ASTM D1135-86(2014)
(Test Method)Standard Test Methods for Chemical Analysis of Blue Pigments
Standard Test Methods for Chemical Analysis of Blue Pigments
SIGNIFICANCE AND USE
3.1 These test methods are suitable for determining if impurities are present and establishing that the required pigments are present. These test methods may be used for manufacturing quality control.
SCOPE
1.1 These test methods cover procedures for the chemical analysis of blue pigments known commercially as iron blue, copper phthalocyanine blue, and ultramarine blue.
1.2 The analytical procedures appear in the following order:
Sections
IRON BLUE PIGMENTS
Identification
6
Moisture by the Brabender Moisture Tester
7 and 8
Moisture by Toluene Distillation
9
Water-Soluble Matter by Extraction
10
Water-Soluble Salts by Electrical Conductivity
11
Detection of Acid-Insoluble Extenders
12 and 13
Detection of Acid-Soluble Extenders
14 to 17
Detection of Organic Colors and Lakes
18
COPPER PHTHALOCYANINE BLUE PIGMENTS
Identification
19
Moisture and Other Volatile Matter
20
Detection of Basic Dye Derivatives
21
Detection of Other Organic Coloring Matter
22
Detection of Ultramarine Blue
23
Detection of Iron Blue
24
ULTRAMARINE BLUE
Identification
25
Moisture and Other Volatile Matter
26
Water-Soluble Matter
27
Detection of Basic Dye Derivatives
28
Detection of Other Organic Coloring Matter
29
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4 This standard does not purport to address the safety concerns 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.
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Designation: D1135 − 86 (Reapproved 2014)
Standard Test Methods for
Chemical Analysis of Blue Pigments
This standard is issued under the fixed designation D1135; 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.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope 2. Referenced Documents
1.1 These test methods cover procedures for the chemical
2.1 ASTM Standards:
analysis of blue pigments known commercially as iron blue,
D280 Test Methods for Hygroscopic Moisture (and Other
copper phthalocyanine blue, and ultramarine blue.
Matter Volatile Under the Test Conditions) in Pigments
D1193 Specification for Reagent Water
1.2 The analytical procedures appear in the following order:
D1208 Test Methods for Common Properties of Certain
Sections
Pigments
IRON BLUE PIGMENTS
D2448 Test Method for Water-Soluble Salts in Pigments by
Measuring the Specific Resistance of the Leachate of the
Identification 6
Moisture by the Brabender Moisture Tester 7 and 8
Pigment
Moisture by Toluene Distillation 9
E11 Specification for Woven Wire Test Sieve Cloth and Test
Water-Soluble Matter by Extraction 10
Sieves
Water-Soluble Salts by Electrical Conductivity 11
Detection of Acid-Insoluble Extenders 12 and 13
Detection of Acid-Soluble Extenders 14 to 17
3. Significance and Use
Detection of Organic Colors and Lakes 18
3.1 These test methods are suitable for determining if
COPPER PHTHALOCYANINE BLUE PIGMENTS
impurities are present and establishing that the required pig-
Identification 19
ments are present. These test methods may be used for
Moisture and Other Volatile Matter 20
manufacturing quality control.
Detection of Basic Dye Derivatives 21
Detection of Other Organic Coloring Matter 22
Detection of Ultramarine Blue 23
4. Purity of Reagents and Water
Detection of Iron Blue 24
4.1 Purity of Reagents—Unless otherwise indicated, it is
ULTRAMARINE BLUE
intended that all reagents shall conform to the specifications of
Identification 25
theCommitteeonAnalyticalReagentsoftheAmericanChemi-
Moisture and Other Volatile Matter 26
cal Society, where such specifications are available. Other
Water-Soluble Matter 27
Detection of Basic Dye Derivatives 28 grades may be used, provided it is first ascertained that the
Detection of Other Organic Coloring Matter 29
reagent is of sufficiently high purity to permit its use without
1.3 The values stated in SI units are to be regarded as
lessening the accuracy of the determination.
standard. No other units of measurement are included in this
4.2 Purity of Water—Unless otherwise indicated, references
standard.
towatershallbeunderstoodtomeanreagentwaterconforming
1.4 This standard does not purport to address the safety
to Type II of Specification D1193.
concerns 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 limita-
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
tions prior to use.
