INTERNATIONAL STANDARD INTERNATIONAL ORGANlZATlON FOR STANDARDlZATlON MEX~YHAPO~HAR OPrAHM3AUMR no CTAHDAPTA3AUAA ORGANISATION INTERNATIONALE DE NORMALlSATlON Cryol i te, natural and arti ficial Deter[.]
INTERNATIONAL STANDARD INTERNATIONAL ORGANlZATlON FOR STANDARDlZATlON MEX~YHAPO~HAR OPrAHM3AUMR no CTAHDAPTA3AUAA ORGANISATION INTERNATIONALE DE NORMALlSATlON Cryolite, natural and artificial - Determination of silica content - Reduced molybdosilicate spectrophotometric method Cryolithe, naturelie et artificielle - Dosage de la slice - Me’thode spectrophotome’trique au molybdosilicate kduit First edition - 976-09-1 js~c :.iJ*‘:Z -;-‘.& L Ref No IS0 620-1 976 (E) UDC 553.634 : 546.284 : 543.42 i : Descriptors : aluminium ores, cryolite, chemical Q2 -‘.4 Y 4; _ analysis, determination of content, silicon dioxide, spectrophotometric analysis Price based on pages FOREWORD I S0 of (the I nternati onal nati onal I nternati onal Member up has Draft the ri ght and be Pri or to by I S0 the Commi tt ee I SO/TC repl aces I S0 47 the has for l i son by wi th the I SO, al so take part Commi tt ees acceptance set i n the work are ci rcul ated as work of revi ewed I S0 transformati on R the are As was Commi tt ees n ow part in of the thi s Recommen dati on I nternati onal R 620- 970 620 Techni cal docu men ts I nternati onal to approved process, R Standard wh i ch by were publ i shed process 620 I S0 of i s techni cal l y the Member bei ng Techni cal and 620 it found it therefore i denti cal Bodi es of the : Austral i a Hu ngary Roman i a I ndi a Sou th Bel g i u m I ran Spai n Sweden Afri ca, Brazi l I srael Chi l e I tal y Swi tzerl and Czechosl ovaki a Netherl ands Thai l and New Tu rkey Arab Rep of Zeal and France Norway Uni ted German y Peru U S S R Greece Pol and Yu gosl avi a Member Every has been organi zati ons, Au stri a Bod y Recommen dati on devel opi ng Commi ttees I nternati onal thei r federati on of Commi t tee Techni cal before work Techni cal a Techni cal Commi ttee Standards Recommen dati on countri es Egypt, Th e of these Recommen dati on fol l owi ng in approval I nternati onal sui tabl e that Th e Counci l resul ts i nto techni cal l y on I S0 whi ch i s a worl dwi de Bodi es) through for adopted for Recommendati on s; transformed I S0 Standards Standardi zati on) Member out a subj ect represented Bodi es the 972, I S0 in non- governmental , Member Standards as to for ( I S0 i s carri ed i nterested I nternati onal the i nsti tutes Standards Bod y governmental to Organi zati on standards on of the fol l owi ng techni cal grounds country expressed Rep of Ki n g d om di sapproval of the : Can ad a No Member I nternati onal I nternati onal Pri nted in Body di sapproved the transformati on Standard Organi zati on Swi tzerl an d for Standardi zati on, 976 of I SO/R 620 i nto an IS0 620-1 976 (E) INTERNATIONAL STANDARD Cryolite, natural and artificial - Determination of silica content - Reduced molybdosilicate spectrophotometric method SCOPE AND FIELD OF APPLICATION specifies a reduced Standard This International molybdosilicate spectrophotometric method for the determination of the silica content of natural and artificial cryolite and of natural and synthetic materials having a molar ratio (NaF/AI Fa) between and approximately The method is applicable to products the phosphorus(V) oxide (P205) content of which does not exceed 0,02 % (m/m) 1 Special case (under study) Phosphorus(V) oxide contents greater than 0,02 % (m/m) REFERENCE IS0 161 9, Cryolite, natural and artificial - Preparation and storage of test samples PRINCIPLE Alkaline fusion of a test portion by means of a