1、BRITISH STANDARD BS 6075-6: 1981 ISO 3196:1975 Methods of Sampling and test for sodium hydroxide for industrial use Part 6: Determination of carbonate content ISO title: Sodium hydroxide for industrial use Determination of carbonates content Titrimetric method NOTEIt is recommended that this Part be
2、 read in conjunction with the information in the “General introduction” published separately as BS 6075-0. UDC 661.322.1:546.3336:543.24.062:546.264BS6075-6:1981 This British Standard, having been prepared under the directionof the Chemicals Standards Committee, was published under the authority oft
3、he Executive Board and comesinto effect on 27February1981 BSI 10-1999 The following BSI references relate to the work on this standard: Committee reference CIC/22 Draft for comment 73/54863 DC ISBN 0 580 12056 2 National foreword This Part of BS6075is identical with ISO3196“Sodium hydroxide for indu
4、strial use Determination of carbonates content Titrimetric method”, published in1975 by the International Organization for Standardization (ISO). Terminology and conventions. The text of the International Standard has been approved as suitable for publication as a British Standard without deviation.
5、 Some terminology and certain conventions are not identical with those used in British Standards; attention is especially drawn to the following. The comma has been used throughout as a decimal marker. In British Standards it is current practice to use a full point on the baseline as the decimal mar
6、ker. Wherever the words “International Standard” appear, referring to this standard, they should be read as “British Standard”. Additional information Test portion. For some grades of sodium hydroxide it may be necessary to adjust the mass of the test portion (see 4.4.1) to ensure that the amount of
7、 carbonate present in the test solution complies with the requirements for the test method. In BS 4130 “Sodium hydroxide (technical grades)” details of a suitable mass for the grades specified are given. NOTETextual error. In clause 6, paragraph 2 “expressed as NaCl 3 ” should be read as “expressed
8、asNaClO 3 ”. 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 from legal obligations. Summary of pages This docume
9、nt comprises a front cover, an inside front cover, pages i and ii, pages 1 to 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 table on the inside front cover. Cross referen
10、ce International Standard Corresponding British Standard BS 6075 Methods of sampling and test for sodium hydroxide for industrial use ISO 3195:1975 Part 5:1981 Sampling and preparation of main test solution (Identical) Amendments issued since publication Amd. No. Date of issue CommentsBS6075-6:1981
11、BSI 10-1999 i Contents Page National foreword Inside front cover 1 Scope and field of application 1 2 Reference 1 3 Preliminary test 1 4 Sodium hydroxide containing neither sulphides nor chlorates 1 5 Sodium hydroxide containing sulphides 2 6 Sodium hydroxide containing chlorates 3 7 Test report 3 F
12、igure Typical apparatus for the determination of carbonates by the barium hydroxide titrimetric method 4 Publications referred to Inside back coverii blankBS6075-6:1981 BSI 10-1999 1 1 Scope and field of application This International Standard specifies a titrimetric method for the determination of
13、the carbonates content of sodium hydroxide for industrial use. The method is applicable to products having carbonates contents, expressed as CO 2 , greater than0,01% (m/m): Three cases, selected by a preliminary test, are envisaged: 1.1 Sodium hydroxide containing neither sulphides nor chlorates. 1.
