1、BRITISH STANDARD BS7319-5: 1990 ISO2482:1973 Analysis of sodium chloride for industrial use Part5: Method for determination of calcium and magnesium contentsBS7319-5:1990 This BritishStandard, having been prepared under the directionof the Chemicals Standards Policy Committee, waspublished under the
2、 authorityof the Board of BSI andcomes into effect on 30September1990 BSI 12-1999 The following BSI references relate to the work on this standard: Committee referencesCIC/22, FAC/23 Draft for comment88/55618DC ISBN 0 580 18534 6 Committees responsible for this BritishStandard The preparation of thi
3、s BritishStandard 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 In
4、dustry 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 Properietors Association Department of Trade and Industry (Laboratory of the Government Chemist)
5、 Food and Drink Federation Milk Marketing Board for Northern Ireland Royal Association of British Dairy Farmers Salt Manufacturers Association Amendments issued since publication Amd. No. Date CommentsBS7319-5:1990 BSI 12-1999 i Contents Page Committees responsible Inside front cover National forewo
6、rd ii 1 Scope 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 calcium and magnesium in a principal solution prepared in an acid medium 3 10 Test report 3 Publication(s) referred to Inside back
7、coverBS7319-5:1990 ii BSI 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 BS9
8、98:1990. The methods for determination 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 ISO2482:1973 “Sodium chloride for industrial use Determination of calcium and magnesium contents EDTA complexometric me
9、thods” published by the International Organization for Standardization (ISO). It supersedes Appendix P 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 s
10、uitable. Units relating to concentration. The units used in this standard are based on normality (N) or molarity (M). The corresponding values, expressed as amounts of substance concentrations are as follows. In the note under8.1.2, the reference to0,002M can be replaced by0.002mol/L. Sampling. It i
11、s recommended that samples should be taken in accordance withBS5309-4. Calculation of results on a moisture free basis. The calcium and magnesium contents, expressed in milligrams per kilogram on a moisture free basis, are calculated by multiplying the result obtained in accordance with8.1.1 or8.1.2
12、, as appropriate, by where H is the moisture content in% (m/m) determined in accordance withBS7319-2. 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 Standar
13、d does not of itself confer immunity from legal obligations. 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 print
14、ed Expressed as amounts of substance concentration 5.1 2N c(NaOH)=2.000mol/L 5.6 0,02M c(EDTA)=0.020mol/L 5.7 0,002M c(EDTA)=0.002mol/L 10 6 100H - Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, pages1 to4, an inside back cover and a back cover. This sta
15、ndard 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.BS7319-5:1990 BSI 12-1999 1 1 Scope This International Standard specifies complexometric methods for determining the calcium and magnesium con
16、tents in sodium chloride for industrial use. 2 Field of application 2.1 General case The method is applicable to the determination of water-soluble calcium and magnesium, in sodium chloride for industrial use, for calcium or magnesium contents greater than0,001% (m/m). 2.2 Special case Determination
17、 of calcium and magnesium in a principal solution prepared in an acid medium. NOTEWhatever the conditions adopted, all related determinations shall be carried out in the same medium, except the determination of chlorides which shall always be carried out in an aqueous solution. 3 Reference ISO2479,
18、Sodium chloride for industrial use Determination of matter insoluble in water or acid and preparation of principal solutions for other determinations. 4 Principle Dissolution of a test portion and separation of insoluble matter. Titration of the filtrate obtained according to ISO2479, of calcium on