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.
1 3
These test methods are under the jurisdiction of ASTM Committee D01 on Reagent Chemicals, American Chemical Society Specifications, American
Paint and Related Coatings, Materials, and Applications and are the direct Chemical Society, Washington, DC. For suggestions on the testing of reagents not
responsibility of Subcommittee D01.31 on Pigment Specifications. listed by the American Chemical Society, see Analar Standards for Laboratory
Current edition approved Dec. 1, 2014. Published December 2014. Originally Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
approved in 1950. Last previous edition approved in 2009 as D1135 – 86 (2009). and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,
DOI: 10.1520/D1135-86R14. MD.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D1135 − 86 (2014)
5. Preparation of Sample
5.1 Mix the sample thoroughly and take a representative
portion for analysis. Reduce any lumps or coarse particles to a
fine powder by grinding.
5.2 Grind extracted pigments to pass a No. 80 (180-µm)
sieve. Discard any skins that do not pass through the sieve.
Mix the finely ground pigment thoroughly.
Detailed requirements for this sieve are given in Specification E11.
IRON BLUE
(Prussian Blue, Chinese Blue, Milori Blue)
consistentresults,thespecimenpositionmustnotbechangedandtheoven
IDENTIFICATION
door must not be opened.
6. Procedure
8.3 Calculation and Report—Plot time against percent loss
in weight on rectilinear cross-section paper. Extrapolate the
6.1 To approximately 0.1 g of pigment in a 50-mL beaker,
linear portion of the curve to zero time. That portion beyond
add15mLofNaOHsolution(50g/L).Heattoboiling.Inafew
about 2 h will be essentially linear. Report the percent loss in
minutes the blue color should be completely destroyed, giving
weight at the extrapolated zero time as the percent moisture in
initsplacethecharacteristicreddishbrownprecipitateofferric
the pigment.
hydroxide.Add HCl (1+1) until faintly acid to litmus.The iron
blue should be reformed, yielding again the characteristic blue
NOTE 3—The pigment undergoes a slight loss in weight due to
color.
decomposition during the heating. The method of plotting and extrapola-
tion corrects for this loss.An approximate value for moisture content may
NOTE 1—If the NaOH treatment does not completely destroy the blue
be obtained by taking the reading at the end of the first hour’s heating.An
color, the evidence is strong that a foreign pigment is present. If this
occasional pigment may decompose rapidly at the oven temperature. In
occurs, it is best to filter the alkaline solution, weakly acidify the filtrate
such cases, determine moisture by the toluene distillation method (Section
with HCl (1+1), and add approximately 2 mL of a ferric salt solution
9).
(ferric sulfate or ferric alum (20 g/L)). The formation of a blue precipitate
established the pigment as consisting, at least in part, of iron blue.
MOISTURE BY TOLUENE DISTILLATION
MOISTURE BY THE BRABENDER MOISTURE
9. Procedure
TESTER
9.1 Determine the moisture content in accordance with
7. Apparatus
Sections 7 and 8 of Test Method D1208, but using 25 g of
7.1 Brabender Moisture Tester—The Brabender moisture pigment and 200 mL of toluene and adjusting the calculation
tester (Fig. 1) consists of a constant-temperature oven with
accordingly.
weighing apparatus attached. Specimens placed in the oven
WATER-SOLUBLE MATTER BY EXTRACTION
may be weighed without opening the oven door or removing
the specimen from the oven, as the balance scale is calibrated
10. Procedure
to read directly in percent of moisture.
