1、BRITISH STANDARD BS 4140-19: 1986 ISO 2865:1973 Incorporating Amendment No. 1 Methods of test for Aluminium oxide Part 19: Determination of boron content ISO title: Aluminium oxide primarily used for the production of aluminium Determination of boron content Curcumin spectrophotometric method NOTEIt
2、 is recommended that this Part be read in conjunction with the general information giveninBS4140-0 “General introduction” which is issued separately. UDC 661.862.22:546.27:543.42BS4140-19:1986 This British Standard, having been prepared under the directionof the Chemicals Standards Committee, was pu
3、blished under the authorityofthe Executive Boardand comes into effect on 28February1986 BSI 11-1999 The following BSI references relate to the work on this standard: Committee reference CIC/24 Draft for comment 85/52368DC ISBN 0 580 15016 X Amendments issued since publication Amd. No. Date of issue
4、Comments 6896 April 1992 Indicated by a sideline in the marginBS4140-19:1986 BSI 11-1999 i Contents Page National foreword Inside front cover 1 Scope and field of application 1 2 Reference 1 3 Principle 1 4 Reagents 1 5 Apparatus 1 6 Procedure 2 7 Expression of results 3 8 Test report 3 Figure 1 Ass
5、embly for preparation of test solution 4 Figure 2 Assembly for distillation 4 Figure 3 Water-bath 5 Publication referred to Inside back coverBS4140-19:1986 ii BSI 11-1999 National foreword This Part of BS4140 is identical with ISO 2865:1973 “Aluminium oxide primarily used for the production of alumi
6、nium Determination of boron content Curcumin spectrophotometric method”, including Technical Corrigendum1 published by the International Organization for Standardization (ISO). The method supersedes clause 19 of Addendum No. 3 (1974) to BS 4140:1967. Part 17 to 19 of this standard collectively super
7、sede Addendum No. 3 (1974) to BS4140:1967 which is withdrawn. 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 certain conventions are not identical with those used in Briti
8、sh Standards; attention is drawn especially to the following. The comma has been used as a decimal marker. In British Standards it is current practice to use a full point on the baseline as the decimal marker. In British Standards it is current practice to use the symbol “L” for litre (and its submu
9、ltiples) rather than “l”. Wherever the words “International Standard” appear referring to this standard, they should be read as “British Standard”. This standard prescribes methods of test only, and should not be used or quoted as a specification defining limits of purity. Reference to this Part sho
10、uld indicate that the method of test used complies with BS 4140-19:1986. 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 i
11、mmunity from legal obligations. Cross-references International Standard Corresponding British Standard BS 4140 Methods of test for aluminium oxide ISO 802:1976 Part 1:1986 Preparation and storage of test samples (Identical) ISO 2927:1973 Part 20:1980 Sampling (Identical) Summary of pages This docume
12、nt comprises a front cover, an inside front cover, pages i and ii, pages1 to 6, 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.BS4140-19:1986 B
13、SI 11-1999 1 1 Scope and field of application This International Standard specifies a curcumin spectrophotometric method for the determination of the boron content of aluminium oxide primarily used for the production of aluminium. The method is applicable to boron contents, expressed as boron oxide
14、(B 2 O 3 ), greater than0,0006% i.e.0,0002% expressed as boron(B). NOTEThe sensitivity of the method, as may be gathered from the calibration curve, is in fact higher. In the case of a very low blank reading, and with sufficiently sensitive apparatus, the lower limit of application of the method may
15、 be extended to0,00008% of boron oxide (B 2 O 3 ), corresponding to0,000025% of boron (B). 2 Reference ISO 802:1976, Aluminium oxide primarily used for the production of aluminium Preparation and storage of test samples. ISO 2927:1973, Aluminium oxide used primarily for the production of aluminium S
16、ampling. 3 Principle Dissolution of a test portion in phosphoric acid. Separation of the boron by distillation as methyl borate. Formation of a red-coloured complex between the boron and the curcumin reagent at pH7. Spectrophotometric measurement of the complex at a wavelength of about550nm. 4 Reage
17、nts Distilled water, or water of equivalent purity, shall be used in the test. 4.1 Orthophosphoric acid, approximately 1,70g/ml, about85% (m/m) solution. 4.2 Methanol, approximately0,79g/ml. 4.3 Ethanol, approximately0,81g/ml. 4.4 Glycerol, alkaline solution. Dissolve1g of sodium hydroxide and0,1g o
18、f sodium chloride in about100ml of water to which has been added3,0ml of glycerol. Store this solution in a silica flask. 4.5 Curcumin reagent solution Add to a250ml silica one-mark volumetric flask: 175 ml of the ethanol (4.3); 3,75 g of oxalic acid (COOH) 2 .2H 2 O; 6,25 ml of hydrochloric acid so
19、lution, approximately1,19g/ml, about38% (m/m) solution; 19 ml of water; 0,087 5 g of curcumin. Shake until completely dissolved, dilute to the mark with the ethanol(4.3) and mix. Store in the dark and at about20 C. This solution is stable for at least2months. 4.6 Boron, standard solution, correspond
20、ing to0,08g of B 2 O 3per litre. Weigh, to the nearest0,0001g,0,1421g of boric acid (H 3 BO 3 ). Transfer to a silica beaker of convenient capacity (for example200ml) and dissolve in water. Transfer the solution quantitatively to a1000ml silica one-mark volumetric flask, dilute to the mark and mix.
