ASTM C146-21

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: C146 − 94a (Reapproved 2014) C146 − 21
Standard Test Methods for
Chemical Analysis of Glass Sand
This standard is issued under the fixed designation C146; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 These test methods cover the chemical analysis of glass sands. They are useful for either high-silica sands (99 % + silica
(SiO )) or for high-alumina sands containing as much as 12 to 13 % alumina (Al O ). Generally nonclassical, thethese test methods
2 2 3
are rapid and accurate. They include the determination of silica and of total R O (see 11.2.4), and the separate determination of
2 3
total iron as iron oxide (Fe O ), titania (TiO ), chromium oxide (Cr O ), zirconia (ZrO ), and ignition loss. Included are procedures
2 3 2 2 3 2
for the alkaline earths and alkalies. High-alumina sands may contain as much as 5 to 6 % total alkalies and alkaline earths. It is
recommended that the alkalies be determined by flame photometry and the alkaline earths by absorption spectrophotometry.
1.2 These test methods, if followed in detail, will provide interlaboratory agreement of results.
NOTE 1—For additional information, see Test Methods C169 and Practices E50.
1.3 TheThese test methods appear in the following order:
Procedures for Referee Analysis: Section
Silica (SiO )—Double Dehydration 10
Total R O —Gravimetric 11
2 3
Fe O , TiO , ZrO , Cr O , by Photometric Methods and 12 – 17
2 3 2 2 2 3
Al O by Complexiometric Titration
2 3
Preparation of the Sample for Determination of Iron 12
Oxide, Titania, Alumina, and Zirconia
Iron Oxide (as Fe O ) by 1,10-Phenanthroline Method 13
2 3
Titania (TiO ) by the Tiron Method 14
Alumina (Al O ) by the CDTA Titration Method 15
2 3
Zirconia (ZrO ) by the Pyrocatechol Violet Method 16
Chromium Oxide (Cr O ) by the 1,5-Diphenylcarbo- 17
2 3
hydrazide Method
Procedures for Routine Analysis:
Silica (SiO )—Single Dehydration 19
Al O , CaO, and MgO—Atomic Absorption Spec- 20–25
2 3
trophotometry
Na O and K O—Flame Emission Spectrophotometry 26-27
2 2
Loss on Ignition (LOI) 28
These test methods are under the jurisdiction of ASTM Committee C14 on Glass and Glass Products and are the direct responsibility of Subcommittee C14.02 on
Chemical Properties and Analysis.
Current edition approved Oct. 1, 2014June 1, 2021. Published October 2014July 2021. Originally approved in 1939. Last previous edition approved in 20092014 as
C146 – 94a (2009).(2014). DOI: 10.1520/C0146-94AR14.10.1520/C0146-21.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C146 − 21
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of
the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory
limitations prior to use.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.
1.5 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
C169 Test Methods for Chemical Analysis of Soda-Lime and Borosilicate Glass
C429 Test Method for Sieve Analysis of Raw Materials for Glass Manufacture
D1193 Specification for Reagent Water
E11 Specification for Woven Wire Test Sieve Cloth and Test Sieves
E50 Practices for Apparatus, Reagents, and Safety Considerations for Chemical Analysis of Metals, Ores, and Related Materials
E60 Practice for Analysis of Metals, Ores, and Related Materials by Spectrophotometry
2.2 Other Documents:NIST Document:
NISTSP260 NIST Special Publication 260
3. Significance and Use
3.1 These test methods can be used to ensure that the chemical composition of the glass sand meets the compositional specification
required for this raw material.
3.2 These test methods do not preclude the use of other methods that yield results within permissible variations. In any case, the
analyst should verify the procedure and technique used by means of a National Institute of Standards and Technology (NIST)
standard reference material or other similar material of known composition having a component comparable with that of the
material under test. A list of standard reference materials is given in the NIST Special Publication 260, current edition.
4. Photometers and Photometric Practice
4.1 Photometers and photometric practice prescribed in these test methods shall conform to Practice E60.
5. Purity of Reagents
5.1 Reagent grade chemicals shall be used throughout. Unless otherwise indicated, it is intended that reagents shall conform to
the specifications of the Committee on Analytical Reagents of the American Chemical Society, where such specifications are
available. Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high purity to permit its use
without lessening the accuracy of the determination.
5.2 Unless otherwise indicated, references to water shall be understood to mean reagent water as defined by Type I, II, or III of
Specification D1193.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Standard samples available from the Available from National Institute of Standards and Technology are listed in U.S. Dept. of Commerce, NIST,(NIST), 100 Bureau
Dr., Stop 1070, Gaithersburg, MD Special Publication 26020899-1070, http://www.nist.gov. (current edition), Washington, DC 20234.
Reagent Chemicals, American Chemical Society Specifications, American Chemical Society, Washington, DC. For suggestions on the testing of reagents not listed by
the American Chemical Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia and National
Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville, MD.
C146 − 21
6. Concentration of Acids and Ammonium Hydroxide
(NH OH)
6.1 When acids and ammonium hydroxide are specified by name or chemical formula only, concentrated reagents of the following
percent concentrations are intended:
Sp Gr %
Hydrochloric acid (HCl) 1.2 36 to 38
Hydrofluoric acid (HF) 1.2 48 to 51
Nitric acid (HNO ) 1.4 69 to 71
Perchloric acid (HClO ) 1.8 70 to 72
Sulfuric acid (H SO ) 1.8 95 to 98
2 4
Ammonium hydroxide (NH OH) 0.9 28 to 30
6.2 Concentrations of diluted acids and NH OH, except when standardized, are specified as a ratio stating the number of volumes
of the concentrated reagent to be added to a given number of volumes of water, as in the following example: HCl (1 + 99) means
1 volume of concentrated HCl (sp gr 1.19) added to 99 volumes of water.
