© ISO 2016 Solid mineral fuels — Determination of phosphorus content — Reduced molybdophosphate photometric method Combustibles minéraux solides — Dosage du phosphore — Méthode photométrique au molybd[.]
INTERNATIONAL STANDARD ISO 622 Second edition 2016-11-15 Solid mineral fuels — Determination of phosphorus content — Reduced molybdophosphate photometric method Combustibles minéraux solides — Dosage du phosphore — Méthode photométrique au molybdophosphate réduit Reference number ISO 622:2016(E) © ISO 2016 ISO 622:2016(E) COPYRIGHT PROTECTED DOCUMENT © ISO 2016, Published in Switzerland All rights reserved Unless otherwise specified, no part o f 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 o f the requester ISO copyright o ffice Ch de Blandonnet • CP 401 CH-1214 Vernier, Geneva, Switzerland Tel +41 22 749 01 11 Fax +41 22 749 09 47 copyright@iso.org www.iso.org ii © ISO 2016 – All rights reserved ISO 622:2016(E) Page Contents Foreword iv Scope Normative references Terms and definitions Principle Reagents 4.1 4.2 Extraction Determination Apparatus Sample preparation Procedure 8.1 Wet oxidation method Determination 8.2 8.3 D ry oxidatio n metho d 9.1 Method of calculation and formulae 0.1 Rep eatab ility 0.2 Rep ro ducib ility Expression of results 10 Precision of the method © ISO 2016 – All rights reserved iii ISO 622:2016(E) Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies) The work o f 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 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 o f electrotechnical standardization The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part In particular the different approval criteria needed for the di fferent types o f ISO documents should be noted This document was dra fted in accordance with the editorial rules of the ISO/IEC Directives, Part (see www.iso.org/directives) Attention is drawn to the possibility that some o f the elements o f this document may be the subject o f patent rights ISO shall not be held responsible for identi fying any or all such patent rights Details o f any patent rights identified during the development o f 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 in formation given for the convenience o f users and does not constitute an endorsement For an explanation on the meaning o f ISO specific terms and expressions related to formity assessment, as well as information about ISO’s 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 The committee responsible for this document is ISO/TC 27, Solid minerals fuels, Subcommittee SC 5, Methods of analysis This second edition cancels and replaces the first edition (ISO 622:1981), which has been technically revised This document incorporates changes related to references and other minor items following its systematic review iv © ISO 2016 – All rights reserved INTERNATIONAL STANDARD ISO 622:2016(E) Solid mineral fuels — Determination of phosphorus content — Reduced molybdophosphate photometric method Scope This document specifies a reduced molybdophosphate photometric method for the determination o f the total phosphorus content of hard coal, lignites and coke Two methods for taking the phosphorus into solution are specified, namely extraction from the coal or coke ash with acid or by repeated oxidation o f the coal or coke, by acid, to remove carbonaceous matter Normative references The following documents are re ferred to in the text in such a way that some or all o f their content constitutes requirements o f this document For dated re ferences, only the edition cited applies For undated re ferences, the latest edition o f the re ferenced document (including any amendments) applies ISO 383, Laboratory glassware — Interchangeable conical ground joints ISO 565, Test sieves — Metal wire cloth, perforated metal plate and electroformed sheet — Nominal sizes of openings ISO 1171, Solid mineral fuels — Determination of ash ISO 18283, Hard coal and coke — Manual sampling Terms and definitions No terms and definitions are defined in this document ISO and IEC maintain terminological databases for use in standardization at the following addresses: — IEC Electropedia: available at http://www.electropedia.org/ — ISO Online browsing