1、BRITISH STANDARD BS4993-1: 1974 Methods of test for Aluminium fluoride for industrial use Part1: Determination of fluorine content UDC 661.862.361:546.623161:543.24:546.16BS4993-1:1974 This British Standard, having been approved by the ChemicalsIndustry StandardsCommittee, waspublished under the aut
2、horityof the Executive Boardon 28February1974 BSI 10-1999 The following BSI references relate to the work on this standard: Committee reference CIC/24 Drafts for comment/approval 71/53613 and73/50651 ISBN 0 580 08312 8 Co-operating organizations The Chemicals Industry Standards Committee, under whos
3、e supervision this British Standard was prepared, consists of representatives from the following Government departments and scientific and industrial organizations: British Steel Industry Chemical Industries Association* Department of Health and Social Security Department of Trade and Industry Ferti
4、lizer Manufacturers Association Limited Ministry of Agriculture, Fisheries and Food National Sulphuric Acid Association Royal Institute of Public Health and Hygiene Soap and Detergent Industry Association The industrial organization marked with an asterisk in the above list, together with the follow
5、ing, were directly represented on the committee entrusted with the preparation of this British Standard: Aluminium Federation British Ceramic Research Association Society for Analytical Chemistry Society of Chemical Industry Amendments issued since publication Amd. No. Date of issue CommentsBS4993-1
6、:1974 BSI 10-1999 i Contents Page Co-operating organizations Inside front cover Foreword ii 1 Scope 1 2 Principle 1 3 Reagents 1 4 Apparatus 2 5 Procedure 3 6 Calculation 3 Figure 1 Typical form of steam distillation apparatus for use in determination of fluorine content 4 Publications referred to I
7、nside back coverBS4993-1:1974 ii BSI 10-1999 Foreword This British Standard has been prepared under the authority of the Chemicals Industry Standards Committee in order to provide methods for the analysis of aluminium fluoride. For some years the United Kingdom has participated in the work of prepar
8、ing methods of test applicable to aluminium fluoride for industrial use, organized by Sub-Committee7 “Alumina and related compounds” of Technical Committee47 “Chemistry” of the International Organization for Standardization (ISO). As international agreement is reached on the methods, it is proposed
9、to publish them as parts of this British Standard. This part is based on International Standard ISO2362 “Aluminium fluoride for industrial use Determination of fluorine content Modified Willard-Winter method”, modified to take into account the comments made by the UnitedKingdom during its developmen
10、t, in particular by omitting the alternatives of spectrophotometric titration and distillation using perchloric acid. This standard prescribes methods of test only, and should be used or quoted as a specification defining limits of purity. Reference to the standard should be in a form of words indic
11、ating that the methods of test used conform to BS4993. 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
12、 obligations. Summary of pages This document comprises a front cover, an 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
13、 the inside front cover.BS4993-1:1974 BSI 10-1999 1 1 Scope This Part of BS4993 specifies a modified Willard-Winter method for the determination of the fluorine content of aluminium fluoride for industrial use. NOTEThe titles of the British Standards referred to in this standard are listed on the in
14、side back cover. 2 Principle A test portion is fused with sodium carbonate and the fluorine is separated by distillation with sulphuric acid. The distillate is titrated with thorium nitrate solution using as indicator either sodium alizarinsulphonate, with or without methylene blue as masking agent,
15、 or methylthymol blue. 3 Reagents The reagents used shall be of recognized analytical reagent quality. Water complying with the requirements of BS3978 shall be used throughout. 3.1 Sodium carbonate, anhydrous. 3.2 Hydrochloric acid, approximately0.06N solution. Dilute5ml of hydrochloric acid, approx
16、imately1.18g/ml, about36%(m/m) solution, with water to1000ml. 3.3 Perchloric acid, approximately N solution. 3.4 Sodium hydroxide, 20g/l solution. Dissolve20g of sodium hydroxide in water and, after cooling, dilute to1000ml. 3.5 Sulphuric acid, approximately23N. Carefully add, in small quantities,20
17、0ml of sulphuric acid, approximately1.84g/ml, about98%(m/m), to approximately100ml of water, cool and dilute to300ml. 3.6 Buffer solution, pH2.7 (for use with sodium alizarinsulphonate indicator) Dissolve9.45g of monochloroacetic acid in50ml of N sodium hydroxide solution and dilute to100ml with wat
