BS 5551-4 1 4-1984 Fertilizers - Chemical analysis - Determination of nitrogen - Method for determination of ammoniacal nitrogen content in the presence of other substances which r.pdf

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1、BRITISH STANDARD BS 5551-4.1.4: 1984 ISO 7408:1983 Fertilizers Part 4: Chemical analysis Section 4.1 Determination of nitrogen Subsection 4.1.4 Method for determination of ammoniacal nitrogen content in the presence of other substances which release ammonia when treated with sodium hydroxide (titrim

2、etric method) ISO title: Fertilizers Determination of ammoniacal nitrogen content in the presence of other substances which release ammonia when treated with sodium hydroxide Titrimetric method UDC 631.8:543.06:543.24:546.171BS5551-4.1.4:1984 This British Standard, having been prepared under the dir

3、ectionof the Chemicals Standards Committee, was published under the authority ofthe Board of BSI and comes intoeffect on 31August1984 BSI 10-1999 The following BSI references relate to the work on this standard: Committee reference CIC/37 Draft for comment 81/53152DC ISBN 0 580 13956 5 Committees re

4、sponsible for this British Standard The preparation of this British Standard was entrusted by the Chemicals Standards Committee (CIC/-) to Technical Committee CIC/37 upon which the following bodies were represented: Association of Public Analysts British Agrochemicals Association Department of Trade

5、 and Industry (Laboratory of the Government Chemist) Fertiliser Manufacturers Association Ltd. Institute of Trading Standards Administration Ministry of Agriculture, Fisheries and Food Amendments issued since publication Amd. No. Date of issue CommentsBS5551-4.1.4:1984 BSI 10-1999 i Contents Page Co

6、mmittees responsible Inside front cover National foreword ii 1 Scope and field of application 1 2 Principle 1 3 Reagents 1 4 Apparatus 1 5 Procedure 2 6 Expression of results 3 7 Precision 3 8 Test report 3 Figure 1 Typical apparatus for the determination of ammoniacal nitrogen content using compres

7、sed air 4 Figure 2 Typical apparatus for the determination of ammoniacal nitrogen content using suction 5 Table Reagents required for titration 2 Publications referred to Inside back coverBS5551-4.1.4:1984 ii BSI 10-1999 National foreword This British Standard has been prepared under the direction o

8、f the Chemicals Standards Committee in order to standardize terminology and labelling, sampling and methods of physical and chemical testing for fertilizers. For some years the United Kingdom has participated in the standardization of methods of analysing fertilizers through Subcommittee4, Chemical

9、analysis, of Technical Committee134, Fertilizers and soil conditioners, of the International Organization for Standardization (ISO). As international agreement is reached on the methods, it is proposed to publish them as Sections of BS5551. The standard is to be published in four Parts, each Part be

10、ing subdivided into Sections and, where appropriate, Subsections. The four Parts are: Part 1: Terminology and labelling; Part 2: Sampling; Part 3: Physical properties; Part 4: Chemical analysis. Part4 is to be divided into five Sections as follows. Section 4.1: Determination of nitrogen; Section 4.2

11、: Determination of phosphorus; Section 4.3: Determination of potassium; Section 4.4: Determination of water; Section 4.5: Determination of other constituents. This Subsection of Part4 is identical with ISO7408:1983 “Fertilizers Determination of ammoniacal nitrogen content in the presence of other su

12、bstances which release ammonia when treated with sodium hydroxide Titrimetric method”. 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

13、 with those used in British Standards; attention is drawn especially 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 words “International Standard” appear, re

14、ferring to this standard, they should be read as “British Standard”. Cross-reference. The Technical Committee has reviewed the provisions of ISO383, to which reference is made inFigure 1, and has decided that they are acceptable for use in conjunction with this standard. A related British Standard i

15、s BS572 “Interchangeable conical ground glass joints”. Additional information. 1) This British Standard specifies a method of test only and should not be used as a specification defining limits of purity. Reference to the standard should indicate that the method of test used is in accordance with BS

16、5551-4.1.4. 2) Until the International Standard, referred to in the footnote to5.1, on the sampling of fertilizers is available, guidance can be found in Part1“Introduction and general principles”, and Part4 “Sampling of solids”, of BS5309 “Methods for sampling chemical products”. 3) With reference

17、to clause3, water complying with the requirements of BS3978 “Water for laboratory use” is suitable.BS5551-4.1.4:1984 BSI 10-1999 iii 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. Co

18、mpliance 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, pages i to iv, pages1 to6, an inside back cover and a back cover. This standard has been updated (see copyright date) and may hav

19、e had amendments incorporated. This will be indicated in the amendment table on the inside front cover.iv blankBS5551-4.1.4:1984 BSI 10-1999 1 1 Scope and field of application This International Standard specifies a method for the determination of the ammoniacal nitrogen content of fertilizers conta

