ASTM E291-18

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.
Designation: E291 − 18
Standard Test Methods for
Chemical Analysis of Caustic Soda and Caustic Potash
(Sodium Hydroxide and Potassium Hydroxide)
This standard is issued under the fixed designation E291; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber 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* 1.7 This international standard was developed in accor-
dance with internationally recognized principles on standard-
1.1 These test methods cover only the analyses usually
ization established in the Decision on Principles for the
required on the following commercial products:
Development of International Standards, Guides and Recom-
1.1.1 Caustic soda (sodium hydroxide), 50 and 73% li-
mendations issued by the World Trade Organization Technical
quors; anhydrous (solid, flake, ground, or powdered), and
Barriers to Trade (TBT) Committee.
1.1.2 Caustic potash (potassium hydroxide), 45% liquor;
anhydrous (solid, flake, ground, or powdered).
2. Referenced Documents
1.2 Theanalyticalproceduresappearinthefollowingorder:
2.1 ASTM Standards:
Alkalinity (Total), Titrimetric (for 50 to 100 % 3to4
D1193Specification for Reagent Water
NaOH and 45 to 100 % KOH)
D6809Guide for Quality Control and Quality Assurance
Carbonate, Gas-Volumetric (0.001 g CO , min) 4 to 7
Carbonate, Gravimetric (0.001 g CO , min) 7 to 10
Procedures for Aromatic Hydrocarbons and Related Ma-
−
Chloride, Titrimetric, (0.001 g Cl ,min) 10to11
terials
Chloride, Potentiometric Titration (0.3 to 1.2 %) 11 to 12
E29Practice for Using Significant Digits in Test Data to
Chloride, Ion Selective Electrode (0.6 to 120 µg/g) 12 to 13
Iron, Photometric (0.005 mg Fe, min) 13 to 15
Determine Conformance with Specifications
Sulfate, Gravimetric, (0.002 g SO ,min) 15to16
E60Practice for Analysis of Metals, Ores, and Related
Keywords 16
Materials by Spectrophotometry
1.3 Units—The values stated in SI units are to be regarded
E180Practice for Determining the Precision of ASTM
asstandard.Nootherunitsofmeasurementareincludedinthis
Methods for Analysis and Testing of Industrial and Spe-
standard with the exception of inch-pound units for apparatus
cialty Chemicals (Withdrawn 2009)
descriptions.
E200Practice for Preparation, Standardization, and Storage
1.4 In determining the conformance of the test results using
of Standard and Reagent Solutions for ChemicalAnalysis
this method to applicable specifications, results shall be
E691Practice for Conducting an Interlaboratory Study to
rounded off in accordance with the rounding-off method of
Determine the Precision of a Test Method
Practice E29.
2.2 Other Document:
OSHA Regulations, 29 CFRparagraphs 1910.1000 and
1.5 ReviewthecurrentSafetyDataSheet(SDS)fordetailed
1910.1200
information concerning toxicity, first-aid procedures, handling,
and safety precautions.
3. Significance and Use
1.6 This standard does not purport to address all of the
3.1 Caustic soda and caustic potash are used in a large
safety concerns, if any, associated with its use. It is the
number of manufacturing processes. The chemicals are avail-
responsibility of the user of this standard to establish appro-
ableinseveralgradesdependingontheirintendeduse.Thetest
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
Specific hazard statements are given in Section 6.
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
These test methods are under the jurisdiction of ASTM Committee D16 on the ASTM website.
Aromatic, Industrial, Specialty and Related Chemicals and are the direct responsi- The last approved version of this historical standard is referenced on
bility of Subcommittee D16.12 on Caustics and Peroxides. www.astm.org.
CurrenteditionapprovedJan.1,2018.PublishedMay2018.Originallyapproved Available from U.S. Government Printing Office, Superintendent of
in 1965. Last previous edition approved in 2009 as E291–09. DOI: 10.1520/ Documents, 732 N. Capitol St., NW, Washington, DC 20401-0001, http://
E0291-18. www.access.gpo.gov.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E291 − 18
methods listed in 1.2 provide procedures for analyzing caustic that representative samples may be ensured. Additional pre-
soda and caustic potash to determine if they are suitable for cautions may be necessary if trace constituents, not covered in
their intended use. these test methods, are to be determined. Instructions for such
procedures may be obtained from the publications of most
4. Apparatus
major producers. Sampling techniques must be such as to limit
or prevent atmospheric exposure since sodium and potassium
4.1 Photometers and Photometric Practice—Photometers
hydroxides, both as aqueous solutions and as anhydrous
and photometric practice used in these test methods shall
products, rapidly absorb moisture and carbon dioxide (and
conform to Practice E60.
