1、BRITISH STANDARD BS 6075-9: 1981 ISO 3697:1976 Incorporating Amendment No. 1 Methods of Sampling and test for sodium hydroxide for industrial use Part 9: Determination of calcium and magnesium contents ISO title: Sodium hydroxide for industrial use Determination of calcium and magnesium contents Fla
2、me atomic absorption method NOTEIt is recommended that this Part be read in conjunction with the information in the “Generalintroduction” published separately as BS6075-0. UDC 661.322.1:546.33 36:543.42.062:546.41 + 546.46BS6075-9:1981 This British Standard, having been prepared under the directiono
3、f the Chemicals Standards Committee, was published under the authority ofthe Executive Board and comesinto effect on 27 February1981 BSI 10-1999 The following BSI references relate to the work on this standard: Committee reference CIC/22 Draft for comment 75/50812 DC ISBN 0 580 12059 7 Amendments is
4、sued since publication Amd. No. Date of issue Comments 3851 December 1981 Indicated by a sideline in the marginBS6075-9:1981 BSI 10-1999 i Contents Page National foreword ii 1 Scope and field of application 1 2 Reference 1 3 Principle 1 4 Reagents 1 5 Apparatus 2 6 Procedure 2 7 Expression of result
5、s 3 8 Test report 3 Annex ISO publication relating to sodium hydroxide for industrial use 4 Publications referred to Inside back coverBS6075-9:1981 ii BSI 10-1999 National foreword This Part of BS 6075 is identical with ISO3697 “Sodium hydroxide for industrial use Determination of calcium and magnes
6、ium contents Flame atomic absorption method”, published in 1976 by the International Organization for Standardization (ISO). Terminology and conventions. The text of the International Standard has been approved as suitable for publication as a British Standard without deviation. Some terminology and
7、 certain conventions are not identical with those used in British Standards; attention is especially drawn to the following. The comma has been used throughout as a decimal marker. In British Standards it is current practice to use a full point on the baseline as the decimal marker. Wherever the wor
8、ds “International Standard” appear, referring to this standard, they should be read as “British Standard”. The standards listed in the Annex are intended for information only. Corresponding British Standards are listed in BS6075-0. Additional information Hydrochloric acid, approximately1.18g/ml, abo
9、ut36% (m/m) solution, which is the corresponding reagent normally obtainable in the UK, is suitable for use in place of the solution specified in 4.1. WARNING. Acetylene is highly flammable and, in some circumstances, can be explosive. Instrument manufacturers recommendations concerning the use of g
10、aseous mixtures containing acetylene (see 5.1) should therefore be closely followed. Attention is also drawn to the need for compliance with the requirements of the Compressed Acetylene Order, 1947 (SR and O1947: No. 805), relating to permissible pressures for the use of acetylene. A British Standar
11、d 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. Cross-reference International Standard Corresponding Briti
12、sh Standard BS 6075 Methods of sampling and test for sodium hydroxide for industrial use ISO 3195:1975 Part 5:1981 Sampling and preparation of main test solution (Identical) Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages1 to 4, an inside back cov
13、er 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.BS6075-9:1981 BSI 10-1999 1 1 Scope and field of application This International Standard specifies a flame atomic
14、 absorption method for the determination of the calcium and magnesium contents of sodium hydroxide for industrial use. The method is applicable to products having Ca and Mg contents greater than 2,5 mg/kg and 0,5 mg/kg respectively, if an acetylene-air flame is used; 0,6 mg/kg and 1,0 mg/kg respecti
15、vely, if an acetylene-dinitrogen monoxide flame is used. 2 Reference ISO 3195, Sodium hydroxide for industrial use Sampling Test sample Preparation of the main solution for carrying out certain determinations. 3 Principle Acidification of a test portion with hydrochloric acid. Aspiration of the solu
16、tion into an acetylene-dinitrogen monoxide or acetylene-air flame, after addition of lanthanum ions in the latter case in order to suppress certain interferences. Measurement of the absorption of the422,7nm and285,2nm lines emitted by calcium and magnesium hollow-cathode lamps. 4 Reagents During the
17、 analysis, use only reagents of recognized analytical grade and only water doubly distilled in borosilicate glass apparatus with ground joints, or water of equivalent purity. 4.1 Hydrochloric acid, approximately 1,19 g/ml, about38% (m/m) solution, or approximately 12 N. 4.2 Lanthanum chloride soluti
