1、BRITISH STANDARD BS 4267-2: 1988 Ammonium nitrate Part 2: Method for determination of total nitrogen content NOTEIt is recommended that this Part of BS 4267 read in conjunction with the information given in the “General introduction”, published separately as BS 4267-0. WARNING. Ammonium nitrate is a
2、 strong oxidizing agent. If necessary, break the test sample up, by crushing rather than grinding. UDC 661.525:546.39:549.751.13:543:620.1BS4267-2:1988 This British Standard, having been prepared under the directionof the Chemicals Standards Committee, was published under the authorityofthe Board of
3、BSI andcomes into effect on 29July1988 BSI 09-1999 The Committees responsible for this British Standard are shown inPart 0. The following BSI references relate to the work on this standard: Committee reference CIC/21 Draft for comment 84/54890 DC ISBN 0 580 16694 5 Foreword This Part of BS4267 has b
4、een prepared under the direction of the Chemicals Standards Committee. It supersedes clause3 of BS4267:1968, which is withdrawn. This Part of BS4267 is related to BS5551-4.1.3:1986 which is identical with ISO5315:1984. This British Standard describes a method of test only, and should not be used or
5、quoted as a specification defining limits of purity. Reference to this Part should indicate that the method of test used is in accordance with BS4267-2:1988. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for thei
6、r correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, pages1to4, an inside back cover and a back cover. This standard has been updated (see copy
7、right date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Amendments issued since publication Amd. No. Date of issue CommentsBS4267-2:1988 BSI 09-1999 i Contents Page Foreword Inside front cover 1 Scope 1 2 Principle 1 3 Reagents 1
8、 4 Apparatus 1 5 Procedure 1 6 Expression of results 2 7 Test report 2 Figure 1 Typical distillation apparatus (using a round bottomed flask) 3 Publications referred to Inside back coverii blankBS4267-2:1988 BSI 09-1999 1 1 Scope This Part of BS4267 describes a titrimetric method for the determinati
9、on of the total nitrogen content of ammonium nitrate for industrial use. NOTEThe titles of the publications referred to in this standard are listed on the inside back cover. 2 Principle The nitrate nitrogen in a sample is reduced to ammonia by chromium powder in an acid medium. Ammonia is distilled
10、from an alkaline solution, absorbed in an excess of standard volumetric sulphuric acid solution which is back-titrated with standard volumetric sodium hydroxide solution, with methyl red or screened methyl red as indicator. 3 Reagents 3.1 General. During the analysis, use only reagents of recognized
11、 analytical grade and water complying with grade3 of BS3978. 3.2 Chromium metal, powder, of particle size not greater than2504m. 3.3 Ammonium nitrate, anhydrous. Heat approximately5g of ammonium nitrate on a clean platinum dish, in an oven controlled at100 2 C, cool in a desiccator and weigh. Repeat
12、 this procedure until successive weighings do not differ by more than0.01g. 3.4 Hydrochloric acid solution, = approximately1.18 g/mL. 3.5 Sodium hydroxide solution, approximately400g/L. 3.6 Sodium hydroxide, standard volumetric solution, c(NaOH) = 0.10mol/L. 3.7 Sulphuric acid, standard volumetric s
13、olution, c(H 2 SO 4 ) = 0.10mol/L. 3.8 Sulphuric acid, standard volumetric solution, c(H 2 SO 4 ) =0.05mol/L. 3.9 Indicator solution, either a) or b). a) Screened methyl red indicator solution. Mix50mL of a2g/L solution of methyl red in95% (V/V) ethanol with50mL of a1g/L solution of methylene blue i
14、n95% (V/V) ethanol. b) Methyl red indicator solution. Dissolve 0.1g of methyl red in50mL of95% (V/V) ethanol. NOTEFor the purposes of3.9, the ethanol may be replaced by industrial methylated spirits95% (V/V) complying with BS3591. It should be noted that the use of industrial methylated spirits is g
15、overned by The Methylated Spirits Regulations,1983 (S.I.1983 No.252). It is not permissible to use duty-free ethanol, received under the provisions of the Alcoholic Liquors Duties Act1972, Section10, for purposes for which industrial methylated spirits is an acceptable alternative. 3.10 pH indicator
16、 paper, wide range. 4 Apparatus 4.1 Ordinary laboratory apparatus 4.2 Distillation apparatus (see Figure 1) 4.2.1 General. The components of the distillation apparatus shall be connected by means of rubber bungs and tubing, or by the use of spherical ground glass joints. NOTERubber bungs and tubing
17、should be replaced when they begin to perish or show signs of wear. The apparatus comprises the items listed in4.2.2 to4.2.5. 4.2.2 Flask, either a round-bottomed flask,1000mL, or a Kjeldahl flask, 800mL. 4.2.3 Single-bulb splash head and separate open-top dropping funnel, 100mL, followed by a deliv
18、ery tube at the outlet. NOTEInformation on splash heads is given in BS 6855. 4.2.4 Allihn condenser, seven-bulb, with an expansion bulb of capacity approximately100mL, followed by a delivery tube at the outlet (see BS5922). 4.2.5 Receiver, either a conical flask or beaker,500mL. 4.3 Burettes, class
19、A, 50mL, complying with BS846. 4.4 One-mark volumetric flask, class A, 500 mL, complying with BS1792. 4.5 Glass beads, 2mm to3mm in diameter. 5 Procedure 5.1 Test portion and preparation of the test solution Weigh 5.000g of the test sample and transfer to the one-mark volumetric flask (4.4). Dissolv