10.1 Determine whether or not the pigment is easily wet by
8. Procedure
water at room temperature by adding a little to some water in
8.1 Set the temperature control at 160°C and allow the oven
a beaker. If it tends to float on top of the water with very little,
to reach this temperature before checking or making any if any, tendency to sink to the bottom or disperse throughout
weighing. Check the scale by placing a sample dish containing
the solution, even after agitation, it contains a hydrophobic
9.200 g standard analytical balance weights in the oven. The treating agent.
apparatus should read 8.0 % moisture. If it does not, adjust to
10.2 Weigh to 1 mg about 2.5 g of the pigment into a
a reading of 8.0 % by turning either the right hand or left hand
250-mL volumetric flask. If the pigment is hydrophobic as
foot screw.
tested above, moisten thoroughly with a few mL of ethyl
8.2 Weigh 10.000 g of the sample into the aluminum dish
alcohol (Note 4). If the pigment is easily wet with water, no
and place in the oven. For a series of specimens, all should be
alcohol is necessary. Fill the flask about half full with water
placed in the oven at as nearly the same time as possible. No
and shake to disperse the pigment thoroughly. Fill to the mark
specimen should occupy the position directly in front of the
and again shake. Allow to remain at room temperature for not
door.Weigh the specimen at the end of each hour for 5 h.After
less than 15 h, shaking from time to time, preferably with an
each weighing, return the specimen to its original place in the
automatic shaking device.
oven.
NOTE 4—Ethyl alcohol denatured with acetone (Formula No. 23A) or
NOTE 2—The dried pigment is very hygroscopic. In order to obtain denatured with methyl alcohol (Formula No. 3A) has been found suitable.
D1135 − 86 (2014)
FIG. 1 Brabender Moisture Tester
10.3 Let settle, filter through a dry filter paper, and discard 13. Procedure
the first 20 mL of the filtrate. Transfer 100 mL of the clear
13.1 Ignite about 1 g (weighed to 0.1 mg) of the sample at
filtrate to a weighed dish, and evaporate to dryness on a steam
a low temperature, just enough to decompose the last trace of
bath. Dry for1hinan oven at 105 6 2°C, cool, and weigh.
pigment but not high enough to render the iron difficultly
10.4 Calculation—Calculate the percent of water-soluble
soluble in HCl (Note 5). Cool, and add 15 mL of HCl (sp gr
matter as follows:
1.19) and a few drops of bromine. Cover with a watch glass
and evaporate to a sirup. Add about 15 mL of water, and boil.
Water 2 soluble matter,% 5 grams of residue 3100
It may be necessary to add a drop or two of HCl to effect
WATER-SOLUBLE SALTS BY ELECTRICAL
complete solution of the ferric iron residue. Filter and wash
CONDUCTIVITY
with hot water. Save the filtrate for the determination of
alumina hydrate (Section 16).
11. Procedure
NOTE 5—The ignition can conveniently be carried out in a 250-mL
11.1 Determine water-soluble salt content in accordance
beaker or a porcelain dish over a free flame. Oxidation of the specimen is
with Test Method D2448.
evidenced by a dull glowing.While being heated, it is advisable to roll the
specimen around in the beaker or dish exposing all of the surface to the
DETECTION OF ACID-INSOLUBLE EXTENDERS
oxygen of the air.Amoderately low flame should be used and the ignition
is complete when the specimen ceases to glow and acquires a uniform
12. Scope brown color.
12.1 Acid-insolubleextendersincludebariumsulfate,silica, 13.2 Aresidue of less than 3 mg that appears as small black
and silicates. Alumina may also be found, in part, with this specks can be neglected, since quite frequently a small amount
group. ofironisrenderedinsolubleorasmallamo
...
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: D1135 − 86 (Reapproved 2009) D1135 − 86 (Reapproved 2014)
Standard Test Methods for
Chemical Analysis of Blue Pigments
This standard is issued under the fixed designation D1135; 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.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope
1.1 These test methods cover procedures for the chemical analysis of blue pigments known commercially as iron blue, copper
phthalocyanine blue, and ultramarine blue.