7. Filter Papers
7.1 Throughout these test methods, filter papers will be designated as “coarse,” “medium,” or “fine” without naming brands or
manufacturers. All filter papers are of the double-acid-washed ashless type. “Coarse” filter paper refers to the porosity commonly
used for the filtration of aluminum hydroxide. “Medium” filter paper refers to that used for filtration of calcium oxalate, and “fine”
filter paper to that used for barium sulfate.
8. Preparation of Sample
8.1 General Considerations—The acquisition and preparation of the sample shall follow the principles stated in Test Method
C429.
8.2 The laboratory sample is reduced for analysis to 10 to 20 g 20 g by use of a small riffle with openings preferably of 6.4-mm
6.4 mm ( ⁄4-in.) size. The analytical sample is then ground in an agate mortar to pass a 150-μm 150 μm (No. 100) sieve. If the
laboratory sample as received contains any large particles that are retained on a 850-μm 850 μm (No. 20) sieve, these shall be
sieved out, crushed (without contamination) so as to pass the sieve, and then mixed back into the laboratory sample before riffling.
9. Precision and Bias
9.1 Precision—The probable precision of results that can be expected by the use of procedures described in these test methods is
shown in the following tabulation. Precision is given as absolute error and is dependent on the quantity of the constituent present
as well as the procedure used.
Probable Precision of Results, Weight %
Constituent Referee Analysis Routine Analysis
SiO (99 %) ±0.1 ±0.25
SiO (85–90 %) ±0.1 ±0.25
R O (1 %) ±0.05 ±0.10
2 3
R O (10–15 %) ±0.1 ±0.15
2 3
Al O (1 %) ±0.05 ±0.10
2 3
Al O (10–15 %) ±0.1 ±0.1
2 3
Fe O ±0.003 .
2 3
TiO ±0.005 .
ZrO ±0.001 to 0.005 .
Cr O ±0.0001 to 0.001 .
2 3
CaO . ±0.001
MgO . ±0.001
Na O . ±0.001
K O . ±0.001
Requirements for sieves are given in ASTM Specification E11.
C146 − 21
Probable Precision of Results, Weight %
Constituent Referee Analysis Routine Analysis
SiO (99 %) ±0.1 ±0.25
SiO (85–90 %) ±0.1 ±0.25
R O (1 %) ±0.05 ±0.10
2 3
R O (10–15 %) ±0.1 ±0.15
2 3
Al O (1 %) ±0.05 ±0.10
2 3
Al O (10–15 %) ±0.1 ±0.1
2 3
Fe O ±0.003 . . .
2 3
TiO ±0.005 . . .
ZrO ±0.001 to 0.005 . . .
Cr O ±0.0001 to 0.001 . . .
2 3
CaO . . . ±0.001
MgO . . . ±0.001
Na O . . . ±0.001
K O . . . ±0.001
9.2 Bias—Standard reference materials or other similar materials of known composition should be analyzed whenever possible to
determine the bias of the results.
PROCEDURES FOR REFEREE ANALYSIS
10. Silica (SiO ) by the Double Dehydration Method
10.1 Weigh 1.000 g of the powdered sample and 2.0 g of anhydrous sodium carbonate (Na CO ) into a clean 75-mL 75 mL
2 3
platinum dish (Note 2); mix well with a platinum or Nichrome wire. Tap the charge so it lies evenly in the bottom of the dish.
Cover evenly with an additional 1.0 g of Na CO . Cover with the platinum lid and heat first at a dull red heat over a clean oxidizing
2 3
flame; gradually raise the temperature until a clear melt is obtained. Properly carried out, little or no spattering should occur, and
the fusion can be performed in 3 to 4 min. When melted, rotate the melt to spread it evenly over the bottom and lower sides of
the dish, gradually withdrawing from the flame. Cover and cool to room temperature. During fusion, the dish should be handled
at all times with platinum-tipped tongs and the fusion performed with a platinum (preferably 90 % platinum and 10 % rhodium
alloy) or silica triangle.
NOTE 2—To obtain accurate repeat weighings, platinum ware must be kept scrupulously clean on the outside of the vessel as well as on the inside. It should
be polished brightly with fine, round grain sand and protected from dirty surfaces. It is recommended that porcelain plates be used for cooling fusions,
and that platinum be set on paper towels or other clean material during filtration.
10.2 Add 20 to 25 mL of HCl (1 + 1) under the platinum cover and digest on a steam bath or hot plate hot plate or similar
evaporation technique until the melt has completely disintegrated; it is also possible to digest the melt in the cold HCl overnight.
Police and rinse the lid with a fine jet of water; rinse down the sides of the dish and evaporate to dryness on a steam bath or under
an infrared lamp. Keep the dish covered with a raised cover glass during evaporation. When evaporation is complete (absence of
HCl), cool, drench the residue with 5 mL of HCl, and then add 20 mL of hot water. Digest for 5 min and filter through a 9-cm
9 cm medium filter paper. Catch the filtrate in a 250-mL 250 mL platinum dish. Transfer the precipitated silica to the filter with
the aid of a policeman and a bit of paper pulp, and wash the precipitate and paper twelve times with hot 2 % HCl. Transfer the
paper and precipitate to the dish used for fusion and dehydration and reserve for subsequent ignition. Wipe the stirring rod and
the periphery of the funnel with a piece of damp filter paper, and add to the dish containing the precipitate for ignition.