20、e in water, dilute to the mark and mix well. Filter through a dry filter paper, discarding the first50mL of filtrate. 5.2 Determination 5.2.1 Reduction. Transfer 25.0mL of the test solution (5.1) to the flask (4.2.2) and add sufficient water to make up the total volume to35mL. Add1.2g of the chromiu
21、m powder (3.2) and 7mL of the hydrochloric acid solution (3.4). Allow the flask to stand for at least5min, but not more than10min, at ambient temperature. Place the flask on a heating device in a fume cupboard with the heat input regulated to a level at which250mL of water at20 C would be brought to
22、 a “rolling” boil in7.0min to7.5min. Heat the flask for4.5min. Remove from the heat and allow to cool. 5.2.2 Distillation. Add about250mL of water to the flask (4.2.2), and a few of the glass beads (4.5). Assemble the apparatus as shown in Figure 1.BS4267-2:1988 2 BSI 09-1999 By means of a burette (
23、4.3) measure into the receiver (4.2.5) 50.0mL of the0.10mol/L standard volumetric sulphuric acid solution (3.7). Add four or five drops of the indicator solution 3.9 a) orb) and place the receiver so that the end of the delivery tube (4.2.4) is below the surface of the acid, adding water to the rece
24、iver if necessary. Pour 30 mL of the sodium hydroxide solution (3.5) into the dropping funnel (4.2.3), and carefully run all but about2mL of this solution into the flask(4.2.2). Close the stop-cock, leaving the remaining2mL in the dropping funnel. Bring the contents of the flask to the boil, increas
25、ing the rate of heating progressively until the contents of the flask are boiling briskly. When at least 150mL of distillate has collected, partially withdraw the receiver so that the delivery tube rests on the rim of the receiver. Test the subsequent distillate with the pH indicator paper(3.10) to
26、ensure that all the ammonia has completely distilled. Remove the source of heat. Detach the splash head from the condenser (4.2.4) and wash the insides of the condenser and expansion bulb with water, collecting the washings in the receiver. Rinse the outside of the delivery tube and collect the rins
27、ings in the receiver. 5.2.2 Titration. Back-titrate the excess of acid with the standard volumetric sodium hydroxide solution(3.6) to the neutral colour of the indicator. 5.3 Blank test Carry out a blank test at the same time as the determination, using the same reagents but omitting the test soluti
28、on (5.1), and using the0.05mol/L standard volumetric sulphuric acid solution (3.8) instead of the0.10mol/L standard volumetric sulphuric acid solution (3.7). The result of the blank test should not exceed1.0mL of the0.05mol/L standard volumetric sulphuric acid solution (3.8). If the result is greate
29、r than1.0mL, check the reagents, especially the chromium powder (3.2), by repeating the procedure described in clause5, using fresh reagents as necessary. 5.4 Check test Carry out a periodic check on the efficiency of the apparatus and the accuracy of the method using an aliquot portion of a freshly
30、 prepared solution of the ammonium nitrate (3.3) containing0.1g of nitrogen. The check shall be made under the same conditions as the determination and the blank test and using the same indicator. 6 Expression of results The total nitrogen content, expressed as a percentage by mass of nitrogen (N),
31、is given by the expression where This expression reduces to the following. (V 4 V 2 ) + 50 0.56 7 Test report The test report shall include the following information: a) a complete identification of the sample; b) a reference to this British Standard, i.e. BS4267-2:1988; c) the results expressed in
32、accordance with clause6; d) any unusual features noted during the determination; e) any operation not included in this Part of BS4267 or regarded as optional. V 1 is the volume of the0.10mol/L standard volumetric sulphuric acid solution (3.7) used for the determination (in mL), i.e.50mL; V 2 is the
33、volume of the sodium hydroxide solution (3.6) used for the determination (in mL); V 3 is the volume of the 0.05 mol/L standard volumetric sulphuric acid solution (3.8) used for the blank test (in mL), i.e.50mL; V 4 is the volume of the sodium hydroxide solution (3.6) used for the blank test (in mL);
34、 V 5 is the volume of the test solution before filtering (see5.1) (in mL), i.e. 500 mL; V 6 is the volume of the aliquot portion taken from the test solution (see 5.2.1) (in mL), i.e. 25mL; m is the mass of the test portion (5.1) (in g), i.e. 5.000g.BS4267-2:1988 BSI 09-1999 3 Figure 1 Typical disti
35、llation apparatus (using a round bottomed flask)4 blankBS4267-2:1988 BSI 09-1999 Publications referred to BS 846, Specification for burettes. BS 1792, Specification for one-mark volumetric flasks. BS 3591, Specification for industrial methylated spirits. BS 3978, Specification for water for laborato
36、ry use. BS 4267, Ammonium nitrate. BS 4267-0, General introduction. BS 5551, Fertilizers. BS 5551-4.1.3, Determination of total nitrogen content (titrimetric method after distillation) 1) . BS 5922, Specification for glass condensers for laboratory use. BS 6855, Recommendation for design and constru
37、ction of glass splash heads for laboratory use. ISO 5315, Fertilizers Determination of total nitrogen content Titrimetric method after distillation 1) . 1) Referred to the forword only.BS 4267-2: 1988 BSI 389 Chiswick High Road London W4 4AL BSIBritishStandardsInstitution BSI is the independent nati
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