1、BRITISH STANDARD BS 6092-11: 1981 Methods of Sampling and test for sodium and potassium silicates for industrial use Part 11: Determination of chloride content of sodium metasilicate NOTEIt is recommended that this Part be read in conjunction with the information in the “General introduction” publis
2、hed separately as BS 6092-0. UDC 661.683/.684:546.32284 + 546.33284:543.24.062:546.131BS6092-11:1981 This British Standard, having been prepared under the directionof the Chemicals Standards Committee, was published under the authorityofthe Executive Boardand comes into effect on 27February1981 BSI
3、12-1999 The following BSI references relate to the work on this standard: Committee reference CIC/22 Draft for comment 73/55424 DC ISBN 0 580 12048 1 A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correc
4、t 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 copyri
5、ght 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 CommentsBS6092-11:1981 BSI 12-1999 i Contents Page 1 Scope 1 2 References 1 3 Principle 1 4 Reagents 1 5 Apparatus 1
6、 6 Procedure 1 7 Expression of results 1 Publications referred to Inside back coverii blankBS6092-11:1981 BSI 12-1999 1 1 Scope This Part of BS6092describes a method of test for determining the chloride content of sodium metasilicate pentahydrate and is applicable to products having chloride content
7、s, expressed as sodium chloride (NaCl) in the range0.03% to0.55% (m/m). There is no International Standard corresponding to this Part of BS 6092. 2 References The titles of the publications referred to in this standard are listed on the inside back cover. 3 Principle A solution of the test portion i
8、s mixed with silver nitrate solution and the excess of silver nitrate is titrated with ammonium thiocyanate solution using ammonium iron (III) sulphate solution as indicator. 4 Reagents The following reagents are required and shall be of recognized analytical quality. Water complying with the requir
9、ements of BS3978shall be used throughout. 4.1 Nitrobenzene. WARNING. Serious risk of poisoning by inhalation, swallowing or skin contact. Avoid breathing vapour. Prevent contact with skin and eyes. 4.2 Nitric acid, approximately5N solution. 4.3 Silver nitrate, 0.1N standard volumetric solution. 4.4
10、Ammonium thiocyanate, 0.1N standard volumetric solution. 4.5 Ammonium iron (III) sulphate indicator solution,100g/l. Dissolve25g of ammonium iron(III) sulphate in250ml of water. Allow the solution to settle and decant if necessary. If the solution is still not clear, add a few drops of approximately
11、5N nitric acid solution. 5 Apparatus Ordinary laboratory apparatus is required. 6 Procedure 6.1 Test portion. Weigh, to the nearest0.1g, 10g of the sample. 6.2 Determination. Transfer the test portion(6.1) to a500ml stoppered flask (an iodine flask, complying with the requirements of BS2735is suitab
12、le). Add250ml of water, warming if necessary to complete dissolution of the solid. Cool the solution to room temperature and add25ml of the nitric acid solution (4.2). Prepare a blank solution from250ml of water and25ml of the nitric acid solution (4.2) in a second, similar, flask. To each flask add
13、10ml of the silver nitrate solution (4.3) from a pipette, followed by2ml of the nitrobenzene (4.1) and1ml of the ammonium iron (III) sulphate indicator solution(4.5). Stopper the flasks and shake them for about30s. Titrate the blank solution with the ammonium thiocyanate solution (4.4) until a faint
14、 pink-brown colour just persists throughout the solution. Similarly titrate the test solution to a matching end-point. 7 Expression of results The chloride content, expressed as a percentage by mass of sodium chloride (NaCl), is given by the formula: where V 1 is the volume of the ammonium thiocyana
15、te solution (4.4) required for the blank test, inml; V 2 is the volume of the ammonium thiocyanate solution (4.4) required for the test solution, inml; 10 is the mass of the test portion, in g.2 blankBS6092-11:1981 BSI 12-1999 Publications referred to BS 2735, Iodine flasks. BS 3978, Water for labor
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