10.3 Evaporate the filtrate to dryness on the steam bath or under an infrared lamp. hot plate or in drying oven. When dry, cool,
drench with 10 mL of HCl (1 + 1), and again evaporate just to dryness; then bake in a drying oven at 105°C105 °C for 30 min.
Cool, drench with 5 mL of HCl, and add 20 mL of hot water and a small bit of filter pulp. Digest hot for 5 min and filter through
a 7-cm 7 cm fine paper. Police the dish with the aid of a bit of paper pulp and wash precipitate and paper eight times with hot 2 %
HCl. Transfer the paper and precipitate to the dish containing the initial precipitation. Wipe the stirring rod and the periphery of
the funnel with a piece of damp filter paper, and add to the dish containing the precipitate for ignition.
10.4 Partially cover the dish with its platinum lid, but leave enough space so air can circulate during ignition. Place the dish in
a cold muffle furnace, and bring the temperature to 1200°C1200 °C for 30 min. Carefully and completely cover the dish before
Nichrome is a registered trademark of the Driver-Harris Co., 308 Middlesex St., Harrison, NJ 07029.
C146 − 21
removing it from the furnace and transfer to a desiccator. Cool to room temperature and weigh the covered dish (W ). Moisten the
silica with 1 to 2 mL of water and add 4 to 5 mL of HF and 0.5 g of oxalic acid crystals. Evaporate to dryness on a sand bath or
under an infrared lamp. hot plate or in drying oven. Carefully sublime any remaining oxalic acid, cover the dish with its platinum
cover, heat to 1000°C1000 °C for 2 min, 2 min, cool, and weigh (W ) as before.
10.5 Calculation—Calculate the percent of SiO as follows:
W 2 W 3100
~ !
1 2
SiO ,%5 (1)
sample weight
11. Total R O by Ammonium Hydroxide (NH OH) Precipitation
2 3 4
11.1 General Considerations—The weight of sample taken for analysis is governed by the amount of Al O known or suspected
2 3
to be present. Sands low in Al O (0.05 to 0.5 %) require a 5-5 to 10-g 10 g sample; sands with larger amounts of Al O require
2 3 2 3
a 0.5-0.5 to 1.0-g 1.0 g sample. Usually experience or prior information will indicate a satisfactory sample weight. The total R O
2 3
serves as a check on the sum of the R O oxides determined separately. It also helps to identify an unknown sand as a low- or
2 3
high-alumina type.
11.2 Procedure:
11.2.1 Weigh a suitable weight of sample into an 80-80 to 100-mL100 mL platinum dish, moisten, and add 10 mL of HF for each
gram of sample taken; add 4 mL of H SO (1 + 1) and evaporate to the first fuming of H SO (Note 3). Cool, carefully wash down
2 4 2 4
the sides of the dish with a minimum of water, and evaporate to the cessation of H SO fumes. Cool, add 10 to 15 mL of HCl
2 4
(1 + 1), 20 mL of hot water, and digest hot until the salts are in solution. If they do not dissolve readily, transfer to a beaker, police
the dish, and boil the solution until the sulfates have dissolved (Note 4).
NOTE 3—Some sands may contain small amounts of organic matter as shown by the presence of carbon or carbonaceous material in the concentrated
H SO . If this is the case, add 2 to 3 mL of HNO and 10 to 15 drops of HClO , and proceed.
2 4 3 4
NOTE 4—High-alumina sands are generally mixtures of quartz and aluminum silicates of the feldspar group. Some of these silicates can contain barium.
If a fine, white, insoluble precipitate persists, it is probably barium sulfate. In this case, partially neutralize the HCl until the solution is about 1 to 2 %
acid, add about ten drops of H SO (1 + 1) and boil gently for about 30 min. Cool, and after 1 to 2 h, filter the solution through a fine paper. The
2 4
precipitate may be ignited and weighed and subsequently tested for barium. If the precipitate is not barium sulfate, it should be tested for silica. If the
precipitate is neither of these, it can be considered R O and added to the R O found by ammonia precipitation.
2 3 2 3
11.2.2 If the expected R O is about 10 mg, dilute the sample to about 75 to 100 mL; if much larger, dilute to about 200 to 250
2 3
mL. Add approximately 2 g of NH Cl, heat to boiling, add three to four drops of methyl red indicator solution and precipitate the
R O with the addition of NH OH (1 + 1). Add the NH OH slowly, stirring to obtain a sharp end point; finally add about four drops
2 3 4 4
in excess for small amounts of precipitate and up to eight drops for large amounts. Boil the solution for about 2 min and filter
through a coarse paper; there is no need to transfer quantitatively all the precipitate at this time. Wash the precipitate three to four
times with hot 2 % NH Cl made neutral to methyl red. Transfer the precipitate back into the beaker and add 10 to 15 mL of HCl
(1 + 1) and digest to disintegrate the paper and dissolve the precipitate. Dilute to approximately the same volume used for the first
precipitation, reprecipitate with NH OH, and filter as before. Police the beaker with a bit of paper pulp to ensure complete recovery
from the beaker. Wash four to five times with hot 2 % NH Cl solution.
11.2.3 Transfer the precipitate to a clean, tared platinum or porcelain crucible and ignite at a temperature of 1200°C1200 °C for
30 min. 30 min. Unglazed porcelain is best for the ignition as it does not change weight at this temperature. If platinum is used,
both outer and inner surfaces should be polished bright. It is also advisable to carry an empty crucible through the ignition cycle
to see if a platinum weight change occurs. A slight loss can be considered normal. If a gain in weight occurs, the platinum can
be considered dirty and should be repolished and cleaned before reuse. The correct weight can be salvaged by brushing the dish
or crucible free of precipitate and reweighing, in which case the original tare weight is not used for computation:
R O ,%5 weight of precipitate / weight of sample 3100 (2)
@~ ! ~ !#
2 3
11.2.4 The R O contains the Al O , Fe O , TiO , ZrO , and Cr O in the sample (phosphoric sample. If present, phosphoric
2 3 2 3 2 3 2 2 2 3
anhydride (P O ) and vanadium pentoxide (V O ) will be included if present, but this is not usual).and may impact precision and
2 5 2 5
accuracy. Al O is estimated by subtracting the sum of the other oxides from the R O .
