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laboratory copy

not to be'taken away REFERENCET.C.23

COMMONWEALTH OF AUSTRALIA

COMMONWEALTH SCIENTIFIC AND" INDUSTRIAL RESEARCH ORGANIZATION

FUEL RESEARCH

PHYSICAL AND CHEMICAL SURVEY

OF THE NATIONAL COAL RESOURCES

!»

DETEmffl\"ATIOH OF THE INORGANIC CONSTITUEMTS

IN AUSTRALIAN CQMiS

BY MPID SEMI-MICRO (PHOTOMETRIC) mTHODS

>

COAL RESEARCH SECTION.P.O. BOX 3.

CHATSWOOD. N.S.W.

JULY, 1957.

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DETERMIMTIOIT OP THE INORGAHIC OOHSTITUEM'S

IH AUSTRALIAN COALS

BY RAPID SEBfl-MICRO (PHOTOMETRIC) lilETHODS

R. A. Durie and H. N, S. Schafer

TABLE OF CONTENTS

Pa^e

SUIffl/IAEY 5

GENERAL IBTEODUCTIQE

1. ASSESSMENT OF SCHEME OF ANALYSIS

PROPOSEB BY PRINGLE (1954) . ^11

1.1. Introduction

1.2. Experimental Details "^2

1.3. Results

1.4. Discussion

1^4,1. Yilet oxidation of coal , "^3

1.4.2, Silica determination "14

1.4.3, Aluminium . ' ^^4

1.4.4. Iron^ titanium^ and pLosphorus 151.4.5. Calcium and magnesium 15

1.4.6, Sodium 15

1.4.7. Potassium 15

1.5. Summaryj Conclusions^ and Recommendations 16

2. ASSESSMENT' OE A PROPOSED ALTERNATIVE CORgLETE PHOTOMETRIC

SCHEI^/IE FOR THE ANALYSIS OF COAL ASH 27

2.1. Introduction 29

2.2. Experimental Details 30

2.3. Results 31

2,4- Discussion 32

2.4.1. Silica 32

2.4.2. Alumina 32

2.4.3. Ironj titanium^ phosphorusj and magnesium 33

2.4.4. Manganese 34

2.4.5. Sodiumj potassiumj and calcium 34

2.4.6. Percentage summations 35

2,5. Conclusion 35

3. REFERENCES 45

4. APPENDIX, PROPOSED SCHEI^IE FOR PHGTGllilETRlC ANALYSIS OF

COAL ASHg DESCRIPTION OF ANALYTICAL PROCEDURE 49

4.1. Preparation of Sample Solutions • 514.2, Methods ■ .52

- 3 - ,

LIST 0 F ■■ ..T A B L E S

TABLE 1A, Reproducibility of the semi'-micrQ method;Sample 2if28 (wet oxidation of coal)(calculated to a dry sulphur-free 775 G ash "basis) 18

TABLE IB, Reproduci'bility of the semi-micro method:Sample 2768 (wet oxidation of coal) ,(calculated to a dry sulphur-free 775 C ash basis) 19

TABLE 2il, Comparison of the semi-micro method and theclassical gravimetric method: Sample 2i4-28 20

TABLE 2B, Comparison of the semi-micro method and theclassical gravimetric method: Sample 2768 20

TABLE 3A. Semi-micro colorimetric analysis on the500°C ash Sample 4-918 21

TABLE 3B. Semi-micro colorimetric analysis on the500°G ash Sample 4766 21

TABLE 30. Semi-micro colorimetric analysis on the500°G ash Sample 5573 ■ . 22

TABLE 3-D. Semi-micro colorimetric analysis on the500 G ash Sample 3911 .22

TABLE 4A. Reproducibility of the semi-micro method:U.S»Bureau of Standards Plastic Glay No, 98 23

TABLE 4B, Gomparison of semi-micro results with accepteddata for Plastic Glay No, 98 23

TABLE 3. Data on coals analysed 24

TABLE 6 A, Gomparison of flame-photometer and semi-microresults for U,S,Bureau of Standards Plastic

Glay No, -98 36

TABLE 6B, Flame-photometer determination of calcium incoal ash: reproducibility and comparison(corrected and uncorrected for interference dueto Na and Mg) with results from Pringle's method 37

TABLE 7» Results for rapid photometric analysis ofNational Bureau of Standards Plastic Glay 37

TABLE 8A. Results for rapid photometric analysis ofU, So Geological Survey Sample G1 38

TABLE 8B, Results for rapid photometric analysis -ofUoS.Geological Survey Sample 38

TABLE 9A, Gomparison of proposed improved scheme andPringle's me thod: Sample 2428 39

TABLE 9B, Gomparison of proposed improved scheme andPringle's method: Sample 2768 39

TABLE 9C. Gomparison of proposed improved scheme and

Pringle ' s'method: Sample 3911 40

- 4 -

LIST OF TABLES (contd)Page

TABLE 9P« Comparison of proposed improved scheme andPringle 's method; Sample 4766 40

TABLE 9E. Comparison of proposed improved scheme and , $Pringle's meiiiod; Sample 4918 4-1

TAHLlE 9F, Comparison of proposed improved scheme and- Pringle's method: Sample 5573 4I

TilELE 10. Summary of photometric detailsTi) Operating range for linear calibration(ii} Plame-photometer calibration for sodium,

j potassium, and calcium , ^ • , ;i,i , 42

LIST OP PIG-U RES

PIG-. 1, Scheme proposed by Pringle for the rapid analysisof inorganic constituents in coal 25

PIG-, Proposed alternative scheme for the rapid analysisof coal ash 43

SUMMARY

Section 1 of the paper describes an application to Australian

coals of a scheme (proposed by Pringlej 1954) semi-micro analy

sis of inorganic constituents in coal. Where the coals submitted to

wet oxidation the scheme has been applied as successfully as Pringle'S

application to British coals. Howeverj the wet oxidation procedure is

not generally applicable to Australian coals, A preliminary 500°^

ashing procedure v/as adopted. The analytical method for aluminium is

the least satisfactory and the procedures for calcium^ magnesium,

sodium, and potassium are tedious and prone to errors. The methods

for iron, titanium, and phosphorus are good.

Section 2 deals with the assessment of a proposed alternative

scheme for the analysis of coal ash and describes how it has been

applied to ten constituents in the ash. It makes use of the best

features of Pringle's scheme and of a scheme developed by the U.S.

Geological Survey for the analysis of silicate rocks. The photometric'

determinations of silica and alumina are not completely satisfactory

(reproducibility not good) but speed up the analyses, and the results

are sufficiently accurate for most purposes. The determination of

sodium, potassium, and calcium with a flame photometer ("Eel") has been

found to be far superior in speed and precision to Pringle's photometric

procedure. The magnesium determination is still somewhat time-consuming,

but with care reliable results are possible.

The proposed scheme as a v\rhole has proved very satisfactory

and has effected a considerable reduction in analysis time. It should

be generally applicable to the analysis of slags, boiler deposits,

etc., as well as of coal ash.

GEITERAL IWTRODUCTIOIT

Many problems associated with coal utilization can he traced

to the presence of mineral matter in coal. Slag formation and clinker

behaviour in furnaces^ and external deposits on boiler tubesj to

mention only two.^ are directly related to the nature and quantity of

certain inorganic constituents in the coal. It is apparent that a

knovfledge of the characteristics of the mineral matter would be useful

in studying such problems. This type of information is required also

in order to determine the true properties of the coal substance itself^

e.g. ultimate chemical analyses and calorific values. Unfortunately

it is not possible to separate the mineral matter from the coal sub

stance by any simple means^ and most investigations of the mineral

matter involve a study of the ash produced from the mineral matter

when the coal is burned.

An important feature of the study of ash is its analysis.

The analysis of coal ash is a complex procedure^ it is akin to silicate

analysis in general and to the analysis of rocks in particular. The

quantitative analysis of coal ash has generally been carried out using

the methods set down in Fuel Research Survey Paper ho, 50 ('1949)» They

arej hov/everj rather time-consuming and require the preparation of a

large amount of ash^ which may necessitate the burning of a considerable

quantity of coal. Accordingly Pringle in 1954 devised a scheme using

semi-micro colorimetric methods in which the' sample is smaller and less

time is required for an analysis.

The original object of the present v/ork was to assess Pringle's

methods in their application to Australian coals. During the course

of these investigations a paper was published by Bannerjee and Colliss

(1955) 0^ "the "t^se of colorimetric methods for analysis of ash from coaland oil shale. Since the methods described appeared to have nothing

to offer in comparison with those under test by the present authorSj

and since Bannerjee and Colliss failed to cover all the elements of

interestj, their paper did not influence the present vrork.

As a result of the experience gained in assessing Pringle's

scheme of analysis and the v/ork of Shapiro and Brannock (195^)5 "the

U.S. Geological Survey5 on the rapid analysis of silicate rocks an

alternative scheme has been proposed and tested.

The assessment of Pringle's scheme is described in Section 1

of this report. The results of the assessment of the proposed alter

native scheme are discussed in Section 2.

a

9 -

DETERlgMTIQI'T OF THE IIORGMIC COHSTITUMTS

III AUSTRALIAN COALS

BY EAPID SEMI-MICRO (PHOTOMTRIC) IIETHOBS

1, ASSESSMENT OF. A SCHEME

OF ANALYSIS PROPOSED

BY PRINGLE (1 954)

0

-11

1.1, MTRODUCTIOH

Recently3 Pringle (1954) described a scheme for the quantita

tive analysis of the inorganic constituents in coal using semi-micro

methods. The analyses are made on the solution obtained directly by

the wet oxidation of coal5 this procedure avoids the laborious ashing

of large quantities of coal which is necessary when conventional

methods of analysis are used. With the exception of silicaj which is

determined gravimetricallys the analyses are made using colorimetric

methods3 which are far more rapid than the standard macro gravimetric

methods. These colorimetric methods have been adapted from established

methods.

The scheme of analysis permits the quantitative determination

of ten elements in coalj namely Si3 AI3 Fe3 Caj haj Kj Tij P3 and Ifo,

The results as obtained express the percentage of these constituents

(as oxides) with reference to the whole coal. For most purposes this

is ideal but 3 by convent ion3 the results are normally reported on a

percentage-in-the-ash basis (since all analyses are usually made 011

the ash), Pringle recommends the calculation of the analytical results

to a sulphur-free ash basis. This is necessary for a comparison with

the figures from the classical method of analysis (also recalculated

to a sulphur-free basis)3 since the ajuount of sulphur in the ash bears

no definite- relationship to any sulphur originally present in the coal

andj for Australian coals3 consists mainly of organic sulphur fixed

as calcium sulphate in the ash,

Pringle has compared the analysis figures obtained3 using

the semi-micro methodj for four British' bituminous coals and eight

British anthracites with those obtained for the same coals using the

classical method. On the basis of this comparisonj the relative sim

plicity of the semi-micro methodj and hence the increased speed of

analysis that is possible3 it was decided to assess the application

of the method to the quantitative analysis of the inorganic consti

tuents in Australian coals.