21、1 ml of this standard solution corresponds to0,08mg of B 2 O 3 . 4.7 Boron, standard solution, corresponding to0,0008g of B 2 O 3per litre. Place10,0ml of the standard boron solution(4.6) in a1000ml silica one-mark volumetric flask, dilute to the mark and mix. 1 ml of this standard solution correspo
22、nds to0,8g of B 2 O 3 . Prepare this solution just before use. 4.8 Thymol blue solution, 0,5 g/l. Dissolve0,05g of thymol blue in water and dilute to100ml. 5 Apparatus Ordinary laboratory apparatus and: 5.1 Silica apparatus, for the boron distillation. The apparatus (an example of which is shown in
23、Figure 1 andFigure 2) comprises: 5.1.1 Distillation flask,250ml with a ground neck; NOTEThe flask shall be replaced as soon as it shows signs of attack by phosphoric acid. 5.1.2 Guard tube, bent and fitted with ground joints; 5.1.3 Adaptor, with three ground joints; 5.1.4 Cylindrical dropping funnel
24、, with ground joint and stopper; 5.1.5 Connector, with two ground joints; 5.1.6 Liebig condenser, with ground joints (effective length, about400mm). NOTEUse different apparatus for the distillation of: the blank test; test portions of B 2 O 3contents less than13g; test portions of B 2 O 3contents gr
25、eater than13g. Carefully wash the apparatus before use by heating100ml of an approximately10N hydrochloric acid solution to boiling and, after rejecting this solution, distilling100ml of the methanol(4.2), acidified with hydrochloric acid.BS4140-19:1986 2 BSI 11-1999 5.2 Silica beaker, capacity abou
26、t250ml. 5.3 Water-bath, capable of being controlled at55 1 C (seeFigure 3). 5.4 Thermometer, covering the temperature range of20to140 C. 5.5 Stirring rod, constructed of plastics material. 5.6 Platinum dish, diameter about75mm, height about35mm. NOTEBefore use, wash the dish carefully first with an
27、approximately10N hydrochloric acid solution and then with the methanol(4.2). Use different dishes for: the blank test; test portions of B 2 O 3contents less than13g; test portions of B 2 O 3contents greater than13g; 5.7 Glycerol or silicone oil bath 5.8 Spectrophotometer 6 Procedure 6.1 Test portion
28、 Weigh, to the nearest0,001g,1g of the laboratory sample, dried at300 C, prepared as described in ISO2927 and ISO802:1976, subclause3.3. 6.2 Blank test Carry out at the same time and following the same procedure a blank test in the absence of pure aluminium oxide, using the same quantities of all re
29、agents used in the test. 6.3 Preparation of the calibration curve 6.3.1 Preparation of standard colorimetric solutions, referring to spectrophotometric measurements made with an optical path length of2cm. Into a series of five platinum dishes(5.6) add the volumes of the standard boron solution(4.7)
30、indicated in the following table. Add to each dish3,0ml of the alkaline glycerol solution(4.4). NOTE 1If4ml of the alkaline glycerol solution(4.4) is used for the determination (see6.4.2), use this volume to establish the calibration curve and for the blank test. Heat the dishes on the water bath(5.
