1、BRITISH STANDARD BS7319-4: 1990 ISO2480:1972 Analysis of sodium chloride for industrial use Part4: Method for determination of sulphate contentBS7319-4:1990 This British Standard, having been prepared under the directionof the Chemicals Standards Policy Committee, waspublished under the authorityof
2、the Board of BSIandcomes into effecton 30 September1990 BSI 12-1999 The following BSI references relate to the work on this standard: Committee references CIC/22, FAC/23 Draft for comment 88/55617 DC ISBN 0 580 18533 8 Committees responsible for this British Standard The preparation of this BritishS
3、tandard 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 Asso
4、ciation 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 Properietors Association Department of Trade and Industry(Laboratory of the Government Chemist) Food and Dri
5、nk Federation Milk Marketing Board for Northern Ireland Royal Association of British Dairy Farmers Salt Manufacturers Association Amendments issued since publication Amd. No. Date CommentsBS7319-4:1990 BSI 12-1999 i Contents Page Committees responsible Inside front cover National foreword ii 1 Scope
6、 1 2 Field of application 1 3 Reference 1 4 Principle 1 5 Reagents 1 6 Apparatus 1 7 Procedure 1 8 Expression of results 2 9 Special case: Determination of sulphate in a principal solution prepared in an acid medium 2 10 Test report 2 Publication(s) referred to Inside back coverBS7319-4:1990 ii BSI
7、12-1999 National foreword BS7319 has been prepared under the direction of the Chemicals Standards Policy Committee, 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 d
8、etermination were previously published as appendices to BS998:1969. A list of the Parts of BS7319 is given in Part1. This Part of BS7319 is identical with ISO2480:1972 “Sodium chloride for industrial use Determination of sulphate content Barium sulphate gravimetric method” published by the Internati
9、onal Organization for Standardization(ISO). It supersedes Appendix J of BS998:1969, which is withdrawn. Additional information Reagents. With reference to clause5, the reagents used should be of recognized analytical grade; water complying with grade3 of BS3978 is suitable. Units relating to concent
10、ration. 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 samples should be taken in accordance with BS5309-4. Calculation of results on a moisture free basis. T
11、he sulphate content, expressed as sodium sulphate(Na 2 SO 4 ) in milligrams per kilogram on a moisture free basis, is calculated by multiplying the result obtained in accordance with8.1 by where H is the moisture contentin%(m/m) determined in accordance with BS7319-2. A British Standard does not pur
12、port 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. Cross-reference International Standard Corresponding British Standard IS
13、O2479:1972 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 as amounts of substance concentration 5.1 6N c(HCl)=6.0mol/L 5.1 12N c(HCl)=12.0mol/L 5.2 36N c(H 2 SO 4 )=18.0mol/L 5.
14、3 N c(BaCl 2 )=0.50mol/L 5.5 14N c(HNO 3 )=14.00mol/L 10 6 100H - Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, pages1 and 2, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorpor
15、ated. This will be indicated in the amendment table on the inside front cover.BS7319-4:1990 BSI 12-1999 1 1 Scope This International Standard specifies a gravimetric method for the determination of sulphate content of sodium chloride for industrial use. 2 Field of application 2.1 General case The me
16、thod is applicable to the determination of sulphate soluble in water, in sodium chloride for industrial use. 2.2 Special case Determination of sulphate in a principal solution prepared in an acid medium. NOTEWhatever the conditions adopted, all related determinations shall be carried out in the same
17、 medium, except the determination of chlorides which shall always be carried out in an aqueous solution. 3 Reference ISO2479, Sodium chloride for industrial use Determination of matter insoluble in water or acid and preparation of principal solutions for other determinations. 4 Principle Dissolution
18、 of a test portion and separation of the insoluble residue. Precipitation of the sulphate ions as barium sulphate in a boiling acid medium. Filtration, washing and ignition of the precipitate. Weighing of the barium sulphate. 5 Reagents Distilled water or water of equivalent purity shall be used in
19、the test. 5.1 Hydrochloric acid, approximately6N solution. Dilute50ml of hydrochloric acid, 1,19g/ml (approximately38%(m/m) solution, or approximately12N), to100ml. 5.2 Sulphuric acid, 1,84g/ml (approximately96% (m/m) solution or approximately36N). 5.3 Barium chloride, approximately N solution. Diss
20、olve122g of barium chloride dihydrate in water in a1000ml one-mark volumetric flask, dilute to the mark and mix. 5.4 Silver nitrate,5g/l nitric solution. Dissolve0,5g of silver nitrate in a little water, add10ml of nitric acid solution, 1,40g/ml approximately, and dilute to100ml. 5.5 Nitric acid 1,4
21、0g/ml (approximately68%(m/m) solution, or approximately14N). 6 Apparatus Ordinary laboratory apparatus and 6.1 Electric furnace, capable of being controlled at800 25 C. 6.2 Desiccator, containing pumice moistened with sulphuric acid, silica gel, or phosphorus pentoxide. 6.3 Platinum or porcelain cru
22、cibles, approximately30mm diameter at the top, and approximately30mm deep. 7 Procedure 7.1 Test portion Take100,0ml of the principal solution A 1)containing100g of the test sample per1000ml. 7.2 Determination Place the test portion(7.1) in a250ml beaker. Add2,0ml of the hydrochloric acid solution(5.
