1、BRITISH STANDARD BS7319-1: 1990 ISO2481:1973 Analysis of sodium chloride for industrial use Part1: Method for determination of sodium chloride contentBS7319-1:1990 This BritishStandard, having been prepared under the directionof the Chemicals Standards Policy Committee, waspublished under the author
2、ityof the Board of BSI andcomes into effect on 30September1990 BSI11-1999 The following BSI references relate to the work on this standard: Committee references CIC/22, FAC/23 Draft for comment88/55614 DC ISBN 0 580 18536 2 Committees responsible for this BritishStandard The preparation of this Brit
3、ishStandard was entrusted by the Chemicals Standards Policy Committee (CIC/-) to Technical Committee CIC/22, upon which the following bodies were represented: British Association for Chemical Specialities Chemical Industries Association Man-made Fibres Producers Committee Soap and Detergent Industry
4、 Association Textile Research Council (FCRA) The following bodies were also represented in the drafting of the standard, through Technical Committee FAC/23: AFRC Institute of Food Research Creamery Proprietors Association Department of Trade and Industry (Laboratory of the Government Chemist) Milk M
5、arketing Board for Northern Ireland Royal Association of British Dairy Farmers Salt Manufacturers Association Amendments issued since publication Amd. No. Date CommentsBS7319-1:1990 BSI 11-1999 i Contents Page Committees responsible Inside front cover National foreword ii 1 Scope and field of applic
6、ation 1 2 Reference 1 3 Principle 1 4 Reagents 1 5 Apparatus 1 6 Procedure 2 7 Expression of results 2 8 Test report 2 Publication(s) referred to Inside back coverBS7319-1:1990 ii BSI 11-1999 National foreword BS7319 has been prepared under the direction of the Chemicals Standards Policy Committee,
7、at the request of Technical Committee FAC/23, Salt, primarily to provide appropriate methods for determination of vacuum salt for food use as specified in BS998:1990. The methods for determination were previously published as appendices to BS998:1969. A list of the Parts of BS7319 is given below. So
8、me of the methods are identical with the corresponding International Organization for Standardization (ISO) methods and attention is drawn to this in the appropriate Parts. Part1: Method for determination of sodium chloride content; Part2: Method for determination of moisture content; Part3: Method
9、for determination of matter insoluble in water or in acid; Part4: Method for determination of sulphate content; Part5: Method for determination of calcium and magnesium contents; Part6: Method for determination of cadmium content; Part7: Method for determination of copper content; Part8: Method for
10、determination of lead content; Part9: Method for determination of mercury content; Part10: Method for determination of pH and total alkalinity; Part11: Method for determination of iron content; Part12: Methods for determination of anti-caking additives content of salt for food use. This Part of BS73
11、19 is identical with ISO2481:1973 “Sodium chloride for industrial use Determination of halogens, expressed as chlorine Mercurimetric method”. It supersedes Appendix E of BS998:1969, which is withdrawn. Additional information Reagents. With reference to clause4, the reagents used should be of recogni
12、zed analytical grade; water complying with grade3 of BS3978 is suitable. Units relating to concentration. The units used in this standard are based on normality (N). The corresponding values, expressed as amounts of substance concentrations, are as follows. Sampling. It is recommended that test samp
13、les should be taken in accordance with BS5309-4. Cross-reference International Standard Corresponding BritishStandard ISO2479:1972 BS7319 Analysis of sodium chloride for industrial use Part3:1990 Method for determination of matter insoluble in water or in acid (Identical) Clause As printed Expressed
14、 as amounts of substance concentration 4.1 14N c(HNO 3 ) =14.00mol/L 4.2 2N c(HNO 3 ) =2.00mol/L 4.3 0,1N c(NaCl) =0.10mol/L 4.5 0,1N cHg(NO 3 ) 2 =0.05mol/LBS7319-1:1990 BSI 11-1999 iii Calculation of results on a moisture free basis. The sodium chloride content of salt, expressed as a percentage b
15、y mass on a moisture free basis, is calculated by multiplying the result obtained in accordance with7.1 by where H is the moisture content in% (m/m) determined in accordance with BS7319-2. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Sta
16、ndards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. 100 100H - Summary of pages This document comprises a front cover, an inside front cover, pagesi toiv, pages1and2, an inside back cover and a back cover
17、. 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.iv blankBS7319-1:1990 BSI 11-1999 1 1 Scope and field of application This International Standard specifies a mercurimetric method fo
