1、BRITISH STANDARD BS 5551-4.1.2: 1982 ISO 5314:1981 Fertilizers Part 4: Chemical analysis Section 4.1 Determination of nitrogen Subsection 4.1.2 Determination of ammoniacal nitrogen, titrimetric method after distillation ISO title: Fertilizers Determination of ammoniacal nitrogen content Titrimetric
2、method after distillation UDC 631.8:543.06:543.846BS5551-4.1.2:1982 This British Standard, having been prepared under the directionof the Chemicals Standards Committee, was published under the authority ofthe Board of BSI and comes into effecton 30July1982 BSI 10-1999 The following BSI references re
3、late to the work on this standard: Committee reference CIC/37 Draft for comment 78/51439 DC ISBN 0 580 12819 9 Cooperating organizations The Chemicals Standards Committee, under whose direction this British Standard was prepared, consists of representatives from the following: Association of Fatty A
4、cid Distillers British Tar Industry Association Chemical Industries Association* Consumer Standards Advisory Committee of BSI Department of Health and Social Security Department of Industry, Laboratory of the Government Chemist* Fertiliser Manufacturers Association Ltd.* Ministry of Agriculture, Fis
5、heries and Food* Ministry of Defence National Sulphuric Acid Association Paintmakers Association of Great Britain Ltd. Royal Institute of Public Health and Hygiene Royal Society of Chemistry Soap and Detergent Industry Association Standardization of Tar Products Tests Committee The organizations mar
6、ked with an asterisk in the above list, together with the following, were directly represented on the Technical Committee entrusted with the preparation of this British Standard: Association of Public Analysts British Agrochemicals Association Institute of Trading Standards Administration Amendments
7、 issued since publication Amd. No. Date of issue CommentsBS5551-4.1.2:1982 BSI 10-1999 i Contents Page Cooperating organizations Inside front cover National foreword ii 1 Scope and field of application 1 2 References 1 3 Principle 1 4 Reagents 1 5 Apparatus 1 6 Procedure 1 7 Expression of results 2
8、8 Test report 3 Figure Typical distillation apparatus 4 Publications referred to Inside back coverBS5551-4.1.2:1982 ii BSI 10-1999 National foreword This British Standard has been prepared under the direction of the Chemicals Standards Committee in order to standardize terminology and labelling, sam
9、pling 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 analysis, of Technical Committee134, Fertilizers and soil conditioners, of the Internation
10、al 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 being subdivided into Sections and, where appropriate, Subsections. The four Parts are: Part
11、 1: Terminology and labelling; Part 2: Sampling; Part 3: Physical properties; Part 4: Chemical analysis. Part 4 is to be divided into five Sections as follows: Section 4.1: Determination of nitrogen; Section 4.2: Determination of phosphorus; Section 4.3: Determination of potassium; Section 4.4: Dete
12、rmination of water; Section 4.5: Determination of other constituents. This Subsection of Part4 is identical with ISO5314:1981 “Fertilizers Determination of ammoniacal nitrogen content Titrimetric method after distillation”. Terminology and conventions. The text of the International Standard has been
13、 approved as suitable for publication as a British Standard without deviation. Some terminology and 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
14、 it is current practice to use a full point on the baseline as the decimal marker. Wherever the words “International Standard” appear, referring to this standard, they should be read as “British Standard”. The Technical Committee has reviewed the provisions of ISO/R385, to which reference is made in
15、 clause2 and5.2, ISO641, to which reference is made inclause2 and ISO648, to which reference is made inclause2 and5.4, and has decided that they are acceptable for use in conjunction with this standard. Related British Standards for ISO/R385, ISO641 and ISO648 are BS846 “Specification for burettes”,
16、 BS2761 “Spherical ground glass joints” and BS1583 “One-mark pipettes” respectively. Additional information. (1) This British Standard specifies methods of test only and should not be used as a specification defining limits of purity. Reference to the standard should indicate that the methods of tes
17、t used are in accordance with BS5551-4.1.2. Cross-references International Standard Corresponding British Standard ISO 1042:1981 BS 1792:1982 Specification for one-mark volumetric flasks (Identical)BS5551-4.1.2:1982 BSI 10-1999 iii (2) Until the International Standard, referred to in the note to6.1,
