1、BRITISH STANDARD BS 6721-11: 1989 ISO 7266:1984 Sampling and analysis of copper and copper alloys Part 11: Method for determination of sulphur in copper and copper alloys: combustion titrimetric method ISO title: Copper and copper alloys Determination of sulfur content Combustion titrimetric method
2、UDC 669.3:543.845:543.24:620.1BS6721-11:1989 This British Standard, having been prepared under the directionof the Non-ferrous Metals Standards Committee, waspublished under the authorityof the Board of BSI andcomes into effect on 28February 1989 BSI 12-1999 The following BSI references relate to th
3、e work on this standard: Committee reference NFM/34 Draft (ref. 86/38277) announced inBSI News, January 1988 ISBN 0 580 17124 8 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Non-ferrous Metals Standards Committee (NFM/-) to Technical C
4、ommittee NFM/34 upon which the following bodies were represented: British Non-ferrous Metals Federation Copper Development Association London Metal Exchange Non-ferrous Metal Stockists Society of British Aerospace Companies Limited Coopted members The following bodies were also represented in the dr
5、afting of the standard, through subcommittees and panels: BNF Metals Technology Centre British Bronze and Brass Ingot Manufacturers Association Copper Smelters and Refiners Association Ministry of Defence National Brassfoundry Association Coopted members Amendments issued since publication Amd. No.
6、Date of issue CommentsBS6721-11:1989 BSI 12-1999 i Contents Page Committees responsible Inside front cover National foreword ii 1 Scope and field of application 1 2 Principle 1 3 Reagents 1 4 Apparatus 1 5 Procedure 1 6 Expression of results 4 7 Notes on procedure 4 8 Test report 5 Figure 1 Apparatu
7、s for the determination of sulfur by combustion 2 Figure 2 Bubbler tube B 2 Figure 3 Metallic cooling for combustion tube 3BS6721-11:1989 ii BSI 12-1999 National foreword This Part ofBS6721 has been prepared under the direction of the Non-ferrous Metals Standards Committee.BS6721 is a multi-part sta
8、ndard and describes methods of sampling and analysis for copper and copper alloys. It is intended that Parts1to3ofBS6721 will describe methods of sampling copper and copper alloys in various forms. The remaining Parts will give methods for the determination of individual elements in copper and coppe
9、r alloys. This Part ofBS6721 is identical withISO7266:1984 “Copper and copper alloys Determination of sulfur content Combustion titrimetric method”, published by the International Organization for Standardization (ISO). Terminology and conventions. The text of the International Standard has been app
10、roved as suitable for publication as a British Standard without deviation. Some terminology and certain conventions are not identical with those used in British Standards; attention is drawn especially to the following. The comma has been used as a decimal marker. In British Standards it is current
11、practice to use a full point on the baseline as the decimal marker. Wherever the words “International Standard” appear, referring to this standard, they should be read as “Part ofBS6721”. In British Standards it is current practice to use the symbol “L” for litre (and in its submultiples) rather tha
12、n “l” and to use the spelling “sulphur”, etc., instead of sulfur, etc. WARNING. Reference is made in4.2.2 to the use of asbestos treated with sodium hydroxide in purging tube A 1 . In view of the hazardous nature of asbestos it is recommended that one of the commercially available substitute materia
13、ls, such as synthetic silicate, is used. 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 Standard does not of itself confer immunity from legal obligations.
14、Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages1 to 5 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.BS6721-11
15、:1989 BSI 12-1999 1 1 Scope and field of application This International Standard specifies a combustion titrimetric method for the determination of the sulfur content of copper and copper alloys. The method is applicable to contents of sulfur greater than0,010% (m/m) in all types of copper and coppe
16、r alloys listed in International Standards. 2 Principle Combustion of a test portion in oxygen at1250 C. Absorption of combustion gases in dilute hydrogen peroxide solution. Titration of the sulfuric acid formed with sodium borate in the presence of a mixed methyl red-methylene blue indicator soluti
17、on. 3 Reagents During the analysis, use only reagents of recognized analytical grade and only distilled water or water of equivalent purity. 3.1 Hydrogen peroxide, approximately3g/l solution. Dilute10ml of hydrogen peroxide,30% (m/m) to1000ml with water. 3.2 Sulfuric acid, solution, c (H 2 SO 4 ) .