platform: available at http://www.iso.org/obp 4.1 Principle Extraction Method 1: Removal o f carbonaceous material by ashing in a mu ffle furnace under specified conditions, and extraction o f phosphorus by treatment with hydrofluoric and sulphuric acids Method 2: Removal o f carbonaceous material by repeated oxidation with nitric acid in the presence o f sulphuric acid 4.2 Determination Addition o f ammonium molybdate and ascorbic acid solution to the acid solution Measurement o f the absorbance o f the resulting blue solution by a suitable optical instrument © ISO 2016 – All rights reserved ISO 622:2016(E) Reagents D u ri ng the ana lys i s , u s e on ly re agents o f re co gn i z e d a na lytic a l grade and on ly d i s ti l le d water or water o f e qu iva lent purity W A v a H R p o N u y d I r N i r o G s f l — i r u o A r i t r q a i c u n a e t c o a i u n d s d , ap p roximately 40 g/l s o lutio n h t y d o x r i o c f l I u t o s r a i c c t a i c o i n d o i s n a t h h e i g s h k i l y n c a o n r d r o e s i y e v e s i l s i q s u t i r d o w n g l h y i c h c o a r t r t o a s c i k v e s , g p l r a o s s d ; u t c i h n e g severe and painful burns which may not be immediately evident and which respond slowly to treatment The solution should be handled only inside a well-ventilated fume cupboard In the e v e n t o f c o n t a c t o r s u s p e c t e d c o n t a c t , f l o o d w i t h w a t e r a n d s e e k i m m e d i a t e m e d i c a l a t t e n t i o n The manufacturer’s literature should be consulted for further information 5.2 Sulphuric acid , ap p roximately 49 5.3 Sulphuric acid 5.4 Nitric acid 5.5 Ammonium molybdate 5.6 Ascorbic acid , concentrated, ρ , g/ml, ap p roximately % ( , 42 g/ml, ap p roximately % ( m /m ) solution , 60 g/l solution fre sh da i ly Antimony potassium tartrate (KSbO·C 4H 4O 6), 1,36 g/l solution Mix 25 ml of the sulphuric acid solution (5.2 of the ascorbic acid solution (5.6 f 5.8 m /m ) solution , 50 g/l solution P rep are the s olution 5.7 , concentrated, ρ g/l s o lutio n Reagent solution 5.5), 10 ml 5.7) Prepare ) , 10 m l o f the am mon iu m molyb date s olution ( ) and m l o fre sh i m me d i ately b e fore u s e 5.9 Phosphorus the anti mony p o ta s s iu m tar trate s olution ( , standard stock solution corresponding to 0,100 g of P per litre Weigh, to the ne are s t , 0 g , ,43 g o f p o ta s s iu m d i hyd ro gen monopho s phate (KH at 110 ° C for PO 4) (dried h) and d i s s olve i n water Tran s fer the s olution quantitati vely to a 0 m l one -mark volu me tric flas k, d i lute to the mark and m i x ml of this standard stock solution contains 0,100 mg of P , standard working solution corresponding to mg of P per litre Transfer 10 ml of the standard phosphorus solution (5.9 5.10 Phosphorus ) to a 0 m l one -mark volu me tric flas k, d i lute to the mark a nd m i x P rep are fre sh i m me d iately b e fore u s e m l o f th i s s tandard worki ng s olution conta i n s μg o f P Apparatus O rd i nar y lab orator y app a ratu s and 6.2 M u f f l e f u r n a c e , as s p ecified in I S O 1 Dish , o f s ilica, p o rcelain o r p latinum, as s p ecified in I S O 1 © ISO 2016 – All rights reserved ISO 622:2016(E) 6.3 Insulating plate , o f s ilica, mm thick, o r its equivalent, o f s uch s ize as to b e an easy s liding fit into the mu ffle furnace ( 6.1) 6.4 Platinum crucible , o f cap acity 6.5 Hot-air bath 6.6 Digestion apparatus ISO 383 6.6.2 F l a s ml to ml, with lid (see Figure 1), constructed of borosilicate glass, consisting of the following: , Kj eldahl flas k, o f cap acity 0 ml, fitted with a 4/2 gro und glas s s o cket co mp lying with k Fume duct, o f o uts ide diameter ap p roximately mm, fitted with a dro p p ing at leas t ml and a 4/2 gro und glas s co ne co mp lying with I S O The o r as s emb led 6.6.3 fro m fume funnel o f cap acity duct may b e o f o ne p iece s p ate units by means o f gro und glas s j o ints Fume extractor, co mp ris ing a glas s tub e o f diameter ap p roximately 40 mm, s ealed at o ne end and drawn o ut at the o ther end to fo rm a co nnectio n to the water p ump The tub e is fitted with a drain stopcock and a series of lipped holes to accommodate a number of fume