Using Pringle's methody or a slightly modified formj six

Australian coals have been analysed for SiO^s Al^O^j Fe^O^j TiO^j CaOjMgOj K2O3 and Pg^^' ^ controlj a U,S, Bureau of StandardsPlastic Clay standard sample (ho, 98) WQ-s also analysed by the method.

The results are reported and discussed below.

„ 12-

1.2. EXPERIMEITOAL DETAILS

Pringle overcame all difficulties in respect of the destruction

of the organic matter in the coals he analysed by using perchloric acid

in addition to the normal sulphuric acid-nitric acid mixtures for the

Y/et oxidation procedure. This treatment produced q, water-white solution

in all casesj which is essential if interference is to be avoided when

colorimetric measurements are being made. However5 only two of the

Australian coals (Samples 2428 and 2768) chosen for analysis responded

to the acid treatment to yield water-white solutions. The other coal

samples gave yellov\f-to orange-coloured solutions even after prolonged

(several days) heating and additions of excess perchloric and nitric

acid. Procedure v/ith these samples was to remove the organic matter

by ignition at 500*^0 and subject the residue to acid treatment3 in the

manner described by Pringle for coalj to decompose and dissolve it.

At the organic matter is burnt off fairly rapidly yet the inor

ganic material (particularly ^^2^3^ likely to undergochanges which at higher temperatures tend to reduce their solubility

in acids.

The plastic clay sample dissolved in acids fairly readily.

The subsequent treatment of the solution and the analytical

procedure were essentially as described by Pringle. For convenience

Pringle's diagrammatic scheme of analysis is reproduced in Pig, 1.

Colorimetric determinations have been made using both a

Hilger Spekker absorptiometer and a Unicam SP6OO spectrophotometer.

The SP6OO is more convenient to use and the possibility of interference

is minimized owing to the improved wavelength selectivity.

1.3. RESULTS

The analysis figures for replicate colorimetric determinations

made directly on the v/hole coal samples 2428 (Borehole seamj WestWallsend Extended Colliery) and 2768 (Borehole seamj Burwood Colliery)are given in Tables 1A and 1B, The results have been calculated to a

sulphur-free ash basis at 775°C. The colorimetric figures for thesetviTO coals are compared with those obtained by the classical gravimetric

methods in Tables 2A and 2Bo

The results for the 500°C ashes prepared from coals 49I8

(Main Greta seam, Aberdare Colliery), 4766 (Young Vifallsend seam,Stockton Borehole Colliery), 5573 (Presumed Bulli seam, Wanganderry

-13-

Mino), and. 3911 (Leigh Creek lignite) are given in Tables

3A3 32j 3C and 3L respectivelyo , These coals resisted the v/et oxidation

procedure. Since results are normally reported on a-775 C ash "basis

an ash correction factor has been applied to the analytical results for

the 500°G ash.

Triplicate determinations for the U^S, Bureau of Standards

Plastic Clay Ho, 98 are listed in Table 4A and the means for these are

compared with the accepted analysis figure in Table 4B,

1,4. BISCUSSIOH

1-,4.1. Vifet Oxidation of Coal

Pringle has successfully applied the wet oxidation procedure

to four British bituminous coals and eight British anthracites. However5 as

stated earlierj all except.two Australian coals studied resisted this

treatment. It may be significant that both samples that v/ere success

fully wet-oxidized came from the same seam^ although from different

locations. Apart from the Leigh Creek lignite sample (3911) there are

no significant differences in the proximate and,ultimate analysis be

tween the coals that completely wet-oxidized and those that did not

(see Table 5)* Since the Leigh Creek sample was far worse than the

others it would appear that the lower the rank the more resistant a

coal is to acid oxidation.

Further experience in these laboratories on the wet oxidation

of coal for the determination of phosphorus has shown that the method

requires too much attention and the majority of coals do not respond,

Consequentlyj the method v/as abandoned in favour of using the coa,l ash

as starting material and decomposing the ash with hydrofluoric and

nitric acids.

In 1956 Pringde (private communication) stated that the

temperature at Yi^hich the acid digestion is carried out must be care

fully controlled. If it is too high the nitric acid evaporates before

it reactsj and if too low very little reaction takes place between the

nitric acid and coal substance. However5 it was felt that this aspect

did not warrant further investigation^ since it v/as considered that- an

essential requirement of a rapid scheme of analysis \7as that it Should

provide a quick method requiring a minimiim of control and attentioiij

of getting the sample into solution.

- 14-

1.4o2. Silica Determination

In the cases where the coal;responded to wet oxidation the

silica obtained v/as in an easily filterable form and replicate deter

minations agreed very welle But with plastic clay and the coal samples

which, were ashed at before acid treatment the silica was in a

much finer form and a small amount would pass through the filter papero

The plastic clay was particularly troublesome in this respect5 even

v/ith a double filter paper (542) the filtrate remained slightly cloudyc

This difficulty accounts for the somewhat low figure obtained for

silica in the plastic clay sam^ple, Howeverj the reproducibility of the

semi-micro method and the general agreement with results from cle.ssical

methods are good. In fact3 the agreement is somewhat better than that

obtained by Pringle»

1o4»3. . Aluminim

Although the agreement between the colorimetric and classical

results compares favourably ?/ith that obtained by Pringle the colori

metric method is not 'very satisfactory„ The reproducibility leaves

much to be desired,, An invariably high blankj together with high pH

sensitivity^ probably account for this. Pre-extraction with 8-hydroxy

quinoline of all reagents used to prevent interference of iron and

titaniumj gives no appreciable reduction in the blank. In addition,

the procedure is very tedious and the 8-hydroxy q.uinoline extraction

is particularly susceptible to manipulative errors.

The colorimetric determination of aluminium as the 8-hydroxy

puinoline complex as originally developed (Gentry and Sherrington 1948)

v/as intended for the estimation of aluminium as a minor constituent.

Its application to the analysis of aluminium as a major constituent

would be more sensitive to effects of pH and interference. .

The use of ferron as an alternative complexing agent for the

colorimetric determination of aluminium (Davenport 1949) iia-s been in

vestigated. Using the precautions outlined by Delevaux and co-workers

(1954) satisfactory results were obtained for synthetic blends, but

inconsistent results were obtained when working on coal and the plastic

clay samples.

It is of interest to note here that Shapiro and Brannock (1952)

in their original scheme for the rapid analysis of silicate rocks pro

posed the estimation of aluminium as the ferron complex. In their re

cently revised scheme (Shapiro and Brannock 1958)j however, the method

has been dropped in favour of alizarin red-S as the complexing agent.

-15-

1o4<'4«' Iron9 Titanium, and Phosphorus

The determination of iron as the ortho—phenanthroline complexj

titanium with "tiron"(disodiura 152, dihydroxy "benzene - 3s5 disulphonate)5and phosphorus as molybdenum blue complex is very satisfactory. The

reproducibility and agreement with classical methods are good.

1.4.5" CgJcium and Magnesium

Before the■estimation of calcium and magnesium (also sodiumand potassium) it is necessary to remove aluminium, iron, titanium, andphosphate. This procedure is time-consuming and considerable care is

necessary to avoid loss of material.

The results for calcium and magnesium are only-fair as far

as replicate determinations are concerned. Once again agreement with

classical methods is as good as, if not better than, Pringle's resultsfor British coals. The lower reproducibility is inherent in the method,

which involves precipitation, centrifuging, removal of supernatantliquid by suction and, finally, dissolving the precipitate and developingthe required colour for measurement. Unless care is taken to avoid

disturbing the precipitate during removal of liquid and in washing theprecipitate to remove precipitating reagent, etc., inconsistent results

will be obtained. Contrary to Pringle's claim, the permanganate reagenthas been found to be unstable.

1.4.6, Sodium

Here also the agreement with classical results compares

favourably v/ith Pringle but reproducibility is only fair. As for mag

nesium and calcium, care has to be exercised in removing the supernatantliquids by suction and in v/ashing the precipitate. With Plastic Clay,high and inconsistent results y^qtq obtained initially owing to co--

precipitation of potassium (Uydahl 1937)? which in this sample wasgreatly in excess of the sodium present. This inconsistency was over

come by dissolving the precipitate and reprecipitating, but the resultwas still considerably higher than the accepted values,

1.4.7. Potassium

As observed by Pringle, the agreement bet^veen semi-micro andclassical figures is not good. For the coals ?/here K^O was generallyless than 1 per cent, fairly consistent results were obtained. However,

- 16 -

in the analysis of the Plastic Clay great difficulties v/ere experienced

in obtaining consistent resultso Provided aliquots of solution con

taining 100 /ig or less of potassium were used consistent but high

results were obtained.

*1,5, SUmiARY, COHCLUSIOIS, MD RECOMIfiENDATIONS

The wet oxidation procedure for the elimination of the organic

matter is not generally applicable to Australian coals, Where the coal

submits to the wet oxidation treatment the agreement between the semi-

micro coloriraetric figures and classical figures compares more than

favourably with the agreement reported by Pringle for British coals.

For the coals that resist the Yiet oxidation treatment a 'lov/-temperature

(500^0) ashing procedure has been adopted, Ro classical figures areavailable for comparison with the figures obtained by the application

of Pringle's'scheme of analysis to these ashes^ but the satisfactory

percentage totals and the figures for the Bureau of Standards Plastic

Clay standard shov^ that the method can be applied as successfully as

to the coals themselves.

Pringle's scheme gives excellent results for ironj titaniumj

and phosphorusj but the determination of sodium^ potassiumj calci-um^

and- magnesium is tedious and subject to errors.

The aluminium method is the least reliable. The use of

ferron for the colorimetric determination of aluminium in coal has

been investigated also but did not prove very satisfactory, A complex

of aliminium with alizarin red-S has been successfully applied to the

colorimetric analysis of aluminium in silicate rocks (Shapiro and

Brannock 1,95^) "the use of this technique for the analysis of aluminium

in coal is described in Section 2,

A colorimetric method for the determination of silica would

be advantageous. Pringle attempted this with his wet oxidation pro

cedure but he experienced difficulties in dissolving the silica residue

in caustic soda solution. Fusion of the ash with sodium hydroxide

should overcome this difficulty and make possible the colorimetric " ,

estimation of silica via the molybdenum blue formed from the reduction

of the yellow silico-molybdate complex (Shapiro and Brannock 1956)®

From the experience gained during this work an alternative

scheme for the rapid colorimetric analysis of the inorganic constituents

in coal is proposed (see Section 2), This scheme incorporates the best

of Pringle's scheme (namely Fe^ Ti, P)^ the use of the flame photometer

for sodiumj potassiujiij and calciumy and adaptation of the methods of

- 17 -

Shapiro and Brannock (195^) alumina and silica» Until a more-

satisfactory method for magnesium can he foimd it is proposed to use

a modification of Pringle's indirect method.

This schemej once all the details have heen provedj, should

result in a marked increase in the speed at which complete analysis

can he made. Pringle's scheme, as it stands, is considerably more

rapid than the classical method.

18

TABLE 1A

REPRQBUCIEILITY OF THE SErll-MICRO METHOD

SAIAPLE 2428 (\TET OXIBATIOR OF COAL)

(CALCULATED TO A DRY SULPIIUR-EREE 775'^C ASH BASIS)

Constituent1 st

Detn.e

2nd

Detn.