19、the one hand and total (calcium+magnesium) on the other, using disodium ethylenediaminetetra-acetate (EDTA) in the presence of glyoxal-bis-(2-hydroxyanil) (GBHA) and mordant black11 (Cl14645) respectively as indicators. 5 Reagents Distilled water, or water of equivalent purity, shall be used in the
20、test. 5.1 Sodium hydroxide, 1,08g/ml, approximately7,5% (m/m) solution or approximately2N. Dissolve80g of sodium hydroxide in water and dilute to1000ml. 5.2 Ethanol,95% (V/V). Alcohol denatured with acetone, but not coloured, can also be used. 5.3 Triethanolamine,25% (V/V) solution. Place25ml of tri
21、ethanolamine in a100ml one-mark volumetric flask, dilute to the mark andmix. 5.4 Buffer solution Dissolve54g of ammonium chloride in water. Add350ml of ammonia solution( 0,920g/ml) and dilute to the mark in a1000ml one-mark volumetric flask. 5.5 Standard end-point matching solution Prepare this stan
22、dard solution immediately before the determination(7.1.2). Pour50ml of water into a250ml conical flask followed by2ml of the triethanolamine solution(5.3),10ml of the sodium hydroxide solution(5.1),15ml of ethanol(5.2) and1,0ml of the glyoxal-bis-(2-hydroxyanil) solution(5.8). 5.6 diSodium ethylened
23、iaminetetra-acetate (EDTA),0,02M standard volumetric solution Weigh, to the nearest0,1mg,7,445g of the EDTA and dissolve this in water. Transfer quantitatively into a1000ml one-mark volumetric flask, dilute to the mark and mix. 5.7 diSodium ethylenediaminetetra-acetate (EDTA),0,002M standard volumet
24、ric solution. Take100,0ml of the0,02M EDTA solution(5.6) and place in a1000ml one-mark volumetric flask; dilute to the mark and mix. 5.8 Glyoxal-bis-(2-hydroxyanil) (GBHA), ethanolic solution approximately2,5g/l. Place approximately0,25g of GBHA in a100ml brown glass flask, fitted with a ground glas
25、s stopper. Add100ml of the ethanol(5.2) and stir until dissolved. 5.9 Mordant black 11 1)(Cl14645) approximately0,4% (m/m) mixture. Intimately mix0,4g of mordant black11with100g of sodium chloride, taking care to make the mixture perfectly homogeneous. 6 Apparatus Ordinary laboratory apparatus. 7 Pr
26、ocedure 7.1 Calcium determination 7.1.1 Test portion Take50,0ml of the principal solution A 2)containing100g of test sample per1000ml. 1) One of the commercial names of this product is “Eriochrome black T”. 2) See clause7.3 of ISO2479.BS7319-5:1990 2 BSI 12-1999 7.1.2 Determination Place the test po
27、rtion(7.1.1) in a250ml conical flask. Add, successively,2ml of the triethanolamine solution(5.3),10ml of the sodium hydroxide solution(5.1),15ml of ethanol(5.2) and1,0ml of the glyoxal-bis-(2-hydroxyanil) solution(5.8). The pH of the solution should then be higher than12. Otherwise add a quantity of
28、 sodium hydroxide solution(5.1) sufficient to raise the pH above this level. Wait for approximately2min and then titrate with the EDTA solution(5.6) until the colour changes from red to pure yellow, corresponding to the colour of the standard end-point matching solution(5.5). Titration should be car
29、ried out in less than3min. 7.2 Total determination of calcium+magnesium 7.2.1 Test portion Take100,0ml of the principal solution A containing100g of the test sample per1000ml. 7.2.2 Determination Place the test portion(7.2.1) into a500ml conical flask. Dilute to approximately200ml. Add2ml of the tri
30、ethanolamine solution(5.3), then5ml of the buffer solution(5.4) and slightly less than twice the volume of EDTA solution(5.6) used for the calcium determination. Heat to50 C and add approximately0,1g of mordant black11(5.9). Continue to add the EDTA solution(5.6), which should be done slowly, partic
31、ularly near the end point, until the colour changes from wine red to true blue (without a violet tint). NOTE 1If the solution has a blue colour after the addition of the mordant black11(5.9), it is advisable, before continuing the titration, to add6drops of a solution containing5g/100ml of magnesium
32、 ethylenediaminetetra-acetate (Mg EDTA) to change the colour of the indicator to red. NOTE 2If the titrations referred to in7.1 and7.2 require more than50ml of the EDTA solution(5.6) reduce the mass of the test portion and take this into account in calculating the results. 8 Expression of results 8.
