SANS 5732-2010 Tin content of tin and lead alloys《锡的锡合金的含量》.pdf

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3、damage whatsoever than may result from the use of this material or the information contain therein, irrespective of the cause and quantum thereof. ISBN 978-0-626-23507-9 SANS 5732:2010Edition 2SOUTH AFRICAN NATIONAL STANDARD Tin content of tin and lead alloys Published by SABS Standards Division 1 D

4、r Lategan Road Groenkloof Private Bag X191 Pretoria 0001Tel: +27 12 428 7911 Fax: +27 12 344 1568 www.sabs.co.za SABS SANS 5732:2010 Edition 2 Table of changes Change No. Date Scope Foreword This South African standard was approved by National Committee SABS TC 1078, Engineering materials Non-ferrou

5、s metals, in accordance with procedures of the SABS Standards Division, in compliance with annex 3 of the WTO/TBT agreement. This document was published in March 2010. This document supersedes SABS SM 732:1971 (first edition). SANS 5732:2010 Edition 2 1 Contents Page Foreword 1 Scope . 3 2 Apparatus

6、 . 3 2.1 Gckel valve 3 2.2 Three-holed rubber stopper 3 3 Reagents 3 3.1 Specific requirements. 3 3.2 Standard potassium iodate solutions 4 3.2.1 Iodate solution 1 . 4 3.2.2 Iodate solution 2 . 4 4 Procedure . 4 4.1 Low tin alloys . 4 4.1.1 Solution of the sample 4 4.1.2 Reduction . 5 4.1.3 Titratio

7、n . 5 4.1.4 Calculation 6 4.2 High tin alloys 6 4.2.1 Solution . 6 4.2.2 Reduction . 6 4.2.3 Titration . 6 4.2.4 Calculation 7 Figures 1 to 2 8-9 SANS 5732:2010 Edition 2 2 This page is intentionally left blank SANS 5732:2010 Edition 2 3 Tin content of tin and lead alloys 1 Scope This standard speci

8、fies a method for determining the tin content of tin and lead alloys, where tin is determined iodimetrically. 2 Apparatus 2.1 Gckel valve (see figure 1) A valve that generates and maintains a carbon dioxide atmosphere in the flask during reduction stage of the procedure. It is mounted in a single-ho

9、ld stopper to enable it to be fitted to the flask. NOTE If a gckel valve is not available the more cumbersome three-holed stopper (see 2.2) may be used for both the reduction and titration stages of the procedure. 2.2 Three-holed rubber stopper (see figure 2) The stopper so closes the flask during t

10、he titration stage of the procedure that carbon dioxide may be passed into the flask through one hole and be vented through an air condenser inserted through a second. The burette tip is inserted through the third hole. 3 Reagents 3.1 Specific requirements Use only analytical grade reagents and dist

11、illed or demineralised water. a) Sulphuric acid, concentrated (relative density at 15 C/15 C = 1,84). b) Hydrochloric acid, concentrated (relative density at 15 C/15 C = 1,16). c) Potassium chlorate. d) Potassium sulphate, fused. e) Sodium bicarbonate, a saturated aqueous solution. f) Potassium iodi

12、de. g) Potassium iodate, twice recrystallize potassium iodate from water and dry at 180 C to constant mass. SANS 5732:2010 Edition 2 4 h) Iron, relatively pure iron (not less than 99,85 % iron) wire strap or rod. i) Nickel, a roll of nickel sheet or a quantity of nickel pellets having an exposed are

13、a of at least 60 cm2. j) Starch solution, 10 g per litre, make a paste 1 g of soluble starch in about 5 mL of water and add this to 100 mL of boiling water. Cool before using. Prepare fresh as required. k) Tin. 3.2 Standard potassium iodate solutions 3.2.1 Iodate solution 1 3.2.1.1 Dissolve 3,5670 g

14、 of the potassium iodate in 200 mL of water containing 1 g of sodium hydroxide. Add 10 g of potassium iodide. 3.2.1.2 When solution is complete, dilute to 1 L in a volumetric flask. 3.2.1.3 Standardize the potassium iodate solution against an accurately weighed portion of a tin, lead, antimony and c