3rd

Detn.

4th

Detn.

5thDetn,

MeanStandard

Deviation

SiO^ 55o02 55.17 55.02 55.17 55.02 55.08 0.08

^2°3 , 30.38 31.36 31.12 30.63 30.87 30.87 0.39

5o55 5.55 5.55 5.55 5.55 5.55 0.00

i TiO 0.98 0.97 0,98 0,98 0.98 0.98 , 0.00

CaO 4.23 4.21 4.74^ 4.02 4.05 4.13 0.10

MgO 0.64 0.67 1.21* 0.57 0.60 0.62 0.04

LgO 0.46

0.47

0.42

0.35

0.30*

0.44

0.41

0.45

0.370.41

0«42)q .p0.42)°-42 0.04

Na^G 0.87 0.58 0,71 0.86 0,35* 0.76 0,14

h°5 2.70 2.65 2.70 2.70 2.58 2.67 0,05

* Rot inoluded in calculation of mean values.

Rote 1 Calculation to a dry sulphur-free 775 8 ash "basis as,follows?

cC/b constituentwte constituent/PQO X 100 x 100 x 100

wt 0 of coal X (100 - M) x A

where M = moisture

and A. = ash (dry aiid calculated to a sulphur-free basis)

Rote 2c- For Sample 2428 (percentages)s

Moisture = 3,01

Ash = 9,66

Ash (dry basis) ■ = 9,96

Sulphur in ash (80^) = O.48Ash (dry and sulphur-free basis) = 9*97

- 19 -

TABLE IB ■

REPROBUCIBILITY OF THE SHvII-MICRO L1ETH0B,'

SAMPLE 2768 (WET QXIDATIQR OF COAL)

(CALCULATED TO A DRY SULPHUR-EREE,773°C ASH BASIS)

Constituent1 st

Detn.

2nd

Detn.

3rd

Detn,

4th

Detn.

5thDetn.

MeanSt andard

Deviation

SiO2

53.02 53.09 53.09 53.12 53.09 53.08 0.04.

AI2O3 19o40 18,97 18,63 19.06 19.40 19.09 0.32

17.92 17.92 17.82 17.82 17.92- 17.88 0.05

TiOg 0,84 0.83 0.89 0.86 0.82 0.85 0,03

CaO 4.27 4.27 4.74 4.50 - 4.44 0,22

MgO 1c45 1.64 1,41 1.50 - 1.50 0,10

KgO 0.73 0.51 0.55 0.51 - 0.58 0.10

Ra^O 0.83 0.61 0.95 0.49 - 0.72 0.21

^2°5 2.21 2.18 3.47^ 2.18 2.18 2.19 0,01 ■

Rot included in calculation of mean value,

Rote." For Sample 2768 (percentages)g

Moisture

Ash

Ash (dry basis)-

Sulphur in ash (SO^) ■ ■=Ash (dry and sulphur-free basis) =

2.91

14.03

14o45

1.05

14.47

- 20 -

TABLE 2A

CGMPARISQ]^ OF THE SEMI-MICRO METHOD ABB

THE CLASSICAL GRAVIMETRIC METHODS SAMPLE 2428

Classical Gravimetric Method Semi-micro Colorimetric Method

Constituent Analysisof ash

Analysisof ash

oalc. to

SO^-free

Analysis on coalcalc, to dryS03-free

775 C ash basis

Analysis on.coalDale, to dry

775°C ash basis'incl. SO^

SiO^ .54.66 .54.92 55.08 54.82■ • Al-O^ V-^ - •29;v20: ■ ^ 29.34 ^ 30.87 ' ■30.72' ■ i

^®2°3 5.57 5.60 5.55 5.52TiOg 0.88 0.88 0.98 0.98CaO 4.35 4.37 4.13 ~ 4.11MgO 0.76. . 0.76 0.62 0.62Na^O 1.05 1,06 0.76 0.76 5KgO • 0.65 0.65 0.42 0.42

^2°5 , 2.83 2.84 ■ 2,67 2.66 'S03 . . 0.48 ' 0-48

100.43 100.42 101.08 : ■ , 101,09

TABLE 2E '

COMPARISON OF THE SEMI-MICRO METHOD MDTHE CLASSICAL GRAVIMETRIC METHODS SAICPLE 2768

Classical Gravimetric Method Semi-micro Colorimetric Method

Constituent Analysis. of ash

Analysis. of ashCalc. toS03-free

Analysis on coalCalc. to dry^S03-free

775 0 ash basis

Analysis on coaloalc,^ to dry

775°C ash basisincl. SO

SiO^ 52.41 52.95 53.08 52.53AI2O3 19.30 19.50 19.09 18.89Pe203 17.41 17.59 17.88 17.69TiO^ ' 0.95 0.96 0.85 . 0.84CaO 4.04 4.08 4.45 4.40MgO 1.49 1.51 1.50 1.48Na^O 0.62- 0.63 0.58 0.57K^O 0.76 0.77 0.72 0.71

^2°5 1.95 1.97 2.19 2.17S03 1.05 1.05

99.98 99.96 100.34 100,33

- 21

TABLE 3A ,

SEMI-MICRO GOLORIlffiTRIC AITALYSIS

OR THE 300^C ASH SAIvIPLE 4918

Constituent 1st Letn. 2nd Letn.Mean

(500°c)(1)Calc. Mean^ ^

775°C ash hasis

SiO^ . 35.96 36.25 36.10 37.73

14.15 14.05 14.10 14.73

TiO 2.05 2.05 2.05 2,14 '

1.68 •1.69 1.68 1.76

CaO 3.86 4.04 . 3.95 4.13

MgO 1.53 1.65 1.59 1.66

K^O • 0.17 0.21 0.19 0.20

Ra^O(2)A1 0^^^

SO3 (3)

2.04 1.85 1.94

31.73

2.03

33.16

2.83

Total 100.37

Rote 1 Conversion factor 500°C analysis to 775°C! "basis

jo ash at 300 C _ 6.25

io ash at 775°C= 1.045

Rote 2.- Alumina determined "by gravimetric method.

Rote 3.- SO^ determined on 775^0 ash.

TABLE 3B

SEMI-MICRO COLORBIETRIG MALYSIS

OR THE 50Q°C ash SMKPm 4766

Constituent 1st Detn. 2nd Detn.Mean

(500°c)(1)Calc, Mean^ '

775°C ash hasis

SiO 69.14 680 90 69.02 69.92

19.15 19.26 19.20 19.45

^®2°3 : 3.80 3.80 3.80 3.85

TiOg 0.65 0.65 0.65 0.66

CaO 1.82 2.06 1.94 1.97

MgO 1.00 0.85 0.92 0.94

K^O 0.57 . 0.41 0.49 0.50

Ra^O 0.89 0.74 0.82 0,83

P 0

4?.0.76 0.73 0.74 0.75

0.50

Total' ■

99.37

Rote 1 Conversion factor 500°C analysis to 775^0 "basis

% ash at 500^0 _ 14» 35 _ -j n-i •:)fo ash at 775^0 " 14<.17 "

Rote 2.- Alumina determined hy gravimetric method.

' 3< SO^ determined on 775 0 ash,

22

TABLE.3C

SEMI-MICRO COLORIMETRIC" AKTALYSIS

OR THE 5Q0°C ash SAMPLE 3373

Constituent 1st Detn, 2nd Detn.Mean

(500°c)Gale. Mean^"^^

775^0.ash basis

' SiO^ ' 67.80 67.97 . 67.88 68.24

^^2°3 . 7.22 7.32 7.27 , ̂ 7.31 ;TiO^ 0.80 0.81 0.80 : 0.81 ;

0.05 ,0.05 ■ 0.05 0.05

CaO , : 0.13 0.15 0.14 0.14,

MgO ■ 0.27 0,30 0.28 ■ 0.29 >

KgO 0.20 0.25 0,22 0.23

Ra 0

A1 0^^)0.34 0.23 0.28

23.00

0.28

23.12

0.20

Total 100.67

HoteJ,.- Conversion factor = ^ ^Rote 2.-- Almina detemined "by gravimetric method.

Rote 3°- SO^ determined on 775°^ ash.

TABLE 3D

SEMI-MICRO GOLORIMETRIG AITALYSIS

OR THE 50Q°C ash SihvIPLE 3911

1,005

Constituent 1st Detn, 2nd Detn,Mean

(500°c)Calc. Mean^''^

775°0 ash basis

SiO . 45.90 45.95 45.92 46.50

' 30.05 30,13 • 30.09 30,47

7.43 7.29. 7.36 7.45

TiO^ ■ 1.97 1.97 1.97 1.99

CaO- 5.37 5.54 , 5.46 5.53

MgO 2,35 2,18 2.26 2.29 .

KgO 0,58 0.50 0.54 0.55

Ra^O 3.02 •2.92 2.97 3.01

PpO.

. SO^1.19 1.28 1.24 - 1.26

2.35

Total 101.40

Rote 1 Conversion factor =fo ash at 500 C 22.65% ash at 775®C ~ 22,37 = 1.0125

Rote 2«- Alumina determined by gravimetric method,

SO^ determined on 775 C ash,Rote 3»-

Rote 4«'- A trace of chlorine was found in this ash.

- 23 -

TABLE 4A

REPRQDUCIBILITY OF THE SEMI-MICRO METHOD

U.S.. BUREAU OF STANDARDS PLASTIC CLAY BO. 98

Constituent1 st

Detn,

2nd

Detn..

3rd

DetiioMean

Greatest

Difference

Let. Detns.

SiO^ 58.24 58.58 58.52 58,45- 0.34

AlgO^ 25 = 86 25,81 27.30* 25.84 1,49

Fe^Os 2.15 2.15 2.13 2,14 0^.02

TiO^ 1=42 1.42 1.42 1,42 0.00

CaO 0.39 0.37 0.30 0.35 0.09

MgO 0,71 0 . 69 0.62 0,67 0.09

KpO 3=37 3.63 3=69 3.56 0.32

Ra^O 0.68 0.59 0.55 0,61 ■ 0.13

0.17 0.11 0.11 0.13 0.06

Rot included in calculation of mean value,

TABLE 4B

COMPARISOR OF SEi^Il-MIGRO RESULTS WITH ACCEPTEB DATA

FOR PLASTIC CLAY RO. 98

Constituent

Analysis

byColorimetric

Methods

Analysis

from

Bureau of

Standards

SiO^'AlgO

58.45

25.84

59.11

25.54

■ TiOg2.14

1.42

2.05

1.43

CaO 0.35 0.21

MgO . 0.»67 0.72

3.58 3.17

Ha 0 0.61 0.28

SO30.13 0.08

Trace 0.07

Loss on

Ignition7.00 7.28

Total 100.19 99.94

Loss on ignition at 800 Cs four determinations gave

the following percentage results - 6.85j 6.965

7.04s mean 7^00.