18、r the determination of halogens expressed as chlorine, in sodium chloride for industrial use. 2 Reference ISO2479, Sodium chloride for industrial use Determination of matter insoluble in water or acid and preparation of principal solutions for other determinations. 3 Principle Titration of the halog
19、en ions with mercury(II) nitrate in the presence of diphenylcarbazone as indicator. 4 Reagents Distilled water, or water of equivalent purity, shall be used in the test. 4.1 Nitric acid, 1,40g/ml, approximately68% (m/m) or approximately14N solution. 4.2 Nitric acid, approximately2N solution. 4.3 Sod
20、ium chloride, 0,1N standard reference solution. Weigh, to the nearest0,1mg,5,8443g of sodium chloride, previously dried for1h at500 C and cooled in a desiccator. Dissolve it in water in a1000ml one-mark volumetric flask, dilute to the mark and mix. 4.4 Standard end-point matching solution Prepare th
21、is standard solution immediately before use. Pour200ml of water into a500ml conical flask, followed by3drops of bromophenol blue solution(4.6) and the nitric acid solution(4.2), added drop by drop until the colour changes from blue to yellow. Add an excess of3drops of this acid, between0,5 and1,0ml
22、of the diphenylcarbazone solution(4.7) and the volume of mercury(II) nitrate solution(4.5) (from a burette) necessary to change the colour of the solution from yellow to mauve (about1drop). 4.5 Mercury(II) nitrate, 0,1N standard volumetric solution. 4.5.1 Preparation of the solution Weigh10,85 0,01g
23、 of mercury(II) oxide (HgO) and dissolve it in10ml of the nitric acid solution(4.1), in a1000ml one-mark volumetric flask, dilute to the mark and mix. Standardize this solution, following the procedure described in4.5.2, adjusting it to the exact concentration if necessary. 4.5.2 Standardization of
24、the solution Transfer40,0ml of the sodium chloride standard reference solution(4.3) to a500ml conical flask, followed by160ml of water and3drops of the bromophenol blue solution(4.6). Add the nitric acid solution(4.2) drop by drop until the colour of the indicator changes from blue to yellow. Add an
25、 excess of3drops of this acid and same volume of the diphenylcarbazone solution(4.7) as in the standard end-point matching solution(4.4). Titrate the chloride with the mercury(II) nitrate solution to be standardized (4.5.1) until the colour matches the mauve of the standard end-point matching soluti
26、on(4.4) and deduct the volume of mercury(II) nitrate solution(4.5.1) added during the preparation of this standard end-point matching solution (about1drop). The correct amount is40,00ml. 4.6 Bromophenol blue,1g/l solution in95% (V/V) ethanol. 4.7 Diphenylcarbazone, 5g/l solution in95% (V/V) ethanol.
27、 Store this solution in a refrigerator and replace it when it no longer gives a sharp colour change. 5 Apparatus Ordinary laboratory apparatus.BS7319-1:1990 2 BSI 11-1999 6 Procedure 6.1 Test portion Take50,0ml of the principal solution A 1) , containing100g of the test sample per1000ml. 6.2 Determi
28、nation 6.2.1 Preparation of the sample solution Place the test portion(6.1) in a500ml one-mark volumetric flask, dilute to the mark and mix. 6.2.2 Titration Place25,0ml of the sample solution(6.2.1) in a500ml conical flask. Dilute to200ml, then add3drops of the bromophenol blue solution (4.6) and th
29、e nitric acid solution(4.2) drop by drop, until the colour changes from blue to yellow. Add a further3drops of this acid and the same volume of the diphenylcarbazone solution(4.7) as in the standard end-point matching solution(4.4). Titrate with the mercury(II) nitrate solution(4.5) until the colour
30、 matches the mauve of the standard end-point matching solution(4.4). 7 Expression of results 7.1 Method of calculation and formula The halogens content, expressed as chlorine (Cl), is given, as a percentage by mass, by the formula: where m is the mass, in grams, of the test portion used for preparin
31、g the principal solution A 1) ; V is the volume, in millilitres, of the standard volumetric mercury(II) nitrate solution(4.5) used for titration; V 1 is the volume, in millilitres, of the standard volumetric mercury(II) nitrate solution(4.5) used in the preparation of the standard end-point matching
32、 solution; 0,003545is the mass, in grams, of chlorine corresponding to1ml of the standard volumetric mercury(II) nitrate solution(4.5). 7.2 Repeatability and reproducibility Comparative analyses on two samples in nineteen laboratories have given the following statistical results: 8 Test report The t
33、est report shall include 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 regarded as optional. 1) Seeclause7.3 in
34、 ISO2479. Evaporated salt Marine salt Mean (percentage by mass) 60,60 59,73 Standard deviation for repeatability ( r ) 0,06 0,06 for reproducibility ( R ) 0,26 0,28 VV 1 () 500 25 - 1 000 50 - 100 m - 0,003 545 141,8 VV 1 () m - =BS7319-1:1990 BSI 11-1999 Publication(s) referred to Seenational forew
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