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1、? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? BS EN 15478:2009 EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN 15478 January 2009 ICS 65.080Supersedes CEN/TS 15478:2006 English Version Fertilizers - Determination of total nitrogen in urea Engrais - Dtermination de lazote total dans
2、lureDngemittel - Bestimmung von Gesamtstickstoff in Harnstoff This European Standard was approved by CEN on 30 November 2008. CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard w
3、ithout any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN Management Centre or to any CEN member. This European Standard exists in three official versions (English, French, German). A version in any other langu
4、age made by translation under the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finlan
5、d, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOM
6、ITEE FR NORMUNG Management Centre: rue de Stassart, 36 B-1050 Brussels 2009 CENAll rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 15478:2009: E BS EN 15478:2009 EN 15478:2009 (E) 2 Contents Page Foreword 3 1Scope 4 2Normative references 4
7、 3Terms and definitions .4 4Principle 4 5Reagents .4 6Apparatus .5 7Sampling and sample preparation 10 8Procedure 10 9Calculation and expression of the result . 11 10Precision 11 11Test report . 12 Annex A (informative) Results of the inter-laboratory tests 13 Bibliography . 14 ? BS EN 15478:2009 EN
8、 15478:2009 (E) 3 Foreword This document (EN 15478:2009) has been prepared by Technical Committee CEN/TC 260 “ Fertilizers and liming materials” , the secretariat of which is held by DIN. This European Standard shall be given the status of a national standard, either by publication of an identical t
9、ext or by endorsement, at the latest by July 2009, and conflicting national standards shall be withdrawn at the latest by July 2009. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN and/or CENELEC shall not be held responsible
10、for identifying any or all such patent rights. This document supersedes CEN/TS 15478:2006. This document has been prepared under a mandate given to CEN by the European Commission and the European Free Trade Association. According to the CEN/CENELEC Internal Regulations, the national standards organi
11、zations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Rom
12、ania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. ? BS EN 15478:2009 EN 15478:2009 (E) 4 1 Scope This European Standard specifies a method for the determination of total nitrogen in urea. This method is applied exclusively to urea fertilizers which are nitrate free. 2 Norm
13、ative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. EN 1482-2, Fertilizers and limin
14、g materials Sampling and sample preparation Part 2: Sample preparation EN 12944-1:1999, Fertilizers and liming materials and soil improvers Vocabulary Part 1: General terms EN 12944-2:1999, Fertilizers and liming materials and soil improvers Vocabulary Part 2: Terms relating to fertilizers EN ISO 36
15、96:1995, Water for analytical laboratory use Specification and test methods (ISO 3696:1987) 3 Terms and definitions For the purposes of this document, the terms and definitions given in EN 12944-1:1999 and EN 12944-2:1999 apply. 4 Principle Urea is transformed quantitatively into ammonia by boiling
16、in the presence of sulfuric acid. The ammonia thus obtained is distilled from an alkaline medium, the distillate being collected in an excess of standard sulfuric acid. The excess acid is titrated by means of a standard alkaline solution. 5 Reagents 5.1 General Use only reagents of recognized analyt
17、ical grade and distilled or demineralized water, free from carbon dioxide and all nitrogenous compounds (grade 3 according to EN ISO 3696:1995). 5.2 Kjeldahl tablets, 5 g/tablet containing 100 parts K2SO4 to 1 part selenium. ? BS EN 15478:2009 EN 15478:2009 (E) 5 5.3 Sulfuric acid, concentrated (20
18、= 1,84 g/ml). 5.4 Sodium hydroxide solution, approximately NaOH 500 g/l. 5.5 Sulfuric acid, c = 0,05 mol/l, to use for the blank test. 5.6 Sodium or potassium hydroxide solution, carbonate free, c = 0,1 mol/l, to use for the blank test. 5.7 Sulfuric acid, c = 0,5 mol/l. 5.8 Sodium or potassium hydro