18、on, corresponding to5g of lanthanum per litre. NOTEThis solution is not required when an acetylene-dinitrogen monoxide flame is employed. Prepare either of the following solutions: 4.2.1 Dissolve 5,9 g of lanthanum oxide (La 2 O 3 ) in15ml of water and15ml of the hydrochloric acidsolution (4.1). Dil
19、ute to the mark with waterina1000ml one-mark volumetric flask andmix. 4.2.2 Dissolve 13,4 g of lanthanum chloride heptahydrate (LaCl 3 .7H 2 O) in water, dilute to the mark with water in a1000ml one-mark volumetric flask and mix. Either solution 4.2.1 or 4.2.2 shall pass the following test: 20,0ml o
20、f the solution, diluted to themark in a100ml one-mark volumetric flask, shall not give absorbances of the calcium and magnesium lines greater than those obtained with a standard aqueous solution containing3 g of Ca and1g of Mg per100ml, when tested in accordance with 6.2.2 and 6.2.3. In addition, th
21、e quantities of Ca and Mg corresponding to the measured absorbances shall be recorded so that account may be taken of these values in checking the purity of the sodium hydroxide (4.3). 4.3 Sodium hydroxide This product, which is used in the preparation of the sodium chloride solution (4.4), should p
22、referably not have Ca and Mg contents greater than2,5mg/kg and0,5mg/kg respectively. Check these contents as follows: Note, from the calibration graphs (6.2.2 and 6.2.3) the absorbances obtained with the standard matching solution No. 0 (6.2.1). The Ca and Mg contents corresponding to these absorban
23、ces shall not exceed2,5g and0,5g, respectively, discounting quantities of Ca and Mg found in the check test on the lanthanum chloride solution (4.2) in the case where this solution is used. 4.4 Sodium chloride, 58,5g/l acid solution. Place 20,0 g of the sodium hydroxide (4.3) in a600ml polyethylene
24、beaker. Dissolve, while cooling, in100ml of water, then acidify by adding carefully, while stirring80ml of the hydrochloric acid solution (4.1). Transfer quantitatively to500ml conical flask, boil for5min, allow to cool, transfer quantitatively to a500ml one-mark volumetric flask, dilute to the mark
25、 and mix. NOTEIf very pure sodium chloride is available, this solution(4.4) can be prepared as follows: Place29g of sodium chloride in a500ml conical flask. Add250ml of water and40ml of the hydrochloric acid solution(4.1). Boil for 5 min, allow to cool, transfer quantitativelyto a500ml one-mark volu
26、metric flask, dilute to the mark and mix. 4.5 Calcium, standard solution corresponding to0,100 g of calcium per litre. 1) Weigh, to the nearest0,0001g, 0,2497g of calcium carbonate previously dried at about250 C for2h and cooled in a desiccator. Place in a250ml beaker and dissolve in a mixture of10m
27、l of the hydrochloric acid solution (4.1) and15ml of water. Transfer quantitatively to a1000ml one-mark volumetric flask, dilute to the mark and mix. 1 ml of this standard solution contains 0,100 mg ofCa. 1) The spectrophotometric standard reference solutions available commercially can also be used.
28、BS6075-9:1981 2 BSI 10-1999 4.6 Calcium, standard solution corresponding to10mg of calcium per litre. Transfer 20,0 ml of the standard calcium solution(4.5) to a200ml one-mark volumetric flask, dilute to the mark and mix. 1 ml of this standard solution contains10g of Ca. Prepare this solution just b
29、efore use. 4.7 Magnesium, standard solution corresponding to0,100g of magnesium per litre. 1) Weigh, to the nearest0,0001g, 0,1000g of magnesium metal of high purity (minimum99,95%). Place in a250ml beaker and dissolve in a mixture of10ml of the hydrochloric acid solution (4.1) and15ml of water. Tra
30、nsfer quantitatively to a1000ml one-mark volumetric flask, dilute to the mark and mix. 1 ml of this standard solution contains0,100mg ofMg. 4.8 Magnesium, standard solution corresponding to10mg of magnesium per litre. Transfer 20,0 ml of the standard magnesium solution (4.7) to a200ml one-mark volum
31、etric flask, dilute to the mark and mix. 1 ml of this standard solution contains10g of Mg. Prepare this solution just before use. 5 Apparatus Ordinary laboratory apparatus, and 5.1 Atomic absorption spectrophotometer, fitted with a burner fed either with acetylene and dinitrogen monoxide or with ace
32、tylene and air. 5.2 Hollow-cathode calcium lamp 5.3 Hollow-cathode magnesium lamp NOTEAll glassware and reagent bottles shall be either of borosilicate glass or of a quality not yielding calcium or magnesium. 6 Procedure 6.1 Test portion Take 25,0 ml of the solution A, prepared in accordance with IS
33、O3195 and containing40g of the test sample per1000ml, stored in a polyethylene bottle. 6.2 Preparation of the calibration graphs 6.2.1 Preparation of the standard matching solutions Into each of a series of five100ml one-mark volumetric flasks, place25ml of the acid sodium chloride solution (4.4) an