23、1), heat to boiling, stirring continuously, and add, drop by drop,10ml of the barium chloride solution(5.3). (Time taken for making the addition, approximately1,5min.) Continue boiling for a few minutes, stirring continuously. Leave standing on a boiling water bath for1h, or approximately12h at ambi
24、ent temperature. Filter the precipitate through an ashless filter paper or a filter paper for which the mass of ash is known, and the pore size of which is sufficiently small to hold back all the precipitate(porosity gradeP1,6 i.e.pore size index up to1,6m) and wash with boiling water until10ml of t
25、he liquid leaving the funnel remains clear for5min after adding10ml of the silver nitrate solution(5.4). If chloride ions are detected, the precipitate should be washed again with small quantities of water, two or three times, until the complete disappearance of chloride ions from the washing water.
26、 1) Seeclause 7.3 of ISO2479.BS7319-4:1990 2 BSI 12-1999 Carefully place the filter paper and contents in the crucible (6.3), previously heated to a red heat, cooled in the desiccator(6.2) and weighed, and place it in an oven at110 2 C until completely dry. Ignite the filter paper at low temperature
27、. This can be carried out with a butane gas or acetylene jet, or in the electric furnace(6.1). Keep the crucible at approximately800 25 C for15min. If the ignited precipitate smells of sulphides(BaS) or has a grey appearance, indicating the presence of carbon black, moisten it with1 drop of the nitr
28、ic acid solution (5.5) and1 drop of the sulphuric acid solution(5.2) and evaporate to dryness on a hot-plate in the crucible, fitted with its lid to avoid loss. Return to the furnace(6.1) and ignite again at800 25 C for15min. Cool in the desiccator(6.2) and weigh to the nearest0,1mg. 8 Expression of
29、 results 8.1 Method of calculation and formula The sulphate(SO 4 ) content is given, as a percentage by mass, by the formula: where m 0 is the mass, in grams, of the test portion used for preparing principal solution A; m 1 is the mass, in grams, of barium sulphate weighed; 0,41153is the conversion
30、factor of BaSO 4to SO 4 . 8.2 Repeatability and reproducibility Comparative analyses on two samples in nineteen laboratories have given the following statistical results: 9 Special case: Determination of sulphate in a principal solution prepared in an acid medium 9.1 Principle Dissolution in an acid
31、 medium and separation of the insoluble residue. Precipitation of sulphate ions in the filtrate in accordance with the general method. 9.2 Reagents Seesection5. 9.3 Apparatus Seesection6. 9.4 Procedure 9.4.1 Test portion Take100,0ml of solution B 2)containing100g of the test sample per1000ml. 9.4.2
32、Determination See7.2. 9.5 Expression of results Use the formula given in section8, where m 0is the mass, in grams, of the test portion used for preparing principal solution B. 10 Test report The test report shall include the following particulars: a) the reference of the method used; b) the results
33、and the method of expression used; c) any unusual features noted during the determination; d) any operations not included in this International Standard, or regarded as optional. Evaporated salt Marine salt Mean(percentage by mass) 0,009 0,117 Standard deviation for repeatability ( r ) 0,0015 0,0033
34、 for reproducibility ( R ) 0,0038 0,0085 m 1 0,411 53 1 000 100 - 100 m 0 - m 1 m 0 -411,53 = 2) Seeclause 9.5.4 in ISO2479.BS7319-4:1990 BSI 12-1999 Publication(s) referred to Seenational foreword.BS7319-4: 1990 ISO2480:1972 BSI 389 Chiswick High Road London W4 4AL BSIBritishStandardsInstitution BS
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