19、xide solution, carbonate free, c = 1,0 mol/l. 5.9 Indicator solutions 5.9.1 Mixed indicator Solution A: Dissolve 1 g of methyl red in 37 ml of 0,1 mol/l sodium hydroxide solution and make up to one litre with water. Solution B: Dissolve 1 g of methylene blue in water and make up to one litre. Mix on
20、e volume of A with two volumes of B. This indicator is violet in an acid solution, grey in a neutral solution and green in an alkaline solution; use 0,5 ml (10 drops). 5.9.2 Methyl red indicator solution Dissolve 0,1 g of methyl red in 50 ml of 95 % ethanol and make up to 100 ml with water. Filter i
21、f necessary. This indicator (4 or 5 drops) may be used instead of the preceding one. This indicator is red in acid solution and yellow in alkaline solution. 5.10 Anti-bump granules, for example pumice stone, washed in hydrochloric acid and calcined. 5.11 Urea, p. a. 6 Apparatus 6.1 Distillation appa
22、ratus Consisting of a round-bottomed flask of suitable capacity connected to a condenser by means of a splash head. The equipment is made of borosilicate glass. NOTE The different types of equipment recommended for this determination are reproduced showing all the features of construction in Figures
23、 1, 2, 3, and 4. Automatic distillation apparatus may be used as well provided that the results are statistically equivalent. ? BS EN 15478:2009 EN 15478:2009 (E) 6 Dimensions in millimetres Key 1 round-bottomed, long-necked flask of 1 000 ml capacity 2 distillation tube with a splash head, connecte
24、d to the condenser by means of a spherical joint (No 18) (the spherical joint for the connection to the condenser may be replaced by an appropriate rubber connection) 3 funnel with a polytetrafluoroethylene (PTFE) tap (6) for the addition of sodium hydroxide 4 six-bulb condenser with spherical joint
25、 (No 18) at the entrance, and joined at the issue to a glass extension tube by means of a small rubber connection (when the connection to the distillation tube is effected by means of a rubber tube, the spherical joint may be replaced by a suitable rubber bung) 5 500 ml flask in which the distillate
26、 is collected 6 PTFE-tap (the tap may likewise be replaced by a rubber connection with a clip) Figure 1 Distillation apparatus 1 ? BS EN 15478:2009 EN 15478:2009 (E) 7 Dimensions in millimetres Key 1 round-bottomed, short-necked flask of 1 000 ml capacity with a spherical joint (No 35) 2 distillatio
27、n tube with a splash head, equipped with a spherical joint (No 35) at the entrance and a spherical joint (No 18) at the issue, connected at the side to a funnel with a polytetrafluoroethylene (PTFE) tap (6) for the addition of sodium hydroxide 3 six-bulb condenser with a spherical joint (No 18) at t
28、he entrance and joined at the issue to a glass extension tube by means of a small rubber connection 4 500 ml flask in which the distillate is collected 5 PTFE-tap a enlarged description Figure 2 Distillation apparatus 2 ? BS EN 15478:2009 EN 15478:2009 (E) 8 Dimensions in millimetres Key 1 round-bot
29、tomed, long-necked flask of 750 ml or 1 000 ml capacity with, a bell mouth 2 distillation tube with a splash head and a spherical joint (No 18) at the issue 3 elbow tube with a spherical joint (No 18) at the entrance, and a drip cone (the connection to the distillation tube may be effected by means
30、of a rubber tube instead of a spherical joint) 4 six-bulb condenser joined at the issue to a glass extension tube by means of a small rubber connection 5 500 ml flask in which the distillate is collected Figure 3 Distillation apparatus 3 ? BS EN 15478:2009 EN 15478:2009 (E) 9 Dimensions in millimetr
31、es Key 1 round-bottomed, long-necked flask of 1 000 ml capacity with a bell mouth 2 distillation tube with a splash head and a spherical joint (No 18), at the issue, connected at the side to a funnel with a polytetrafluoroethylene (PTFE) tap (5) for the addition of sodium hydroxide (a suitable rubbe
32、r bung may be used instead of the spherical joint 3 six-bulb condenser with a spherical joint (No 18) at the entrance, joined at the issue, by a rubber connection, to a glass extension tube (when the connection to the distillation tube is effected by means of a rubber tube, the spherical joint may b