34、d, if using the acetylene-air flame, 20ml of the lanthanum chloride solution(4.2). Then add the volumes of the standard calcium solution (4.6) and standard magnesium solution(4.8) indicated in the following table: Dilute to the mark and mix. 6.2.2 Calibration graphs for calcium 6.2.2.1 ADJUSTMENT OF
35、 THE APPARATUS Install the hollow-cathode calcium lamp (5.2) in the apparatus (5.1) and leave it switched on for the time necessary to achieve stability. Adjust the lamp current, the attenuation and the slit, to suit the characteristics of the apparatus. Adjust the wavelength in the region of422,7nm
36、 in order to obtain the maximum absorbance. Adjust the acetylene and air or dinitrogen monoxide pressuresaccording to the characteristics of the aspirator-burner. 6.2.2.2 SPECTROPHOTOMETER MEASUREMENTS Aspirate the series of standard matching solutions(6.2.1) into the flame and measure the absorbanc
37、e for each. Take care to keep the rate of aspiration constant throughout the preparation of the calibration graph. NOTEPass water through the burner after each measurement. 6.2.2.3 PLOTTING THE CALIBRATION GRAPH Plot a graph having, for example, the numbers of micrograms of Ca contained in100ml of t
38、he standard matching solutions as abscissae and the corresponding values of the measured absorbances, reduced by the measured value for the standard matching solution No. 0, as ordinates. 6.2.3 Calibration graph for magnesium Repeat the operations specified in 6.2.2.1, 6.2.2.2 and6.2.2.3, after havi
39、ng fitted the hollow-cathode magnesium lamp(5.3) to the apparatus and having adjusted the wavelength to about285,2nm. NOTEThe calibration graphs obtained should be linear as far as possible. Standard matching solution No. Standard solutions Corresponding masses calcium (4.6) magnesium (4.8) Ca Mg ml
40、 ml g g 0 a 0 0 0 0 1 1,0 0,2 10 2 2 5,0 1,0 50 10 3 10,0 2,0 100 20 4 20,0 4,0 200 40 a Blank test on reagents for calibration graphs.BS6075-9:1981 BSI 10-1999 3 6.3 Determination 6.3.1 Preparation of the test solution Transfer the test portion (6.1) to a100ml conical flask, add20ml of water and, s
41、lowly while stirring,4,0ml of the hydrochloric acid solution(4.1). Boil gently for5min, cool and transfer quantitatively to a100ml one-mark volumetric flask. If using the acetylene-air flame,add20,0ml of the lanthanum chloride solution (4.2). Dilute to the mark and mix. 6.3.2 Blank test Carry out a
42、blank test at the same time as the determination, following the same procedure and using the same quantities of reagents as used in the determination, but omitting the test portion. 6.3.3 Spectrophotometric measurements Following the procedures specified in 6.2.2 and6.2.3, determine, in order, the a
43、bsorbances for the following solutions: the five standard matching solutions (6.2.1); the test solution (6.3.1); the blank test solution (6.3.2); the standard matching solution (6.2.1) for which the absorbance is closest to that of the test solution. 6.3.4 Check test Verify the absence of interferen
44、ces by repeating the operations specified in 6.3.1 with the addition of known quantities of the standard calcium and magnesium solutions (4.6 and 4.8). If interferences are detected, repeat the calibration using the standard additions method, starting with test solutions prepared as specified in 6.3
45、.1. In this case, ensure that the operations are carried out in the linear part of the calibration graph. 7 Expression of results 7.1 The calcium content, expressed as milligrams of Ca per kilogram, is given by the formula where A 0is the absorbance of the blank test solution(6.3.2); A 1is the absor
46、bance of the test solution (6.3.1); A 2is the mean of the measurements on the standard matching solution closest in absorbance to that of the test solution, carried out before and after the latter; A 3is the absorbance of the standard matching solution No. 0 (6.2.1); m 0is the mass, in grams, of the
47、 test sample used in the preparation of the main solution A; m 1is the mass, in micrograms, of Ca contained in the standard matching solution closest in absorbance to that of the test solution. 7.2 Calculate the magnesium content according to7.1, using the relevant absorbances for magnesium. 8 Test
48、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 in this International Standard or in the International Standard
49、 to which reference is made, or regarded as optional.BS6075-9:1981 4 BSI 10-1999 Annex ISO publications relating to sodium hydroxide for industrial use ISO 979, Method of assay. ISO 980, Determination of carbonates content Gas-volumetric method. ISO 981, Determination of chloride content Mercurimetric method. ISO 982, Determination of sulphate content Barium sulphate gravimetric method. ISO 983, Determination of iron content 1,10-Phenanthroline photometric method. ISO 984, Determination of silica content Reduced silicomoly
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