ducts 6.7 Spectrophotometer , or photoelectric absorptiometer , o f the required s ens itivity Sample preparation T he s a mple o f co a l or coke sh a l l b e the a na lys i s s a mple, grou nd to p as s a 2 μm te s t s ieve complyi ng with the requirements of ISO 565, taken and prepared in accordance with ISO 18283 The sample shall b e thorough ly m i xe d , pre ferably b y a me chan ica l me an s , i m me d i ately b e fore the de term i nation Procedure 8.1 8.1.1 Dry oxidation method D etermine the p ercentage o f as h in the co al o r co ke as s p ecified in I S O 1 Grind the as h in an agate mo rtar to p as s a 63 μm s ieve co mp lying with I S O 8.1.2 Weigh, to an accuracy o f , mg, ab o ut , g o f the as h into the p latinum crucib le ( 6.4) Add 2,0 ml of the sulphuric acid solution (5.2 f (5.1) Place the lid on the crucible and digest on a boiling water bath for 30 in a well-ventilated fume cupboard Remove and rinse the lid, collecting the washings in the crucible Allow the solution to 8.1.3 ) and ab o ut , ml o the hydro fluo ric acid s o lutio n evap o rate o n the water b ath until mo s t o f the hydro fluo ric acid and water have b een removed Transfer the crucible to the hot-air bath (6.5), evaporate until dense white fumes from the sulphuric acid have evolved for a few minutes Allow to cool, add 0,5 ml of the sulphuric acid solution (5.2), heat for a few minutes and allow to cool 8.1.4 NO TE I t i s e s s enti a l th at the co ntents o f the c r uc ib le a re no t e vap orate d co mp le tel y to d r yne s s at a ny s tage © ISO 2016 – All rights reserved ISO 622:2016(E) Add about 20 ml of water to the crucible and digest on the water bath for 30 min, when all the extract should be in one solution Allow to cool, transfer the solution to a 100 ml one-mark volumetric 8.1.5 flask and dilute with water to the mark (solution A) If the sample has a high arsenic content, this can interfere with the result and the solution should be reduced before the phosphorus determination 8.1.6 8.2 Prepare a blank solution exactly as described above, but omitting the coal or coke ash Wet oxidation method 8.2.1 Weigh, to an accuracy o f mg, about g o f the coal or coke sample Transfer the test portion (8.2.1 ) to the clean, dry Kjeldahl flask (6.6.1) Assemble the apparatus (6.6) as shown in Figure 1, in a well-ventilated fume cupboard Add ml of the sulphuric acid (5.3) and 3,5 ml of the nitric acid (5.4) by means o f the dropping funnel, rotating the flask so as to wash down any sample remaining in the neck 8.2.2 8.2.3 After the initial reaction has subsided, heat the flask care fully so that the reaction proceeds smoothly and without frothing Continue heating the flask under the same conditions until only fumes o f sulphuric acid are evolved Add 0,2 ml to 0,4 ml of the nitric acid (5.4) to the dropping funnel and run the acid, drop by drop, into the flask NOTE I f violent frothing occurs on addition o f the mixed acid, apply a damp cloth to the neck o f the flask and heat intermittently as the frothing subsides 8.2.4 Heat for to until no more dense brown fumes are evolved Repeat the addition of the nitric acid and the heating, rotating the flask periodically to wash down any carbonaceous matter adhering to the sides o f the flask, until all visible carbonaceous matter has been oxidized and the solution is a pale greenish-yellowish colour This may take 1/2 h to h, or even longer in exceptional cases with some coke samples NOTE For the first 15 o f heating a coal sample, the reaction mixture is a tarry mass; subsequently, it changes its colour from black to dark reddish-brown, to amber, and finally to a pale greenish-yellow I f a black liquid still remains after 45 heating, either a) too low a temperature has been used and the nitric acid has not reacted with the sample; raise the temperature to distil off excess nitric acid, then continue the normal oxidation as described, or b) too high a temperature has been used, nitric acid being distilled o ff without reacting; cool, add more nitric acid and heat the mixture as described Heat the flask more strongly until white fumes appear and allow to fume for Cool the flask to approximately room temperature, remove the dropping