- 24, -

TABIiE 3

DATA. PIT COALS MALYSED (P.AcF. BASIS)

(Results are given as percentagGS "by weight escopt where otherwise stated)

Sample Do, s

Seams

Gollierys

2428(P159) ■

" Borehole

West Walls-

end Ext' d

2768(P179)

Borehole

Burwood

3911(P215)

Lignite

Leigh Gk,

4766(P223)

Y,Wallsend

Stockton

Borehole

4918(PG246)

Main Greta

Aherdare

5573(0267)

Presumed-

Bulli

Wangan-

derry

C 83.2 82,9 72,2 83.5 82,7 83.7

H 5.8 5.7 4.9 5.6 6.2 5.5-- '

.0 •8.4 806 21.1 . 8.4 7.7 8.2

VJI. 38,5(Uncorr0)

38.4(Gorr.GOg)

40.8

40.0

43.3 '

42.6

39.1

380 9

46.4

46.2

36.7

36.0

Gal« val0 143820 B.t.u,/lh 14,680 11^760 14,750 15j060 14,640

Wet

Oxidation* -x- / / ! ̂* Successful, -f Unsuccessful,

25

A1

1 ..cm cell

395 m p.

1 cm cell

510 myu

Ti

1 cm cell

410 m/j.

m

100 ml

Ca

2 cm cell

510 m/j.

ppt.

Ppt.discarded

soln„

ppt •1 cm cell

830 m/i

4 ml Na

1 cm cell

395 m/a

ppt

PPtoSoln. i Dipicry1a-

i mine

FerrocyanideMg uranylacetate

DH phosphate

o~ph en ant hr01in e

Persulphate

oxidation

Molyhdate &reducing agent

DH. oxalat e

pH 4.5

Da acetate to

pH 4.5

Molyhdate andreducing agent

,Pptno Ca and Mgas carbonates

Tartrat63 KCDand H„0^ at pH9

Piltrat e-

made to

200 ml

(SolnoA)

liMnO^ + MnSOin 35/0 H„SO.

Filtrate,

evapdo &made to

10 ml

(SolnoB)

8-hydroxy .quinolineextraction in CHCl-

Ppt« ignitedj weighed^ treatedwith HFj and weighed again

2 g coal &Vvet oxi

dation with

aaid HGIO

FIG. 1o - SCHHiE PROPOSED BY PRIDGLE FOR THE

RAPID ADALYSIS OF INORGMIC CODSTITUEHTS IH COAL

t

- 27 -

DETERMBTATION OP THE IITORGAHIC COHSTITUEHTS

IH AUSTRALIAH COALS

BY RAPID SEMI-MICRO (PHOTOl^/lETRIC) METHODS

2. ASSESSMENT OP A PROPOSED

ALTERNATIVE COMPLETE

PHOTOMETRIC S C. H E M E P 0 R

THE ANALYSIS OP COAL ASH

- 29 -

2 010 IFTRODUCTION

In Section 1 of this report it has been shovm that the

scheme of analysis for mineral matter in coal as proposed by Pringle

has many undesirable features= In particularj there is the difficultyassociated with the wet oxidation of the coalsy the unreliable nature

of the 8—hydroxy c3_uinoline method for aluminiumj the tedious and painstaking nature of the procedures associated v/ith the determination of

calcium and magnesiumj andj finallyy the uncertainties of the sodium

and potassium,methods. On the other hand the procedures given for

iroiiy titaniumy and phosphorus have proved very satisfactory.-

Recentlyy Shapiro and Brannock (1956)3 U.S. Geological

Surveyy have published a scheme for the rapid analysis of silicate

rocks. This scheme consists of direct photometric methods except for

calcium and magnesiumy where photometric titration procedures were

used, A direct adaptation of this scheme could have been tested on the

analysis of coal ash but it was felt that a complete direct photometricprocedure making use of available facilities was preferable. Conse-

ciuently a scheme of analysis ?/as proposed making use of the best

features of both Pringle's and Shapiro and Brannock's schemes. The

proposed scheme .is shown in outline in Pig. 2 and covers the analysis

of Siy Aly Pey Tfy Py y Mgy ^ Cay Ruy and K.

In this scheme the methods for iroiiy titaniumy phosphoruSy

and magnesium were adapted from those of Pringle (Shapiro and Brannockdetermined these elements by a similar procedure),

Shapiro and Brannock's procedure was used for silicay aluminay

and manganeseI •sodiumy potassiumy and calcium were determined by flamephotometry (Shapiro and Brannock also determined sodium and potassium

by'flame photometry but with an instrument allowing the use of an

internal standard), There are no novel features in the proposed method^,

in planning it5 existing methods have merely been adjusted where

necessary to suit the analysis of coal ash.

It was assessed initially by applying it to the analysis of

the U.S. Bureau of Standards Plastic Clay standard Ro. 98 aud to two

standard rock samplesy granite G1 and diabase W1y supplied by the U.S.

Geological Survey (Pairbaim et al. y 1951 )• was then further tested

on the analysis of the ashes of the six coal samples referred to in

Section 1. The results and conclusions are given below. An interesting

comparison has been made with the results of Shapiro and Brannocky who

also tested their methods on the analysis of G1 and W1.

- 30 -

2o2» ■ experhcental details

Pringle's scheme- in its initial form used coal as the

■starting materialo The proposed alternative scheme has heen hased on

the use of 775°C ash prepared under standard conditions, Ahout onegram of ash is sufficient for a complete analysis in duplicate. Two

solutions are prepared from the ashj one (solution A) for the determination of silica, ,and aluminaj the other (solution.B) -for .the determination of the remaining constituents (excepting sulphur).

Solution A is prepared hy fusion of a weighed portion,ofash with sodium hydroxide in a nickel crucible. Duplicate reference

I

standard solutions (from standards with known alumina and silica content) and a reference reagent blank solution are prepared at the sametime using the same procedure. Silica is determined as molybdenum blue

after reduction of the silicomolybdate complex. Aluminium is estimated

as an aluminium-calci-um-alizarin red-S complex.

Solution B is prepared by digestion of a weighed ash sample

with hydrofluoriCj perchloricj and sulphuric acids in a platinum

crucible. Solutions of the reference standard and a reagent blank are

prepared in the same way. Solution B is used for the■determination of

iron as o-phenanthroline complexj titanium via its complex with "Tiron"

(disodium -1j2 dihydroxybenzene -335 disulphonate)3 phosphorus asmolybdenum blue after the reduction of the phosphomolybdate complexj

and manganese as permanganate after periodate oxidation, Aluminiumj

iron3 titaniumj and phosphate are removed by double hydroxide precipi

tation from an aliquot of solution B to obtain solution C, Solution C

is then used for the determination of sodiumj potassiumj and calcium

by flame'photometry3 and of magnesium indirectly as molybdenum blue

after removal of calcium and precipitation of magnesium ammonium'phos-

phat e,

The detailed experimental procedure is given in the Appendix,

All spectrophotometric determinations were made using a.

Unicam SP6OO spectrophotometer. An "Eel" flame photometer was used

for the determination of sodiumj potassiumj and calcium.

- 31

2«3. RESULTS

In Table 6A the results of replicate flame-photometer

determinations for sodium3 potassium; and.calcium in the Rational

Bureau of Standards Plastic Clay sample are compared with values

obtained with Pringle's "semi-micro" methodo Table 6B lists the flame-

photometer results for calcium, in the six 775^C coal ash samples. ■

These results serve to illustrate the reproducibility of the flame-

photometer method. It will be noted that the calcium figures have

been corrected to allow for interference due to sodium and magnesium

using the procedure developed by Edgecombe and Hevifett (1954)" This

correction results in an improvement in the agreement with existing

values.

In Tables 7 8A and 8B the results of the complete analy

sis using the proposed alternative scheme are given for the Rational

Bureau of Standards Pla.stic Clay sample (Ro, 98) and the U.S. Geologi

cal Survey standard rock samples G1 and ?/1 respectively. These results

are also compared with the accepted analysis for the standard sample

and the results obtained by Shapiro and Brannock. -Pure reference

standard solutions were used for calibration in the analysis' of the

Plastic Clay sample for all elements; and for all elements except Si;

Alj and Ti in samples G1 and . Mixed reference standard solutions

prepared from the standard Plastic Clay were used as standards for

alumina; silica; and titania in the ana.lysis of G1 and W1 . The reasons

for this procedure will be discussed later.

The results obtained with the proposed improved scheme for

the complete analyses of the six 775°C coal ash samples are given in

Tables 9A to 9E inclusive. The results from Pringle's method are also

listed for direct comparison. Pure reference standard solutions were

again used throughout for calibration for all elements except silicon;

aluminium; and titanium^ for these elements standard plastic clay was

used.

Details of the lohotometric calibration ranges are summarized

in Table 10.

" 32 -

2=4. DISCUSSION

2.4. . Silica

Inspection of the tables shov/s that the photometric procedure

fpr the determination of silica compares favourably with Pringle's

gravimetric determination for coal ashes and gives reasonable agreement

with accepted values for silica in the plastic clay and standard rock

samples. For the coal ashes there is a consistent tendency for the

photometric determinations to be higher than the gravimetric values=

This tendency holds also for the standard Plastic Clay samplCj with

the photometric value closer to the accepted value^ and suggests that

incomplete recovery of the silica is being effected in the gravimetric

procedure.

Although pure silica reference standards can be used for

calibration of the photometric method it has been found preferable to.

use standard plastic clay for this purpose and recalibrate for each

batch of samples by running through, in parallel, duplicate plastic

clay samples (as v/as done by Shapiro and Brannock). With this procedure a marked improvement in reproducibility is achieved. In the pro-

bedure as described in the Appendix the optical density (i.e. colour

development) is proportional to the silica concentration over the range

0 - 400 yug of silica per 100 ml of solution5 this corresponds to aconcentration range of 0 — 80 per cent, silica in the original samples.

2.4.2. Alumina

The alizarin red—S procedure for the estimation of aluminium

did not give any marked improvement over the 8-hydroxy quinoline method

in the q_uality of the results. HoY/ever, since it is more direct and

convenient the former method is to be preferred and for most purposes

the results are of sufficient accuracy. To obtain optimum results ex

treme care is necessary in the calibration. Calibration witn pure

alumina proved to be unsatisfactory. Although for pure alumina the

optical density varied linearly with concentration over the range of

0 — 150yug alumina per 100 ml of solution, reproducibility and agreement v/ith accepted alumina values for the reference standards were

both poor. Prom the results it was clear that standard solutions pre

pared from standard Plastic Clay and the standard rock samples G1 and

W1 all shovired greater optical density (colour developm.ent) and sensitivity to changes in concentration than the pure alumina standards.

Further, it was established that the slopes of the optical density

versus concentration plots for all of these clay and rock standards

- 33 -

v/GrG idGntical and wGrG "fcliG sarnG as tho slops of thG optical donsity

versus concentration curve olsserved for a coal-ash sample« The optical

density was now only linear with.respect to concentration over the

range 0- 100 /ig of alumina per 100 ml of solution.

In the present series of experiments the colour development

was much more pronounced than that obtained hy Shapiro and Brannock.

