ISO INTERNATIONAL STANDARD 11263 First edition 1994-12-01 Soil quality - Determination of phosphorus Spectrometric determination of phosphorus soluble in sodium hydrogen carbonate solution Qualite du sol Dosage du phosphore -Dosage spectrometrique du phosphore soluble dans une solution d'hydrogenocarbonate de sodium TSO Reference number ISO 11263:1994(E) Copyright Intermational Organization for Standardization Not for Resale 11263:1994(E) ISO Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (lSO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. E Each member body interested in a subject for which a technical committee has been established has the right to be and non-governmental, in liaison with IsO, also take part in the work. IsO collaborates closely with the internationai Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International a vote. International Standard ISO 11263 was prepared by Technical Committee ISO/TC 190, Soil quality, Subcommittee SC 3. Chemical methods and soil characteristics. Annex A of this International Standard is for information only ISO1994 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utiized in any form or by any means, electronic or mechanical, including photocopying and microfim, without permission tn writing from the publisher. International OrganizationforStandardization Case Postale 56· CH-1211 Geneve 20· Switzerland Printed in Switzerland := Copyright International Oorganizatin for Standardization d without license from IHS Not for Resale ISO11263:1994(E) INTERNATIONAL STANDARD ISO Soil quality Determination of phosphorus Spectrometric determination of phosphorus soluble in sodium hydrogen carbonate solution 1 Scope 3 Principle This International Standard specifies an extraction A soil, pretreated according to ISO 11464, is treated method and analytical conditions to determine the with a 0,5 mol/l sodium hydrogen carbonate solution content of soil phosphorus soluble in sodium hydro- atpH8.50toreducetheconcentrationof calcium, gen carbonate solution. After the extraction step, two aluminiumandiron(ill)ionsbyprecipitationofcalicium different methods of colour development are poss- carbonate and aluminium and iron(ill) hydroxides and ible.Subclause 4.2 specifies colour development at to release phosphate ions into solution. room temperature. Subclause 4.3 specifies colour The clear extract is analysed for phosphorus by a development after heating to a high temperature. This spectrometric method involving the formation of an International Standard is applicable to ail types of antimony-phosphate-molybdate complex (at room soils. temperature, 4.2) or a phosphate-molybdate complex (at a high temperature, 4.3) both reduced with ascorbic acid to form a deep-coloured, blue complex. Reagents 2 Normative references All reagents shalil be of recognized analytical grade. Use water complying with grade 2 of isO 3696. The following standards contain provisions which, through reference in this text, constitute provisions 4.1 Reagents used in both colour developments of this Internationat Standard. At the time of publi- cation, the editions indicated were valid. All standards 4.1.1 Sodium hydroxide solution, aresubjectto revision,andpartiesto agreements c(NaOH) = 1 mol/l. based on this International Standard are encouraged to investigate the possibility of applying the most re- Dissolve 40,0 g ± 0,4 g of sodium hydroxide (NaOH) cent editions of the standards indicated below. pellets in water. Cool and dilute to 1 000 ml with Members of IEC and ISO maintain registers of cur- water.Store inan inert and hermetically sealedbottle. rently valid Internati