1、BRITISH STANDARD BS1728-22: 1972 Method for The determination of magnesium in aluminium and aluminium alloys (volumetric CDTA method)BS1728-22:1972 This British Standard, having been approved by the Non-ferrousMetals Industry Standards Committee, was published under the authority ofthe Executive Boa
2、rd on 14September1972 BSI11-1999 The following BSI references relate to the work on this standard: Committee reference NFE/-/3 Draft for comment71/40285 ISBN 0 580 07257 6 Co-operating organizations The Non-ferrous Metals Industry Standards Committee, under whose supervision this British Standard wa
3、s prepared, consists of representatives from the following Government departments and scientific and industrial organizations: Aluminium Federation* Association of Bronze and Brass Founders British Bronze and Brass Ingot Manufacturers Association British Electrical and Allied Manufacturers Associati
4、on British Lead Manufacturers Association British Non-ferrous Metals Federation British Non-ferrous Metals FederationHigh Conductivity Copper Group British Non-ferrous Metals Research Association* Copper Development Association Department of Trade and Industry (Marine Division) Electric Cable Makers
5、 Confederation Institute of British Foundrymen Institute of Metals Institution of Mechanical Engineers (Automobile Division) Institution of Mining and Metallurgy Institution of Production Engineers Institution of Structural Engineers Lead Development Association Light Metal Founders Association* Lon
6、don Metal Exchange Magnesium Industry Council Ministry of Defence, Army Department* Ministry of Defence, Navy Department National Brassfoundry Association Non-ferrous Metal Stockists Post Office Royal Institute of British Architects Society of Motor Manufacturers and Traders Ltd. Tin Research Instit
7、ute Zinc Development Association Individual manufacturer The Government department and scientific and industrial organizations marked with an asterisk in the above list, together with the following, were directly represented on the sub-committee entrusted with the preparation of this British Standar
8、d: Association of Light Alloy Refiners and Smelters Ltd. Department of Trade and IndustryLaboratory of the Government Chemist Individual analysts Amendments issued since publication Amd. No. Date CommentsBS1728-22:1972 BSI 11-1999 i Contents Page Co-operating organizations Inside front cover Forewor
9、d ii 1 Introduction 1 2 Apparatus 1 3 Solutions required 1 4 Sampling 2 5 Procedure 2 6 Standardization 3 7 Calculation 4 8 Notes 4BS1728-22:1972 ii BSI 11-1999 Foreword This standard makes reference to the following British Standards: BS1499, Sampling non-ferrous metals. BS3978, Water for laborator
10、y use. This method for the determination of magnesium is the twenty-second of a series which will form a complete British Standard under the collective title “Methods for the analysis of aluminium and aluminium alloys”, each being published as a separate part. Other methods in the series are as foll
11、ows: Part1: Copper; Part2: Magnesium; Part3: Zinc (mercuric potassium thiocyanate method); Part5: Copper (absorptiometric method); Part6: Iron (volumetric: titanous chloride method); Part8: Iron (absorptiometric1:10-phenanthroline method); Part9: Manganese (volumetric:arsenite/nitrite method); Part1
12、0: Manganese (absorptiometric method); Part11: Silicon (perchloric acid method); Part12: Silicon (absorptiometric molybdenum blue method); Part13: Titanium (absorptiometric chromotropic acid method); Part14: Nickel (gravimetric method); Part15: Nickel (photometric method); Part16: Chromium (photomet
13、ric method); Part17: Chromium (volumetric method); Part18: Zinc (ion-exchangevolumetric EDTA or polarographic method); Part19: Magnesium (atomic absorption method); Part20: Lead (atomic absorption method); Part21: Zinc (atomic absorption method) 1) . The preparation of this series of methods has bee
14、n authorized by the Non-ferrous Metals Industry Standards Committee as part of a general programme for the standardization of methods for the sampling and analysis of non-ferrous metals. The methods have been found to give reliable and reproducible results and, while in some instances they may appea
15、r to be lengthy, it should be appreciated that they are primarily intended as “referee” methods to be used in cases of dispute. This method is substantially the same as the corresponding method approved by ISO/TC79 which will be published as International Standard (ISO) 1) . . . . . A British Standa
16、rd 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 document comprises a front cover, a
17、n inside front cover, pagesi andii, pages1 to4, 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. 1) In course of preparation.BS1728-22:1972 BSI