18、 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 toclause4, water complying with the requirements ofBS3978 “Water for laboratory u
19、se” is suitable. NOTETextual error. In7.2, line2, “operations” should be read as “operators”. 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 n
20、ot of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i to iv, pages1to 4, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This wil
21、l be indicated in the amendment table on the inside front cover.iv blankBS5551-4.1.2:1982 BSI 10-1999 1 1 Scope and field of application This International Standard specifies a titrimetric method, after distillation, for the determination of the ammoniacal nitrogen content of fertilizers. The method
22、 is applicable only in the absence of urea or its derivatives, of cyanamide and of organic nitrogenous compounds. 2 References ISO/R 385, Burettes. ISO 641, Laboratory glassware Interchangeable spherical ground joints. ISO 648, Laboratory glassware One-mark pipettes. ISO 1042, Laboratory glassware O
23、ne-mark volumetric flasks. 3 Principle Distillation of the ammonia from an alkaline solution, absorption in an excess of standard volumetric sulphuric acid solution and back-titration with standard volumetric sodium hydroxide solution in the presence of methyl red or screened methyl red as indicator
24、. 4 Reagents During the analysis, use only reagents of recognized analytical grade and only distilled water or water of equivalent purity. 4.1 Ammonium sulphate, dried at105 C to constant mass. 4.2 Hydrochloric acid solution Dilute concentrated hydrochloric acid, . =1,18g/ml,1+1 with water. 4.3 Sodi
25、um hydroxide, approximately400g/l solution. 4.4 Sodium hydroxide, standard volumetric solution, c(NaOH) =0,20 mol/l. 1) 4.5 Sulphuric acid, standard volumetric solution, c(H 2 SO 4 )=0,10mol/l. 1) 4.6 Indicator solution 4.6.1 Screened methyl red indicator, ethanolic solution. Mix50ml of a2g/l ethano
26、lic solution of methyl red with50ml of1g/l ethanolic solution of methylene blue, or 4.6.2 Methyl red indicator, ethanolic solution. Dissolve0,1g of methyl red in50ml of95% (V/V) ethanol. 4.7 pH indicator paper, wide range. 5 Apparatus 5.1 Distillation apparatus The components of the apparatus may be
27、 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 shall be replaced when they begin to perish or show signs of wear. A suitable apparatus is illustrated
28、in the Figure and comprises: 5.1.1 Round bottomed flask, of nominal capacity1litre. 5.1.2 Single-bulb splash head and separate open-top cylindrical dropping funnel, of capacity100ml. 5.1.3 Allihn condenser, seven-bulb, with an expansion bulb, of approximate capacity100ml, followed by a delivery tube
29、 at the outlet. 5.1.4 Receiver (conical flask or conical beaker), of capacity500ml. 5.2 Two burettes, of capacity50ml, complying with the requirements of ISO/R385, class A. 5.3 One-mark volumetric flask, of capacity500ml, complying with the requirements of ISO1042, classA. 5.4 One-mark pipettes, of
30、capacities102550 and100ml, complying with the requirements of ISO648, classA. 5.5 Mechanical flask shaker, with a rotary or reciprocating action. 5.6 Anti-bumping granules or an anti-bumping device consisting of a100mm 5mm glass rod connected to a25mm length of polyethylene tubing. 6 Procedure 6.1 T
31、est portion Weigh, to the nearest0,001g, about10g of the analytical sample and transfer to the one-mark volumetric flask (5.3). NOTEProcedures for the preparation of analytical samples will form the subject of a future International Standard. 6.2 Preparation of test solution 6.2.1 Products soluble i
32、n water Add about400ml of water at20 C and shake the flask continuously for30min using the mechanical flask shaker (5.5). 1) Hitherto expressed as “0,20N standard volumetric solution”.BS5551-4.1.2:1982 2 BSI 10-1999 6.2.2 Products containing water-insoluble material likely to retain ammonia Add50ml
33、of water and20ml of the hydrochloric acid solution (4.2) to the test portion (6.1). Mix the contents of the flask and allow to stand undisturbed until any liberation of carbon dioxide has ceased. Add about400ml of water at20 C and shake the flask continuously for30min using the mechanical flask shak
34、er. NOTEComplete dissolution of the test portion is not necessary. The procedure described extracts all the ammoniacal nitrogen. 6.3 Determination Dilute the contents of the flask to the mark with water, mix well and filter through a dry medium rate and retention low ash grade of filter paper into a