mixture of sodium carbonate and boric acid Dissolution of the fused mass in excess nitric acid so that the final pH of the solution is between 0,7 and 0,9 after dilution to 500 ml, or between 0.3 and 0,5 after dilution to 250 ml Formation, in a suitable aliquot, of the (yellow) oxidized molybdosilicate under clearly defined conditions of acidity, concentration of reagents, temperature and time Selective reduction of the complex in a high-acidity sulphuric medium and in the presence of tartaric acid Spectrophotometric measurement of the reduced coloured complex at a wavelength of about 81 nm REAGENTS During the analysis, use only reagents of recognized analytical grade and only redistilled water 4.1 Sodium carbonate, anhydrous 4.2 Boric acid (H,BO,) 4.3 Nitric acid, approximately N solution Dilute 540 ml of nitric acid, p approximately I,40 g/ml, about 68 % (m/m) solution, with water to 000 ml 4.4 Sodium molybdate, 95 g/l solution (0,8 M approximately) In a polytetrafluoroethylene (PTFE) beaker, dissolve 9,5 g of sodium molybdate dihydrate (NapMo0,.2H,0) in hot water and, after cooling, dilute to 00 ml Transfer the solution to a bottle made of silica-free material and, if necessary, filter before use 4.5 Tartaric acid.1 00 g/l solution 4.6 Sulphuric acid, approximately N solution Carefully add 450 ml of sulphuric acid, p approximately I,84 g/ml, about 96 % (m/m) solution, to about 500 ml of water Cool, dilute to 000 ml and mix 4.7 Reducing solution Use either of the following two solutions : 4.7.1 4-Amino-3-hydroxy-I-naphthalene sulphonic acid, ,5 g/l solution a) Dissolve g of anhydrous sodium sulphite (Na,SOa) in 50 ml of water Add I,5 g of 4-amino-3hydroxy-I-naphthalene sulphonic acid (C,oH,NO,S) b) Dissolve 90 g of anhydrous sodium metabisulphite (Na,S205) in 900 ml of water Mix the two solutions a) and b), dilute to 000 ml and mix Filter if necessary Store in a cool place in an amber-coloured bottle made of silica-free material 4.7.2 Ascorbic acid, 20 g/l solution Prepare this solution just before use I S0 620- 976 Si l i ca, Si O, per (El standard sol uti on correspondi ng to 0, 500 g of 5 Spectroph otometer l i tre N OTE I nto a pl ati num nearest 0, 001 cruci bl e of sui tabl e capaci ty, wei gh, to the - wi th g, ei ther 0, 500 g (H, Si O, ) , the of i gni ted resul ts each of ti me 0, 001 Si O, at two in obtai ned 000 “C from to constant consecuti ve a desi ccator, pure si l i ci c mass, wei ghi ngs, not di ffer by i gni ted to g at the of fi nel y 000 ‘C cruci bl e thoroughl y, ground for Add compl ete the hot di l ute 000 ml water i nto to a more to one- mark Transfer the vol umetri c i mmedi atel y of to Mi x and fuse heat gentl y the thi s standard al kal i ne sh ou l d ri nsed not be dri ed sol uti ons a bottl e to the mad e to to sampl e, dri ed the sol uti on contai ns to mark of 0, 500 per standard sol uti on 110 0, 001 “C g, (see 3 exactl y of I S0 of the cal i brati on g of the test 61 9) g raph Preparati on of to and Wei g h i nto the carbonate Cover Si O, 0, 020 of the base sol uti on a si l i ca-free mg correspondi ng nearest at Preparati on materi al quanti tati vel y di l ute porti on Wei gh, g of 550 pl ati num (4 ) and the di sh the f 25 i ts from unti l the the (5 ) the bori c a pl ati num lid and at 550 control l ed di sh “C of wi th wi th (5 2) , di sh g preferabl y i sol ate Si l i ca, fl oor reacti on 12 g of aci d (4 2) , the sodi u m and mi x spatul a pl ace f of it 25 the in “C, the el ectri c taki ng furnace care to Mai ntai n at subsi des l i tre N OTE Transfer 000 for It sol uti on si l i ca-free transfer fl ask, (4 ) spatul a, transfer made