14、2 Sodium hydroxide containing sulphides. 1.3 Sodium hydroxide containing chlorates. 2 Reference ISO 3195, Sodium hydroxide for industrial use Sampling Test sample Preparation of the main solution for carrying out certain determinations. 3 Preliminary test 3.1 Principle Boiling of an acidified test s
15、ample, containing methyl orange and with a lead acetate paper strip in the vapour. The presence of sulphides produces blackening of the paper and the presence of chlorates decolorizes the methyl orange. 3.2 Reagents During the analysis, use only reagents of recognized analytical reagent grade and on
16、ly distilled water or water of equivalent purity, free from carbon dioxide. 3.2.1 Hydrochloric acid, approximately6N solution. 3.2.2 Methyl orange, 0,5g/l solution. 3.2.3 Lead acetate paper, cut into strips about15mm 80mm. 3.3 Procedure Place about20g of the test sample in a300ml conical flask. Add1
17、50ml of water and3drops of the methyl orange solution (3.2.2). Neutralize with the hydrochloric acid solution (3.2.1) and add an excess of5ml of this acid. Fix a lead acetate paper strip (3.2.3) inside the neck of the conical flask, curling it over the outside of the flask. Boil the solution for5min
18、 and select the procedure to be followed according to the following table. 4 Sodium hydroxide containing neither sulphides nor chlorates 4.1 Principle Liberation of carbon dioxide by acidification and heating. Entrainment in a flow of gas and absorption in an excess of barium hydroxide solution. Tit
19、ration of the excess barium hydroxide with a standard volumetric hydrochloric acid solution, in the presence of thymolphthalein as indicator. 4.2 Reagents Reagents listed in 3.2, and 4.2.1 Nitrogen, or air, free from carbon dioxide. 4.2.2 Barium hydroxide approximately0,1N solution. Weigh about15,0g
20、 of barium hydroxide octahydrate Ba(OH) 2 .8H 2 O, dissolve in water, transfer the solution quantitatively to a 1000ml one-mark volumetric flask, dilute to the mark and mix. Allow precipitated barium carbonate to settle out before use. 4.2.3 Hydrochloric acid, 0,1N standard volumetric solution. 4.2.
21、4 Thymolphthalein, 5g/l solution in95% (V/V) ethanol. 4.3 Apparatus Ordinary laboratory apparatus and: 4.3.1 Apparatus for the release, absorption and titration of carbon dioxide. See the Figure for an example of a typical apparatus, which comprises: A Flask, capacity 500 ml; B Separating funnel, ca
22、pacity 100 ml; C 1and C 2 Gas-washing bottles, Drechsel type, containing20% (m/m) sodium hydroxide solution; C 3 Gas-washing bottle, Drechsel type, containing saturated barium hydroxide solution; D Spiral condenser; E Absorption vessel; F Absorption coil, minimum length70cm; G Burette, 50ml, graduat
23、ed in0,1ml; Appearance Case number Procedure solution paper red white 1.1 Clause 4 red blackened 1.2 Clause 5 colourless white 1.3 Clause 6BS6075-6:1981 2 BSI 10-1999 H V-bore stopcock; I and JInlet and outlet, for nitrogen or air(4.2.1). 4.4 Procedure 4.4.1 Test portion Weigh, to the nearest0,01g,
24、in a weighing bottle with lid, a mass of test sample, solid or liquid (see ISO 3195), corresponding to not more than25g of NaOH and which will release not more than50mg of carbon dioxide. 4.4.2 Blank test After the determination, carry out a blank test, following the procedure described in 4.4.3, us
25、ing the same apparatus but omitting the test portion. 4.4.3 Determination 4.4.3.1 Pass the nitrogen or air (4.2.1) for10min into the apparatus (4.3.1) at the rate of approximately5bubbles per second. 4.4.3.2 Stop the gas flow and add respectively: to the separating funnel (B): approximately90ml of t
26、he hydrochloric acid solution (3.2.1); to the flask (A): the test portion (4.4.1),150ml of water and3drops of the methyl orange solution (3.2.2); to the absorption vessel (E):50,00ml of the barium hydroxide solution (4.2.2) and3drops of the thymolphthalein solution (4.2.4). 4.4.3.3 Close the apparat
27、us, start the flow of water through the condenser (D) and allow the acid to flow very gently from the funnel (B) into the flask (A) until the indicator changes to red, then add a further5ml, approximately, of acid, taking care to leave at least a few millimetres of liquid above the stopcock (H). 4.4