18、 11-1999 1 1 Introduction 1.1 Principle. The sample is dissolved in hydrochloric acid and the magnesium is co-precipitated with added iron from sodium hydroxide solution. The precipitate is dissolved in hydrochloric acid, and residual iron, manganese, aluminium and titanium are precipitated with zin
19、c oxide and potassium permanganate. The magnesium is titrated with CDTA in the presence of masking agents. 1.2 Range. The method is recommended for magnesium contents between0.10and5%. 1.3 Reproducibility. Experiments have been carried out independently by a number of analysts using this method. The
20、 degree of reproducibility that can be expected is shown by the following analysis of the results obtained. 2 Apparatus 2.1 Class A volumetric glassware complying with the appropriate British Standards shall be used throughout. 2.2 pH meter 3 Solutions required All reagents shall be of the highest p
21、urity obtainable 2)and distilled or demineralized water complying with BS3978 3)shall be used throughout. Standard magnesium (1mlN 1mg of magnesium). Dissolve1.0g of high purity magnesium in30ml of hydrochloric acid(50%). Transfer to a1litre volumetric flask, dilute to the mark and mix. Standard mag
22、nesium (1mlN 0.2mg of magnesium). Transfer100ml of standard magnesium solution(1mlN 1mg of magnesium) to a500ml volumetric flask, dilute to the mark and mix. CDTA (0.04 M ). Dissolve15g of CDTA (cyclohexanediamine-tetra-acetic acid) (HOOC.CH 2 ) 2 N-CH(CH 2 ) 4 CH-N(CH 2 COOH) 2 .H 2 O in about500ml
23、 of water containing10ml of sodium hydroxide solution(20%) and mix. Then add sodium hydroxide solution(20%) slowly with stirring until the solid suspension dissolves. Dilute to about800ml and filter through a close textured filter paper into a1litre volumetric flask. Wash the filter with water and c
24、ollect the washings in the volumetric flask. Dilute to the mark and mix. CDTA (0.01M). Transfer250ml of CDTA solution(0.04M) to a1litre volumetric flask. Dilute to the mark and mix. Ammonia (50%v/v). Dilute500ml of ammonia solution (sp. gr.0.880.91) to1litre and mix. Ammonia (10%v/v). Dilute100ml of
25、 ammonia solution (sp. gr.0.880.91) to1litre and mix. Bromine water (saturated). To100ml of water add5ml of bromine, shake and allow to stand until saturated. EGTA (2%w/v). Dissolve2.0g of EGTA ethylene glycol-bis(3-aminoethyl ether) tetra-acetic acid: (HOOC.CH 2 ) 2 .NCH 2 CH 2 OCH 2 CH 2 OCH 2 CH
26、2 N(CH 2 COOH) 2 in25ml of sodium hydroxide solution(2%) and dilute to100ml. Ferric chloride (0.5%w/v). Dissolve0.5g of ferric chloride (FeCl 3 . 6H 2 O) in10ml of hydrochloric acid(20%). Dilute to100ml and mix. Hydrochloric acid (50%v/v). Dilute500ml of hydrochloric acid (sp. gr.1.161.18) to1litre
27、and mix. Hydrochloric acid (20%v/v). Dilute200ml of hydrochloric acid (sp. gr.1.161.18) to1litre and mix. Hydrochloric acid (2.5%v/v). Dilute25ml of hydrochloric acid (sp. gr.1.161.18) to1litre and mix. Magnesium content Standard deviation % 0.20.7 1.0 4.2 0.0060 0.018 0.033 2) For certain reagents
28、an extra high quality is now available but this special grade of material is not required unless specifically stated. 3) BS3978 “Water for laboratory use”.BS1728-22:1972 2 BSI 11-1999 Hydroxylammonium chloride (2%w/v). Dissolve2.0g of hydroxylammonium chloride in water. Dilute to100ml and mix. Indus
29、trial methylated spirit 4) (25%v/v). Dilute25ml of industrial methylated spirit to100ml and mix. Nitric acid (40%v/v). Dilute400ml of nitric acid (sp. gr.1.42) to1litre and mix. Potassium cyanide (25%w/v). Dissolve25g of potassium cyanide in water. Dilute to100ml and mix. This solution should be fre
30、shly prepared. Potassium permanganate (1%w/v). Dissolve1g of potassium permanganate in water. Dilute to100ml and mix. Sodium hydroxide (20%w/v). Dissolve200g of sodium hydroxide in water. Dilute to1litre and mix. This solution should be prepared in a plastics beaker (water-cooled if necessary) and s
31、tored in a plastics bottle. Sodium hydroxide (2%w/v). Dissolve20g of sodium hydroxide in water. Dilute to1litre and mix. Sulphuric acid (25%v/v). To400ml of water add cautiously250ml of sulphuric acid (sp. gr.1.8.4). Mix, cool, dilute to1litre and mix. Indicator. Mix0.1g of methyl thymol blue (sodiu
32、m salt of3,3bis (NN-dicarboxy-methyl)-aminomethyl-thymol-sulphonphthalein) with10g of sodium chloride until homogeneous. 4 Sampling Recommended methods of obtaining a suitable sample for the analytical procedure given below are described in BS1499, “Sampling non-ferrous metals”. 5 Procedure 5.1 Weig
33、h2 0.001g of sample and transfer to a400ml beaker. Add50ml of water. Then add gradually50ml of hydrochloric acid(50%). 5.2 Carry out simultaneously a blank determination following the same procedure and using the same amounts of reagents as with the sample. 5.3 When the reaction subsides, heat gentl
34、y to assist the attack and add10ml of nitric acid(40%). Heat without boiling until the evolution of hydrogen ceases. Then boil gently for about10minutes. Rinse the walls of the beaker and watchglass with hot water, collecting the washings in the same beaker. 5.4 Dilute to about150200ml with hot wate