ml , a desi ccator carbonate cruci bl e, Test furnace Si Oz vessel s water chromi c- PROCEDU RE careful l y, of gl ass redi sti l l ed hot thoroughl y than materi al ml of wi th previ ousl y in pl ati nu m and 500 quartz, cool ed sodi u m a beaker about pure and the wi th di ssol uti on quanti tati vel y Cool , h g of preferabl y careful l y mi x wi th wash ed precauti ons, g, or 0, 500 Add fi nal l y careful l y necessary unti l cool i ng - u se be al l an d the shal l taki ng aci d i e after aci d, water Avoi d - Gl assware sul phuri c 40 ml ml of one- mark the standard vol u metri c si l i ca fl ask, sol uti on di l ute to (4 8) the to mark a and - Avoi d materi al s To exampl e, contact i sol ate pl ati n u m of it the from pl ati nu m the vessel fl oor of the wi th refractory furnace, use, for supports mi x Transfer ml of thi s Prepare standard thi s sol uti on Si l i ca, Si O, per sol uti on j ust standard contai ns before sol uti on 0, 020 mg of Si Oz 750 f fl oor use correspondi ng to 0, 005 the 25 of di sh to “C, taki ng the furnace for more than and al l ow to the el ectri c care It mi n cool to in furnace i sol ate mu st i t, not Remove stay the (5 3) , control l ed as before, at di sh thi s at from the temperature from the furnace r g of Add l i tre boi l i ng water to the di sh and heat gentl y to compl ete di ssol uti on Transfer 200 50, O ml ml of one- mark the standard vol umetri c si l i ca fl ask, di l ute sol uti on to (4 9) the mark to a and After cool i ng PTFE mi x ni tri c ml of thi s Prepare standard thi s sol uti on sol uti on j ust contai ns before 0, 005 mg of Si 02 use APPARATUS Ordi nary Pl ati nu m matel y wi th 70 mm a pl ati num aci d wi th di sh, and apparatus fl at and bottomed, hei ght of approxi matel y di ameter 35 approxi mm, fi tted El ectri c at 550 i 25 at col l ecti ng for boi l i ng poi nt f 25 fu rnace, fu rnace, “C to pH meter (4 3) the few cool i ng, to the 2 in a somewh at a 00 Prel i mi nary ml for the and the and and the 20 di sh ml di sh then PTFE to of and transfer the vol u metri c lid wi th near a the hot beaker; temperature one- mark mark test wash sol uti on at of contai ni ng washi ngs to di l ute aci d mi nutes cool contents Careful l y ni tri c quanti tati vel y heat to the sol uti on fl ask After mi x the control and adj u stment of PH capabl e of bei ng control l ed capabl e of bei ng control l ed 20 ml of the base sui tabl e capaci ty Add of standard si l i ca the val ue Thi s of mol ybdate wi th val ue adj ust a the capaci ty, l i d “C El ectri c 740 transfer sui tabl e the gentl y sodi u m of water, Transfer of sol uti on ml Al l ow l aboratory sl i ghtl y, beaker a the the pH shoul d pH graduated by to sol uti on the sol uti on sol uti on meter lie pi pette 15 (4 0) (4 4) ; to ml of and mi x and and 0, 90 a beaker water, ml check of 15 ml of the the pH (5 4) between sl owl y (6 ) beaker 0, 85 addi ng, or drop burette, by If drop, mi xi ng i t does not, by mean s after each I S0 addi ti on, (4 3) the sol u ti on, 65 requi red Di l ute, if after ml and quanti ty necessary, the agai n addi ti on ch eck of so of the the that the pH ni tri c the fi nal ni tri c val u e aci d sol uti on vol u me of aci d is 0, 85 Note Determi n ati on Preparati on the pH vol u me and of the di scard ni tri c the aci d sol uti on sol u ti on added to correct _ I nto FUSI ON the for an of the spectrophotometri c opti cal path standard cal ori metri c measu remen ts l ength of u si ng each fl asks, the of pl ace pH in seri es 20 ml of the vol u me the a the of the 00 ml a cel l one- mark base sol u ti on (6 ) aci d sol u ti on (4 3) test (6 2) ni tri c prel i mi nary havi ng Cover the add sol u ti on to the (4 0) fl asks sh own the vol u mes i n the fol l owi ng and the then to add of by standard * mass of 0, 025 0 0, 050 at fl oor To 0, 075 Remove 0, 00 Ad d 25 each 0, 25 di ssol u ti on sol u ti ons to approxi matel y 60 ml “C Then 11 ml of ml to of the add and 25 add the ml al l ow the to of to ml and the of mol ybdate for to the 15 tartari c aci d sol u ti on mi x sod i u m stand su l phu ri c redu ci ng mark aci d sol uti on (4 25 at 20 sol u ti on (4 6) or sol u ti on mi n Spectrophotometri c After 10 but (4 5) , and 2) fi nal l y Mi x, di l ute havi ng l onger than 40 (5 5) adj usted at Cal i brate i nstru men t carry out mean s a wavel ength the compen sati on mi n , by measu remen ts spectrophotometer - Pl otti ng in mi l l i g rams, and, absorbances at at di sh the mi x whol e spatul a it 25 from in the ‘ C, the wh i ch el ectri c taki ng fl oor there the of the i s no ri sk the reacti on su bsi des ( ti me mi n ) to “C, the taki ng in the el ectri c fu rnace care i sol ate thi s temperatu re the 20 for as from before 30 mi n and of 750 + 25 temperatu re TH E the to mann er (5 3) it the ‘C mi n OF from to same that l east water FU SED fu rnace the M AS S and di sh , al l ow heati ng to cool in moderatel y r unti l occu rs of to about zero 20 the th e cel l s u sed for th e the cal i brati on havi ng, of Si Op for per as ordi nates, ml of the resi du e sol u ti on and col l ecti ng transfer exampl e of the ni tri c of aci d ( mai n l y the contents PTFE) sol u ti on i ron(l l l ) di sh, wi th wash the di sh wash i n g s i n the pl asti cs the di sh to capaci ty, (4 3) oxi de) ml carefu l l y the of su i tabl e of and sti l l the lid adheri ng ni tri c in hot aci d water, beaker Heat for boi l i ng a few poi nt mi n u tes unti l cool , transfer mark vol u metri c the the at a compl ete sol u ti on fl ask, to the i mmedi atel y to mark to approachi ng occu rs quanti tati vel y di l ute sol u ti on temperature di ssol u ti on Al l ow a 250 and ml to one- mi x a fl ask made of si l i ca materi al Col oured reacti on the of the 81 n m, absorbace sol u ti on accu ratel y sl i gh tl y, (for wal l s Take TAKI NG two 50, O (6 2) and the in other OF ml ALI QUOT al i quot pl ace a 00 one ml PORTI ON S porti ons in a beaker on e- mark from of the su i tabl e vol u metri c test sol u ti on capaci ty and fl ask measu remen ts PRELI M I N ARY TEST ADJ USTM EN T OF FOR THE CONTROL pH graph Add a graph sol uti on, for the AN D Pl ot ensu re the 2 6 f from unti l fu rnace stay cool i ng free measu remen ts not spectrophotometri c NOTE mi x pl ati nu m pl ace 550 di sh 30 di sh shal l beaker mi n the sodi u m and to agai n agai nst the boi l i ng Transfer after and at “C + 25 mu st contai ni ng devel opmen t fl ask, mi x and a the sol u ti on Col ou r (4 4) , lid the DI SSOLUTI ON Di ssol ve the of di sh After the (6 ) wi th a support + 25 750 i s mai ntai ned a Di l u te of 550 at 20 Compen sati on (4 2) , i mpu ri ti es transfer Th e mq 5, O i ts : approxi matel y operator 0” of aci d porti on i sol ati ng i ntroduci ng Then Si O, ml 12 g bori c si l i ca : Correspondi ng si l i ca (4 0) wei gh the adj u st the Stan dard of test wi th mean s control l ed sol u ti on (5 ) , control l ed of fu rnace vol u metri c u sed tabl e PORTI ON preferabl y di sh Mai ntai n of the (5 2) , requi red Then TEST g carefu l l y, fu rnace si x sol u ti on sol u ti ons, cm of THE and Add precau ti on I nto test di sh (4 ) quanti ty Preparati on the OF pl ati n u m carbonate carefu l l y of and 0, 901 the (E) the sol u ti on, (between 