funnel and fume duct assembly and add a few glass beads to the contents o f the flask 8.2.5 NOTE If the colour reverts to amber or deep red, add a further 0,2 ml to 0,4 ml of the nitric acid, heat to fuming and allow to fume for Add cautiously 10 ml o f water, heat until white fumes appear and then allow to fume gently for 10 Cool the flask until the evolution o f the white fumes ceases, add 0,2 ml o f the nitric acid, reheat the flask and allow to fume for a further 10 8.2.6 8.2.7 To ensure complete oxidation, cool the flask to approximately room temperature and repeat the procedure described in 8.2.5 © ISO 2016 – All rights reserved ISO 622:2016(E) Cool the flask to approximately room temperature, add 10 ml o f water, heat to fuming and allow 8.2.8 to fume for 20 Add a further 10 ml of water, heat to fuming, allow to fume for 10 and cool Add a further 20 ml o f water to the flask and digest on the boiling water bath for 30 min, when all the extract should be in solution Filter the solution through a hardened, acid-washed filter paper, allow to cool, trans fer the filtrate to a 100 ml one-mark volumetric flask and dilute with water to the mark 8.2.9 (solution B) (see the note in 8.1.5) 8.2.10 8.3 Prepare a blank solution exactly as described above, but omitting the coal or coke sample Determination Pipette 10 ml of solution A or B as appropriate (see 8.1.5 or 8.2.9 ) (the aliquot portion taken may be varied according to the phosphorus content of the sample), 10 ml of the blank solution (see 8.1.6 or 8.2.10 as appropriate) and 10 ml of the standard solution (5.10) into separate 50 ml one-mark volumetric 8.3.1 flasks A fourth 50 ml flask is required for the reagent blank Calibration is linear for aliquot portions containing up to 30 μg o f phosphorus With high phosphorus coals or cokes, it may be necessary to take a smaller aliquot portion Pipette ml of the reagent solution (5.8 ) into each flask, swirling the contents during the addition, dilute with water to the mark, and mix thoroughly Allow to stand for 20 8.3.2 Measure the absorbance of the solutions against water, in the spectrophotometer (6.7) using 40 mm 8.3.3 cells at a wavelength o f 710 nm or in the photoelectric absorptiometer fitted with an appropriate filter 9.1 Expression of results Method of calculation and formulae Calculate the percentage o f phosphorus (P) in the analysis sample, using Formulae (1) and (2) a) Dry oxidation method (see 8.1): ( A D1 − D ( ) 000 Vm D3 − D where A m V D1 D2 D3 D4 ) (1) is the percentage o f ash in the analysis sample; is the mass, in grams, o f ash taken; is the volume, in millilitres, o f sample solution taken for colour development; is the absorbance o f the sample solution; is the absorbance o f the sample blank solution; is the absorbance of the standard phosphorus solution (5.10); is the absorbance of the reagent blank solution © ISO 2016 – All rights reserved ISO 622:2016(E) b) Wet oxidation method (see 8.2): (D 10 where ( − D2 ) Vm D3 − D (2) ) m f V, D1 , D2 , D3 and D4 have the same meaning as in a) above i s the mas s , i n gram s , o the te s t p or tion; Rep or t the re s u lt, pre ferably the me an o f dupl ic ate de term i nation s , to the ne a re s t , 01 % 10 Precision of the method 10.1 Repeatability T he re s u lts o f dupl ic ate de term i nation s , c arrie d out at d i fferent ti me s i n the s ame lab orator y b y the same operator with the same apparatus on two representative portions taken from the same sample (see Clause ff Table ) , shou ld no t d i er b y more tha n the va lue s given i n 10.2 Reproducibility The means of the results of duplicate determinations, carried out in two different laboratories on representative portions taken from the same sample (see Clause ff values given Table ) , shou ld no t d i er by more tha n the Table Phosphorus content of c o a l m /m ) o % ( r c o k e Less than 0,02 Equal to or more than 0,02 Repeatability 0,002 absolute the results 10 % o f the me a n o f Reproducibility 0,005 absolute the results % o f the me a n o f Key to pump Figure — Apparatus for wet oxidation of the sample © ISO 2016 – All rights reserved ISO 622:2016(E) ICS 75.160.10 Price based on pages © ISO 2016 – All rights reserved