1.2 The analytical procedures appear in the following order:
Sections
I ron Blue P igments
IRON BLUE PIGMENTS
Identification 6
Moisture by the Brabender Moisture Tester 7 and 8
Moisture by Toluene Distillation 9
Water-Soluble Matter by Extraction 10
Water-Soluble Salts by Electrical Conductivity 11
Detection of Acid-Insoluble Extenders 12 and 13
Detection of Acid-Soluble Extenders 14 to 17
Detection of Organic Colors and Lakes 18
C opper Phthalocyanine Blue Pigments
COPPER PHTHALOCYANINE BLUE PIGMENTS
Identification 19
Moisture and Other Volatile Matter 20
Detection of Basic Dye Derivatives 21
Detection of Other Organic Coloring Matter 22
Detection of Ultramarine Blue 23
Detection of Iron Blue 24
U ltramarine Blue
ULTRAMARINE BLUE
Identification 25
Moisture and Other Volatile Matter 26
Water-Soluble Matter 27
Detection of Basic Dye Derivatives 28
Detection of Other Organic Coloring Matter 29
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4 This standard does not purport to address the safety concerns 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.
2. Referenced Documents
2.1 ASTM Standards:
D280 Test Methods for Hygroscopic Moisture (and Other Matter Volatile Under the Test Conditions) in Pigments
These test methods are under the jurisdiction of ASTM Committee D01 on Paint and Related Coatings, Materials, and Applications and are the direct responsibility of
Subcommittee D01.31 on Pigment Specifications.
Current edition approved June 1, 2009Dec. 1, 2014. Published June 2009December 2014. Originally approved in 1950. Last previous edition approved in 20042009 as
D1135 – 86 (2004).(2009). DOI: 10.1520/D1135-86R09.10.1520/D1135-86R14.
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’sstandard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D1135 − 86 (2014)
D1193 Specification for Reagent Water
D1208 Test Methods for Common Properties of Certain Pigments
D2448 Test Method for Water-Soluble Salts in Pigments by Measuring the Specific Resistance of the Leachate of the Pigment
E11 Specification for Woven Wire Test Sieve Cloth and Test Sieves
3. Significance and Use
3.1 These test methods are suitable for determining if impurities are present and establishing that the required pigments are
present. These test methods may be used for manufacturing quality control.
4. Purity of Reagents and Water
4.1 Purity of Reagents—Unless otherwise indicated, it is intended that all 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.
4.2 Purity of Water—Unless otherwise indicated, references to water shall be understood to mean reagent water conforming to
Type II of Specification D1193.
5. Preparation of Sample
5.1 Mix the sample thoroughly and take a representative portion for analysis. Reduce any lumps or coarse particles to a fine
powder by grinding.
5.2 Grind extracted pigments to pass a No. 80 (180-μm) sieve. Discard any skins that do not pass through the sieve. Mix the
finely ground pigment thoroughly.
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.
Detailed requirements for this sieve are given in Specification E11.
IRON BLUE
(Prussian Blue, Chinese Blue, Milori Blue)
IDENTIFICATION
6. Procedure
6.1 To approximately 0.1 g of pigment in a 50-mL beaker, add 15 mL of NaOH solution (50 g/L). Heat to boiling. In a few
minutes the blue color should be completely destroyed, giving in its place the characteristic reddish brown precipitate of ferric
hydroxide. Add HCl (1+1) until faintly acid to litmus. The iron blue should be reformed, yielding again the characteristic blue
color.
NOTE 1—If the NaOH treatment does not completely destroy the blue color, the evidence is strong that a foreign pigment is present. If this occurs,
it is best to filter the alkaline solution, weakly acidify the filtrate with HCl (1+1), and add approximately 2 mL of a ferric salt solution (ferric sulfate or
ferric alum (20 g/L)). The formation of a blue precipitate established the pigment as consisting, at least in part, of iron blue.
MOISTURE BY THE BRABENDER MOISTURE TESTER
7. Apparatus
7.1 Brabender Moisture Tester—The Brabender moisture tester (Fig. 1) consists of a constant-temperature oven with weighing
apparatus attached. Specimens placed in the oven may be weighed without opening the oven door or removing the specimen from
the oven, as the balance scale is calibrated to read directly in percent of moisture.