35、 dry beaker. Discard the first50ml of filtrate and then transfer an aliquot portion of the filtrate, by means of a pipette (5.4), into the flask (5.1.1). The aliquot portion shall contain preferably between75and100mg of ammoniacal nitrogen but, in any case, shall be in the range25to100mg. Dilute the
36、 contents of the flask to about200ml with water and add a few anti-bumping granules or the anti-bumping device (5.6) to prevent bumping during the distillation. Add a few drops of the indicator solution (4.6). Assemble the apparatus as shown in the Figure. Measure50,0ml of the standard volumetric su
37、lphuric acid solution (4.5) with a burette (5.2) into the receiver (5.1.4) and add4 or5 drops of the indicator solution (4.6). Place the receiver so that the end of the delivery tube (see5.1.3) is below the surface of the acid, adding water to the flask if necessary. Pour15ml of the sodium hydroxide
38、 solution (4.3) into the dropping funnel. If20ml of the hydrochloric acid solution (4.2) has been added to dissolve the test portion (see6.2), use25ml of the sodium hydroxide solution (4.3). Cool the contents of the distillation flask to room temperature and add the sodium hydroxide solution(4.3). W
39、hen nearly all the sodium hydroxide solution has been added, close the stop-cock, leaving about2ml in the dropping funnel. Bring the contents of the flask to the boil, increasing the rate of heating progressively until the contents of the flask are boiling briskly. The contents of the flask shall re
40、main alkaline during the distillation period. When at least150ml of distillate has collected, partially withdraw the receiver so that the delivery tube rests on its rim. Test the subsequent distillate with the pH indicator paper (4.7) to ensure that all the ammonia has completely distilled. Remove t
41、he source of heat. Detach the splash head from the condenser and wash the condenser and expansion bulb through with water, collecting the washings in the receiver. The outside of the delivery tube shall also be rinsed into the flask. Back-titrate the excess of acid with the standard volumetric sodiu
42、m hydroxide solution (4.4) to the neutral colour of the indicator. 6.4 Blank test Carry out a blank test at the same time as the determination, using the same reagents but omitting the test solution. The result of the blank test should not exceed0,25ml of0,10mol/l sulphuric acid solution. 6.5 Check
43、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 prepared solution of the ammonium sulphate (4.1) containing100mg of nitrogen. The check shall be made using the same conditions as for the sample and blank determin
44、ations and with the same indicator. 7 Expression of results 7.1 Calculation The ammoniacal nitrogen content, expressed as nitrogen (N) as a percentage by mass, is given by the formula where NOTEIf the concentrations of the standard volumetric solutions used are not exactly as specified in the list o
45、f reagents, appropriate corrections should be made. V 1 is the volume, in millilitres, of the standard volumetric sulphuric acid solution (4.5) used for the determination (50,0ml); V 2 is the volume, in millilitres, of the standard volumetric sodium hydroxide solution (4.4) used for the determinatio
46、n; V 3 is the volume, in millilitres, of the standard volumetric sulphuric acid solution (4.5) used for the blank test (50,0ml); V 4 is the volume, in millilitres, of the standard volumetric sodium hydroxide solution (4.4) used for the blank test; m is the mass, in grams, of sample in the aliquot po
47、rtion taken for the determination.BS5551-4.1.2:1982 BSI 10-1999 3 7.2 Precision The statistical information given below was obtained from analysis of22sets of results (two operations in each case, each operator carrying out two determinations) from laboratories in seven different countries. 7.2.1 Re
48、peatability The difference between successive test results, obtained by the same operator with the same apparatus under constant operating conditions on identical test material should not, in the long run, in the normal and correct operation of the test method, exceed the value of0,03% (m/m) at a co
49、nfidence level of95%. 7.2.2 Reproducibility The difference between two single and independent results, obtained by different operators working in different laboratories on identical test material should not, in the long run, in the normal and correct operation of the test method, exceed the value of0,08% (m/m) at a confidence level of95%. 8 Test report The test report shall include the following particulars: a) the reference of the method used, i.e.ISO5314; b) the results and the method of expression used; c) any unusual featur