18、er; or 3.7 Buffer solution, pH3.4 (for use with methylthymol blue indicator) Dissolve6.7g of glycine and11g of sodium perchlorate in11ml of N perchloric acid and dilute to100ml with water. 3.8 Thorium nitrate, standardized solution, approximately0.067N. 1ml of this solution is equivalent to approxim
19、ately1.3mg of fluorine. 3.8.1 Preparation of the solution. Dissolve10.01g of thorium nitrate hexahydrate Th (NO 3 ) 4 .6H 2 O in water and dilute to1000ml. 3.8.2 Standardization of the solution 3.8.2.1 Preparation of the standard reference solution. Weigh, to the nearest0.1mg, about200mg of anhydrou
20、s sodium fluoride, previously heated at600 C in a platinum dish and cooled in a desiccator. Transfer, using20ml to30ml of water, into the distillation flask(4.4.1) containing several soda-lime glass balls (2mm to3mm diameter). Stopper the distillation flask and add, through the dropping funnel(4.4.5
21、),50ml of the sulphuric acid(3.5). Carry out the distillation as described in5.3.2. Collect the distillate in a500ml one-mark volumetric flask, complying with the requirements of BS1792, dilute to the mark and mix. NOTEIf analytical reagent grade sodium fluoride is not available, recrystallize the p
22、roduct as follows. Dissolve approximately5g of pure sodium fluoride in125ml of water and, after dissolution, filter under vacuum through a small Buchner funnel. Evaporate the solution in a platinum dish down to about60ml. Cool to about50 C and separate the sodium fluoride crystals by centrifuging. W
23、ash the crystals three times by centrifuging with small quantities of cold water. Transfer the product to a platinum dish and dry in an electric oven, with natural draught, controlled at110 5 C. Remove the dish from the oven, cool in a desiccator, grind the product in an agate mortar and sieve it th
24、rough a sieve with a mesh size of0.355mm (seeBS410). Place the sieved sodium fluoride in a platinum dish, heat for2h at600 C and then allow to cool in a desiccator. 3.8.2.2 Titration. Transfer a50.0ml aliquot portion of the standard reference solution(3.8.2.1) to the beaker(4.7) and titrate as descr
25、ibed in5.3.3. Towards the end of the titration add the last few drops of the thorium nitrate solution(3.8.1) carefully with vigorous stirring. 3.8.2.3 Blank test. Carry out a blank test following the same procedure (distillation as described in5.3.2 and titration as described in5.3.3) using the same
26、 quantity of all the reagents as in the procedure described in3.8.2.1 and3.8.2.2, but omitting the sodium fluoride.BS4993-1:1974 2 BSI 10-1999 3.8.2.4 Calculation of the strength of the solution. The mass, in milligrams, of fluorine (F) corresponding to1ml of thorium nitrate solution is given by the
27、 formula: where 0.4525 is the conversion factor from sodium fluoride to fluorine. 3.9 Sodium alizarinsulphonate, 0.5g/l solution 1) . Dissolve0.05g of sodium alizarinsulphonate in water and dilute to100ml. 3.10 Methylene blue, 0.5g/l solution 1) . Dissolve0.05g of methylene blue (oxidation-reduction
28、 indicator grade) in water and dilute to100ml. 3.11 Methylthymol blue, 0.5g/l solution 1) . Dissolve0.05g of methylthymol blue in water and dilute to100ml. 4 Apparatus Ordinary laboratory apparatus and the following are required. 4.1 Platinum crucible, flat bottom type, upper diameter approximately3
29、0mm, lower diameter approximately15mm and height approximately30mm, fitted with a platinum lid. 4.2 Electric furnace, capable of being controlled at800 20 C. 4.3 Steam generator, such as a flask, capacity approximately3000ml, fitted with a stopper into which are inserted the following three glass tu
30、bes,a), b) and c), of internal diameter about6mm: a) a vertical recovery bend tube, for introducing the steam into the distillation flask(4.4.1) (one limb dipping into the distillation flask); b) a tube for regulating the steam flow, fitted at its outer end with a rubber tube fitted with a Mohr clip
31、; c) a safety tube, about1m long. 4.4 Steam distillation apparatus, borosilicate glass, with ground glass joints. A typical form of apparatus is illustrated in Figure 1 and consists of the following components. 4.4.1 Claisen flask, 250ml capacity, preferably having the following dimensions: diameter
32、 of central neck:36mm; length of side neck including Vigreux distillation column(4.4.2):275mm; distance between side neck and central neck:65mm; diameter of side neck:20mm. 4.4.2 Distillation column, Vigreux type, preferably having the following dimensions: column length between the first and last o
33、f the series of points:120mm; 11groups of three points, spaced at120 on the circumference, at12mm separation. 4.4.3 Thermometer sheath 4.4.4 Thermometer, covering the range0 C to200 C, with an effective length of about250mm. 4.4.5 Dropping funnel, Walter type, about100ml capacity, for insertion in t
34、he Vigreux column. 4.4.6 Graham condenser, with an effective length of about400mm, complying with the requirements of BS1848. 4.5 Electric heater, for heating the distillation flask(4.4.1) up to150 C and capable of being controlled to within1 C. 4.6 pH meter, fitted with a glass electrode. Essential
