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है”ह”ह

IS 1527 (1972): Methods for chemical analysis of highsilica refractory materials [MTD 13: Ores and RawMaterials]

Is : 1527 - 1972 ( Reallirmed 1997)

Indian Standard

METHODS FOR CHEMICAL ANALYSIS OF HIGH SILICA

REFRACTORY MATERIALS

( First Revision )

Fourlh Rrprint JANUARY 1990

UDC 666.762.2:543

@ Copyright 1973

BUREAU OFINDIAN STANDARDS MANAK BHAVAN. 9 BAHADUR SHAH ZAFAK MARG

NJZWDELHI11OOUZ

Gr I February 1973

lStl527-1972

hiian Stan&d METHODS FOR

CHEMICAL ANALYSIS OF HIGH SILICA REFRACTORY MATERIALS

(First Revision)

Methods of Chemical Analysis Sectional Committee, SMDC 2

Cboirmon w-* DR R. K. Durr~ Hindgusapteel Ltd ( Durgapur Steel Plant),

Members

SHRI ii. C. BHAR~AVA India Government Mint, Bombay SHRI J. B~TTACHARJEB Ministry of Defence ( DC1 ) SHRI A. K. BHA~ACHARYYA National Tat House. Calcutta

SARI S. DAS GUF-TA ( Alhnotc) DR H. P. BHATTACHAR~A National Metalhtrgical

Jd=k= LaboPatory ( CSIR ),

Da U. N. BHIWW Indian Iron & Steel Co Ltd, Burnpur SHRI A. C. bfVKHRRJKR ( dkdC)

DR V. M. BHVCHAR National Physical Laboratory ( CSIR ), New Delhi ,$‘dRl P. CHAKRA Indian Metals and Ferro Alloys Ltd, Koraput DR B. N. CHAKRAVARTHI Hindustan Steel Ltd ( Bhilai Steel Plant ), Bhilai

SHRI Y. B. S. BISHNOI (Afirmotr) SHRI A. K. CHATI-KRJRR Binani Metal Works Limited, Calcutta CHEMIST AND M E I A t L u R Q x s T, Ministry of Railwaya

SOUTH CENTRAL RAILWAY, SECUNDERABAD

A.w~sRcv=y;v~=T).

STANDARDS ORGAN&~, CIV~ARANJAN ( A1tcmk)

JR A. N. CHOWVHVRY Geological Survey of India, Calcutta SHRI B. N. BHATTAC~IARYA (&em&)

&RI S. N. DASGVPTA Direczrte Gcoaal of Suppks & Dispos&, New

SHRI K. L. MIJR~~ ( Alfemafe) DR R. DWITA

SHRl S. ROY ( dkmuk) The Eyre Smelting Private Ltd, Calcutta

SHRI C. S. GovRIs~~ANKA~ Directorate General, Ordnance Factoria ( Ministry

SHRI J. W. GAWATHRK.~R ( Alfenta&) of De&x), Calcutta

( ~hmcd on pasr 2 )

BUREAU OF INDIAN STANDARDS MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 1 loo02

I23 : 1527 - 1972

( cotltinliedfrom page 1)

Members

SHRI s. s. HONAVAR

-

Italab Private Ltd. Bombay SHRI J. C. DEY ( Altmalr I ) SHRI J. P. PATEL ( Aftmuzle II )

SHRI D. P..JAIN Saru Smelting Priv8te Ltd, Mccrut SRRI fi. N. CIUKRABOR~Y (~~) -

SHRI K. B. JAPE De%%ra~u+~ R-

SHRI S. L. N. ACHARYULU ( Almu&) SHRI G. L. JETHWANX Hindu&m Zittc Limited, Udtipur DR A. K. MUKHERJEE Hinduscan Steel Ltd (Alloy Steel Plant), Durgapur