18、0,0025 mol/l Dilute14ml of sulfuric acid ( 1,84g/l) to1000ml. Dilute10ml of this solution to1000ml. 3.3 Sodium borate, standard solution. Dissolve1,1895g of sodium borate decahydrate (Na 2 B 4 O 710H 2 O) in water and dilute to the mark in a1000ml one-mark volumetric flask. 1ml of this standard solu
19、tion is equivalent to1004g of S. 3.4 Mixed indicator Dissolve0,120g of methyl red and0,080g of methylene blue in100ml of ethanol. 4 Apparatus Ordinary laboratory apparatus, and 4.1 Burette,25ml, with0,05ml graduations. 4.2 Combustion apparatus (seeFigure 1), consisting of the following: 4.2.1 Oxygen
20、 bottle with pressure regulator and flowmeter (D). The oxygen must be sulfur-free. 4.2.2 Purging tubes (A 1and A 2 ). A 1is packed with asbestos 1)treated with sodium hydroxide. The bottom part of A 2is filled to three-quarters of its height with anhydrous magnesium perchlorate; the top part is fill
21、ed with phosphorus(V) oxide. The two substances are separated by a plug of glass wool. 4.2.3 Two-way valve (R), with3to4mm tubing, such that oxygen can flow into the combustion tubeT (4.2.6) and the combustion gases can flow into the bubbler tube B (4.3.2). 4.2.4 Mercury check valve (S), with an equ
22、ilibrium flask and a safety tube. The level of mercury is adjusted, by means of the equilibrium flask, so that a seal is made when, with valve R (4.2.3) open, the gas flows from the combustion tube at a rate of2,5l/min. When valve R is opened, an overpressure is created, and the mercury seal operate
23、s until normal pressure is established. 4.2.5 Pressure-release container (V) 4.2.6 Combustion tube (T), made of non-porous refractory material, in which the combustion boat containing the test portion is placed (see7.2). 4.2.7 Combustion boats, previously calcined at1250 C in a stream of oxygen (see
24、7.3). 4.2.8 Tube furnace (F), capable of maintaining the heated portion of the combustion tube T (4.2.6) at1250 C, with a metal cooling head for the combustion tube (seeFigure 3). 4.2.9 Glass outlet tube, of the same diameter as the combustion tube T (4.2.6), connected to the combustion tube by a ru
25、bber sleeve (b). 4.2.10 Water cooling coil (r), to cool combustion gases. 4.2.11 Flexible plastic tubing for all fixed connections. 4.3 Absorption apparatus, consisting of the following (seeFigure 1 andFigure 2): 4.3.1 Absorption vessel,250ml 4.3.2 Bubbler tube (B) with holes in one end (seeFigure 2
26、), immersed in a solution of hydrogen peroxide (3.1). 4.3.3 Outlet valve (C), between purging tubes A 1and A 2and bubbler tube B. With this valve, it is possible to maintain a slight oxygen flow into the absorption vessel (4.3.1), thereby preventing the hydrogen peroxide solution (3.1) from flowing
27、up into the bubbler tube B (4.3.2). 5 Procedure 5.1 Test portion Weigh1 0,001g of sample into a combustion boat(4.2.7). For samples with high zinc content, particularly the brasses, add to the sample in the combustion boat five times its mass in pure tin (see7.1). 1) See national foreword for warnin
28、g on the use of asbestos.BS6721-11:1989 2 BSI 12-1999 A1 and A2 Purging tubes (4.2.2) F Combustion furnace (4.2.8) B Bubbler tube (4.3.2) S Mercury check valve and safety tube (4.2.4) C Outlet valve (4.3.3) R Two-way valve (4.2.3) D Pressure regulator and flowmeter (4.2.1) V Pressure-release contain
29、er (4.2.5) b Rubber sleeve (4.2.9) T Combustion tube (4.2.6) r Cooling coil (4.2.10) Figure 1 Apparatus for the determination of sulfur by combustion Figure 2 Bubbler tube B (4.3.2) (Diameter of holes:0,05mm)BS 6721-11:1989 BSI 12-1999 3 Figure 3 Metallic cooling head for combustion tubeBS6721-11:19
30、89 4 BSI 12-1999 5.2 Blank test Calcination of the combustion tube and combustion boats makes a blank test of this apparatus unnecessary. In the case of high zinc alloys, a blank test shall be carried out using the same mass of tin added to the combustion boat. 5.3 Determination Pre-heat the furnace
31、 F (4.2.8) to1250 C. Ensure that the cooling coil r (4.2.10) is working, and connect the combustion tube T (4.2.6) at both ends. Open valves R (4.2.3) and C (4.3.3) and pass oxygen through the system at a rate of2,5l/min, regulating the flow rate with the pressure regulator and flowmeter D (4.2.1).