35、 requirements are given in BS2586, and in BS3145 or BS3422. 4.7 Beaker, of borosilicate glass,250ml, tall form. 4.8 Burette, 10ml with0.02ml divisions. 4.9 Stirrer, magnetic. NOTEAll the glassware should be carefully rinsed with a hot chromic-sulphuric acid mixture, then thoroughly rinsed with water
36、 and finally with water complying with the requirements of BS3978. m 1 is the mass of sodium fluoride (NaF) contained in the aliquot portion of the standard reference solution(3.8.2.1) taken for the titration (mg); V 1 is the volume of the thorium nitrate solution(3.8.1) used for the titration of th
37、e aliquot portion of the standard reference solution(3.8.2.1) taken for the titration (ml); V 2 is the volume of thorium nitrate solution(3.8.1) used for the titration of the blank solution(3.8.2.3) (ml); 1) Instead of using the two indicators3.9 and3.10 (see5.3.3), the sodium alizarinsulphonate sol
38、ution(3.9) may be used alone. Alternatively the methylthymol blue(3.11), or any other indicator that gives equivalent results with the appropriate buffer and in the specified pH range, may be used. m 1 0.4525 V 1 V 2 -BS4993-1:1974 BSI 10-1999 3 5 Procedure 5.1 Test portion. Weigh, to the nearest0.1
39、mg, about200mg of the dried test sample 2)into the platinum crucible(4.1). 5.2 Blank test. Carry out at the same time, using the same procedure, a blank test with the same quantities of all the reagents used for the determination, but omitting the test portion(5.1). 5.3 Determination 5.3.1 Preparati
40、on of the test solution. Introduce into the crucible(4.1) containing the test portion(5.1)2g of the sodium carbonate(3.1) and mix carefully, preferably by means of a platinum wire. Place the crucible in the electric furnace(4.2), previously heated to about200 C, and heat to800 20 C. Maintain at this
41、 temperature until the carbon dioxide is eliminated and the sample has melted (20min approximately). Remove the crucible from the furnace and cool rapidly by plunging the base of the crucible into a bath of cold water. Transfer the fused mass directly to the distillation flask(4.4.1), containing sev
42、eral soda-lime glass balls (2mm to3mm diameter), and wash the crucible carefully with20ml or30ml of hot water in order to dissolve that part of the melt still adhering to the crucible, collecting the washings in the distillation flask(4.4.1). 5.3.2 Distillation. Place a500ml one-mark volumetric flas
43、k under the condenser (4.4.6) to collect the distillate. Connect the distillation flask to the condenser(4.4.6) and start the water circulation. Stopper the distillation flask and add, through the dropping funnel(4.4.5),50ml of the sulphuric acid(3.5). Using the electric heater(4.5), heat the distil
44、lation flask until the solution reaches150 C. Pass steam from the generator(4.3) into the distillation flask so as to maintain the solution at150 1 C and collect about400ml of the distillate over a period of about90min. Disconnect the distillation flask from the steam generator(4.3), allowing the st
45、eam to escape to atmosphere, and remove the heater(4.5). Wash the condenser with a jet of water. Dilute the distillate to the mark in the collecting flask and mix. 5.3.3 Titration. Transfer50.0ml of the contents of the collecting flask(5.3.2) to the beaker(4.7). Add to the beaker about50ml of water
46、and0.50ml of the sodium alizarinsulphonate solution(3.9) and then, in small portions, the sodium hydroxide solution(3.4) until a pink coloration appears (pH of the colour change 6.6 to 6.8). Checking by means of the pH meter(4.6), add the hydrochloric acid solution(3.2) drop by drop until the pH val
47、ue is between4.9 and5.2 (yellow coloration of the solution). Add3.0ml of the sodium alizarinsulphonate solution and then, still checking with the pH meter, add the buffer solution(3.6) in small portions until the pH is3.4 0.1 (about1ml of the buffer solution is needed). Add0.50ml of the methylene bl
48、ue solution(3.10) (green coloration of the solution). Place a small glass-encased iron bar in the solution and stir vigorously using the stirrer(4.9). Fill the burette(4.8) with the thorium nitrate solution(3.8) and titrate just to the development of a blue-violet colour. Ensure that the same lighti
49、ng conditions are used as for the standardization of the thorium nitrate solution(3.8.2.2). NOTE 1Carry out the titration in daylight or under fluorescent lighting. The titration must not be carried out with the illumination provided by a tungsten filament lamp. NOTE 2If the methylthymol blue(3.11) is used as indicator, the pH3.4 buffer solution(3.7) should be used instead of pH2.7 buffer solution(3.6) and pH adjustments carried out with the perchloric acid solution(3.3) instead of the hydrochloric acid(3.2).