35、r and filter if necessary (Note8.1) through a close-textured filter paper containing a small quantity of paper-pulp. Wash the filter and residue carefully eight to ten times with hot hydrochloric acid(2.5%), collecting the filtrate and washings in a400ml beaker. If there is considerable residue tran
36、sfer the filter and residue to a platinum crucible and dry in an oven at about120 C. Then ignite carefully until combustion of the filter is complete (the temperature should not exceed550 C) taking care that the filter paper does not catch alight. Cool, add5ml of hydrofluoric acid 5) ,2ml of sulphur
37、ic acid(25%) and finally add nitric acid(40%) dropwise until a perfectly clear solution is obtained. Evaporate until elimination of the white sulphuric acid fumes is complete, then heat for10minutes at a temperature not exceeding700 C. Allow to cool and take up with a few millilitres of hot water an
38、d12ml of hydrochloric acid(50%). Heat gently, filter if necessary and add the solution obtained to the test solution. 5.5 Proceed as follows according to the magnesium content: 5.5.1 For magnesium contents up to 1.5%. Concentrate the solution to about100ml. Add5ml of ferric chloride solution(0.5%) a
39、nd mix. Transfer the solution to a400ml beaker containing100ml of sodium hydroxide solution(20%) using the smallest possible quantity of lukewarm water for washing. Mix carefully, add3ml of hydrogen peroxide(100vol.), then boil for5 to10minutes. Remove from the source of heat, add7.5ml of potassium
40、cyanide solution(25%), then boil gently for5minutes. Dilute if necessary to about270ml with hot water, cover the beaker with a watchglass and heat gently without boiling for20minutes. Add a small quantity of paper-pulp, mix, then filter through a close-textured filter paper. Wash the filter and resi
41、due carefully five times with hot sodium hydroxide solution(2%) (Note8.2). 4) It should be noted that the use of industrial methylated spirit is governed by The Methylated Spirits Regulations1952(SI1952, No.2230). 5) This refers to the usual analytical reagent grade of40%w/w.BS1728-22:1972 BSI 11-19
42、99 3 5.5.2 For magnesium contents over 1.5%. Transfer the solution to a200ml volumetric flask, dilute to the mark and mix. Take the appropriate aliquot in accordance with the following table, transfer to a250ml beaker and dilute if necessary to100ml. Add5ml of ferric chloride solution(0.5%) and mix.
43、 Transfer the solution to a400ml beaker containing70ml of sodium hydroxide solution(20%) using the smallest possible quantity of lukewarm water for washing. Mix carefully, add2ml of hydrogen peroxide(100vol.), then boil for5 to10minutes. Remove from the source of heat, add5ml of potassium cyanide so
44、lution(25%), then boil gently for5minutes. Dilute if necessary to about200ml with hot water, cover the beaker with a watchglass and heat gently without boiling for20minutes. Add a small quantity of paper-pulp, mix, then filter through a close-textured filter paper. Wash the filter and residue carefu
45、lly five times with hot sodium hydroxide solution(2%) (Note8.2). 5.6 Open the filter over the beaker used for the hydroxide precipitation and with a jet of hot water wash the precipitate off the paper into the beaker. Wash the filter with a hot mixture of50ml of hydrochloric acid(20%) and2ml of hydr
46、oxylammonium chloride solution(2%). Then complete the washing with hot water, taking care to keep the final volume below80ml. Heat to complete the dissolution of the precipitate, filter through a medium-textured filter paper, wash the filter and beaker, first with hot water then with hot hydrochlori
47、c acid(2.5%), collecting the filtrate and washings in a400ml beaker. Add bromine water (saturated) in small portions until there is a persistent bromine colour, then add3ml in excess. Boil to remove the excess of bromine, adjust the volume to about70ml and allow to cool to room temperature. 5.7 Usin
48、g a pH meter adjust the pH of the solution first with ammonia solution(50%) to approximately pH4, then with ammonia solution(10%) to pH4.4 0.2 (Note8.3). Mix, heat to boiling, remove from the source of heat, add0.3g of zinc oxide and mix carefully. Add potassium permanganate solution(1%) drop-wise u
49、ntil a persistent pink colour is obtained. Heat to boiling, remove from the source of heat and add2ml of industrial methylated spirit(25%). Mix carefully, cover the beaker with a watchglass and allow to stand on a boiling water bath for5minutes. Add a further2ml of industrial methylated spirit(25%), mix and allow to stand on a boiling water bath for10minutes. Add a small quantity of paper-pulp and mix. Filter through a close-textured filter paper, wash the filter and residue eight times with hot water, and collect th