SHRI M. M. CHAKRAVARTY ( A~MI~J ) SHRI K. RAMA~RISHNA SHR~ A. SANOAMESWARA RAO

Jzsscn & Co, BangJore

SHRI G. RAJA RAO ( Alfemafr ) Fare Alloys Corporation Ltd, Sbreeratnnagar

DR B. C. SINHA’ Central Glass and Ccsamic Raearch Institute

SHRI B. K. AGARWAL ( Altw~te ) ( CSIR ), Calcutta

DR P. R. SUBBARAYAN DR CH VENKATE~WARLU

National Chemical Laboratory ( C SIR ), Pooua

DR C. S. P. IYER ( Alfemafe I) Bhahha Atomic Research Ccntre, Bombay

SHRI P. MURUQNYAN ( Altema~c II ) SHRI R. K. SRIVASTAVA,

Deputy Director (Strut & Met) I)mctor Gcnd, IS1 (ET+& Men&r)

*m SW S. L. BALI

Deputy Director ( Met ), IS1

Refractory Materials Analysis Panel, SMDC 2/P : 34

Conocnar DR B. C. SINHA Central Glass and Ceramic Research Inrtitute

( CSIR ), Calcutta

Members SHRI BHASKAR RAO

DR H. P. BXATTACXARYYA

DR A. N. CHOWDHURY SHR~ T. MOTILAL

SHRI H. F. K. NAD~O ( Ak~fe SHRI T. K. S. RAO SHRI A. SANGAMESWARA &o

Kumardhubi Fircclay Kumardhubi

and Silica WorlrJ Ltd,

National Metallurgical Laboratory ( CSIR ), Jamshedpur

Geological Survey of India. Calcutta

1 Bhilai Steel Plant ( Hindustan Steel Ltd ), Bhilai

Bum & (20 Ltd, Raniganj, Dirt Burdwvl FCITO Alloys Gxporatioo Ltd, Shrceramnagar

2

IS I 1527 - 1972

Indian Standard METHODS FOR

CHEMICAL ANALYSIS OF HK;H SILICA REFRACTORY MATERIALS

( First Revision )

0. FOREWORD

0.1 This Indian Standard ( First Revision ) was adopted by the Indian Standards Institution on 25 October 1972, after the draft finalized by the Methods of Chemical Analysis Sectional Committee had been approved by the Structural and Metals Division Council.

0.2 This standard was earlier published in 1960. On the basis of the experience gained during these years, it was felt that some of the methods need modifications. While revising these methods actual investigations have been carried out and due weightage has been given to the inter- national practices followed in this field. The methods prescribed in this standard may be used as referee methods and could also be used for routine analysis.

0.3 In reporting the result of a test or analysis made in accordance with this standard, if the final value, observed or calculated, is to be rounded off, it shall be done in accordance with IS : 2-1960*.

1. SCOPE

1.1 This standard covers the methods for determination of the loss on ignition and of the oxides of silicon, aluminium, iron, titanium, calcium, magnesium and the alkali metals in high silica materials ( over 94 percent SiO, ). However these methods could be used for similar materials having silica content of not less than 90 percent.

2. SAMPLING AND PREPARATION OF SAMPLE

2.1 The materials shall be sampled in accordance with the procedure laid down in IS : 1528-1962t.

.

*Rules for rounding off numerical values ( revised ) .

tMethods of sampling and physical tests for refractory materials

3

IS : 1527 - 1972

2.2 Laboratory Sample - The samples shall be crushed in any type of crusher with hardened tool steel faces with due precautions to prevent contamination of the sample with steel particles from the sampling equip- ment during crushing and grinding. After quartering, 20 g of the sample shall be carefully gone over with a magnet to remove extraneous iron particles. It shall then be ground in an agate mortar so that it passes completely through IS Sieve 15 ( aperture 149 microns, see IS : 460-1962* ).

2.3 Test Sample - It is prepared for the purpose of chemical analysis by drying a sufficient quantity of the laboratory sample in a glass weighing bottle in an air oven at 105 to 110°C.

3. QUALITY OF REAGENTS

3.1 Unless specified otherwise, pure chemicals and distilled water (see IS : 1070-196Ot ) shall be used.

NOTE - ‘ Pure chemicals ’ shall mean chemicals that do not contain impurities which affect the results of analysis.

4. DETERMINATION OF LOSS ON IGNITION

4.1 Transfer one,gram of the test sample to a weighed platinum crucible and introduce it into a muffle furnace and slowly raise the temperature to 950 to 1 000°C. After about 30 minutes, remove the crucible and cool in a r zsiccator and weigh. Repeat the ignition, if necessary. Calculate the loss of weight of the sample.