2 3 2 3
C146 − 21
12. Preparation of the Sample for Determination of Iron Oxide, Titania, Alumina, and Zirconia
12.1 Reagents: Fusion Mixture—Weigh an approximate 1 + 1 mole portion of lithium carbonate (Li CO ) and anhydrous sodium
2 3
tetraborate (Na B O ), 74 and 201 g, respectively, and mix intimately.
2 4 7
12.2 Procedure for Low-Alumina, High-SilicaLow-alumina, High-silica Sands—Weigh 4 g of sample dried at 110°C110 °C into
a 75-75 to 100-mL 100 mL platinum dish, add 40 mL of HF, and evaporate to near dryness. Wash down the sides of the dish with
10 mL of HF (use a small plastic cylinder or polyethylene dropping pipet) and evaporate to dryness (Note 5). Without any prior
heating, evenly cover the residue in the dish with 2 6 0.02 g of fusion mixture; heat over a gas burner until the residue is in solution
in the melt (Note 6). To the fused residue, add 10 mL water and 20 mL of HClO (1 + 4); cover and digest hot until the melt is
in solution (Note 7). Transfer to a 200-mL 200 mL volumetric flask, cool, dilute to the mark, and mix (Note 8). The sample is now
prepared for the determination of Fe O , Al O , TiO , and ZrO ; the sample for Cr O is prepared separately (see Section 17).
2 3 2 3 2 2 2 3
Prepare a reagent blank with the samples. Aliquots identical to those for Fe O , TiO , and ZrO are used as the photometric
2 3 2 2
reference solutions (Note 9).
NOTE 5—In the procedure for high-alumina sands (12.3), it is preferable to add a few drops of H SO with the second addition of HF. This eliminates
2 4
the chance of volatilizing aluminum and titanium fluorides as the fusion is started.
NOTE 6—The fusion is rapid and can be performed simply as follows: Heat over a Meeker-type burner at a moderate heat until the mixture melts, apply
just enough additional heat to give a moderate red heat. No lid is required if the initial heating is not too high. The fusion can be done in 2 min 2 min
per sample. The dish must be handled with clean platinum-tipped tongs. The only allowable substitute is pure nickel tongs and these must be considered
only in an emergency.
NOTE 7—Some samples may develop a cloudiness or precipitate after solution of the fusion or transfer to the volumetric flask. Tests have shown this will
not affect results for Fe O , TiO , or Al O . After diluting to the mark of the flask and mixing, the precipitate is allowed to settle; sample aliquots are
2 3 2 2 3
pipeted without disturbing the precipitate. The precipitate is probably a fluoborate.
NOTE 8—An aliquot of this solution can now be used for the Cr O analysis (Section 17).
2 3
NOTE 9—Use of a predetermined amount of buffer for the determination of Fe O and TiO obviates the use of indicators and speeds the analysis when
2 3 2
a group of samples must be analyzed. Preparation for this is made as follows: Weigh 2 g of fusion mix into a 250-mL 250 mL beaker, add 100 mL of
water and 20 mL of the HCl (1 + 4), cover, and boil for several minutes to eliminate CO . Cool and transfer to a 200-mL 200 mL volumetric flask, dilute
to the mark, and mix. Transfer a 25-mL 25 mL aliquot to a 150-mL 150 mL beaker and dilute to about 70 to 80 mL. Add from a 100-mL 100 mL buret
(which is used for dispensing) enough 2M sodium acetate solution to give a pH of 3.1 (make measurements with a pH meter). Record the volume used
for the determination of iron. Continue adding sodium acetate until a pH of 3.8 is reached; record for the determination of titanium.
12.3 Procedure for High-Alumina, Low-SilicaHigh-alumina, Low-silica Sands—The method and technique is identical to 12.2
with the exception of weights and volumes. Weigh 2 g of sample dried at 110°C110 °C into a 75-mL 75 mL platinum dish and
add 20 mL of HF; evaporate to near dryness. Wash down the sides of the dish with 5 mL of HF as in 12.2 and evaporate to dryness.
Add 3 g of fusion mix and fuse as in 12.2. Add 15 mL of water and 26 mL of HCl (1 + 4) and digest until in solution. Transfer
to a 100-mL 100 mL volumetric flask; cool, dilute to the mark, and mix (Note 7). The amounts of predetermined buffer should
be nearly the same as for 12.2; however, test the pH before proceeding (Note 8).
13. Iron Oxide (as Fe O ) by the 1,10-Phenanthroline Method
2 3
13.1 Reagents:
13.1.1 Hydroxylamine Hydrochloride (10 % weight/volume in water)—Filter if necessary.
13.1.2 1,10-Phenanthroline—The solution may be prepared from the monohydrate or the hydrochloride. The latter is readily water
soluble; the monohydrate requires heating. Dissolve 12.0 g of the monohydrate by adding to 800 mL of hot water, stir and heat
until in solution, cool and dilute to 1 L; store in a dark bottle or in a dark place. If the hydrochloride is used, dissolve 13.0 g in
200 to 300 mL of water and dilute to 1 L; protect from light during storage. Two millilitres of either solution will complex 1.2
mg. This will cover the absorbance curve for the area of interest depending on instrumentation.
