ISO INTERNATIONAL STANDARD 18191 Firstedition 2015-09-01 Water quality Determination of pHt in sea water - Method using the indicator dye m-cresol purple Qualite de I'eau-Détermination dupHtdansI'eaudemer- Méthode utilisant I'indicateurcoloré aupourpre de m-cresol Reference number IS018191:2015(E) ISO Intermational Organization for Standardization @IS02015 Jardization 5956617 ted without license from IHS IS0 18191:2015(E) COPYRIGHTPROTECTEDDOCUMENT IS02015,Published in Switzerland 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 requested from either ISO at the address below or ISO's member body in the country of the requester. ISOcopyrightoffice Ch. de Blandonnet 8.CP 401 CH-1214 Vernier, Geneva, Switzerland Tel. +41 22 749 01 11 Fax +4122749 0947 [email protected] www.iso.org networking permited without license from IHS Not for Resale, 2015/11/11 08:39:29 IS018191:2015(E) Contents Page Foreword ..iv Introduction. 1 Scope. 2 Terms and definitions 3 Principle ..2 4 Reagents. ..2 5 Apparatus. ..3 6 Sampling. 7 Procedure ..4 8 Calculationandexpressionofresults ..4 8.1 Correction of measured absorbances. 8.2 CalculationofthepHtoftheseawaterand indicator .5 8.3 Correction for pHt change resulting from addition of the indicator .6 AnnexA(informative)Performancedata .7 Annex B (informative) Storage stability ..8 Bibliography .10 iii dardization5956617 thout license from IHS