4.2 Calculation

where

Loss on ignition, percent = $X 100

A = loss of mass in g on ignition, and

B = mass in g of the sample taken.

5. D$;;~EF;NATION OF SILICA BY THE GRAVIMETRIC

5.1 outline of the Method - The sample is decomposed by fusion with sodium carbonate and extracted with acid. Silica is then determined by dehydration and baking followed by hydrofluorization as usual. The residual silica is determined photometrically.

*+&cation for test sieves ( revised ). tspecification for water, distilIed quality ( revised).

4

k

IS : 1527 - 1972

5.2 Reagents

5.2.1 Sodium Carbonate - anhydrous.

5-2.2 Dilute Hydrochloric Acid - 1 : 1, 1 : 3 and 1 : 19 ( V/V ).

502.3 Dilute Sulflhuric Acid- 1 : 1 ( v/v ).

5.2.4 Hydrojuorfc Acid - 40 percent.

5.2.5 Potassium Pyrosul&hate - Solid.

502.6 EDTA Solution ( 0,025 M Appoximately ) - Dissolve 9.31 g of disodium salt of ethylene-diamine ( C~,HuN&‘,Cs, 2HsC )

tetraacetic acid, dihydrate in water and dilute to 1 litre.

5.2.7 Phenolphthalein Sob&on - of rectified spirit.

Dissolve 1 g of phenolphthalein in 100 ml

5.2.8 Dilute Ammonia Solution - 1 : 3 ( v/v).

5.2.9 Ferric Ammonium Sulphate Solution ( l-12 mg Fe/ml ) - Dissolve 482 g of ferric ammonium sulphate [ NH,Fe ( SO, )s, 121&O ] in water containing 80 ml of dilute hydrochloric acid ( 1 : 1 ) and dilute to 500 ml in a volumetric flask.

5.2.10 Ammonium Molybdate Solution -Dissolve 100 g of ammonium lolybdate in water containing a few drops of dilute ammonia ( 1 : 3 ),

liter if necessary and dilute to 1 litre.

5.2.11 Oxalic Acid Solution - Dissolve 100 g of oxalic acid in water and dilute to 1 litre.

5.2.12 Ascorbic Acid Solution ( 10 percent ) - Dissolve 10 g of the acid in 100 ml water and filter if necessary. Preserve in an amber-coloured bottle. The solution, thus preserved, could be used up to 5 days.

5.2.13 Standard Silica Solution ( 0.04 mg/ml ) a) First prepare a stock solution with 0.4 g/l; for this purpose fuse

0.200 g of pure silica ( 99.8 percent ) in 5 g of sodium carbonate in a platinum crucible. Dissolve in 300 ml of water, containing 8 to 10 g of sodium hydroxide, using a polvthene beaker. and dilute with water in a volumetric flask’to 500 ml.

Cool Store in

a polythene bottle. b) Prepare immediately before use a standard solution containing

0.04 mg/ml by diluting the above stock solution appropriately.

5.3 Procedure

5.3.1 Decomposition oJ the Sample - Weigh accurately about 0.5 g of the finely ground test sample ( see 2.3 ) into loo-ml platinum dish. Add 3 g of sodium carbonate; after mixing intimately, cover the dish with lid and

5

IS : 1527 - 1972

heat over a Meker burner slowly, increasing the temperature with caution until the mixture fuses. Keep at this temperature for 10 minutes and finally heat till a clear melt is obtained. Remove from the burner and Cool.

5.3.1.1 Add about 30 ml of dilute hydrochloric acid ( 1 : 1 ) and O-5 ml of dilute sulphuric acid. Allow the covered dish to stand on a steam bath until disintegration of \he melt is complete. flakes with a flattened end of a glass rod.