13.1.3 Sodium Acetate (Buffer) Solution (2M)—Dissolve 272 g of sodium acetate (CH COONa·3H O) per litre of aqueous solution
3 2
prepared. Filter before use if necessary. Since sodium acetate solutions tend to develop mold growth with age, a preservative can
be used; 0.025 g of para-chlorometaxylenol per litre has been found satisfactory for this purpose.
13.2 Fe O Procedure (For All Sands):
2 3
C146 − 21
13.2.1 For sand with an iron content between 0.01 and 0.12 % Fe O , pipet an aliquot equivalent to 0.5 g (25 mL) into a 100-mL
2 3
100 mL volumetric flask if the Fe O is between 0.10 and 0.24 %, transfer the aliquot to a 200-mL 200 mL volumetric flask (Note
2 3
10). If the Fe O is higher than 0.24 %, a proportionally smaller aliquot will be necessary. By choice of volume and size of aliquots,
2 3
a single standard curve should be adequate for the percentages of iron normally encountered in glass sand.
13.2.2 To the sample in the flask, add 1 mL of hydroxylamine hydrochloride and the predetermined amount of buffer, dilute to
⁄4 the volume of the flask, and add either 1 or 2 mL of 1,10-phenanthroline, depending on the iron present, mix, dilute to the mark,
and after 5 min, measure the absorbance at 508 nm on a suitable (spectro) photometer. The reagent blank is used as the reference
solution.
13.2.3 Calculation—Convert the photometric reading to milligrams of Fe O by means of the standard curve, and calculate the
2 3
percent Fe O as follows:
2 3
A 3B 3100
% Fe O 5 (3)
2 3
C 3D 31000
where:
A = milligrams of Fe O from the calibration curve;
2 3
A = milligrams of Fe O from the calibration curve,
2 3
B = total volume from 12.2, mL;
B = total volume from 12.2, mL,
C = sample weight from 12.2, g; and
C = sample weight from 12.2, g, and
D = millilitres of aliquot from 13.2.1.
NOTE 10—If color is developed in a volumetric flask other than 100-mL 100 mL volume, then this must be taken into account in the calculation in 13.2.3.
13.3 Preparation of the Standard Curve for Standard Iron Solution—Weigh 0.4911 g of ferrous ammonium sulfate into a 1-L 1
L volumetric flask, dissolve in water, add 8 to 10 mL of HCl, dilute to the mark and mix; 1 mL = 0.1 mg of Fe O ; (the fact that
2 3
the iron may slowly oxidize is of no consequence as it is subsequently reduced when developing the complex). Prepare a series
of 100-mL 100 mL volumetric flasks containing 0, 1, 2, 3, 4, 5, and 6 mL of the standard iron solution, dilute to 20 to 30 mL, and
proceed as described in 13.2. The zero iron solution is the photometric reference. Plot on linear graph paperCreate linear plot of
absorbance versus concentration in milligrams of Fe O .
2 3
14. Titania (TiO ) by the Tiron Method
14.1 Reagents:
14.1.1 Buffer (2M Sodium Acetate)—See 13.1.3.
14.1.2 Acetate Buffer (pH 4.5)—To 1 L of 1M sodium acetate solution add 390 mL of glacial acetic acid. Adjust to a pH of 4.5
with either solid sodium acetate or glacial acetic acid using a pH meter.
14.1.3 Thioglycolic Acid (CH SHCOOH, Reagent, Assay 96 to 97 %)—Prepare a 20 % v/v solution; keep refrigerated.
14.1.4 Tiron Reagent (Disodium-1,2-di-Hydroxybenzene-3,5-Disulfonate) —(Disodium-1,2-di-Hydroxybenzene-3,5-
Disulfonate)—Prepare a 5 % w/v solution. Filter if necessary. The solution should be nearly colorless. Protect from light in storage.
14.1.5 Titanium Dioxide, Standard Solution (1 mL = 1.0-mg mL = 1.0 mg TiO )—Weigh 1.0026 g of National Institute of
Standards and Technology SRM No. 154b titanium dioxide and prepare 1 L of solution as directed by the certificate furnished with
the material for use as a standard for colorimetry. (If an older supply, Nos. 154 or 154a, is available, use the appropriate weight
as determined from the certified percentage of TiO .)
14.1.6 Titanium Dioxide, Dilute Standard Solution (1 mL = 1.0-mg(1 mL = 1.0 mg TiO )—Pipet 50 mL of the 1.0-mg 1.0 mg
TiO /mL standard solution into a 500-mL 500 mL volumetric flask, add 15 mL of H SO , and dilute to about 400 mL; mix by
2 2 4
swirling. Cool to room temperature, if necessary; dilute to volume and mix.
C146 − 21
14.2 TiO Procedure (for All Sands):
14.2.1 Pipet an aliquot equal to 0.5 g of sample (25 mL) into a 50-mL 50 mL volumetric flask for sand with TiO between 0.005
to 0.05 % (Note 11), and add in order, with mixing, 1 mL of 20 % thioglycolic acid, 5 mL of Tiron reagent, the predetermined
amount of 2M sodium acetate solution (to adjust the pH to approximately 4.5), and then 10 mL of the acetate buffer pH 4.5. Dilute
to the mark, mix, and, after 15 min, measure the absorbance in 10 mm or comparable cells at 380 nm. The reagent blank is the
reference solution.
NOTE 11—Samples suspected to contain more than 0.05 % TiO should be pipeted into 100-mL 100 mL volumetric flasks, or less sample and 2M sodium
acetate buffer solution should be taken, or a combination of both. Since this reagent is about nine times as sensitive to titanium as peroxide, 0.25 mg
0.25 mg of TiO /50 mL or 0.5-mg/100-mL 0.5 mg/100 mL volume is the maximum that can be handled.