20、ining other substances, such as urea or urea-aldehyde condensates, which release ammonia in the presence of sodium hydroxide. 2 Principle Entrainment, by means of a strong current of air, of the ammonia from a moderately alkaline test mixture at ambient temperature into standard volumetric sulfuric

21、acid solution. Back-titration of the excess sulfuric acid with standard volumetric sodium hydroxide solution. 3 Reagents During the analysis, use only reagents of recognized analytical grade, and only distilled water or water of equivalent purity. 3.1 Nonyl alcohol (nonanol) 3.2 Potassium carbonate,

22、 saturated solution at room temperature. 3.3 Sulfuric acid, approximately 590g/l solution. 3.4 Sulfuric acid, standard volumetric solution, c(H 2 SO 4 )=0,25mol/l. 1) 3.5 Sulfuric acid, standard volumetric solution, c(H 2 SO 4 )=0,05mol/l. 2) 3.6 Sodium hydroxide, approximately 120g/l solution. 3.7

23、Sodium hydroxide, standard volumetric solution, c(NaOH)=0,50mol/l. 1) 3.8 Sodium hydroxide, standard volumetric solution, c(NaOH)=0,10mol/l. 2) 3.9 Mixed indicator solution, screened ethanolic methyl red solution. Mix 50ml of a 2g/l ethanolic methyl red solution with 50ml of a 1g/l ethanolic methyle

24、ne blue solution. The colour of this indicator changes from lilac in acid medium, via grey at pH5,4, to green in alkaline medium. 3.10 Ammonium sulfate, dried to constant mass at100 C. 3.11 Urea 4 Apparatus Ordinary laboratory apparatus and 4.1 Entrainment apparatus The components of the apparatus m

25、ay be connected by means of rubber bungs and tubing or by the use of ground glass joints. Ground glass joints should be held by spring clamps to ensure that they are leak-tight. Rubber bungs and tubing should be replaced when they begin to perish or show signs of wear. A suitable apparatus is illust

26、rated inFigure 1 andFigure 2 and comprises the following components: 4.1.1 Double-necked bottle, of capacity350 to400ml. 4.1.2 Inlet tube, fitted with a mushroom-shaped air distributor. This distributor has an external diameter of 20mm and has six openings in the rim, each1 0,2mm in diameter. NOTETh

27、e shape of the distributor and the number of holes and their diameters are important in ensuring adequate distribution of air bubbles despite the strong flow of air. 4.1.3 Outlet tube, with a single bulb splash head. If ground glass joints are used, the inlet tube (4.1.2) and the outlet tube with it

28、s splash head (4.1.3) form one rigid glass assembly. If a rubber bung is used, the inlet and outlet tubes shall be separate and the inlet tube shall be straight and shall be of uniform diameter at the top end. 4.1.4 Inlet tube, similar to that described in4.1.2. 4.1.5 Conical flask, of capacity 500m

29、l. 4.1.6 Three-necked flask (or conical flask of capacity500ml), fitted with an inlet tube, an outlet tube and a stopcock (only required when suction is used instead of compressed air). 4.2 Washing bottles 4.2.1 Two washing bottles, of capacity 500ml, with the usual inlet and outlet tubes of diamete

30、r 6mm without bulb splash head. 4.2.2 Washing bottle, similar to those described in4.2.1, but with a shorter inlet tube. 1) Hitherto expressed as “0,50N standard volumetric solution”. 2) Hitherto expressed as “0,10N standard volumetric solution”.BS5551-4.1.4:1984 2 BSI 10-1999 4.3 Four pipettes, of

31、capacities 502520 and10ml. 4.4 Three burettes, of capacities 5025 and 10ml. 4.5 Compressed air source, fitted with a regulator capable of controlling the air flow rate at about3000ml/min, or 4.6 Suction device, for example a water jet pump, capable of maintaining an air flow rate through the apparat

32、us at about 3000ml/min. 4.7 Flowmeter, to measure the flow of air. 5 Procedure 5.1 Test portion Weigh, to the nearest 0,001g, approximately 1g of the laboratory sample. 3) Transfer the test portion to the double-necked flask(4.1.1). 5.2 Assembly of the apparatus Assemble the entrainment apparatus (4

33、.1). Connect in series with the double-necked bottle(4.1.1), in the following order (seeFigure 1): a) one of the bottles (4.2.1) in which has been placed 250ml of the sodium hydroxide solution(3.6); b) the other bottle (4.2.1) in which has been placed 250ml of the sulfuric acid solution (3.3); c) th