Crush any large

5.3.2 Gravimetric Determination of Insoluble Silica

5.3.2.1 Evaporate the solution in the dish to dryness and allow the dish to remain on a steam bath. ( The evaporation may be facilitated by occasional use of a glass rod to break up the crust of salt that covers the liquid and tends to prevent further evaporation ). Transfer the dish to an air oven maintained between 105 to 110°C and bake it for one hour. Cool the dish and its contents slightly, then add 20 ml of the dilute hydrochloric acid ( 1 : 1 ). After about one minute, add 30 ml of hot water and stir the mixture for a few moments until solution of soluble salts appears to be complete. Cover the dish and allow the mixture to digest on a steam bath for 10 minutes without stirring. Filter through No. 42 filter paper and rinse the dish with dilute hydrochloric acid ( I : 19 ), scrubbing the basin with a rubber-tipped glass rod. Wash the precipitate five times with hot dilute hydrochloric acid ( 1 : 19) and then with hot water until free from chlorides. Transfer the filtrate and washings to a 500-ml volumetric flask and make up to the mark (solution S).

5.i.2.2’ Transfer both paper and precipitate to an ignited and weighed platinum crucible. Ignite at a low temperature until the precipitate is free from carbonaceous matter and then heat in the furnace at 1050°C to constant weight ( one hour being normally sufficient ). Cool and weigh. Moisten the contents of the cold crucible with water, add five drops of dilute sulphuric acid and 10 ml of hydrofluoric acid. Evaporate to dr+ ness on a hot plate or sand bath in a fume cupboard, taking care to avoid spurting.

5.3.2.3 Heat the crucible and residue, cautiously at first, over a gas flame until the disappearance of white fumes and finally for five minutes in the furnace at 105O”C, cool and weigh. If the residue weighs more than 10 mg, repeat the treatment with dilute sulphuric and hydrofluoric acids.

5.3.3 Molybdenum Blue Method

5.3.3.1 Transfer 20 ml aliquot of the solution S ( 5.3.2.1) to a lOO-ml measuring flask. Add 5 ml of EDTA solution, a drop of phenolphthalein solution and then dilute ammonia solution dropwise until the colour changes to red. Add 5 ml of ferric ammonium sulphate solution and

6

IS : 1527 - 1972

dilute to about 40 ml with water. (The PH of the sol&on should be 1 to 1.5 ).

5.3.3.2 Add 5 ml of the ammonium molybdate solution and allow to stand for 10 minutes. Then add 5 ml of oxalic acid solution followed immediately by 5 ml of ascorbic acid solution and dilute the volume to 100 ml. Allow the solution to stand for 30 minutes for development of full colour.

5.3.3.3 Transfer a suitable portion of the coloured solution to an absorption cell and take photometric reading using light band centred approximately at 810 nm against a referend test blank solution prepared in the same way without the sample.

NOTE -Test blank solution-It is prepared by taking all reagents and solutions except the sample in accordance with the general procedure for the determination of residual silica. However, fusion may be omitted to avoid undue attack on platinum crucible.

5.3.3.4 Calibration curve - Transfer 0, 1, 2! 3 and 4 ml of standard silica solution to lOO-ml volumetric flasks. Dilute each to 10 ml with water. Add a drop of phenolphthalein solution an! acidify with a few drops of dilute hydrochloric acid ( 1 : 3 ), Carry out the entire stages of procedure as described in 5.3.3.1 ( except the addition of 10 ml of solu- tion S) and 5.3.3.2 using the same quantities of reagents and record the photometric readings of all these solutions against the blank ( ‘ 0 ’ ml ).

5.3.3.5 Convert the photometric reading of the test solution’ to milli- grams of silica by means of the calibration curve and calculate the silica content in grame in 500 ml of solution S ( 5.3.2.1 1

5.4 Calculation

Silica, percent = (B---C’++

A

I*

x 100

where

B = mass in g of dish and contents treatment,

before hydrofluoric acid

C = mass in g of dish and residue after hydrofluoric acid treat- ment,

D = mass in g of silica present in 500 ml of solution S, and

A = mass in g of sample.

6. DETERMINATION OF ALUMINA BY EDTA METHOD

6.1 Outline of the Method - Aluminium ( also iron and titanium when present ) is complexed quantitatively with EDTA by boiling with an excess of the reagent. The excess EDTA is back titrated with standard zinc

7

Is : 1527 - 1972

solution at about PH 5.2 using xylenol orange indicator. The aluminium EDTA complex ( also titanium-EDTA complex, if present ) on boiling with ammonium fluoride liberates EDTA which when titrated with standard zinc solution gives the amount of aluminium present in the solution, Due correction for titania is also carried out.