14.2.2 Calculation—Convert the photometric reading to milligrams of TiO by means of the standard curve and calculate as for
iron (see 13.2.3).
14.3 Preparation of the Standard Curve for Standard Titanium Solution—Prepare a series of 50-mL 50 mL volumetric flasks
containing 0.00, 0.05, 0.10, 0.15, 0.20, and 0.25 mg of TiO and proceed as described in 14.2. The zero solution is the photometric
reference. Plot concentration on linear graph paper.Create linear plot of absorbance versus concentration in milligrams of TiO .
The absorbance for 0.3 mg 0.3 mg of TiO in 50-mL 50 mL volume is about 1.150.
15. Alumina (Al O ) by the CDTA Complexiometric Titration
2 3
15.1 Reagents:
15.1.1 1,2-Cyclohexylene Dinitrilo Tetraacetic Acid (CDTA) Solution—Dissolve 7.3 g of CDTA in 200 mL of water by the slow
addition of 20 % w/v NaOH solution with stirring. When the reagent has dissolved, adjust the pH to 7 with HCl (1 + 10) using
a pH meter, dilute to 1 L, and store in a polyethylene bottle. It is usually practical to prepare 2 to 4 L at a time. One millilitre will
complex approximately 1.0 mg of Al O .
2 3
15.1.2 Zinc Standard Solution—Prepare from ACS reagent or spectroscopically pure metal freed of oxide surface film. Dissolve
1.283 g of metal in 30 mL of HCl (1 + 4), and dilute to 2 L with water. One millilitre of Zn solution = 0.500 mg of Al O and
2 3
approximately 0.50 mL of CDTA solution. Since the zinc solution is the standard for the Al O determination, it must be prepared
2 3
with care and accuracy.
15.1.3 Xylenol Orange Tetrasodium Salt (Indicator) Solution—Dissolve 0.5 g in 100 mL of water and add one or two drops of
HCl as stabilizer.
15.2 Standardization of CDTA Solution with Standard Zinc Solution—Accurately pipet 10 or 15 mL of CDTA solution into a
150-150 or 250-mL 250 mL beaker and dilute to about 40 to 50 mL. Add 5 mL of 2M sodium acetate buffer and while stirring
on a magnetic stirrer, adjust the pH to 5.3 by the addition of acetic acid using a pH meter, or by using xylenol orange as a pH
indicator (Note 12 in 15.3.4). Titrate with the standard zinc solution to the first perceptible color change from yellow to pinkish
red. A circle of filter paper placed under the beaker will aid in detecting the end point. Repeat on at least two additional aliquots
and average the titers. Millilitres of zinc solution divided by millilitres of CDTA equals millilitres of zinc equivalent of CDTA.
15.3 Al O Procedure:
2 3
15.3.1 Transfer an aliquot equal to a 0.5-g 0.5 g sample (25 mL) to a 150-150 or 250-mL 250 mL beaker. Add sufficient CDTA
to provide an approximate excess of 5 mL. Place a magnetic stirring bar in the solution, stir the solution, and slowly add sufficient
2M sodium acetate buffer solution to raise the pH to 3.2 to 3.5. Heat the solution to a gentle boil; the stirring bar is conveniently
left in the beaker. Boil for 1 min to assure complete complexation of aluminum. Cool to room temperature, preferably in a
cold-water bath.
15.3.2 Place the beaker on a magnetic stirrer with a circle of filter paper underneath the beaker to aid in detecting the end point.
Stir the solution, add one or two drops of xylenol orange indicator, and adjust the pH to 5.3. Titrate with the standard zinc solution
to the first perceptible color change from yellow to pinkish red.
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15.3.3 Calculation of Al O and Correction for Fe O , TiO , and so forth (ZrO and MnO , if determined)—Calculate the net zinc
2 3 2 3 2 2 2
titer by subtracting the zinc back titer from the millilitres zinc equivalent of CDTA used. Since the zinc solution equals 0.5-mg
0.5 mg Al O /mL and 0.5 g of sample is titrated, calculate the uncorrected percentage of Al O as follows:
2 3 2 3
Al O ,% uncorrected 5 net zinc titer 30.1 (4)
~ !
2 3
15.3.4 Example—If 15 mL of CDTA are added (estimated Al O = 2.0 %), then:
2 3
If 15 mL of CDTA are added (estimated Al O = 2.0 %), then:
2 3
15 32.02 12 mL CDTA 5 2.02 2 mL zinc solution (5)
~ !
5 30.3 2 mL zinc equivalent CDTA
If zinc back titer 5 8.80 mL, then (6)
30.30 2 8.80 5 21.50 mL
~ !
52.15 % Al O uncorrected
2 3
If zinc back tilter = 8.80 mL, then:
30.30 2 8.80 5 21.50 mL52.15 % Al O uncorrected (6)
~ !
2 3
To correct for Fe O and TiO :
2 3 2
~% Fe O 1% TiO !30.637 5 equivalent % Al O (7)
2 3 2 2 3
If % Fe O = 0.045 and % TiO = 0.018, then:
2 3 2
~0.04510.018!5 0.063 30.637 5 0.040 (8)
2.15 2 0.040 5 2.11 % Al O corrected for Fe O and TiO (9)
2 3 2 3 2
ZrO is corrected by multiplying % ZrO × 0.413; and % MnO × 0.719. If determined, ZrO and MnO equivalents are added to
2 2 2
the correction for Fe O and TiO and the whole subtracted from percent uncorrected Al O .