15、opper mixture in approximately the proportions present in the sample, or of a similar alloy of known tin content, or of the tin. 3.2.1.4 In all cases use such a quantity as will give approximately the same titre as the sample1), and proceed according to 4.1.1, 4.1.2, and 4.1.3. 3.2.1.5 Calculate the

16、 tin equivalence of the iodate solution (which should be of the order of 1 mL = 0,006 g of tin). 3.2.2 Iodate solution 2 Dissolve 3,0000 g of the potassium iodate in water and dilute to 1 L in a volumetric flask (1 mL = 0,003 g of potassium iodate). 4 Procedure 4.1 Low tin alloys 4.1.1 Solution of t

17、he sample 4.1.1.1 Transfer 0,3 g to 4 g (weighed to 0,1 mg) of the finely divided and thoroughly mixed sample (containing 0,10 g to 0,30 g of tin) to a 500 mL flask. 4.1.1.2 Add 20 mL of the sulphuric acid and 5 g of the potassium bisulphate and heat to decompose the sample. NOTE Avoid too high temp

18、eratures during the initial heating otherwise the sample may melt and incomplete decomposition may result. 1) The tin equivalent of the iodine or potassium iodate solution in the determination of tin is empirical rather than theoretical and may vary with the volume of potassium iodate used in a titr

19、ation. No provision is made for the deduction of a blank, since these cancel out when the titration for the sample and standard solutions are approximately equivalent. It is, therefore, essential that such masses of sample and standard sample be used as will give approximately equivalent titrations.

20、 In some cases it may be necessary to run a series of standards containing various amounts of tin to correspond to samples of varying tin content. SANS 5732:2010 Edition 2 5 4.1.1.3 When decomposition is complete, heat vigorously over an open flame to expel or wash down sulphur from the walls of the

21、 flask. 4.1.1.4 Cool and add 180 mL of water. 4.1.2 Reduction If 0,01 g or more of copper is present, or the antimony content is so high that the precipitated metal formed during the reduction interferes with the reduction or both (or the end point in the tin titration or both), proceed according to

22、 4.1.2(a) and 4.1.2(b) or 4.1.2(c). Otherwise proceed according to 4.1.2(b) or 4.1.2(c). a) Procedure. Add 50 mL of the hydrochloric acid to the solution and a piece of the iron2) weighing at least 5 g. Cover with a watch glass, heat to boiling point and boil for 30 min. Filter off the iron, copper

23、and antimony through a coarse paper or through glass wool into a 500 mL flask and wash with hot water. Reserve the filtrate and washing. Wash the copper and antimony precipitate back into the original flask, add 10 mL of the hydrochloric acid and a few crystals of the potassium chlorate, and heat ge

24、ntly to effect complete the solution of the metal. Dilute to 50 mL and boil to expel free chlorine. Add approximately 3 g of the iron and boil gently for 15 min. Filter through a coarse paper into the 500 mL flask containing the reserved filtrate. b) Reduction with iron. To the solution if obtained

25、in accordance with 4.1.1, add 60 mL of the hydrochloric acid. If obtained in accordance with 4.1.2(a) no further addition of acid is necessary. Add at least 5 g of the iron and stopper the flask with the gckel valve (see 2.1). Heat to boiling and boil with continuous evolution of gas for at least 30

26、 min. Some undissolved iron should remain after the reduction. c) Reduction with nickel. To the solution if obtained in accordance with 4.1.4, add 75 mL of the hydrochloric acid or if obtained in accordance with 4.1.2(a) add only 20 mL of the hydrochloric acid. Introduce the roll of nickel sheet or

27、the nickel pellets; and stopper the flask with the gckel valve (see 2.1). Heat to boiling and boil with continuous evolution of gas for at least 45 min. If the nickel coil surfaces become heavily coated with a black deposit, insert a second coil or more pellets after 30 min of boiling and continue t

28、he boiling for at least 15 min. 4.1.3 Titration a) After reduction is complete fill the gckel valve with the sodium bicarbonate solution and cool the contents of the flask to below 10 C. Replenish the sodium bicarbonate solution in the valve to continuously maintain an atmosphere of carbon dioxide i

29、nside the flask. b) Remove the gckel valve and replace it with the three-rubber stopper (see 2.2). Maintain the atmosphere of carbon dioxide by passing carbon dioxide gas through the flask. c) Add 5 mL of the starch solution and titrate in the presence of the iron or nickel with the iodate solution.