32、Close valve R and adjust the oxygen flow rate to0,5l/min by means of valve C. To the absorption vessel (4.3.1) add40ml of the hydrogen peroxide solution (3.1),160ml of water, and4to6drops of the mixed indicator solution (3.4). Immerse the bubbler tube B (4.3.2) in the solution. Turn the indicator vi
33、olet by the addition of sulfuric acid solution (3.2) if necessary. Open valve R and pass oxygen through the system at a rate of2,5l/min for2min, in order to expel carbon dioxide. If necessary, readjust the pressure regulator and flowmeter D. Close valve R and add the sodium borate solution(3.3) to t
34、he absorption vessel until the solution is neutralized. The indicator will change from violet through blue to green. Stop adding solution when the indicator changes from blue green to bright green. Remove the stopper from the furnace head. Insert the combustion boat (4.2.7) containing the test porti
35、on into the hottest zone of the furnace using a refractory metal rod. Replace the stopper on the combustion tube and wait2min. Slowly open valve R. Pass oxygen through the combustion tube for2min, then close valve R. Remove to stopper and take out the combustion boat (see7.4). Titrate the solution i
36、n the absorption vessel with the sodium borate solution until the indicator turns bright green. 5.4 Check test Make a preliminary test of the apparatus using a standard material or a synthetic sample containing a known amount of sulfur and carrying out the procedure as specified in5.1 to5.3. 6 Expre
37、ssion of results The sulfur content, expressed as a percentage by mass, is given by the formula where V is the volume, in millilitres, of the sodium borate solution (3.3) used in the titration; m is the mass, in grams, of the test portion(5.1); 0,000 1is the mass, in grams, of sulfur equivalent to1m
38、l of the sodium borate solution(3.3). In the case of high zinc alloys, the calculated sulfur content must be reduced by the sulfur content of the tin blank (5.2). 7 Notes on procedure 7.1 Analysis of high-zinc copper alloys The method can be applied to copper alloys with high zinc content, in partic
39、ular the copper-zinc alloys (brasses), by adding to the sample in the combustion boat five times its mass in pure tin. If this precaution is omitted, zinc is distilled during heating and the zinc oxide thus formed interferes with the volumetric determination of sulfur. 7.2 Pre-treatment of combustio
40、n tubes When a new tube is used, as much of it as possible must be calcined at or above the temperature at which it is to be used (1250 C) by moving the tube lengthwise in the furnace. 7.3 Calcination of combustion boats Calcination should be carried out on the day the boat is to be used. Boats shou
41、ld be stored in a desiccator. The absence of sulfur must be verified by means of blank tests. 7.4 Multiple determinations A series of5or6determinations can be carried out with the same bubbler tube and the same absorption solution. To reduce time loss to a minimum, the next test portion can be inser
42、ted as soon as combustion of the previous test portion is completed, and titration can be carried out during the2min waiting period.BS6721-11:1989 BSI 12-1999 5 8 Test report The test report shall include the following particulars: a) an identification of the sample; b) the reference of the method u
43、sed; c) the results and the method of expression used; d) any unusual features noted during the determination; e) any operation not included in this International Standard, or regarded as optional, which might affect the results.BS 6721-11: 1989 ISO 7266:1984 BSI 389 Chiswick High Road London W4 4AL
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