31、3) until removal of the water is complete. Then heat at130 C in an electric oven until the residue is dry. Add to each dish5,0ml of the curcumin reagent solution(4.5), rinsing down the contents by running the solution down the wall. Develop the colour by heating on the water bath(5.3), to complete e
32、vaporation, checking, by means of the thermometer(5.4), that the temperature of the water bath is55 1 C. Continue heating for a further20min after evaporation is complete. NOTE 2As the colour reaction is influenced by the humidity of the atmosphere above the dishes, the water level in the bath(5.3)
33、is automatically maintained15cm from the top. Separate the dishes from each other by distances approximately equivalent to their diameter. Remove the dishes from the bath and allow to cool in a desiccator. Dissolve the residues in25ml of the ethanol(4.3), stirring with the plastics rod(5.5). Transfe
34、r the solutions quantitatively to50ml one-mark volumetric flasks, dilute to the marks with the ethanol(4.3) and mix. Filter the solutions through dry fine grade filter papers direct into dry cells of optical path length2cm. Prepare a new calibration curve each time a fresh batch of the curcumin reag
35、ent solution(4.5) is prepared. 6.3.2 Spectrophotometric measurement Carry out the spectrophotometric measurements using the spectrophotometer(5.8) at a wavelength of about550nm, after having adjusted the apparatus to zero absorbance against the compensation solution. 6.3.3 Preparation of the calibra
36、tion chart Plot a graph having, for example, on the abscissae the values, expressed in milligrams, of the masses of B 2 O 3per50ml of standard colorimetric solution and the corresponding values of absorbance on the ordinates. Standard boron solution (4.7) Corresponding mass of B 2 O 3 ml g 0 a 0 1,0
37、 0,8 4,0 3,2 8,0 6,4 12,0 9,6 a compensation solution.BS4140-19:1986 BSI 11-1999 3 6.4 Determination 6.4.1 Preparation of the test solution Place the test portion(6.1) in the distillation flask(5.1.1) and add20,0ml of the phosphoric acid solution(4.1). Introduce a plastics-coated magnetic stirring r
38、od. Place the guard tube(5.1.2) in position (seeFigure 1) so as to ensure that the solution is not contaminated during the dissolution of the test portion. Carefully heat the phosphoric acid, with stirring, until the test portion is completely dissolved. Allow to cool to between50and60 C, replace th
39、e guard tube by the adaptor(5.1.3) and fit the cylindrical dropping funnel(5.1.4), the connector(5.1.5) and the condenser(5.1.6). (SeeFigure 2.) Add35,0ml of the methanol(4.2) through the dropping funnel(5.1.4), mix carefully and note the level of liquid in the distillation flask(5.1.1). 6.4.2 Disti
40、llation Place3,0ml of the alkaline glycerol solution(4.4) in the beaker(5.2), and add1to3drops of the thymol blue solution(4.8) and35,0ml of water. Place the beaker so that the lower end of the condenser(5.1.6) is immersed in this absorption solution. Heat the distillation flask containing the test
41、solution(6.4.1) to100 C by means of the glycerol or silicone oil bath(5.7). Add, through the dropping funnel(5.1.4),55,0ml of the methanol(4.2) in10ml portions, the final portion being15ml. After each addition, mix the solution by means of the magnetic stirrer, without removing the flask from the he
42、ating bath, and distil down to the level previously noted. When the methanol has distilled completely, allow the temperature to rise to between120and130 C. The colour of the solution in the beaker should never become yellow; if such is the case add a further1ml of the alkaline glycerol solution(4.4)
43、. (See6.3.1 Note1.) Rinse the condenser(5.1.6) with water and add the rinse to the distillate. The total volume of water added shall be equal to at least half the volume of methanol distilled. 6.4.3 Colour development Transfer the contents of the beaker quantitatively to a platinum dish(5.6). Heat c
44、arefully on the water-bath(5.3) controlled at55 1 C until removal of the water is complete. Then heat at130 C in an electric oven until the residue is dry. Increase the temperature to600 C in an electric furnace in order to destroy the thymol blue. Maintain at this temperature until the residue is p
45、erfectly white. If the residue starts to melt or does not form a uniform layer on the surface of the dish, redissolve it in some water and dry once again, following the procedure already described. Add5,0ml of the curcumin reagent solution(4.5) to the dish, rinsing down the contents by running the s
46、olution down the wall. Develop the colour by heating on the water bath(5.3) to complete evaporation, checking, by means of the thermometer(5.4), that the temperature of the water bath is55 1 C. Continue heating for a further20min after evaporation is complete. Remove the dish from the bath and allow
47、 to cool in a desiccator. Dissolve the residue in25ml of the ethanol(4.3), stirring with the plastics rod(5.5). Transfer the solution quantitatively to a50ml one-mark volumetric flask, dilute to the mark with the ethanol(4.3) and mix. Filter the solution through a dry fine-grade filter paper direct
48、into a dry cell of optical path length2cm. 6.4.4 Spectrophotometric measurement Carry out the spectrophotometric measurement using the spectrophotometer(5.8) at a wavelength of about550nm after having adjusted the apparatus to zero absorbance against the blank test solution. 7 Expression of results
49、Using the calibration curve(6.3.3), determine the mass of boron oxide corresponding to the value of the spectrophotometric measurement. The content of boron oxide (B 2 O 3 ) is given, as a percentage by mass, by the formula where m is the mass, in milligrams, of B 2 O 3found in the test solution. 8 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 determin