34、e empty bottle (4.2.2). Connect the flowmeter (4.7) to the empty bottle(4.2.2). If compressed air is used, connect the compressed air source (4.5) to the flowmeter (4.7). If suction is used, connect the suction device (4.6), via the flask(4.1.6) to the conical flask (4.1.5), as shown inFigure 2. NOT

35、EThe flask (4.1.6) prevents water entering the apparatus in the event of pressure fluctuations. Ensure that all the connections are airtight. 5.3 Determination 5.3.1 Fertilizers of known composition Depending on the expected ammoniacal nitrogen content of the sample, measure into the flask (4.1.5),

36、by means of a pipette, the appropriate volume of the appropriate sulfuric acid solution (3.4 or3.5) specified in the table. Add water until the level of the liquid is about 50mm above the orifice of the inlet tube (4.1.4) and then add 5drops of the mixed indicator solution (3.9). Add, through the si

37、de-neck of the double-necked bottle (4.1.1), 50ml of water, a few drops of the nonyl alcohol (3.1) and render the solution alkaline by adding 50ml of the saturated potassium carbonate solution (3.2). NOTEThe addition of nonyl alcohol prevents foaming when the air is passed. Immediately close the sid

38、e-neck of the bottle and, using compression or suction as appropriate, startthe air flow. Adjust the air flow rate to about3000ml/min and pass air through the apparatus for 2h. Lower the conical flask so that its lip supports the end of the inlet tube (4.1.4). Rinse the outside of the tube with wate

39、r, collecting the rinsings in the flask, and stop the air flow. Titrate the residual acid in the conical flask with the appropriate sodium hydroxide solution (see the Table) to the neutral colour (grey) of the mixed indicator solution (3.9). Table Reagents required for titration 5.3.2 Fertilizers of

40、 unknown composition Carry out the procedure specified in5.3.1 for samples having ammoniacal nitrogen contents greater than 3,5% (m/m) and then continue as follows. After removing the conical flask (4.1.5), substituteanother similar flask containing 10,0ml of the standard volumetric sulfuric acid so

41、lution(3.4), 5drops of the mixed indicator solution (3.9) and sufficient water for the level of liquid to be 50mm above the orifice of the inlet tube. Restart the air flow, adjust it to about 3000ml/min and pass the air for 1h. Lower the conical flask so that its lip supports the end of the inlet tu

42、be (4.1.4). Rinse the outside of the tube with water, collecting the rinsings in the flask and stop the air flow. Titrate the residual acid in the conical flask with the sodium hydroxide solution (3.7) to the neutral colour (grey) of the mixed indicator solution (3.9). Combine the results of each de

43、termination. 3) The preparation of samples of fertilizers will form the subject of a future International Standard. Expected ammoniacal nitrogen content, % (m/m) Sulfuric acid solution added to the conical flask (4.1.5) Sodium hydroxide solution used for the titration Identity Volume, ml Identity (c

44、oncentration) 3,5 W 1,0 and u 3,5 1,0 3.4 3.5 3.5 40,0 40,0 10,0 3.7 (0,5 mol/l) 3.8 (0,1 mol/l) 3.8 (0,1 mol/l)BS5551-4.1.4:1984 BSI 10-1999 3 5.4 Blank test At the same time as the determination, carry out a blank test using the same reagents but omitting the test portion and using the sulfuric ac

45、id solution (3.5) and the sodium hydroxide solution (3.8). 5.5 Check test Periodically, carry out a check test on the efficiency of the apparatus and the accuracy of the test method, as follows. Weigh 4,716g of the ammonium sulfate (3.10) and25g of the urea (3.11) into a 250ml one-mark volumetric fl

46、ask. Dissolve in 200ml of water and dilute to the mark with water. Use as the test portion 25,0ml of this solution, equivalent to 100mg of ammoniacal nitrogen, and use the same conditions as for the determination and the blank test and with the same indicator. 6 Expression of results The ammoniacal

47、nitrogen content, expressed as nitrogen (N) as a percentage by mass, is given by the formula where c 1is the concentration, in moles per litre, of the sulfuric acid solution used for the determination and for the blank test; c 2is the concentration, in moles per litre, of the sodium hydroxide soluti

48、on used for the determination and for the blank test; V 1is the volume, in millilitres, of the sulfuric acid solution used for the determination and for the blank test; V 2is the volume, in millilitres, of the sodium hydroxide solution used for the determination; V 3is the volume, in millilitres, of

49、 the sodium hydroxide solution used for the blank test; m 0is the mass, in grams, of the test portion (5.1). 7 Precision Precision data have been analysed statistically froman inter-laboratory study in which 16 laboratories (6countries) participated with 7levels. No statistical relationship between repeatability (r) or reproducibility (R) and the mean value of the ammoniacal nitrogen content of the samples was found. 7.1 Repeatability, r The difference between two individual test results, obtained simultaneously or in rapid successi