6.2 Reagents

6.2.1 Dilute Sulphuric Acid- 1 : 1 ( v/v ). Add 100 ml of concentrated sulphuric acid (sp gr 1.84) cautiously with stirring to 100 ml of water and cool.

6.2.2 Hydrojluoric Acid - 40 percent.

6.2.3 Sodium Carbonate - solid.

6.2.4 Dilute Hydrochloric Acid - 1 : 1 ( v/v ).

6.2.5 EDTA Solution ( O-025 M ) - See 5.2.6.

6.2.6 Methyl Orange - Dissolve @05 g of methyl orange in 100 ml of water.

6.2.7 Dilute Ammonia ( 1 : 5 ) - Dilute 25 ml of concentrated ammonia ( sy gr 0.90 ) to 150 ml.

6.2.8 Acetate Bu& (PH 5.2 ) ( CHsCOONa, 3HsO )

- Dissolve’ 21.5 g of sodium acetate in 300 ml of water containing 2 ml ofglacial acetic

acid and dilute to 1 litre.

6.2.9 Standard Aluminium Solution ( 1.0 mg Al,Os/ml ) - Weigh O-529 3 g of aluminium metal ( 99.9 percent purity ) into a beaker containing 40 ml of dilute hydrochloric acid ( 1 : 1 ) and small drops of mercury. Heat the beaker over a water bath. Transfer the solution to a 1 OOO-ml volumetric flask and make up to the mark.

NOTE - Mercury will not dissolve and may be removed while transferring the solu- tion to 1 OOO-ml volumetric flask.

6.2.10 Standard zinc Solution ( 0.025 M ) - Dissolve 5.484 5 g of zinc acetate [ Zn ( CHsCOO )a, 2HsO] in 50 ml of water, 0.5 ml of glacial acetic acid and 25 ml of acetate buffer ’ 6.2.8 ) and dilute tcJ 1 litre in a measuring flask. Find out the equiva ent A&O, in g per ml from i the procedure given in 6.3.2 taking 20 ml of standard aluminium solution (6.2.9).

6.2.11 Xylenol Orange - Dissolve 0.1 g of xylenol orange in 100 ml of water containing two drops of dilute hydrochloric acid ( 1 : 1 ).

6.2.12 Ammonium Fluoride (20 percent) - Dissolve 20 g of ammonium fluoride in 100 ml of water. Add 3 drops of xylenol orange ( 6.2.11)‘ and then dilute hydrochloric acid ( 1 : 9 ) dropwise till the colour changes to yellow,

8

IS : 1527 - 1972

6.3 Procedure 6.3.1 Solution of the Sample - Weigh accurately about 2 g of the finely

ground test sample ( Jee 2.3) in a platinum dish. Moisten the sample with 5 ml of water. Add 3 ml of the dilute sulphuric acid and 20 ml of the hydrofluoric acid and evaporate slowly to dryness on the sand bath. or hot plate in a fume cupboard, taking care to avoid spurting. Repeat the process with 10 ml of hyd,rofluoric acid. Cool, add 2 ml of the dilute sulphuric acid and evaporate as before, Heat the dry residue cautiously until fumes of sulphur trioxide cease to be evolved. Raise the temperature to 1000°C and ignite for five minutes. Cool and fuse the residue with about 3 g of sodium carbonate. Dissolve the residue in 30 to 40 ml dilute hydrochloric acid, cool and dilute to 250 ml in a calibrated flask, Reserve the solution for determination of iron, titania and aluminii.

6.3.2 Transfer. 100 ml aliquot of the solution to a 500.ml conical flask. Add sufficient EDTA solution to provide an excess of at least 5 mi over the expected amount of alumina and iron ( 1 ml of 0.025 M EDTA = 1.25 mg Al,O, approximately ). Add 2 to 3 drops of methyl orange and then dilute ammonia dropwise until the colour. changes from red to yellow. Add 5 ml of acetate buKer and about 25 ml water and heat to boiling for 5 minutes. Cool, add 5 ml of buffer solution and titrate with standard zinc solution using 5 to 6 drops of xylenol orange indicator. The end point is indicated by a clear change from yellow to deep orange colour. Add 10 ml of ammonium fluoride solution and heat to boiling for 5 minutes. Cool, add 5 ml of buffer solution and titrate the liberated EDTA with standard zinc solution.