Titanium interferes with this method for the determination of aluminium

and a correction factor has been develope.d by Shapiro and Brannock to

allow for this interferenceo That this correction factor is still

valid despite the marked increase In sensitivity is amply illustrated

by the coincidence of the alumina optical density versus concentration

curves for the three standard samples (titanium contents varying from

0.23 per cent, to 1,4 per cent,). The reasons for this improved sensi

tivity and the behaviour of the pure alumina and natural standards are

not understoodj but may be connected in some way with the alizarin red—Sreagent,

Adopting Shapiro and Brannock-s procedure of running duplica-be

Plastic Clay standards v/ith each batch of test samples resuloed in a

considerable improvement in reproducibility between duplicate deter

minations (when compared with pure alum.ina standards). Generally thereproducibility was as good as that obtained by Shapiro and Brannock,

The conditions as described in the Appendix permit a linear calibration

for alumina over the range 0 — 4C cent, alumina in the test samples.

2.4,3, Iron, Titariium^ Phosphorus, and Magnesiimi

The procedures for the determination of these elements are

reasonably simple and straightforward. For iron very good agreement

was obtained with accepted (and/or earlier) values except with ash from.

Sample 27689 which has a very high iron content - that iSj near the

upper limit of linear calibration—resulting in high optical density

(0,I). Aril,4) readings with a greater chance of error in this optical-density value. Further dilution should have resulted in an improvement.

Calibration v/ith pure iron solution proved very satisfactory (linearcalibration range 0 — 19 per cent, sample).

Good agreement with accepted values was obtained for titanium

in the case of the reference standards9 but the agreement was not quite

so good between the two sets of observations (i,e, Pringle's m.ethod and

that of the present authors) on the coal ashes. It has been found pre

ferable to run through duplicate Plastic Clay standards with each batch

of samples for calibration since standard titanium sulphate solution

deteriorates on standing and consequently cannot be used v^rith confidence

34

Moreoverj the Plastic Clay contains I.4 per cento TiO^j which is v/ithinthe range occupied, hy the TiO^ in the majority of ashes from AustraliancoalSj namely 0,5 - 1.5 per cento^ also the calibration has "been foundto he linear over the range 0 - 3.3 per cent, TiO^.

Phosphorus determinations were very satisfactory. Calibration

is linear over the range 0-1,4 per cent, ̂ 2*^5 sample.

Magnesium results were only fair for the coal ashesj perhaps

because of variations in precipitating conditions which result in a

mixture of magnesium ammonium phosphates. With, more Care, and experience

the values obtained for ma,gnesium in the standard rocks G1 and 7/1 proved

to be very good.

2,4=4. Manganese

Pringle's method using persulphate as oxidant and silver

nitrate as catalyst gave incomplete colour development for standard

manganese solutions and so no attempt Y/as made to apply this method

to the coal-ash samples, A modification of Shapiro and Brannock's

method using periodate as the oxidant was'found to be' reliable. With

'the rocks G1 and W1 good agreement was obtained with the accepted

values. Calibration 'was linear over the range 0 - 0,7 per cent,

Mn^O^ for the conditions used,

2.4.5. Sodium, Potassium^ and Calcium

Edgecombe and Hewett (1954) have described the application of

the "Eel" flame photometer to the determination of calcium in coal ash,

Collins and Polkinhorne (1952) have discussed the use. of this instru

ment for the determination of sodium and potassium in general.

The present results for sodium, potassium, and calcium in

the U.S. Bureau of Standards Plastic Clay sample and the U.S. Geological

Survey standard rocks W1 and G1 show that the "Eel" flame photometer

is capable of giving reliable and accurate results when used with the

proposed scheme of analysis. There was also a marked improvement in

the reproducibility of these flame-photometer determinations compared

with Pringle's photometric methods. It is evident that the flame-

photometer method is superior to Pringle's method by virtue of its

speed and convenience and the improved accuracy of the results.

- 35 -

2o4»6. Percentage Summations

Although in general the sum of the percentages for each con

stituent is close to 100 per cent, the tendency is for the value to he

on the high side. It, is felt that this is due to errors associated

with the silica and alumina determinations5 because the agreement he-

t?/een present and accepted figures for the other constituents in the

Plastic Clay and the standard rocks G1 and 7/1 is good, Shapiro and

Brannock's practice of running duplicate reference standards with each

analysis for silica and alumina is probably an attempt to compensate

for the poor reproducibility with these constituents.

2.5, COhCLUSIOI/

ThG proposed scheme of analysis for coal ashj as tested in

the laboratories of the Coal Research Section of the Commonwealth

Scientific arid Industrial Research Organizationj is considered to be an

improvement on Pringle's original scheme. Sample preparation and the

estimation of silica and alumina are more rapid. Although there is no

marked improvement in the reproducibility. of the silica^ and particularly

the aluminaj determinations the results are adequa,te for most purposes.

The flame-photometer method for the estimation of sodiumj

potassiuffij and calcium is superior in speed,'convenience, reproducibility,

and accuracy to Pringle's somev\/"hat cumbersome procedure.

The' determination of magnesium is not completely satisfactory

but with care' reliable results are possible. The separation of calcium

and removal of all oxalate ion is tedious and adds considerably to the

time required for a complete analysis. However, there are difficulties

associated with all known photometric procedures.

Any claim for the speed of an analysis scheme must be made

cautiously since many factors such as the experience of the analyst

and the occurrence of unforeseen difficulties are involved, nevertheless,

it may justifiably be- claimed that with the proposed scheme an experienced

analyst could complete the analysis of eight single samples or four

duplicates for Si, Al, Mg, Ti, Pe,. P, Ca, Ha, K, and Mn (i.e. 80

determinations) in five days provided no unforeseen complication occurred.

This scheme of analysis should be applicable to other sub

stances of similar composition, such as slags and boiler deposits.

- 36

TABLE 6A

COIffl^ARISQN OF ELME-PHOTOMETER AILD'SEMI-MICRO RESULTS

EOR U,S. BUREAU OF STAILARLS PLASTIC CLAY ROo 98

Ra^O

Sample No, 1 2 3 4

Aliquot 1 0.23 0,26 0.28 0.26

Aliquot 2 0o31 0.27 0.19 ' 0.22

Aliquot ,3 0.26 0.23 0.22 0.28

Mean 0.27 0.26 0.23 0.25

i.e. Mean flame-photometer value = 0.25^

Accepted Bureau of Standards

value = 0.28

Semi-micro (Pringle) value = 0.61

K^O

Sample No. 1 ' 2 3 4

Aliquot 1 3.19 3.04 3.20 2.96

Aliquot 2 3.02 3.07 3.07 2.96

Aliquot 3 3.08 3.10 3.09 2.93

Mean 3.10 3o07 3.12 2.95

i.e. Mean flame-photometer value = 3.O6/0

Accepted Bureau of Standards

value = 3.17

Semi-micro (Pringle) value = 3.58

CaO

Sample Ro. 1 ■ 2 3 4

/o CaO 0.21 0.24 0.23 0.23

Mean flame-photometer value = Q.23/0= 0.22

(corrected for Ra and Mg)

Accepted Bureau of Standards

value = 0.21

Semi-micro (Pringle) value = 0.35

- 37 -

TABLE 6E

FLAl-lE-PHOTOMETER BETERMBTATIOE OF CALCIIE/I IE COAL ASHs

REPROLUCIBILITY MD COIiliPAIlISOE

(CORRECTED AND URCORRECTED FOR IRTERFERERCE DUE TO Ra AMD Mg)WITH RESULTS FROM' PRIRGLE'S METHOD

Sample Ro.

Flame-photometerSemi-micro

(Pringle)" ' ' 1Uncorrected Corrected.

r

Uncorrected Corrected Mean

242,8 4.16 4.12 4.12 4.08 4.10 4.11

2768 4.50 4.43 4.58 4.52 4.48 4.40

3911 5.76 5.52 5.64 5.40 5.46 5.53

4766 1o94 1.89 2,02' 1.97 1.93 1.97

4918 4.27 4.18 4.31 4.22 4.20 4.14

5573 0.12 0,12 0.17 0.17 0.15 0,14

Rote 1 The flame-photometer determinations were made on ash prepared at 775 C,

Rote 2<.- CaO figures have "been corrected for sodium and magnesium interferenceby the formula due to Edgecombe and Plewett (1954)? viz.

TABLE 7

RESULTS FOR RAPID PHOTOMETRIC ARALYSIS

OF RATIORAL BUREAU OF STMDARDS PLASTIC CLAY

Constituent1st

Detn,

2nd

Detn.Mean

Previous

Detn,*

Bureau of

Standards

"Value

S. and B,^

SiOg 59.95 59.51 59.73 58.45 59.11 58.6

A1 0 R,D. R.Dc ' 25.84 25.54 25.2

2.16 1.92 2.04' 2.14 2.05

TiO^ 1.43 1.37 1.40 1,42 1.43 1.4'

• MnO 0.00 0.00 0.00-

o.bo 0.00

■ CaO ' ■ 0.22 0.35 0,21 , 0.23

MgO 0.84 0.63 0.74 0.67 0.72 0.70

Ra^O^ ■0,25 0.61 0.i28 0.32

: K 0 3.06 3.58 3.17 3.1

LY . 0.11 0.09 0,10i

0,13 0.08 0.12

* See Section I5 Table 4B0

-f Shapiro and Brannock analysis,^ From Table 6A.R.D. Rot determined.

38

TABLE 8A

RESULTS FOR RAPID PHOTOMETRIC MALYSIS

OF. Uo So GEOLOGICAL-'SURVEY. SAI\([PLE G1

Constituent1 st

Detn.

2nd

Detn.'Mean

U.S. GeologicalSurvey

S. and B. *

72.63 72.38 72.50 72.5 ,72.4

AlgO^ ■14.87 14.99 14.93 ■ 14.3 14.51.73 ■1.71 1.72 ; 1.89

I .p.23 0.24 0.24 ; ,0.25 0.24MnO 0.02 0.02 0.02 0.03 0.02

CaO 1.43 ,1.43 1.43 1,4 1.4MgO 0.35 0.37 0.36 0.36 0.31Ra^O 3.32 3.23 3.28 3.3 3.3

5.53 5o63 5.58 5.5 . 5.4

^2°5, 0.07 0.08 0,08 0.09 0,08

Cao/ 1.37 1.27 1.32 1.4

* Shapiro and Brannock analysis.,/ Determined by Pringle's colorimetric method.

TABLE 8B

RESULTS FOR RAPID PHOTOICETRIC ANALYSIS

OF UoSo GEOLOGICAL SURVEY SiiMPLE ' Vifl

Constituent1 st

Detn.2nd

Detn.Mean ^

U.S. GeologicalSurvey S. and B, *

SiO^ 53.49 53.23 .53.36 52.6 52.7

AI2O3 14.86 15.35 15.10 15.2 15.1

^®2^3 11.13 11.09 11.11 10,97

TiO^ 1.10 1.08 1.09 1.1 1.0

MnO 0.16 0.18 0.17 0.16 0.19

CaO

CaO^10.91 10.94 10.92 10.9 10,7

10.82 10.69 10.76 10.9

MgO 6.63 6,47 6.55 6.6 6.6

Ra^O 2.16 2.00 2.08 2.1 2.. 2

. K^O 0.63 0.63 0.63 0.66 0.64

^2^ 0.15 0.13 0.14 0.15 0,16

* Shapiro and Brannock analysis.