2 3 2 2 3
NOTE 12—To provide a 5-mL 5 mL excess of CDTA for complete complexation of aluminum, using a sample aliquot equal to 0.5 g, a sample containing
1.5 % Al O will require 12.5 mL and a sample containing 3.0 % Al O , 20 mL, respectively. The pH of the sample solution may be adjusted to 5.3 by
2 3 2 3
adding a predetermined amount of 2M sodium acetate buffer solution; or, more practically, by using xylenol orange as a pH indicator as follows: After
addition of the indicator, stir the solution and add 2M sodium acetate until the indicator begins to change color (pH about 5.7 to 6). Add acetic acid until
the color is again a clear bright yellow. Proceed with the zinc back titration.
16. Zirconia (ZrO ) by the Pyrocatechol Violet Method (for All Samples)
16.1 Reagents:
16.1.1 Tri-n-Octyl-Phosphine Oxide (TOPO) Reagent—Prepare an approximately 0.05M solution by dissolving 2 g of reagent in
100 mL of cyclohexane.
16.1.2 Nitric Acid (7M)—)—Approximately 7M acid is prepared by diluting one volume of HNO (sp gr 1.42) with one volume
of water.
16.1.3 Pyrocatechol Violet—Prepare a 0.15 % solution (weight/volume) in absolute ethyl alcohol by dissolving 37.5 mg of reagent
in 25 mL of absolute ethyl alcohol. The solution must be prepared daily or just before use. The quality of pyrocatechol is always
suspect and should be tested for sensitivity before use. This can be done by extracting a known quantity of ZrO , developing the
complex as called for in 16.2, and comparing the actual absorbance with the expected absorbance. If it does not satisfactorily meet
this level, it should be discarded.
16.1.4 Ethyl Alcohol, Absolute, 100 % or 200 proof reagent quality.
16.1.5 Pyridine, analytical reagent.
16.2 ZrO Procedure (for All Samples):
16.2.1 Pipet an aliquot of the sample solution equal to 0.2 g (10 mL) into a 60-mL 60 mL Squibb separatory funnel, preferably
C146 − 21
fitted with a TFE-fluorocarbon stopcock plug. Add 10 mL of HNO ; and, if the solution has warmed significantly, cool to room
temperature. Pipet 5 mL of TOPO-cyclohexane into the solution and extract zirconium by shaking or mixing for 10 min. 10 min.
Allow the liquid layers to separate, drain off the aqueous layer, and discard. Add 10 mL of 7M HNO , shake for 2 min; allow the
layers to separate, drain, and reject the acid layer.
16.2.2 Transfer with a dry pipet 2 mL of the cyclohexane extract into a dry 25-mL 25 mL volumetric flask. Add in order, while
mixing, 10 mL of absolute alcohol, 1 mL of 0.15 % pyrocatechol violet, and 5 mL of pyridine. Finally, dilute to the mark of the
flask with absolute alcohol and mix. Measure the absorbance in 10-mm 10 mm cells at 655 nm. The reagent blank is the reference
solution.
16.2.3 Calculation—Convert the photometric reading to micrograms of ZrO by means of the standard curve and calculate percent
ZrO as follows:
ZrO ,%5 ~A/B! 3@A/~B1C!# 310 (10)
where:
A = micrograms of ZrO ,
B = grams of sample in sample aliquot, and
C = millilitres of TOPO aliquot per total millilitres of TOPO used.
found in 2 mL of TOPO-cyclohexane extract of 10-mL 10 mL sample aliquot:
Example:Example 20-μg —20 μg ZrO
24 24
20/~0.2 30.4!310 5 20/0.08 310 (11)
5250 310
50.025 % ZrO
0.2 5 grams of sample in 10 2 mL aliquot (12)
0.4 5 22 mL fraction of 5 mL
of TOPO 2 cyclohexane extract
16.3 Preparation of Standard Curve—Standardize reagent quality zirconyl nitrate by careful ignition to the oxide as follows:
Weigh 2.0 g of the nitrate into a tared platinum dish or crucible and gradually heat from room temperature to 1000°C.1000 °C.
Weigh a sufficient amount of the standardized nitrate to make 1 L of solution containing 0.1 mg of ZrO /mL. Transfer to a 1-L1 L
volumetric flask and dissolve in HNO (1 + 2). This stock solution is relatively stable. A dilute standard equal to 0.01 mg ⁄mL
(10 μg ⁄mL) is prepared from stock as needed; dilute with water. Prepare a series of solutions in 60-mL 60 mL separatory funnels
containing 0, 25, 50, 75, 100, and 125 μg of ZrO ; dilute to at least 10 mL, then proceed as described in 16.2 for the determination
of ZrO . Since 2-mL 2 mL aliquots are 0.4 of the amount of ZrO taken, the standard curve plot will represent, therefore, 10, 20,
2 2
30, 40, and 50 μg of ZrO (Note 13). The zero solution is the reference. Plot on semilog paper, percent transmittance on the log
scale, and concentration scale and concentration, in micrograms, on the linear scale.
NOTE 13—The colored complex follows Beers’ law up to a concentration of 60 μg/25 mL. The maximum amount of ZrO that can be completely extracted
is about 125 to 150 μg. When more than 50 μg is found in the 2-mL 2 mL aliquot taken for color development, a smaller aliquot should be taken and
the procedure repeated.
Pressure may develop in the separatory funnel during extraction. After a minute or two of shaking, invert the funnel and carefully vent through the
stopcock.
It is essential to use dry pipets and volumetric flasks as water will affect the intensity of the colored complex. Also, care must be taken not to get water
into the pipet when taking aliquots from the separatory funnel.
