ISO 25475-2016 Fertilizers - Determination of ammoniacal nitrogen《肥料 氨态氮的测定》.pdf

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1、 ISO 2016 Fertilizers Determination of ammoniacal nitrogen Engrais Dtermination de lazote ammoniacal INTERNATIONAL STANDARD ISO 25475 First edition 2016-04-15 Reference number ISO 25475:2016(E) ISO 25475:2016(E)ii ISO 2016 All rights reserved COPYRIGHT PROTECTED DOCUMENT ISO 2016, Published in Switz

2、erland All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission. Permission can be re

3、quested from either ISO at the address below or ISOs member body in the country of the requester. ISO copyright office Ch. de Blandonnet 8 CP 401 CH-1214 Vernier, Geneva, Switzerland Tel. +41 22 749 01 11 Fax +41 22 749 09 47 copyrightiso.org www.iso.org ISO 25475:2016(E)Foreword iv 1 Scope . 1 2 No

4、rmative references 1 3 T erms and definitions . 1 4 Principle 1 5 Reagents 1 6 Apparatus . 2 7 Sampling and sample preparation 7 8 Procedure. 7 8.1 Preparation of the solution 7 8.2 Analysis of the solution 7 8.3 Blank 9 8.4 Control test . 9 9 Calculation and expression of the result . 9 10 Precisio

5、n . 9 10.1 Inter-laboratory test. 9 10.2 Repeatability . 9 10.3 Reproducibility 10 11 Test report 10 Annex A (informative) Results of the inter-laboratory tests 11 Bibliography .12 ISO 2016 All rights reserved iii Contents Page ISO 25475:2016(E) Foreword ISO (the International Organization for Stand

6、ardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right

7、to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. The procedures u

8、sed to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the different types of ISO documents should be noted. This document was drafted in accordance with the editorial rules

9、 of the ISO/IEC Directives, Part 2 (see www.iso.org/directives). Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any patent rights identif

10、ied during the development of the document will be in the Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents). Any trade name used in this document is information given for the convenience of users and does not constitute an endorsement. For an explanation o

11、n the meaning of ISO specific terms and expressions related to conformit y assessment, as well as information about ISOs adherence to the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following URL: www.iso.org/iso/foreword.html. ISO 25475 was prepared by

12、 CEN/TC 260 as EN 15475:2009 and was adopted (without modification other than those stipulated below) by Technical Committee ISO/TC 134, Fertilizers and soil conditioners. Modifications were made in the following subclauses: a) General: The references to EN 1482-1 and -2 were changed to ISO 14820-1

13、and -2; b) 5.9: added “mass fraction”; c) 5.12: p.a. = pro analysis = analytical grade; d) 6.1: First two sentences joined together. e) 6.4: “35 to 40 revolutions per minute” was changed to “35 r/min to 40 r/min”; f) 8.1: “Filter through a filter into a 500 ml graduated flask and make up to the volu

14、me with water” was changed to “Pass the solution through a filter into a 500 ml graduated flask and make up to the volume with water”; g) 8.2, Table 3: “F = factor comprising the amount weighed, the dilution, the aliquot part of solution of the sample to be distilled and the volumetric equivalent. e

15、xpressed as percentage of ammoniacal nitrogen in the fertilizer” was changed to “F = factor comprising the amount weighed, the dilution, the aliquot part of the solution of the sample to be distilled and the volumetric equivalent”. h) 10.1 Line 1: “Test was carried out in 2004 with 24, respectively

16、22 participating labs” was changed to “A test was carried out in 2004 with 24 participating labs”; i) Bibliography: Reference 3 was removed.iv ISO 2016 All rights reserved INTERNATIONAL ST ANDARD ISO 25475:2016(E) Fertilizers Determination of ammoniacal nitrogen 1 Scope This International Standard s

17、pecifies a method for the determination of the ammoniacal nitrogen content in fertilizers. The method is applicable to all nitrogenous fertilizers including compound fertilizers, in which nitrogen is found exclusively either in the form of ammonium salts or ammonium salts together with nitrates. Thi

18、s International Standard is not applicable to fertilizers containing urea, cyanamide or other organic nitrogenous compounds. 2 Normative references The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated reference