33、1 Method of calculation and formulae 8.1.1 Calcium content The water-soluble calcium content, is given, as a percentage by mass, by the formula: where V is the volume, in millilitres, of EDTA solution(5.6) employed for the calcium determination; m is the mass, in grams, of the test portion used for
34、preparing the solution A; 0,02 0,04008is the mass, in grams, of calcium corresponding to1ml of EDTA solution(5.6). 8.1.2 Magnesium content The water-soluble magnesium content is given, as a percentage by mass, by the formula: where V 1 is the volume, in millilitres, of EDTA solution(5.6) used for th
35、e total determination (calcium+magnesium); 0,02 0,02432is the mass, in grams, of magnesium corresponding to1ml of EDTA solution(5.6). NOTEIf the calcium and magnesium contents are less than0,02% and0,01% (m/m) respectively, use the0,002M EDTA solution(5.7) and substitute0,002 for0,02 in the formulae
36、. 8.2 Repeatability and reproducibility Comparative analyses on two samples in nineteen laboratories have given the following statistical results: V 0,02 0,040 08 1000 50 - 100 m -1,603 2 V m - = V 1 2V ()0,02 0,02432 1000 100 - 100 m - V 1 2V () m - = 0,486 4 Determination of Ca Determination of Mg
37、 Evaporated salt Marine salt Evaporated salt Marine salt Mean (percentage by mass) 0,014 0,048 0,0014 0,006 Standard deviation for repeatability( r ) 0,0003 0,0013 a 0,0003 for reproducibility( R ) 0,0012 0,0022 a 0,0009 a These calculations could not be carried out because the results, which were v
38、ery low, were not all given to the necessary fourth decimal place.BS7319-5:1990 BSI 12-1999 3 9 SPECIAL CASE: Determination of calcium and magnesium in a principal solution prepared in an acid medium 9.1 Principle Solution of the test portion in an acid medium and separation of the insoluble residue
39、. Titration of calcium ions and calcium+magnesium ions as in section4. 9.2 Reagents As described in section5. 9.3 Apparatus As described in section6. 9.4 Procedure 9.4.1 Calcium determination 9.4.1.1 TEST PORTION Take50,0ml of the solution B 3) , containing100g of the test sample per1000ml. 9.4.1.2
40、DETERMINATION Proceed as described in7.1.2. 9.4.2 Total determination (calcium+magnesium) 9.4.2.1 TEST PORTION Take100,0ml of the solution B, containing100g of the test sample per1000ml. 9.4.2.2 DETERMINATION Proceed as described in7.2.2. 9.5 Expression of results 9.5.1 Calcium content Calcium conte
41、nt, soluble in an acid medium under the specified conditions, is given, as a percentage by mass, by the formula in8.1.1, where V is the volume, in millilitres, of the EDTA solution(5.6) used for the calcium determination and m is the mass, in grams, of the test portion used for preparing solution B.
42、 9.5.2 Magnesium content Magnesium content, soluble in an acid medium under the specified conditions, is given, as a percentage by mass, by the formula in8.1.2, whereV 1is the volume, in millilitres, of EDTA solution(5.6) used for the total determination (calcium+magnesium) and m is the mass, in gra
43、ms, of the test portion used for preparing solution B. 10 Test report The test 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
44、in this International Standard, or regarded as optional. 3) See clause9.5.4 of ISO2479.4 blankBS7319-5:1990 BSI 12-1999 Publication(s) referred to See national foreword.BS7319-5: 1990 ISO2482:1973 BSI 389 Chiswick High Road London W4 4AL BSIBritishStandardsInstitution BSI is the independent national
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