ISO-11261-1995.pdf
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1、INTERNATIONAL STANDARD IS0 11261 First edition 1995-03-01 Soil quality - Determination of total nitrogen - Modified Kjeldahl method Qualit du sol - Dosage de I azote total - MBthode de Kjeldahl modifike Reference number IS0 11261 :I 995(E) Copyright International Organization for Standardization Pro
2、vided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/27/2007 03:24:13 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 11261:1995(E) Foreword IS0 (the International Organization for Standardization) is a worldwide federati
3、on of national standards bodies (IS0 member bodies). The work of preparing International Standards is normally carried out through IS0 technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee
4、. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. IS0 collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. Draft International Standards adopted by the techni
5、cal committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. International Standard IS0 11261 was prepared by Technical Committee lSO/rC 190, Soil quality, Subcommittee SC 3, Chemical m
6、ethods and soil characteristics. Annex A of this International Standard is for information only. 8 IS0 1995 All nghts reserved. Unless otherwise specified, no part of this publication may be reproduced or utlllzed in any form or by any means, electronic or mechanical, lncludlng photocopytng and micr
7、oftlm, without permlssron in writing from the publisher. InternatIonal Organization for Standardlzatlon Case Postale 56 l CH-1211 Genhve 20 l Switzerland Pnnted in Switzerland ii Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical S
8、tandards 1/9972545001 Not for Resale, 04/27/2007 03:24:13 MDTNo reproduction or networking permitted without license from IHS -,-,- INTERNATIONAL STANDARD Q IS0 IS0 11261:1995(E) Soil quality - Determination of total nitrogen - Modified Kjeldahl method 1 Scope This International Standard specifies a
9、 method for the determination of the total nitrogen (ammonium-N, nitrate-N, nitrite-N and organic N) content of a soil. Nitrogen in N-N-linkages, N-O-linkages and some het- erocyclics (especially pyridine) is only partially deter- mined. This International Standard is applicable to all types of soil
10、s. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publi- cation, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on
11、 this International Standard are encouraged to investigate the possibility of applying the most re- cent editions of the standards indicated below. Members of IEC and IS0 maintain registers of cur- rently valid International Standards. IS0 3696:1987, Water for analytical laboratory use - Specificati
12、on and test methods. IS0 5725:1986, Precision of test methods - Deter- mination of repeatability and reproducibility for a standard test method by inter-laboratory tests. IS0 11464: 1994, Soil quality - Pretreatment of sam- ples for ph ysico-chemical analyses. IS0 11465:1993, Soil quality - Determin
13、ation of dry matter and water content on a mass basis - Gravimetric method. 3 Principle The method is based on the Kjeldahl-digestion, but titanium dioxide (TiO,) is used as the catalyst instead of selenium. NOTE 1 Titanium dioxide is ecotoxicologically less harmfull than selenium. 4 Reagents All re
14、agents shall be of recognized analytical grade. Use water of grade 2 complying with IS0 3696. 4.1 Salicylic acid/sulfuric acid. Dissolve 25 g of salicylic acid in 1 litre of concentrated sulfuric acid (e = I,84 g/cm3). 4.2 Potassium sulfate catalyst mixture. Grind and thoroughly mix 200 g of potassi
15、um sulfate, 6 g of copper sulfate pentahydrate and 6 g of titanium dioxide, with the crystal structure of anatase. 4.3 Sodium thiosulfate pentahydrate. Crush the crystals to form a powder that passes through a sieve with an aperture of 0,25 mm. 4.4 Sodium hydroxide, c(NaOH) = 10 mol/l. 4.5 Boric aci
16、d solution, p(H,BO,) = 20 g/l. 4.6 Mixed indicator. Dissolve 0,l g of bromocresol green and 0,02 g of methyl red in 100 ml of ethanol. 4.7 Sulfuric acid, c(H+) = 0,Ol mol/l. 1 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Stan
17、dards 1/9972545001 Not for Resale, 04/27/2007 03:24:13 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 11261:1995(E) 63 IS0 5 Apparatus Usual laboratory equipment and 5.1 Digestion flasks or tubes, of nominal volume 50 ml, suitable for the digestion stand. 5.2 Digestion
18、 stand. NOTE 2 Glass tubes placed in holes drilled into an alu- minium block are also suitable. 5.3 Distillation apparatus, preferably of the Parnas-Wagner type. 5.4 Burette, graduated in intervals of 0,Ol ml or smaller. 6 Pretreatment of soil samples Samples shall be pretreated according to IS0 114
19、64. NOTE 3 Losses of nitrogen can occur with samples of high ammonium-N and nitrate-N content. Therefore, ex- cessive drying (105 “C) should be avoided. 7 Procedure Place a test portion of the air-dried soil sample, of about 0,2 g (expected nitrogen content z 0,5 %) to 1 g (expected nitrogen content
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