19、s, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 3696, Water for analytical laboratory use Specification and test methods ISO 14820-2, Fertilizers and liming materials Sampling and sample preparation Part

20、 2: Sample preparation EN 12944-1, Fertilizers and liming materials Vocabulary Part 1: General terms EN 12944-2, Fertilizers and liming materials Vocabulary Part 2: Terms relating to fertilizers 3 T erms a nd definiti ons For the purposes of this document, the terms and definitions given in EN 12944

21、-1 and EN 12944-2 apply. 4 Principle Displacement of ammonia by means of an excess of sodium hydroxide, distillation and determining the yield of ammonia in a given volume of a standard sulfuric acid and titration of the excess acid by means of a standard solution of sodium or potassium hydroxide. 5

22、 Reagents 5.1 General Use only reagents of recognized analytical grade and distilled or demineralized water, free from carbon dioxide and all nitrogenous compounds (grade 3 according to ISO 3696). 5.2 Hydrochloric acid, diluted. Mix one volume of (HCl) = 1,18 g/ml with one volume of water. 5.3 Sulfu

23、ric acid (for variant a), c = 0,05 mol/l. 5.4 Sodium or potassium hydroxide solution (for variant a), carbonate free, c = 0,1 mol/l. 5.5 Sulfuric acid (for variant b, see NOTE in 8.2), c = 0,1 mol/l. ISO 2016 All rights reserved 1 ISO 25475:2016(E) 5.6 Sodium or potassium hydroxide solution (for var

24、iant b, see NOTE in 8.2), carbonate free, c = 0,2 mol/l. 5.7 Sulfuric acid (for variant c, see NOTE in 8.2), c = 0,25 mol/l. 5.8 Sodium or potassium hydroxide solution (for variant c, see NOTE in 8.2), carbonate free, c = 0,5 mol/l. 5.9 Sodium hydroxide, 30 % (mass fraction), of approximately (NaOH)

25、 = 1,33 g/ml, ammonia free. 5.10 Indicator solutions. 5.10.1 Mixed indicator. Solution A: Dissolve 1 g of methyl red in 37 ml of sodium hydroxide solution (5.4) c = 0,1 mol/l and make up to 1 l with water. Solution B: Dissolve 1 g of methylene blue in water and make up to 1 l. Mix one volume of A wi

26、th two volumes of B. This indicator is violet in acid solution, grey in neutral solution and green in alkaline solution. Use 0,5 ml (10 drops) of this indicator solution. 5.10.2 Methyl red indicator solution. Dissolve 0,1 g of methyl red in 50 ml of 95 % ethanol. Make up to 100 ml with water and fil

27、ter if necessary. This indicator may be used (four to five drops) instead of the preceding one. This indicator is red in acid solution and yellow in alkaline solution. 5.11 Anti-bump granules (i. e. pumice stone, glass pearls), washed in hydrochloric acid and calcined. 5.12 Ammonium sulfate, p. a. (

28、p.a. = pro analysis = analytical grade). 6 Apparatus 6.1 Distillation apparatus The equipment is made of borosilicate glass and consists of a round-bottomed flask of suitable capacity connected to a condenser by means of a splash head. The different types of equipment recommended for this determinat

29、ion are reproduced, showing all the features of construction in Figures 1, 2, 3 and 4. An automatic distillation apparatus may also be used, provided that the results are statistically equivalent.2 ISO 2016 All rights reserved ISO 25475:2016(E) Dimensions in millimetres Key 1 round-bottomed, long-ne

30、cked flask of 1 000 ml capacity 2 distillation tube with a splash head, connected 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

31、) for the addition of sodium hydroxide 4 six-bulb condenser with spherical joint (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 ma

32、y be replaced by a suitable rubber bung) 5 500 ml flask in which the distillate is collected 6 PTFE tap (the tap may likewise be replaced by a rubber connection with a clip) Figure 1 Distillation apparatus 1 ISO 2016 All rights reserved 3 ISO 25475:2016(E) Dimensions in millimetres Key 1 round-botto