30、 2) Certain types of high purity iron may exhibit a tendency to become passive under the conditions existing in this method. If any difficulty is encountered in precipitating the antimony, it is best to use a relatively impure form of iron. SANS 5732:2010 Edition 2 6 4.1.4 Calculation = 100ABTCwhere

31、 T is the tin content, %; A is the volume of the iodate solution 1 required to titrate the sample, mL; B is the tin equivalent of the iodate solution 1, g/mL; and C is the mass of the sample used, g. 4.2 High tin alloys 4.2.1 Solution a) Transfer from 2 g to 5 g (weighed to 0,1 mg) of the sample, ap

32、proximate tin content of which is known, to a 750 mL flask. b) For a reference standard, transfer to a 750 mL flask an accurately weighed portion of tin, lead, antimony and copper mixture in approximately the proportions present in the sample or of a similar alloy of known tin content, or of the tin

33、. In all cases use such a quantity as will contain approximately the same mass of tin as is present in the sample taken for analysis. c) Treat both the sample solution (see 4.2.1(a) and referenced standard (see 4.2.1(b) according to 4.1.1, using 25 mL of the sulphuric acid, and proceed as described

34、in 4.2.2, 4.2.3 and 4.2.4. 4.2.2 Reduction a) If the sample contains more than 0,01 g of copper or the antimony content is so high that the precipitated metal formed during the reduction interferes with the reduction or both (or the end point in the tin titration or both), proceed as described in 4.

35、1.2(a), and then 4.2.2(b). Otherwise proceed according to 4.2.2(b). b) Adjust the sample solution to contain approximately 250 mL of water and 75 mL of hydrochloric acid. Introduce the roll of nickel sheet, or nickel pellets and stopper the flask with the gckel valve (see 2.1). Heat to boiling and b

36、oil with continuous evolution of gas for at least 45 min. If the nickel surfaces become heavily coated with a black deposit, insert a second coil or more pellets after 30 min of boiling and continue the boiling for at least 15 min. 4.2.3 Titration a) After reduction is complete, cool the contents of

37、 the flask below 10C. Replenish the sodium carbonate in the valve to continuously maintain an atmosphere of carbon dioxide inside the flask. b) Remove the gckel valve and replace it with the three-holed rubber stopper (see 2.2). Maintain the atmosphere of carbon dioxide by passing carbon dioxide gas

38、 through the flask. c) Transfer to a 250 mL beaker sufficient potassium iodate weighed out to the nearest 0,1 g to oxidize all but 0,02 g to 0,04 g of the tin (1 g will oxidize about 1,1 g of tin). Add approximately 20 % more by mass of the potassium iodide than of the potassium iodate and approxima

39、tely 0,5 g of sodium bicarbonate, and dissolve the mixture in 75 mL of cold water. Transfer this solution quantitatively to the cooled solution (a) above). Add 5 mL of the starch solution and titrate in the presence of the nickel with the iodate solution 2. SANS 5732:2010 Edition 2 7 4.2.4 Calculati

40、on a) Calculate the tin equivalent of the potassium iodate as follows: =+ 0,003BACdwhere A is the tin equivalent, g tin/g potassium iodate; B is the mass of tin in the tin standard used, g; C is the mass of the potassium iodate weighed out and added to the tin reference standard, g; and d is the vol

41、ume of the iodate solution 2 used in the titration of the reference standard, mL. b) Calculate the tin content as follows: ( + 0,003 )= 100EfATGwhere T is the tin content, %; E is the mass of potassium iodate weighed out and added to the sample, g; f is the volume of the iodate solution 2 used in th

42、e titration of the sample, mL; A is the tin equivalent, g tin/g potassium iodate; and G is the mass of sample used, g. SANS 5732:2010 Edition 2 8 Dimensions in millimetres NOTE All diameters shown are internal. Figure 1 The Gckel valve SANS 5732:2010 Edition 2 9 Figure 2 Three-holed stopper in flask

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