/ Detemined by Pringle's colorimetric method.

39

TABLE 9A.

CQMPARISOIT OF .PROPOSED UmOVEl) SCHME AKD PRINGLE'S METHODS SAMPLE 2428

Constituent1 st

Detn,

2nd

Betno-Mean

Previous

Betn.*

. Sio^ 55ol8 54:47 54.82 54.82

28087 29o14 29.00 30.72

^"2°3 5o53 5.50 5.52 5.52

TiO^ 0.90 0.93 0.92 0.98 ^

Mh-O. '3 4

0.04

CaO 4.12 4.08 ■ 4.10 4.11

MgO Oo76 0.68 0.72 0,62 i

Na^O 0.42 0,46 ̂ 0.44 0.76

K2O 0.56 0.59 0.58 0.42

^2°5 2.71. 2.75 2.73 2.66

S03 Oe48 0.48

Total 99.35 101,09

^ See Section 1j TaLle 2Ac

•f Single determination onlyo

TABLE 9B

COMPARISON OF PROPOSED ̂ PROVED SCHEME AtTB PRIIFGLE'S METHODg SAMPLE 2768

Constituent1st

Betn,

■2ndBetn.

MeanPreviousBetn,

SiO^ 53^20 53^16 53.18 52.53AlgO^ ■■ 19,09 18159 18.84 18.89

^®2°3 18,59 18,39 18.49 17,69 ,TiOg 0,75 o;78 0.76 0.84

''^3°4 0,46CaO 4,43 4,52 4.48 4.40

MgO 1.22 1,16 1.19 1.48Na^O 0.38 0.40 0,39 0.57 ■

^2° ol 50 o!,51 0,50 0.71

L°5 2;. 20 2,18 2.19 2.17

1,05 1,05

Total 101.53 100.33

* See Section 1, TaLle 2B,

- 40 -

TABLE 9C

CQLB?ARISO¥ OF PROPOSED IMPROVEI) SCHEME. Ain) PRBTGLE'S METHOD s SAAgLE 3911

Constituent1st

Detno

2nd

Detn. .Mean

Previous

Detn.*

•sio^ : 48.82 48."98 48.90 46.50 .

AI2O3 30.64 29.65 30.14 30.47

7o17 7.05 7.11 7.45 :

2.07 2.06 2.06 1.99 ;

'^3°4 0.17 ■- 0.17

CaO 5.52 5.40 5«46 5e53MgO 2.19 1.91 2.05 2.29Na^O 2.78 2.82 2.80 3.01

K^O 0.44 0.43 0.44 0.55

^2°5 1.25 1, .25 1.25 1.26

■ ®°3 2.35 2.35

Total 102.73 ' 101.40

See Section 2q TaLle 3B,

TABLE 9D

COMPARISON OF PROPOSED IMPHQVEI) SCHEME AITD PRIITGLE^S METHOBg SAldPLE 4766

Constituent1st

Betn,2nd

Betn.Mean

PreviousBetn.*

■ S102 .69.80 70.59 70.20 69.92AI2O3 20.23 ■ 19c67 19.95 19.45

^^2^3 . 3.76 3« 66 3.71 3.85

, TiOg , 0.77 0.68 0.72 0.66

^3^4 0.02- 0.02

CaO 1.89 1.97 1.93 1.97MgO • O..99 0.91 0.95 0.94

Na^O 0,76 0.75 0.76 0.83K^O 0.58 ■ 0.59 0.56 0,50

: ̂ 2^ : 0.80 0.80 0.80 0.75SO3, 0.50 0.50

Total 100.12 99.37

* See Section 1. Table 3Bo

- 41 -

TABLE :9E. ■

COMPARISON OF PROPOSED II\/[PROVEI) SCHME MB PRIIJGLB-^S METHOD s SAMPLE 4918

Constituent •1 st

Detn„

2n(i

Betn.Mean

Previous

Betn.*

SiO^ ■ 38.63 39.43 39.03 37.73

AI2O3 31.59 31.20 31.40 33.16

15.02 14.92 14.97 14.73,

■ TiOg 2.00 1.95 1.98 2.14-

161304 O0O4 - 0.04

CaO 4.18 4.22 4.20 4.13

MgO 1.71 1.50 ■ 1.60 : 1.66

Na^O 1o73 1.81 1.77 2.03

0.37 0.37 0.37 0.20

PgOj 1.72 1.69 1,70 : 1.76

SO3• 2,83 2.83

Total 99.89 100.37

* See Section 1= Table 3A,

TABLE 9E

COMPARISON OF PROPOSER n/IPROVEB SCHEME MB PRINGLE'S METHODS SAMPLE 5^73

Constituent1 st

■ Betn.

2nd

Betn.Mean

Previous

Betn,* .

. SiO^ 69:. 34 69.30 : 69.32 68.24

AI^O^ 23:.02 22.18 ■ 22,60 ■ 23.12!

^®2°3 7.41 7.30 7.36 7.31:

TiOg .0.72 0.75 0.74 p.81'

MU3O4 0.20-

0.20

CaO .0.12 0.17 . 0.14 0,14

MgO 0.16 0.10 0.13 0.29

Na^O 0.02 0.03 0.02 ■ ^ 0.28 •

^2° ' 0.42 , 0,43 0,42 0,23

P2O5 6,06 • 0,06 0,06 0,05

SO3

0.20 0,20

Total 101.19 100,67

* See Section 1. Table 3C,

- 42 -

TABLE 10

SUMMARY OF PHOTOMETRIC DETAILS

(i.) OPERATMG RAJTGE FOR LINEAR CALIBRATION

Constituent AliquotLinear

Calibration

Range

OpticalDensityRange

Cell

Corresponding

^ Range in ■OriginalSample ;

Wavelength

SiOgTO ml'

(solution a)0-400 /ug/100 ml 0-0.52 1 cm O-BO^o 650 ra yu

Al.O,2 j

:5(solution a)

0-100 yug/lOO ml 0-0.28 1 cm O-40/0 475 myu

Fe1-2 ml

(solution B)0-260 /jigPe/50ml 0-1.4 1 cm 0-19/0 Fe^O^ 510 myu

Ti5 ml

(solution B)0-100 /ugTi/50ml 0-0.5 1 cm O-l.ii TiOg 410 myu

P5-10 ml

(solution B)0-60 yug P/lOOml 0-1.0 1 cm 0-1.4^ PgOj 830 myu

In10 ml

(solution B)0-50 yug Mn/50ml 0-0.09 2 cm 0-0,7^ ̂ 0^7!

Hr525 m/u

Iffote 1.- Percentage range given is for higher aliquot (refer to Fe and P)o

Note 2,- In all cases except aluminium^ linearity of calihration persists"beyond the range notedo

(ii) FLAME-PHOTOMETER CALIBRATION FOR

SODIUM, POTASSIUM, AND CALCIUM

Calibration

Concentrat ion*

Calibration

Linear Range

Corresponding ̂Range in

Original Sample

CaO . 50 p.p.m. O-5O p.p.m. 0-12.5/0 CaO

Na 5 p<.P»m. 0-4 p.p.m. Q-1.35/^ ̂ ^a^O

K '10 p.p.m. 0-8 p.p.m. 0-2.70/0 K^O

* Flame photometer adjusted to give full-scale deflection,

Note 10- Flame photometer set at zero with special- distilled watero

Note^ 2o- 20 ml aliquot solution B > 50 final solution.

- 43 -

Ash prepared

at 7T5°C

0.1 g

0.05

HCIO4+ HF-dil. H^SO^

Na acetate — o-phenanthroline

pH 4.5

'Tiron'; 50^ IFa^S^O,224

pH 4c 5

100 ml

Soln.B

NaOH

fusion

3 - 10 ml Molyhdate & reducing agent

Periodate oxidation

Distilled v;rater

20 ml 1g1 HCl

dilute to 1 litre

10 ml

Soln.A

Ppt. AI5 Fej Ti,PO^ v/ith mi^OH ppt.

Filtrate

5 ml

Amm,molyhdate Alizarin red-Sreducingsolution

Si - 1 cm cell

' 650 m^i

50 ml

Soln.C

Pe

1 cm cell

510 myu

-> ^1 cm cell

410 m;W.

-> P1 cm cell

830 m^ p.

2 cm cell

525 myu

discard

Flame photometer - ̂

Ca

A1 - 1 cm cell

475 m/u

Evapo to dryness toremove salts

iDisSo residue in dil.

discard ppt. HCljppt. Ca oxalate

\Filtrate

remove oxalate

Amm. phosphateDH^OH

Molyhdate andreducing agent

^ (via P)1 cm cell

830 myu

PIG. 2c - PROPOSED ALTERNATIVE SCHELIE FOR THE RAPID AHALYSIS OF GOAL ASH

eft

45

DETERI^/LIMTIOIT OP THE IHORGMIC COHSTITUEHTS

IH AUSTMLIM COALS

BY RAPID SEMI-MICRO (PHOTOMETRIC) METHODS

3o REFERENCES

.tt

#

" 47

BMEERJEEj No N.^ and COLLISS, Be A, (1955)« - Rapid analysisof ash from coals and oil shale "by colorimetric methodsoFuel 34gS71-S83o

COLLINS5 Go Coj and POLKINHORNEj H. (1952)» - An investigationof anionic interference in the determination of small (Quantities of potassium and sodium with a new flam,e photometer.Analyst 77.°430-6,

DAVENPORT5 Wo Ho (1949)0 - Determination of aluminium in presenceof iron. Anal. Chem. 21§710-11°

DELEVAUXj Mo 5 SMITHj R. 5 and GRIMLDIj P. S. (l954)o - The photometric determination of aluminium in phosphate materials withferron. U.S. Atomic Energy Commission T.EoI. 450°

EDGECOMBEj L. J.j and HEWETTj D. R. (1954)° - Rapid flame-photometricmethod for the determination of calcium in coal ash and coke ash.Analyst 79^755-8.

PAIRBAIRNj Ho W.3 SCHLECHTj W. G.3 STEVENS, R. E.3 DENNEN, W. D.,AHREI^TS, L, Ho, and CHillES, P. (1951)° ~ A co-operative investigation of precision and accuracy in chemical, spectrechemical,and modal analysis of silicate rocks. U.S. Geol. Survey Bull. No. 9^0

Great Britain, D.SoIoRo Fuel Research Survey Paper No. 50 (1949)° - .Improved methods for the (Quantitative analysis of coal ash and cokee.sh. (HoMo So Oo gLondono )

GENTRY, Co Ho R., and SHERRINGTON, L. G. (1946). - Direct photometricdetermination of aluminium with hydroxy-(Quinoline. Analyst 71g432-8.

NYDAHL, Po (1937)° - Determination of sodium in the presence of theother alkali metals, ammonium, and the alkaline earths. Ann. Agric.Coll. Sweden _6g37-87.