620- 976 exampl e, 00 the ml as absci ssae, of standard correspondi ng the val u es, cal ori metri c val u es of the ml the al i quot and mi x (5 4) , speci fi ed of the Ch eck adj u st sodi u m porti on to i n 2 of the a and val u e mol ybdate the pH of di scard test val u e in u si ng the between thi s sol u ti on sol u ti on 0, 85 (4 4) the pH and to beaker meter 0, 90 as sol uti on I S0 620- 976 3 (El COLOU R the DEVELOPM EN T qu anti ti es of si l i ca spectrophotometri c To the al i quot on e- mark aci d sol u ti on ml test and col ou red of the fl ask, (4 3) prel i mi nary 60 porti on vol u metri c u sed mi x Then sol u ti on the to (6 2) , reacti on test add adj u st adj u st proceed as speci fi ed the of the the wi th in in vol u me 00 the pH vol u me devel opment of the test sol uti on and the about of Th e si l i ca mass, ( Si Oz) i s gi ven by Carry to the out the the procedure speci fi ed to zero in measu remen t 5, absorbance after agai nst accordi ng Bl an k havi ng adj u sted water m, i s the the al i qu ot test PREPARATI ON Prepare the speci fi ed bl ank in OF test , di l ute SOLUTI ON accordi ng to a fi nal the to the vol u me DEVELOPM ENT Devel op the as speci fi ed 3 SPECTROPHOTOMETRI C out col ou r the sol uti on expressed as a percentage by formu l a 500 x - =p 000 - m, ) mo- m, g mass, in mi l l i g rams, porti on of the of dri ed of the test test sampl e) si l i ca ( SO, ) sol u ti on taken found in (contai ni ng for the deter- 250 spectrophotometri c i s the mass, in mi l l i g rams, correspondi ng al i quot of si l i ca porti on ( Si Oz) of the found bl ank in test sol u ti on procedure of ml COLOU R in TH E sol u ti on but 33 Carry the mi nati on; ml 3 test of porti on where 0, 200 3 bl ank val u es al i quot M EAS U REM EN T spectroph otometri c i nstru ment the the the the SPECTROPH OTOM ETRI C of content, the ( mo to of ni tri c in to ml correspondi ng measu remen ts TEST The i n 3 REPORT test report shal l i ncl u de a) the reference of the b) the resu l ts and c) any the method fol l owi ng parti cu l ars u sed; M EASU REM EN T measu rement the method of expressi on u sed; as speci fi ed u nusu al features noted duri ng the deter- mi nati on; EXPRESSI ON OF d) RESULTS any Standard By reference to the cal i brati on graph (see 5) , determi ne reference operati ons or in i s made, not the or i ncl u ded I nternati onal regarded in thi s Standard as opti onal I nternati onal to wh i ch : I S0 620- 976 (E) AN N E X I S0 PUBLI CATI ONS and of test TO CYROLI TE, I S0 61 - Preparati on I S0 620 - Determi nati on of si l i ca I S0 693 - Determi nati on of fl uori ne I S0 694 - Determi nati on of i ron I S0 2366 - Determi nati on of sodi u m I S0 2367 - Determi nati on of al u mi n i u m content - 8- Hydroxyqu i nol i ne I S0 2830 - Determi nati on of al u mi n i u m content - Atomi c I S0 3391 - Determi nati on of cal ci u m I S0 3392 - Determi nati on of water I S0 3393 - Determi n ati on of moi stu re I S0 4277 - Eval u ati on I S0 4280 - Determi n ati on I S0 , - of storage RELATI NG - Redu ced content - - mol ybdosi l i cate Modi fi ed ARTI FI CI AL - content Fl ame - - content Fl ame emi ssi on and atomi c method method ph otometri c method atomi c absorpti on g ravi metri c absorpti on El ectrometri c - spectrophotometri c Wi l l ard- Wi nter , l O-Phenanthrol i ne content content AN D sampl es content content NATURAL spectrophotometri c meth ods method method absorpti on method method Gravi metri c free fl uori des content - Conventi onal of su l ph ates content - Bari u m method ti tri metri c sul phate method gravi metri c method Sampl i n g