NOTE - If titania content is well above O-5 percent, it may effect the sharpness of the end point.,

6.4 Calculation

Alumina, percent = L;x x 100 - 0.637 8 D

where A = volume in ml of standard zinc required for the titration

of liberated EDTA,

B = equivalent Al,Os in g per ml of standard zinc solution, G = mass in g of the sample represented by 100 ml of solution

taken, and D = percent of TiO, present in the sample. The value is

obtained from, photometric determination ( see 8.4 ).

7. DETERMINATION OF IRON BY THE ORTHO-PHENAN- ‘FHROLINE (PHOTOMETRIC ) METHOD

7.1 Outline of the Method-The orange-red complex produced in acid solution of the sample (flH 4 to 6 ) by the addition ofO-phenanthroline is determined photometrically at approximately 510 nm.

IS t 1527 - 1972

7.2 Reagents

7.2.1 Turtaric Acid Solution - 10 percent ( m/v).

7.2.2 Hydroxylamine Hydrochloride Solution ( 10 g/l ) - Dissolve 1 g of the reagent in water. Transfer the solution to loo-ml volumetric flask, Dilute to the mark and mix well.

7.2.3 Ortho-Phenanthroline Solution ( One Percent ) - Dissolve one gram of the 0-phenanthroline monohydrate in 90 ml of water with gentle heating and constant stirring. Cool and dilute to 100 ml.

7.2.4 Acetate Buffer - Dissolve 21.5 g of sodium acetate ( CH,COONa, 3H,O ) in 300 ml of water containing 2 ml of glacial acetic acid and dilute to 1 litre.

7.2.5 Standard Iron Solution ( 1 ml = 0.02 mg Fe ) - Dissolve 0.2 g of pure iron in concentrated hydrochloric acid. Dilute the solution to 100 ml. Take the solution in a I-litre volumetric flask, dilute to the mark and mix well. Transfer 100 ml of this solution to l-litre measuring flask and dilute to the mark with water. Mix well.

7.3 Procedure

7.3.1 Transfer a 5 ml aliquot of the solution preserved under 6.3.1 to a 100~ml measuring flask. Add 2 ml of tartaric acid solution, and 2 ml of the hydroxylamine hydrochloride solution. Stir well. To this, add 5 ml of the ortho-phenanthroline solution and 10 ml of acetate buffer solution. Allow to stand for 15 minutes and dilute to 100 ml. Shake well.

7.3.2 TranSfer a suitable portion of the solution to an absorption cell and take photometric reading using a light band centred approximately at 510 nm against a reference test blank solution.

7.3.3 Calibration Curve - Transfer 0, 1,2, 4, 8 and 10 ml of the standard iron solution in lOO-ml volumetric flasks, using same quantities of reagents. Carry out the entire stages of procedures as described under 7.3.1 and 7.3.2 and record the photometric readings of all the standard solutions against the blank.

7.4 Calculation -Convert the photometric reading of the sample to milligrams of iron by means of a calibration curve and calculate the ‘per- centage of iron as follows:

where

Ferric oxide, percent = ; x 0,142 9

A = mass in mg of iron found in aliquot, and

B = mass in g of the sample represented by the aliquot taken,

10

IS : 1527 - 1972

8. DETERMINATION OF TITANIA BY THE PHOTOMETRIC METHOD

8.1 Outline of the Method - The yellow coloured complex produced in acid solution of the sample by the addition of hydrogen peroxide is deter- mined photometrically at approximately 410 nm.