PRINGLE, Wo Jo So (1954)0 - Mineral analysis of coal hy semi-micromethods, G. B. Nat. Coal Board, Coal Survey laboratory, privatecommuni cod ion.

SHAPIRO, Lo, and BRANNOCK, W. W. (1952), - Rapid analysis ofsilicate rocks. U.S, Geol. Survey Circ. No. I65.

SHAPIRO, L., and BRANNOCK, W, W. (1956). - Rapid analysis ofsilicate rocks. UoS, Geol, Survey Bull. No. IO36-C.

&

- 49 -

DETEEMINATIOF OP THE INORGAHIC COHSTITUEHTS

IN AUSTEALIAH COALS

BY RAPID SEMI-^MICRO (PHOTOMETRIC) METHODS

4. APPEHLIXo . PROPOSED SCHEME

FOR P HOTOMETRIC AHALYSIS

OP COAL ASHs

D E S C R I P TIOH OP ANALYTICAL

PROCEDURE BASED ON

SHAPIRO AND BRAN NOCK'S

MET H OD OP PRESENTATION

(3)

(i§i

«■

i

- 51 -

4.1. PREPARATIQ]^ OF SAMPLE SOLUTIONS

Two solutions designated" solution A and solution B are pre

pared for the analysis.

, Solution Aj used for, the, determination of SiO^ andprepared hy fusing approximately 0,05 8 sample with RaOH. .

Solution Bj used in the determination of

MgOj Ra Oj K O3 and P O^.^ is prepared hy digesting approximately 0.1 g^

of sa,mple with HF and HClO^j followed hy H^SO^j in a platinum crucihle.

Reagents

RaOH 15 pe^:' cent. 5 stored in a plastic bottle

HP 40 per cent,

HCIO^ 70 per cent.H^SO^ approx. 5R solutionHCl 10 R

Solution A

(1) Transfer 10 ml of RaOH solution to each of a number of nickelcrucibles of ' about 75 capacity.

(2) Evaporate the solutions to dryness on a sand bath.

(3) Accurately weigh approximately O.O5 g of sample ground to pass200 B.S. mesh (previously dried for 2 hours at 110-120 C) and two

0,05 g portions of Rational Bureau of Standards Plastic Clay Ro. 98''Transfer each to a nickel crucible containing RaOH, Reserve one

crucible for preparation of a reference blank solution,

(4) Cover the crucibles and heat to dull redness for 5 minutes. Allow

to cool,

(5) Add approximately 50 of water to each crucible and allow to

stand overnight.

(6) Transfer contents of crucibles to beakers containing about 4OO mlof water and 10 ml of HCl. Scrub the crucibles with a rubber policeman

and wash into appropriate beaker.

* (7) Transfer the solutions to 1-litre volumetric flasks3 dilute to the

markj and mix well.

Solution B

(1) Weigh accurately approximately 0.1 g sample ground to pass 200 B.S.mesh'and two portions of Rational Bureau of Standards Plastic Clay Ro. 98

(all previously dried) into platinum crucibles of about 30 ml capacity.

Reserve one crucible for preparation of a reference blank solution.

- R52 -

(2) Add 1 ml HCIO and 5 i^il HF to . each., crucilDle and evaporate almost4

to dryness on a sand bath«

(3) Add 5 nil 5NH2S0^ to each crucible and evaporate to strong fumes ofSO^ but not completely to' dryneSs'^

(4) Coolj add about I5 nil of distilled water to each cruciblsj and

digest until residue dissolves,

(5) , Transfer the solution to 100ml volumetric flasks and dilute to the

markj mix v;ell.

4o2. METHODS

SiO^

In the determination of silica the yellow silicomolybdate

complex is reduced to molybdenum blue and the optical density measured

at 650 ra^o

Reagent s

Ammonium molybdate reagent solutions Dissolve To5 S of ammonium molybdate

in 75 nil of v/ater. Add 10 ml Isl H^SO^ and dilute to 100 ml. Store in aplastic bottle,

Tartaric Acid solutiong 10 per cent - store in a plastic bottle. Discard

and prepare fresh solution when an appreciable amount of sediment forms.

Reducing.solutiong Dissolve 0,7 g sodium sulphite in 10 ml water. Add

0,15 g of 1~amino-2-naphthol-4-sulphonic acid and stir until dissolved.

Dissolve 9 g of sodium metabisulphite in 90 ml of water and add this

solution to the solution above and mix. Store in a plastic bottle.

Procedure

(1) Pipette 10 ml sample solution Aj 10 ml of each reference standardj

and 10 ml solution A blank solution into separate 100ml volumetric flasks,

(2) Add 1 ml ammonium molybdate reagent with a pipette^ swirling the

flasks during the additions. Mix well and allow to stand for 10 minutes,

(3) Add 4 nil of tartaric .acid solution with a pipettCj swirling the

flasks during the additions^ and mix well,

(4) Add 1 ml of reducing solution with a pipette^ while swirling the flasksj

dilute to volume and mix wellj allow to stand for at least 30 minutes,

(5) Measure the optical density for each solution at 65O m/a, using the

solution prepared from the solution A blank solution as the reference

blank solution.

4

- 53 - .

Calculations

(1) Using original sample vi/eights calculate optical-density values to

50 mg weight "basis -

Optical density z ga,mple'^weight " OP"tical density ^Omg sample

(2) Calculate factor for two comparison standards -

fo Si02 in comparison standard _ p^ctorOptical density of comparison standard on 50i^g "basis

(3) Calculate average from two factors,

(4) Calculate ̂ SiO^ in sample -Average factor x Optical density of sample on ^Omg "basis = % SiO^

^2°3

Alumina is determined "by measuring the optical density at

475 of a solution containing the complex of aluminium^ calciumj and

alizarin red-S, The complex formed hy ferric iron and titanium also

a"bsor"bs light at this wavelength. The effect of iron is eliminated "by

the formation of ferricyanide prior to the addition of alizarin red-S,

Im empirical correction is applied for titanium hy subtracting 0,5 x

TlO^l from the apparent % Al^O^*,

Re.agents

Hydroxylamine hydrochlorides 10 per cent solution.

Calcium chlorides Transfer 7 g CaCO^ to a 250ml beaker. Add 5*3 ml water,~ 1 3 ,Add dilute UCl dropwise with stirringj until the CaCO^ is dissolved.Boil for 1 to 2 minutes. Cool and dilute to 5OO ml, .

Potassium ferricyanide; 1 per cent, solution. Do not store for more

than one day.

Buffer solutions 70 S sodium acetatej and 30 ml glacial acetic acid

diluted to 5OO ml with distilled water.

Alizarin red-Sg 0,1 per cent, solution, .

Procedure

(1) Pipette 5 of sample solution and 5 of each reference standard

into individual 100ml flasks and add to each 15 rnl of solution A blank

solution. Also measure 20 ml solution A blank solution into another

100ml flask for a reference blank solution,/

(2) Add 1 ml of CaCl^ solution to each flask and mix.

See Note 1 (page 54)-

/ See Note 2 (page 54)-

- 54 -

(3) Add 1 ml hydroxylamine hydrochloride solution and miXo

(4) Add 1 ml potassium ferricyanide to each flaskj mixj and allow to

stand for 5 minutes,

(5) Add 10 ml buffer solutiouj mixj and allow to stand for 10 minutes,

(6) Add 5 nil alizarin red-Sj ,dilute to volurnej mixj and allov/ to stand

for 1 to 2 hours,

(7) Determine optical density at 475 nya for each sample solution andtwo comparison standards5 using solution from solution A blank solution

as reference blank solution.

Calculations

(1) Using original sample weights calculate optical-density values to

50 mg weight basis - *• 50

Optical density x 77-— , , = Optical density on 50 mg sampleSample weight

(2) Calculate a factor for each comparison standard -

i -^^2^3 of comparison standardOptical density of comparison standard (on 50nig basis)

(3) Calculate an average from two factors.

(4) Determine apparent per cent, Al^O^ in sample -

Average factor x Optical density of sample solution on 50 nig basis

= Apparent ̂ ̂^2^3

(5) Obtain per cent, Al^O^ in sample by subtraction of O.5 x fo TiO^ fromapparent fo Al^Oy

Dote 1

Shapiro and Brannock's correction factor for titanium inter

ference has been found to be valid stillj despite increased sensitivity.

Dote 2

In the method for Al^O^ as set down by Shapiro and Brannock20 ml of sample solution is normally taken5 but if the ̂

greater than 20 only 10 ml of solution is taken and this is made up to

20 ml with solution A blank solution to maintain the correct pH value.

I

In the present case it has been established that the upper

limit for linear calibration with Plastic Clay, is reached when the

solution contains only 100^ug Al^O^/lOO ml (I50yug/l00 ml if pure Al^O^used). To keep below this concentration only 5 nil aliquot of sample and

reference standard solutions are used. Each aliquot is made up to 20 ml

Y/ith solution A blank solution.

f,

55

ft

-**

i

After reduction of the iron and adjustment of the pH to 4o5

Yirith sodium acetatej the orange-red ferrous o-phenanthroline compound

is formedo The optical density at 5^0 m/u is measuredo

Reagents

Hydroxylamine hydrochlorideg 10 per cent» solutiono

Sodium acetates 2 M solution»

o-phenanthrolineg • Go25.per cent, solution.

Procedure

(1) Pipette 2 ml solution B and 2 ml solution B "blank solution into

50ml volumetric flasks5 dilute with water.

(2) Add 5 rnl 10 per cent, hydroxylamine hydrochloride and a small

square of congo red paper.

(3) Titrate with 2 M sodium acetate solution until colour of indicator

paper Just changes from blue to red.

(4) Add 4 irl 0.25 per cent, solution of o-phenanthroline.

(5) Make up to volume and mix v/ellj allow to stand overnight.

(6) Measure optical density in 1cm cells against reference blank

solution at myu,

(7). Determine Pe^O^ content from calibration graph.

TiO^

"Tiron"reagent (lj2 dihydroxy benzene-3s5 sulphonic acid) formecoloured compounds Yrith titanium and ferric iron. The iron com^pound is

used as an internal indicator when the pH is adjusted and is removed by

reduction with sodium dithionite Just prior to measuring the optical

density of the titanium complex at 410 nyu.

Tiron solution 4 psr cent.s Dissolve 4 g ̂ f the disodium salt, of 1.2

dihydroxy benzene 3«5 sulphonic acid in water and make up to 100 ml.

Ammonium hydroxides' 50 cent, solution.

Acetate Buffer pH 4-11 A solution molar in sodium acetate and acetic acid,

Sodium dithionites Solid.

- 56

Procedure

(1) Pipette 5 of sample solution 5 nil of each plastic clay ^solution By and of solution B blankj into separate 50nil flasks. ^

(2) Add 5 nil Tiron solution with a pipette and mix well.

(3) Titrate with 50 cent. NH^OH to the purple colour of the ironcomplex (or to the colour change of congo red paper if the iron is-lov;

or absent).

(4) C00I5 add 5 nil acetate bufferj mix wellj and make up to volume.

