591, “Method for determination of distillation characteristics of organic liquids (other than petroleum products)”. 10) 1mbar=100N/m 2 =0.750mmHg. where M 1 = mass, in grammes, of the residue and M 2 = mass, in gra
32、mmes, of sample taken. 11) BS612, “Nessler cylinders”. 12) BS1792, “One-mark volumetric flasks”. 13) BS3978, “Water for laboratory use”. 10 6 M 1 M 2 -BS2068:1970 4 BSI 12-1999 D.4.2 If the solution is not clear, pass it through a chloride-free filter paper. This should remove turbidity due to alumi
33、nium. D.4.3 Transfer the solution prepared from the test sample (seeD.4.1) to a100ml Nessler cylinder, add2ml of the nitric acid solution, dilute to the mark with water and mix. D.4.4 To prepare the chloride solution of known concentration add to a100ml Nessler cylinder1.0ml of the standard chloride
34、 solution, dilute to about50ml with water, add2ml of the nitric acid solution, dilute to the mark with water and mix. This diluted solution corresponds to a chloride content, expressed as Cl, of50 parts per million in the original material. D.4.5 Add to each Nessler cylinder1ml of the silver nitrate
35、 solution and mix. Allow the cylinders to stand in the dark for5 minutes then compare the turbidities produced. Appendix E Limit test for inorganic sulphates E.1 Outline of method The turbidity produced when barium chloride is added to a solution prepared from the sample in presence of hydrochloric
36、acid is compared with that similarly obtained from a standard sulphate solution. E.2 Apparatus 1) Nessler cylinders, 100ml capacity, complying with BS612 14) . 2) One-mark volumetric flask 15) , 100ml capacity. E.3 Reagents The reagents used shall be of a recognized analytical reagent quality. Water
37、 complying with BS3978 16)shall be used throughout. 1) Sodium carbonate, approximately N solution. 2) Hydrochloric acid, approximately N solution. 3) Barium chloride, BaCl 2 .2H 2 O, 100g/l solution. 4) Standard sulphate solution, 1ml=0.0001g SO 4 . Dilute20.8ml of0.1N sulphuric acid solution to1000
38、ml. E.4 Procedure E.4.1 Weigh8g of the sample into an evaporating basin and allow it to dissolve in about100ml of water, cooling if necessary; add0.2ml of the sodium carbonate solution and evaporate to dryness on a boiling water bath. Dissolve the residue in95ml of water containing1ml of the hydroch
39、loric acid solution. E.4.2 If the solution is not clear, pass it through a sulphate-free filter paper. This should remove turbidity due to aluminium. E.4.3 Transfer the solution prepared from the test sample (seeE.4.1) to a100ml Nessler cylinder, add2ml of the hydrochloric acid solution, dilute to t
40、he mark with water and mix. E.4.4 To prepare the sulphate solution of known concentration, add to a100ml Nessler cylinder4.0ml of the standard sulphate solution, dilute to about50ml with water, add2ml of the hydrochloric acid solution, dilute to the mark with water and mix. This diluted solution cor
41、responds to a sulphate content, expressed as SO 4 , of50 parts per million in the original material. E.4.5 Add to each Nessler cylinder2ml of the barium chloride solution and mix. Allow the cylinders to stand for5 minutes, mix again, and compare the turbidities produced. 14) BS612, “Nessler cylinders”. 15) BS1792, “One-mark volumetric flasks”. 16) BS3978, “Water for laboratory use”.