8. Procedure
8.1 Set the temperature control at 160°C and allow the oven to reach this temperature before checking or making any weighing.
Check the scale by placing a sample dish containing 9.200 g standard analytical balance weights in the oven. The apparatus should
read 8.0 % moisture. If it does not, adjust to a reading of 8.0 % by turning either the right hand or left hand foot screw.
8.2 Weigh 10.000 g of the sample into the aluminum dish and place in the oven. For a series of specimens, all should be placed
in the oven at as nearly the same time as possible. No specimen should occupy the position directly in front of the door. Weigh
the specimen at the end of each hour for 5 h. After each weighing, return the specimen to its original place in the oven.
D1135 − 86 (2014)
FIG. 1 Brabender Moisture Tester
NOTE 2—The dried pigment is very hygroscopic. In order to obtain consistent results, the specimen position must not be changed and the oven door
must not be opened.
8.3 Calculation and Report—Plot time against percent loss in weight on rectilinear cross-section paper. Extrapolate the linear
portion of the curve to zero time. That portion beyond about 2 h will be essentially linear. Report the percent loss in weight at the
extrapolated zero time as the percent moisture in the pigment.
NOTE 3—The pigment undergoes a slight loss in weight due to decomposition during the heating. The method of plotting and extrapolation corrects
for this loss. An approximate value for moisture content may be obtained by taking the reading at the end of the first hour’s heating. An occasional pigment
may decompose rapidly at the oven temperature. In such cases, determine moisture by the toluene distillation method (Section 9).
MOISTURE BY TOLUENE DISTILLATION
9. Procedure
9.1 Determine the moisture content in accordance with Sections 7 and 8 of Test Method D1208, but using 25 g of pigment and
200 mL of toluene and adjusting the calculation accordingly.
WATER-SOLUBLE MATTER BY EXTRACTION
10. Procedure
10.1 Determine whether or not the pigment is easily wet by water at room temperature by adding a little to some water in a
beaker. If it tends to float on top of the water with very little, if any, tendency to sink to the bottom or disperse throughout the
solution, even after agitation, it contains a hydrophobic treating agent.
D1135 − 86 (2014)
10.2 Weigh to 1 mg about 2.5 g of the pigment into a 250-mL volumetric flask. If the pigment is hydrophobic as tested above,
moisten thoroughly with a few mL of ethyl alcohol (Note 4). If the pigment is easily wet with water, no alcohol is necessary. Fill
the flask about half full with water and shake to disperse the pigment thoroughly. Fill to the mark and again shake. Allow to remain
at room temperature for not less than 15 h, shaking from time to time, preferably with an automatic shaking device.
NOTE 4—Ethyl alcohol denatured with acetone (Formula No. 23A) or denatured with methyl alcohol (Formula No. 3A) has been found suitable.
10.3 Let settle, filter through a dry filter paper, and discard the first 20 mL of the filtrate. Transfer 100 mL of the clear filtrate
to a weighed dish, and evaporate to dryness on a steam bath. Dry for 1 h in an oven at 105 6 2°C, cool, and weigh.
10.4 Calculation—Calculate the percent of water-soluble matter as follows:
Water 2 soluble matter,%5 grams of residue 3100
WATER-SOLUBLE SALTS BY ELECTRICAL CONDUCTIVITY
11. Procedure
11.1 Determine water-soluble salt content in accordance with Test Method D2448.
DETECTION OF ACID-INSOLUBLE EXTENDERS
12. Scope
12.1 Acid-insoluble extenders include barium sulfate, silica, and silicates. Alumina may also be found, in part, with this group.
13. Procedure
13.1 Ignite about 1 g (weighed to 0.1 mg) of the sample at a low temperature, just enough to decompose the last trace of pigment
but not high enough to render the iron difficultly soluble in HCl (Note 5). Cool, and add 15 mL of HCl (sp gr 1.19) and a few drops
of bromine. Cover with a watch glass and evaporate to a sirup. Add about 15 mL of water, and boil. It may be necessary to add
a drop or two of HCl to effect complete solution of the ferric iron residue. Filter and wash with hot water. Save the filtrate for the
determination of alumina hydrate (Section 16).