(5) Pill 1 cm cell (or 2cm if lev; in Ti) v\fith solution and add 1 or

2 mg of solid sodium dithionite. ,

(6) Stir to dissolve and discharge iron colour (do not stir vigorously •—

the reducing agent is readily aerially oxidized and the iron colour tends

to reappearj giving erratic results).

(7) Read the absorption (optical density) at 410 m/u against distilled

water.

(8) Correct each reading for the blank,

(9) Calculate each reading to a 0.1 g basis,

(10) Calculate a mean factor from the knovm per cent, fiO^ in plasticclay and the. reading on a 0,1 g basis.

(11) Calculate per cent. TiO^ in sample,

Phosphomolybdic acid is formed at the appropriate acidity and

reduced to molybdenum blue by heating v/ith a mixture of hydrazine and

metabisulphite. Optical density is measured at 83O myu. .

Reagents

Sodium hydroxides 5 solution.

Sulphuric Acids 5 R solution.

Reducing solutions Dissolve 0.6 g hydrazine sulphate and 1 g sodium

metabisulphite in water and. make up to 100 ml.

Ammonium rnolybdates 1 per cent, solution.

$

ur

- 57 -

-ii

y

Procedure

(1) Pipette 5 of sample solution and 5 solution B "blank

into conical flaskso .

(2) Dilute mdth distilled water to about 20 ml,

(3) Add 7<>5 nil of sodium hydroxide and one drop phenolphthalein,(

(4) Titrate with sulphuric acid to the. end point and add 7«5 nil in

excess.

(5) Add 2 ml of reducing solution with a pipette.

(6) Add 5 nil of molyhdate solution Y\rith a pipette.

.(7). Mix well and heat for I5 minutes in a "boiling virater bath.

(8) Cool5 transfer to a 50ml volumetric flaskj and dilute to volume.

(9) Read optical density in 1om cells versus blank solution at 83O myu,.

(10) Determine content from calibration graph,

(11) Calculate per cent, ̂ 2^5 sample.,

1^304

Manganese is oxidized to permanganate using potassium periodate

as the oxidizing agent. .The optical density is measured at 525 niyu.

Reagents

Potassium periodateg Dry pov/der.

Acid mixtures Solution containing 10 per cent., phosphoric and 25 per cent

sulphuric acid by volume.

Procedure

(1) Pipette 10ml. aliquots of solution B and solution B blank solution

into lOOrnl beakers.

(2) Add 25 ml of acid mixture,

(3) Add approximately 0.2 g .KIO4'

- 58 "

(4) Cover the heakersj "bring to boil, and continue "boiling for 5 minutes,

(5) Cool in a v/ater batho

(6) Transfer solutions to 50ml volumetric flasks-, dilute to the mark,

and mix well, ' ^

(7) Read the optical density at 525 myu in 2cm cells versus reagentblank solution,

(8) Read Mn content from calibration graph or calculate from standard

Mn solution run concurrently,

(9) Calculate per cent, Mn^O^ in sample.

Ra^O, K^Oj and CaO

After removal of Pe, Al, etc., from solution B the Ra^O,and CaO are determined using a flame photometer. Part of this solution

is also used for the determination of MgO after removing the calcium.

Reagents

Ammonium hydroxides I5 R

Sulphuric acids 5 R

Sodium chloride solutions 0,1272 g ITaCl dissolved in v/ater and made to

500 ml to give 100 p,p,m. Na, Dilute appropriate aliq.uot to give. ̂

5 p.p.m, Ra solution as required. Store in a plastic bottle.

Potassium chloride solutions O.I908 g KCl dissolved in v/ater and made

up to 500 ml to give 200 p.p,m, K, . Dilute an appropriate aliquot to

give 10 p,p.m, K solution as required. Store in a plastic bottle.

Calcium sulphate solutions O.O892 g CaCO^ dissolved in H280^ and dilutedto 500 ml to give an acid concentration of 0,5 Ro ■ Dilute appropriate

aliquot to give 50 p,p,m, CaO solution as required. Store in a plastic

bottle, .

Procedure

(1) Pipette 20 ml aliquot of sample and blank solution B into separate

centrifuge tubes,

(2) One drop methyl red is added and then I5 N ammonium hydroxide drop-

wise with stirring until the indicator just changes colour,

(3) Place the tubes in boiling water for 10 minutes,

(4) Centrifuge for 5 minutes and decant the solution into 50ml

volumetric flasks,

(5) Dissolve the precipitate in 5 ml 5R^H9S0,,-^ dilute to 10 ml.

>■

4

■«

- 59 -

(6) Repeat steps 2,5 3? and 4«

(7) Make solutions in 50nil volumetric flasks to volume (solution C),%

v (S) Set flame photometer with appropriate standard solution — 5 p.p.m.f Na solution for Raj 10 p,p.mo K solution for Kj and 50 Pop.m, CaO solution

for CaO.

(9) Determine scale deflection for sample solution and blank solution.

(10) Read from calibration graphs the Ra, Kj and CaO contents.

(11) Calculate per cent, Ra^O, K^O and CaO content of saraplej allowingfor sodium and magnesium interference in case of CaO.

CaO — Alternative Colorimetric Method

The calcium is precipitated as calcium oxalate and a special

permanganate reagent is then added. The decrease in optical density of

the permanganate reagent due to the oxalate is measured as the difference

in optical density between the test solution and the reagent.

Reagents

* . Ritric acids I5 R

Hydrochloric acidg 10 per cent, v/v

B.D.H. 4»5 indicators Sodium acetate 2M.

Ammonium oxalateg 4 per cent, solution.

Wash solutions 2 per cent. RH^OH in equal parts water, alcohol, and ether,

Ritric acidg 50 Per cent, v/v

Stock WinO reagents 2,1 g KEi/InO. dissolved in 1 litre diluent,4 4

Diluentg 35 per cent, v/v H^SO^ containing 50 g/l IfoSO^ dH^O,

Diluted KHitnO. reagents dilute stock lOilnO. with diluent to give an optical4 4

density of approximately 1,0 in 2cm cells measured against diluent.

Procedure

(1) Pipette 25 nil aliquot of sample solution and blank solution of

solution C into 100ml beakers.

^ (2) Evaporate solution to about 10 ml and then add 10 ml 15RHR0^„

(3) Evaporate to dryness to remove ammonium salts.

(4) Heat sides of beakers with gas flame to complete removal of

ammonium salts.

(5) Cool, add 0.5 ml 10 per cent. HOI and 3 nil water — warm to

dissolve residue.

- 60 -

(6) Transfer solution to centrifuge tube — 15ml conical type»

(T) Add 2 drops BoDoHo 4<■5 indicator and titrate to grey-blue point ^with sodium acetate, ^

(8) Add 2 ml ammonium oxalatsj rniXj ajid allow to stand overnight,

(9) CentrifugOj remove supernatant liquid by suction into 100mlconical flasks,

(10) Wash precipitates with 2 ml wash solutionj centrifugCj removewashings by suction into appropriate 100ml flask.

(11) Repeat item 10,

(12) Dry tube and precipitate at 110°C — cool.

(13) Add 2 drops 50 per cent, dissolve precipitate^

(14) Add 10 ml diluted MnO^ reagent3 mix wellj and stand for 30 minutes.(15) Measure optical density at 5'10 myu in 2cm cells3 by reading 10 mldiluted KMhO^ reagent + 2 drops 50 per cent. ^^WO^ against test solution.(16) Determine GaO content from oalibration graph.

(17) Calculate per cent, CaO in samples.

I

t

The solution and washings from the calcium precipitation are

taken to dryness with cone, ®T0^ to remove, oxalate. The residue isdissolved in dilute HCl and the Mg is precipitated as the magnesium

ammonium phosphate^ the phosphorus in the precipitate is then determined.

Reagents

Ammonium phosphates 10 per cent, solution.

Wash solutions 10 per cent, v/v WH^OH,

Procedure

(1) Boil solution from Ca precipitation to remove alcohol.and ether,

(2) Add 10 ml cone, M0^9 evaporate to dryness on hot plate —■ takecare to avoid spattering,

(3) Coolj add 1 ml 10 per cent, HCl — to dissolve,solid material, ^

(4) Transfer solution to 15ml conical centrifuge tubej with 7 ml water,

(5) Add 1 ml 10 per cent, ammonium phosphate.

(6) Neutralize to methyl red with cone, NH^OHj add 1 ml excess,(7) Mix wellj scratch lower part of tube to start precipitation. Leaveovernight.

4

1

- 61 -

(8) Centrifuge for 5 minutes and remove supernatant liquid "by suction.

(9) Wash precipitate with 5 ml wash solution — centrifugej and remove

wash liquid by suction, . . .

(10) Repeat item 9''

(11) Dissolve precipitate in two drops 5®^ and 5 nil water, wash

into 50ml volumetric flask and make up to volume.

(12) Determine phosphorus content by taking a 10ml or 5ml aliquot and

carrying out procedure for phosphorus determination.

(13) Determine phosphorus content from calibration graph — calculate

Mg content from P content x O.785O0

(14) Calculate per cent, MgO in sample.

i

'v#

SO,

After extracting the ash with bromine water and hydrochloric

acid, the sulphate is determined gravimetrically as barium sulphate.

Reag.ents

Bromine water

Hydrochloric, acids 10 per cent, solution.

Barium chlorideg 100 g/litre, 10 per cent.

(1

(2

(3

(4

(5

(6

"by

(7

(8

(9

Procedure

ViTeigh accurately about O.5 g dry ash.

Transfer to 400ml beaker.

Add 5 ml bromine water and 100 ml 10 per cent. HCl — boil for 1 hour.

Filter through Yi/hatman Ho, 42 paper and wash residue with hot water.

neutralize the filtrate with cone, HH^OH and add 2 ml conc. HCl,

Boil solution and v/hile boiling add 15 ml 10 per cent. BaCl^ dropdrop — boil for further I5 minutes.

Allow to stand for 4 hours or overnight.

Filter on vYhatman Ho, 42 paper and determine BaSO^ in usual way.

Calculate per cent, SO^ in sample.

- 62 -

Notes

(1) Special care should he taken with sample weighingSj volume

measurementSj and spectrophotometer readings for the silica determination^

.Conversion Factors

Pe to Fe^O^ 1.4298 K to

ro0

1.2046

Ti to TiOg 1# 6681 ■ lHh to ^304 1.3889

Ca to CaO 1«3992 P to 2.2912

Mg to MgO 1#6579 BaSO^ to S03 0.3430

Na to Na 02

1.3479

M

because silica as the predominant constituent req.uires relatively more 'p,

precise values (errors amplified by dilution factor) than constituents

in lo?/er concentration#

.(2),,, For the preparation of solution B it is desirable to use distilled

water that has been distilled from Pyrex glass and stored in Pyrex or

plastic containers0 Distilled water stored, in soda glass containers

becomes contaminated with sodium- after some time, and renders accurate

Na determination impossible# In all proc©dures involved in the alkali

determination5 especially the sodium determination, it is very desirable

to use v/ater distilled as mentioned#

(3) When solution B has been prepared it is preferable to prepare the

solution for the alkali determination (solution C) immediatelyi this

solution can be stored in plastic bottles until it is convenient to

determine the alkalies, etc.

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