33、med, short-necked flask of 1 000 ml capacity with a spherical joint (No 35) 2 distillation 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 (5) for

34、the addition of sodium hydroxide 3 six-bulb condenser with a spherical joint (No 18) at the 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 ap

35、paratus 24 ISO 2016 All rights reserved ISO 25475:2016(E) Dimensions in millimetres Key 1 round-bottomed, 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) a

36、t the entrance and a drip cone (the connection to the distillation tube may be effected by means 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

37、 Figure 3 Distillation apparatus 3 ISO 2016 All rights reserved 5 ISO 25475:2016(E) Dimensions in millimetres 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

38、funnel with a polytetrafluoroethylene (PTFE) tap (5) for the addition of sodium hydroxide (a suitable rubber bung may be used instead of the spherical joint; the tap may be replaced by a rubber connection with an appropriate clip) 3 six-bulb condenser with a spherical joint (No 18) at the entrance,

39、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 be replaced by a suitable rubber bung) 4 500 ml flask for the collection of the distillate 5 PTFE tap Figure 4 Distillat

40、ion apparatus 4 6.2 Pipettes, capacity of 10 ml, 20 ml, 25 ml, 50 ml, 100 ml and 200 ml.6 ISO 2016 All rights reserved ISO 25475:2016(E) 6.3 Gr aduat ed flasks, capacity 500 ml. 6.4 R otary shak er, 35 r/min to 40 r/min. 7 Sampling and sample preparation Sampling is not part of the method specified

41、in this International Standard. A recommended sampling method is given in ISO 14820-1. Sample preparation shall be carried out in accordance with ISO 14820-2. 8 Procedure 8.1 Preparation of the solution According to Table 1, Table 2 or Table 3, depending on the variant chosen, weigh to the nearest 0

42、,001 g a quantity of 5 g, 7 g, or 10 g of the prepared sample and transfer it into a 500 ml flask. Add 50 ml of water and then 20 ml of hydrochloric acid (5.2). Shake. Leave undisturbed until the evolution of carbon dioxide has ceased. Add 200 ml of water and shake for half an hour with the rotary s

43、haker (6.4). Pass the solution through a filter into a 500 ml graduated flask and make up to the volume with water. 8.2 Analysis of the solution According to the variant chosen, place in the receiving flask a measured quantity of standard sulfuric acid as indicated in Table 1, Table 2 or Table 3. Ad

44、d the appropriate quantity of the chosen indicator solution (5.10.1 or 5.10.2) and, if necessary, water in order to obtain a volume of at least 50 ml. The end of the extension tube of the condenser shall be below the surface of the solution. Transfer by precision pipette, according to the details gi

45、ven in Table 1, an aliquot portion of the clear solution, into the distillation flask of the apparatus. Add water in order to obtain a total volume of about 350 ml and several grains of pumice in order to control the boiling. Assemble the distillation apparatus and, taking care to avoid any loss of

46、ammonia, add to the contents of the distillation flask 10 ml of concentrated sodium hydroxide solution (5.9), or 20 ml of the sodium hydroxide solution (5.9) in the cases where one has used 20 ml hydrochloric acid (5.2), in order to dissolve the test sample. Gradually warm the flask; avoid boiling v

47、igorously. When boiling commences, distil at a rate of about 100 ml in 10 min to 15 min; the total volume of distillate should be about 250 ml. The condenser shall be regulated so that a continuous flow of condensate is ensured. The distillation should be completed in 30 min to 40 min. When no more

48、ammonia is likely to be evolved, lower the receiving flask so that the tip of the condenser extension is above the surface of the liquid. Test the subsequent distillate by means of an appropriate reagent to ensure that all the ammonia is completely distilled. Wash the condenser extension with a litt

49、le water and titrate the surplus acid with the standard solution of sodium or potassium hydroxide prescribed for the variant adopted. Standard solutions of different strengths may be used for the back titration provided that the volumes used for the titration do not, as far as possible, exceed 40 ml to 45 ml. ISO 2016 All rights reserved 7 ISO 25475:2016(E) Table 1 Weighing, dilution and calculation variant a Declaration % N Amount to be weighed g Dilution ml Solution of sample to be distilled ml Expression of the