28、.3.4 Allow the gas to flow, regulated at2bubbles per second, for10min. Then, without interrupting this flow heat the contents of the flask (A) to boiling and maintain boiling for20min. Turn off the heat, increase the flow of gas to5bubbles per second, and titrate the excess of barium hydroxide solut
29、ion, contained in vessel (E), with the standard volumetric hydrochloric acid solution (4.2.3) from the burette (G), until the indicator changes from blue to colourless. 4.5 Expression of results The carbonates content, expressed as a percentage by mass of carbon dioxide (CO 2 ), is given by the form
30、ula where V 0is the volume, in millilitres, of the standard volumetric hydrochloric acid solution (4.2.3) used for the blank test; V 1is the volume, in millilitres, of the standard volumetric hydrochloric acid solution (4.2.3) used for the determination; T is the actual concentration, expressed as n
31、ormality, of the standard volumetric hydrochloric acid solution (4.2.3); m is the mass, in grams, of the test portion(4.4.1); 0,022 is the mass, in grams, of carbon dioxide corresponding to1ml of exactly1N standard volumetric hydrochloric acid solution. 5 Sodium hydroxide containing sulphides In the
32、 case of sodium hydroxide containing sulphides, the acidification of the product causes the liberation of hydrogen sulphide which is absorbed in the barium hydroxide solution at the same time as the carbon dioxide, giving a result in excess of the true value. A preliminary treatment of the test port
33、ion is therefore necessary. The method is applicable to products containing up to1g of sulphides, expressed as Na 2 S, per kilogram. 5.1 Principle Oxidation of the sulphides by hydrogen peroxide and boiling of the test sample before acidification. Determination according to the method specified in c
34、lause 4. 5.2 Reagents Reagents listed in 3.2 and 4.2, and: 5.2.1 Hydrogen peroxide, 30% (m/m) solution. 5.3 Apparatus See 4.3.BS6075-6:1981 BSI 10-1999 3 5.4 Procedure Follow the procedure specified in 4.4.3, applying the following modifications: in 4.4.3.2: place the test portion (4.4.1) in the fla
35、sk (A), then add150ml of water and5drops of the hydrogen peroxide solution (5.2.1); in 4.4.3.3: before pouring the acid into the flask (A), boil the contents of the flask for 5 min under a gas flow, then cool and add3drops of the methyl orange solution (3.2.2). 5.5 Expression of results See 4.5. 6 S
36、odium hydroxide containing chlorates In the case of sodium hydroxide containing chlorates, acidification of the product causes the liberation of chlorine, which is absorbed in the barium hydroxide solution at the same time as the carbon dioxide, giving a result in excess of the true value. A prelimi
37、nary treatment of the test portion is therefore necessary. The method is applicable to products containing up to2g of chlorates, expressed as NaCl 3 , per kilogram. 6.1 Principle Prior reduction of the chlorates to chlorides by addition of iron(II) sulphate. Determination according to the method spe
38、cified in clause 4. 6.2 Reagents Reagents listed in 3.2 and 4.2, and: 6.2.1 Iron(II) sulphate solution, containing28g of iron(II) sulphate heptahydrate (FeSO 4 .7H 2 O) and4drops of the hydrochloric acid solution (3.2.1) in100ml. 6.3 Apparatus See 4.3. 6.4 Procedure Follow the procedure specified in
39、 4.4.3, applying the following modification: in 4.4.3.2: place in the flask (A) the test portion(4.4.1),150ml of water,3drops of the methyl orange solution (3.2.2), and5ml of the iron(II) sulphate solution (6.2.1) and then mix. 6.5 Expression of results See 4.5. 7 Test report The test report shall i
40、nclude the following particulars: a) the reference of the method used; b) the results and the method of expression used; c) any unusual features noted during the determination; d) any operation not included in this International Standard or in the International Standard to which reference is made, o
41、r regarded as optional.BS6075-6:1981 4 BSI 10-1999 Figure Typical apparatus for the determination of carbonates by the barium hydroxide titrimetric methodBS6075-6:1981 BSI 10-1999 Publications referred to See national foreword.BS 6075-6: 1981 ISO 3196:1975 BSI 389 Chiswick High Road London W4 4AL BS
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