8.2 Reagents

8.2.1 Dilute Sulphuric Acid - 1 : 1 ( v/v ).

8.2.2 Phosphoric Acid - Add 400 ml of phosphoric acid ( sp gr I.75 ) to 500 ml of iater, cool and dilute to 1 litre.

8.2.3 Hydrogen Peroxide - 20 volumes.

8.2.4 Standard Tiitania Solution - Fuse 0.5 g of dried TiO, with 5 g of potassium pyrosulphate and dissolve by heating at a low temperature to avoid hydrolysis in 200 ml of water containing 20 ml of concentrated sulphuric acid ( sp gr 1.84 ) . flask ( 1 ml = 0.5 mg TiO, ).

Cool and dilute to 1 litre in a measuring

8.3 Procedure

8.3.1 Transfer 50 ml aliquot of the solution from 6.3.1 to a loo-ml measuring flask. Add 5 ml of dilute sulphuric acid, 10 ml of the phospho- ric acid and 10 ml of hydrogen peroxide. Dilute the solution to 100 ml.

8.3.2 Transfer a suitable portion of the solution to an absorption ceil and take a photometric reading using a light band centred approximately at 410 nm against a .reference test blank solution.

8.3.3 Calibration Curue - Transfer 0, 1, 2, 4 and 6 ml of the standard titanium solution to lOO-ml volumetric flasks, using the same quantity of reagents, carry out the entire stages of procedure as in 8.3.1 and 8.3.2 and record the photometric readings of all the standard solutions against the blank.

8.4 Calculation -Convert the phototietric reading of the sample to milligrams of titania by means of calibration curve and calculate the percentage of TiO, as follows:

A Titania, percent = .li- x -&

where

A = mass in mg of titania determined in the aliquot solution, and

B = mass in g of sample represented by the aliquot taken,

II

IS : 1527 - 1972

9. DETERMINATION OF CALCIUM OXIDE AND MAGNESIUM OXIDE BY THE EDTA METHOD

9.1 Oailine of the Method - In an aliquot of the sample solution, R,O, group e’lements are masked by triethanolamine, and calcium and mag- nesium are titrated with EDTA solution at pH 10 using eriochrome black T indicator. In another aliquot magnesium is precipitated out at #H 12 in presence of triethanolamine and calcium is titrated with EDTA using Patton and Reader ( P & R ) indicator. Subtracting the titre value of calcium from that of calcium and magnesium, the titre vaiue for mag- nesium is obtained.

9.2 Reagents

9.2.1 Concentrated .Nitric Acid - sp gr 1.42 (conforming to IS: 264- 1968* ).

9.2.2 Perchloric Acid - 70 percent.

9.2.3 HydroJIuoric Acid - 40 percent.

9.2.4 Concentrated Hydrochloric Acid - sp gr 1.16 ( conforming to IS : 265- 1962t ).

9.2.5 Triethanolamine SnZuti& - 30 percent ( v/v). Dilute 60 ml of triethanolamine to 200 ml.

9.2.6 Sodium Hydroxide Solution ( 5N Approximately ) - Dissolve 100 g of sodium hydroxide in water, cool and dilute to 500 ml and store in a polythene bottle.

9.2.7 P & R Indicator - Mix by grinding togjether 0.1 g of P & R indi- cator and 30 g of sodium chloride. About 0.2 g of the mixture is required for each titration.

9.2.8 Standard ED IA Solution ( 0.01 M ) - Dissolve 3.72 g of disodiub salt of ethylenediamine tetra acetic acid dihydrate in warm water, filter if neces- sary, cool and dilute to one litre. Store in a polythene bottle. Standardize against- the standard calcium solution (see 9.2.9 ) using P $i R indicator and against the standard magnesium solution ( SPY 9.2.10) using ‘Mixed’ indicator.

9.2.9 Standard Calcium Solution - Dissolve 1.7848 g of calcium carbonate dried at 150°C in a slight excess of hydrochloric acid, boil to expel carbon dioxide, cool and dilute to 1 litre ( 1 ml L- 1 mg CaO ).

9.2.10 Standard Magnesium Solution - M7ash a piece of magnesirmi in dilute hydrochloric acid to remove any oxide film, then with water and

*Specification for nitric acid (Jirst rev&m ).

tSpecification for hydrochloric acid (rcukf ).