NOTE 5—The ignition can conveniently be carried out in a 250-mL beaker or a porcelain dish over a free flame. Oxidation of the specimen is evidenced
by a dull glowing. While being heated, it is advisable to roll the specimen around in the beaker or dish exposing all of the surface to the oxygen of the
air. A moderately low flame should be used and the ignition is complete when the specimen ceases to glow and acquires a uniform brown color.
13.2 A residue of less than 3 mg that appears as small black specks can be neglected, since quite frequently a small amount of
iron is rendered insoluble or a small amount of blue pigment escapes destruction. Ignite the residue and weigh. If appreciably more
than 3 mg are present, extenders should be suspected, and if it is required to know which extenders are present, analyze the residue
for silica, barium sulfate, and alumina.
NOTE 6—If alumina is present, it may appear both with the acid-insoluble and acid-soluble extenders. As a rule, most of it will appear with the
acid-soluble extenders.
DETECTION OF ACID-SOLUBLE EXTENDERS
14. Scope
14.1 Acid-soluble extenders include the alkaline earth carbonates or sulfates, magnesium carbonate, and alumina hydrate.
15. Reagents
15.1 Ammonium Oxalate Solution—Dissolve 40 g of ammonium oxalate monohydrate in warm water and dilute to 1 L.
15.2 Ammonium Phosphate Solution—Dissolve 100 g of (NH ) HPO in water and dilute to 1 L.
4 2 4
16. Procedure for Alumina Hydrate
16.1 To the filtrate from 13.1, add NaOH solution (50 g/L) until just alkaline; then add 5 mL excess. Boil for about 2 min and
let stand in a warm place until the hydrous iron oxide is coagulated. Filter through a rapid filter paper, wash a few times with hot
water, and discard the precipitate.
16.2 To the filtrate add 7 mL of HCl (1+1). Add NH OH (1+4) until just ammoniacal. Boil about 2 min. If no precipitate is
apparent, allow to stand about ⁄2 h. If the solution is still clear, no alumina hydrate is present. A white gelatinous precipitate
indicates alumina hydrate. Filter and save the filtrate for the detection of alkaline earth and magnesium salts (Section 17).
16.3 If a rough estimate of the amount of alumina hydrate is desired, the residue may be washed, dried, ignited, and weighed
as Al O .
2 3
17. Procedure for Alkaline Earth and Magnesium Salts
17.1 To the filtrate from Section 16, add HCl (1+1) until faintly acid. Divide the filtrate into two portions.
D1135 − 86 (2014)
17.2 To one portion of the filtrate, add 15 mL of (NH ) HPO solution and neutralize with NH OH (sp gr 0.90). Add 10 mL
4 2 4 4
excess NH OH. If no precipitate forms immediately, let stand for a short time in a cool place with occasional vigorous stirring.
Rub the inside of the beaker from time to time with a glass rod to initiate crystallization. A white microcrystalline precipitate
indicates the presence of magnesium salts and possibly some alkaline earth salts as well.
17.3 To the other portion of the filtrate, add 5 mL of ammonium oxalate solution. Make slightly alkaline with NH OH (sp gr
0.90). If no precipitate forms immediately, warm on a hot plate and let stand for a short time. A white microcrystalline precipitate
indicates the presence of alkaline earth salts. If it is required to know specifically which acid soluble extenders are present, any
of the established tests for these metal salts may be employed.
DETECTION OF ORGANIC COLORS AND LAKES
18. Procedure
18.1 Boil 2 g of the sample for 2 min with 25 mL of water. Let settle and decant the supernatant liquid. Similarly, boil the residue
with 25 mL of denatured ethyl alcohol (95 %) and decant as before. Likewise boil with 25 mL of chloroform and again decant.
If any one of the above solutions is colored, organic colors are present. If all solutions remain colorless, disregarding
...
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