17. Chromium Oxide (Cr O ) by the 1,5-Diphenylcarbohydrazide Method
2 3
17.1 Reagents:
17.1.1 1,5-Diphenylcarbohydrazide—Dissolve 4 g of phthalic anhydride in 100 mL of ethyl alcohol by boiling under a reflux,
cool, add 0.25 g of the reagent. Transfer to a glass-stoppered bottle, and store in a dark, cool place (a refrigerator is most
satisfactory). So prepared, despite a slow yellow discoloration, the reagent is reasonably stable. However, it is advisable to test it
with a standard chromate solution (10 or 20 μg) every three to four weeks.
17.1.2 Fusion Mixture—Same as for iron (12.1).
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17.1.3 Polyphosphate Solution (approximate 10 % weight/volume for complexing iron)—Weigh 6.04 6 0.02 g of sodium
phosphate dibasic (Na HPO ) and 5.87 6 0.02 g of sodium phosphate monobasic (NaH PO ·H O) into a 100-100 or 125-mL 125
2 4 2 4 2
mL platinum dish. (If a dish this large is not available, a smaller charge should be prepared.) Mix well and fuse by slowly raising
the heat of a gas burner until the melt is a cherry-red and only a few bubbles remain. Remove the dish from the burner
(platinum-tipped tongs) and rotate the melt to thin out the liquid layer of phosphate. When the melt has lost all color from heat,
plunge it halfway into a pan of cold water. The resulting mass should be transparent or only slightly opalescent. When cool,
dissolve in 100 mL of cold water and store.
17.1.4 Potassium Permanganate Solution—A 0.3 % weight/volume solution in water.
17.1.5 Sodium Azide Solution—A 1% weight/volume in solution in water.
17.2 Procedure:
17.2.1 Weigh 1 to 3 g of sample into a 75-mL 75 mL platinum dish and add 10 mL of HF for each gram taken. If the sand is high
in alumina (+10 %), restrict the sample size to 1 g. Add 2 mL of H SO (1 + 1) and evaporate to incipient fumes of H SO . Cool
2 4 2 4
and wash down the sides of the dish with 10 mL of HF with the aid of a plastic dropper. Continue the evaporation to complete
expulsion of H SO . Some precaution will likely be necessary when attacking high-alumina sands. The reaction of the fluorides
2 4
when converting to sulfates may cause considerable effervescence. In this case, cover about ⁄8 of the dish with a platinum lid
(TFE-fluorocarbon is suitable), and continue heating until the reaction is complete. Cool, rinse off the lid and down the sides of
the dish, and evaporate to the expulsion of H SO .
2 4
17.2.2 When evaporation is complete, weigh into the dish 1 g of Na CO 6 0.02 g and 1 g of fusion mixture 6 0.02 g (as used
2 3
for iron), and mix the precipitate and fusion materials thoroughly with a glass rod. Fuse the sample over a gas burner or in a muffle
furnace at a moderate temperature until the mass is clear, but do not prolong the time of fusion so as to avoid the loss of chromium.
NOTE 14—It is during the fusion of the residue that contamination is most likely to occur. Avoid chromium-containing triangles, tongs, and muffle furnaces
with exposed metallic heating elements.
17.2.3 When the fusion is complete, cool the melt, add 10 mL 10 mL of HClO (1 + 1) and 10 to 15 mL of water; digest until
solution is complete. Transfer to a 50-mL 50 mL volumetric flask (the volume should not exceed 35 to 40 mL), add three to four
drops of permanganate solution (enough to give a persistent color), and digest in boiling water for 30 to 40 min; all chromium will
+6
be oxidized to Cr . Remove from the boiling water, add sodium azide solution dropwise at about 20-s intervals between drops.
When the permanganate has been reduced, add 1 mL of polyphosphate solution and cool to room temperature. Add 2 mL of
diphenylcarbohydrazide, dilute to the mark and mix, and measure percent transmittance on a spectrophotometer at 540 nm after
10 min but before 30 min from time of color development. For 1 to 15 μg of Cr O , the preferred cell light path is 50 mm; for
2 3
15 to 70 μg, 10-mm 10 mm cells are required. If the photometer cannot accommodate 50-mm 50 mm cells, the largest for the
available instrument should be used. The blank is the reference solution.
17.2.4 Calculation—Convert the photometric reading to micrograms of Cr O by means of the appropriate standard curve and
2 3
calculate percent Cr O as follows:
2 3
Cr O ,%5 ~A/B! 310 (13)
2 3
where:
A = micrograms found in the sample solution,
B = grams of sample represented by the sample solution, and
−4
10 = factor to convert 1 μg/g of sample to percent. The = sign needs to be moved to just before the word “factor.”
where:
A = micrograms found in the sample solution,
B = grams of sample represented by the sample solution, and
−4
10 = factor to convert 1 μg/g of sample to percent.
17.3 Preparation of the Standard Curve:
C146 − 21
17.3.1 Standard Chromate Solutions—Weigh 0.1935 g of K Cr O or 0.2555 g of K CrO into a 1-L 1 L volumetric flask and
2 2 7 2 4
dilute to the mark; 1 mL = 0.1 mg/mL of Cr O . Dilute 10 mL of this solution to 1 L in a volumetric flask to equal 1.0 μg of
2 3
Cr O /mL; and 100 mL/L to equal 10.0 μg/ml.
2 3
17.3.2 Perchloric Acid Solution (1 + 4 (1 + 4) )——To 400 mL of water add 100 mL of 70 to 72 % HClO and heat to about
60°C.60 °C. Add dropwise sufficient N/10 permanganate solution to give a light pink color. Heat to near boiling until the
permanganate has been reduced. Add more permanganate solution, dropwise, until a faint pink color appears. Continue t
...