IS t 1527 - 1972

dry it with ethanol followed by ether. Dissolve 0’603 2 g of the metal in a slight excess of dilute hydrochloric acid, cool and dilute to 1 litre in a calibrated flask ( 1 ml = 1 mg MgO ).

9.2.11 Ammonia-ammbnium Chloride Bu$r Solution ( ~JH = 10 ) - Dissolve 57.5 g of ammonium chloride in 250 ml of water, and 570 ml of ammonia ( sp gr = 0.88 ) and dilute to 1 litre and mix thoroughly.

9.2.12 Eriochrome Black T Indicator Solution - Dissolve 0.4 g of the sodium sait of eriochrome black T in a mixture of 20 ml of ethanol and 30 ml of triethanolamine. This solution is stable for at least 3 months when kept in a tightly closed plastic dropping bottle.

9.3 Procedure 9.3.1 Solution of the Sample -Weigh accurately about 1 g of the test

sample (see 2.3 ) into a platinum dish. Add 5 ml of concentrated nitric acid, 5 ml of perchloric acid and about 10 ml of hydrofluoric acid. Cover the dish with a lid. Allow the reaction to proceed for at least 15 minutes, then remove the lid and evaporate the mixture to dryness on a sand bath in a fume cupboard, taking care to avoid spurting. Cool, add 5 ml of perchloric acid, rinse the lid and sides of the dish with water and again evaporate carefully to dryness. To the cool, dry residue, add 2 ml of concentrated hydrochloric acid and about 15 ml of deionized water. Digest on a steam bath for 10 minutes, cool, filter if necessary and dilute the solution with deionized water to 250 ml in a calibrated flask. Reserve the solution for determination of calcium and magnesium oxides as well as alkali metals in a polythene bottle.

g-3.111 Determination of calcium - Pipette 50 ml ( = 0.2 g ) of the solution into a 250-ml conical flask. Add 10 ml triethanolamine solution, 5 ml of sodium hydroxide solution dropwise while shaking the solution, and then add 0.2 g of P & R indicator. Titrate immediateIy with a standard EDTA solution from 10 ml semi-micro burette until the colour changes from pink to blue. .

NOTE - If sharp end point is not ‘obtained, 2 ml of potassium cyanide ( 10 percent m/u ) may be added after the addition of triethanolamine in 9.3.1.1 and 9.3.2.

9.3.1.2 Calculation

Calcium oxide, perceht = c-- AXBX 100

where

A E volume in ml of standard EDTA solution required for titration,

B = (=a0 equivalent in g/ml of the standard EDTA solution, and

C i= mass in g of the sample represented by the aliquo: sample solution taken.

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.., _ . . . . “. ^___. _ .___ _ .

ISt1527- 1972

9.3.2 Determination of Magnesium Oxide - Pipette out 50 ml ( E 0.2 g ) oc solution reserved in 9.3.1 into a 250-ml conical flask. Add 10 ml of triethanolamine solution. Add 15 ml of *ammonia-ammonium chloride buffer solution. Add 4 to 5 drops of eriochrome black T indicator solu- tion and imm,ediately titrate with the standard EDTA solution from a lo-ml semi-microburette until the colour changes from wine red to blue. .

9.3.2.1 Calculation

Magnesium Oxide, percent = --D- tA--) Cx.100

where

A = volume in ml of standard EDTA solution required for titration of total calcium and magnesium obtained in 9.3.2,

B = titre value for calcium,

C= MgO equivalent in g/ml of the standard EDTA solution, and

D = mass in g of the sample represented by the aliquot taken.

10. DETERMINATION OF ALKALI METALS

10.1 From the solution reserved in 9.3.1 alkali metals are determined by using a flame photometer.

10.2 Determine the alkali metal contents on aliquots of solution by com- parison with solutions containing-known amount of potassium and sodium using a suitable flame photometer. for the type of flame photometer

The procedure should be appropriate and

on standard samples of solutions. should be confirmed by determination The standard solutions should be of

similar composition as far as possible to the sample solution being analysed.

10.3 The alkali metal contents are calculated as oxides by reference to previously prepared calibration graphs.

1 IO.4 A procedural blank should also be carried out and necessary correc- tion made in t.he final calculation.

NOTE - Wherever required, only deionized water shall be used.

14

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