33、e replaced by a suitable rubber bung) 4 500 ml flask for the collection of the distillate 5 PTFE-tap (the tap may be replaced by a rubber connection with an appropriate clip) Figure 4 Distillation apparatus 4 ? BS EN 15478:2009 EN 15478:2009 (E) 10 6.2 Graduated flask, capacity 500 ml. 7 Sampling an
34、d sample preparation Sampling is not part of the method specified in this document. A recommended sampling method is given in EN 1482-1. Sample preparation shall be carried out in accordance with EN 1482-2. 8 Procedure 8.1 Preparation of the solution Weigh to the nearest 0,001 g about 500 mg of the
35、prepared sample and transfer with 10 ml demineralised water to a 800 ml Kjeldahl flask. Add, while gently swirling 30 ml sulfuric acid (5.3) and 1 Kjeldahl tablet (5.2). 8.2 Analysis of the solution 8.2.1 Digestion step Put the Kjeldahl flask in a fume cupboard. Place on a heating device and heat un
36、til boiling, with an input that is required to bring 250 ml of water at 25 C to a “rolling boil“ in 20 min to 30 min. Continue to heat the flask and contents for approximately 1 h, until dense white fumes of sulfuric acid are escaping for at least 15 min. Allow the flask to cool to 25 C. 8.2.2 Disti
37、llation step Measure into a 500 ml Erlenmeyer receiving flask 30,00 ml of the 0,5 mol/l sulfuric acid solution (5.7). Add 270 ml water and add four or five drops of the indicator solution (5.9.) and place the Erlenmeyer flask in such a way that the end of the delivery tube is at least 3 cm below the
38、 surface of the liquid. Add 250 ml water to the Kjeldahl flask and several grains of pumice stone (5.10) in order to control the boiling. Assemble the distillation apparatus and taking care to avoid any loss of ammonia, add to the contents of the Kjeldahl flask carefully 120 ml of the sodium hydroxi
39、de solution (5.4). Agitate the flask to thoroughly mix the contents. Apply heat increasing the rate of heating progressively until finally the contents of the flask are boiling briskly. Most of the ammonia is expelled within 15 min. Continue the distillation until 150 ml of distillate has been colle
40、cted. Then lower the Erlenmeyer flask receiver so that the end of the delivery tube is out of the liquid and continue the distillation for a few more minutes. Rinse the outside of the delivery tube with a small amount of water into the Erlenmeyer flask. Back titrate the excess of acid with the 1,0 m
41、ol/l sodium hydroxide solution (5.8) to the neutral colour of the indicator (5.9). 8.3 Blank At the same time as the determination carry out a blank test, using the same apparatus and the same quantities of all the reagents and water, but omitting the test portion and using 20,00 ml of the 0,05 mol/
42、l sulfuric acid solution (5.5) and back titrating with the 0,1 mol/l sodium hydroxide solution (5.6). 8.4 Control test Before carrying out the analysis, check that the apparatus is working properly and that the correct application of the method is used, using an aliquot part of a freshly prepared so
43、lution of urea (5.11). ? BS EN 15478:2009 EN 15478:2009 (E) 11 9 Calculation and expression of the result Express the result of the analysis as a percentage of nitrogen (N) contained in the fertilizer as received for analysis. Calculate the mass fraction of total nitrogen, wN in percent, using the f
44、ollowing equation: m tVttVt w 10014)220()230( 423211 N = (1) where 30 is the volume, in millilitres of the 0,5 mol/l sulfuric acid solution (5.7); 20 is the volume, in millilitres of the 0,05 mol/l sulfuric acid solution (5.5); V1 is the volume, in millilitres of the 1,0 mol/l sodium hydroxide solut
45、ion (5.8) used for the determination; V2 is the volume, in millilitres of the 0,1 mol/l sodium hydroxide solution (5.6) used for the blank test; t1 is the titre of H2SO4 0,5 mol/l; t2 is the titre of NaOH 1,0 mol/l; t3 is the titre of H2SO4 0,05 mol/l; t4 is the titre of NaOH 0,1 mol/l; m is the mas
46、s, in milligrams, of the sample taken for the determination. 10 Precision 10.1 Inter-laboratory test An inter-laboratory test was carried out in 2004 with 19 participating laboratories and one sample of urea. This test yielded the data given in Annex A. Repeatability and reproducibility were calculated according to ISO 5725-1. The values derived from this inter-laboratory test might not be applicable to co