other acid gases) from the atmosphere. The aqueous solutions
5. Reagents
arecorrosiveandsamplingdevicesandsamplecontainersmust
beselectedtoavoidcontaminationwithanyconstituentlaterto
5.1 Purity of Reagents—Reagent grade chemicals shall be
be determined. Strong aqueous solutions of these alkalies are
used in all tests. Unless otherwise indicated, it is intended that
available commercially under the names liquid caustic soda
all reagents shall conform to the specifications of the Commit-
and liquid caustic potash. Liquid caustic potash at a concen-
tee onAnalytical Reagents of theAmerican Chemical Society,
tration of 45% remains liquid at temperatures down to−29°C,
where such specifications are available. Other grades may be
and freezing or crystallization will only be encountered under
used, provided it is first ascertained that the reagent is of
severe cold weather. Caustic soda liquors are usually shipped
sufficiently high purity to permit its use without lessening the
in insulated tank cars at elevated temperatures, and minimum
accuracy of the determination.
temperatures must be maintained if unloading and sampling
5.2 Purity of Water—Unless otherwise indicated, references
problems are to be avoided. Viscosity increases near the
to water shall be understood to mean Type II or Type III
freezing point and creates pumping problems. Even partial
reagent water conforming to Specification D1193.
freezing changes the composition of the remaining liquor and
causes sampling and analysis problems. Be sure contents are
6. Hazards
completely liquid and well mixed before sampling. The fol-
6.1 Sodium and potassium hydroxides are caustic alkalies
lowingminimumtemperaturesshouldbemaintainedforproper
which, in their anhydrous or strong solution form, are hazard-
sampling of bulk shipments:
ous materials. In contact with the skin they produce burns
50 % NaOH liquor 20°C
which may be quite serious unless promptly treated. Their
53 % NaOH liquor 30°C
actionisinsidioussincetheyproducenoimmediatestingingor 70 to 73 % NaOH liquor 71°C
burningsensationanddamagemayresultbeforetheirpresence
7.2 Sample Containers—The choice of container construc-
is realized.
tionmaterialisimportantforcausticliquorsamples,especially
6.2 Eyes are particularly vulnerable to severe damage from
for those to be taken or held at elevated temperatures. Glass
these alkalies. can be used except where silica is to be determined. Polyeth-
ylene or polypropylene containers which have high-
6.3 Laboratory workers handling these alkalies should use
temperature properties may also be used. Nickel is the best
safety goggles or face shields and rubber gloves and avoid
practical metal for a metallic sample container for caustic
spillage on clothing. These materials rapidly attack wool and
liquors.Fortheanalysisof73%causticsoda,theentiresample
leather.
should be in the liquid state before removing any portion, and
6.4 Spilledcausticshouldbeflushedawaywithwaterwhere
such portions must then be used in their entirety to avoid the
possible, or covered with absorbent material (such as sawdust,
factor of segregation on freezing. Caustic soda of 73%
vermiculite, or baking soda) and swept up and discarded in
concentrationmayalsobe“cast”intoglassorplasticbottlesor
accordance with all applicable federal, state, and local health
tubes, or nickel or silver metallic molds. The molds are later
and environmental regulations. Last traces may be neutralized
removed and the samples chipped or crushed for analysis. If
with dilute acetic acid and the area washed with water.
this is done, the factors of segregation on freezing and
6.5 Perchloricacidistoxic,corrosive,andastrongoxidizer. atmospheric exposure while crushing must be borne in mind.
Laboratory workers handling this acid should use safety
7.3 Sampling Devices and Techniques:
goggles or face shields and rubber gloves.
7.3.1 Liquid Caustic—Simple “dipper” or “tap” samples
from large quantity shipments or tanks of caustic liquor are
7. Sampling
inadequate for purchaser and vendor purposes. Numerous
7.1 General—Thenatureofthecausticalkaliesissuchasto
specially designed devices are available to procure samples
require special care at all points of sampling and preparation
fromvariouslevelsintanks.Ausefultypeofsuchsamplersfor
for analysis. The following information is included in order
smalltankshasthreeorfivecontainersmountedonasinglerod
so that when the device is lowered into a tank and the stoppers
are pulled, samples are simultaneously taken at the different
Reagent Chemicals, American Chemical Society Specifications, American
Chemical Society, Washington, DC. For suggestions on the testing of reagents not
levels. These are then combined to provide a representative
listed by the American Chemical Society, see Analar Standards for Laboratory
average sample. Shipments should be sampled at least at the
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
upper,middle,andlowerthirds.Samplesshouldneverbetaken
and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,
MD. at the surface of the liquid. If it is not necessary to analyze the
E291 − 18
TABLE 1 Sample Size for Total Alkalinity
liquor before unloading, sampling may be accomplished by a
“continuous drip” from a small tap-off with the regulating Sample Sample Size, g
valve in a vertical section of the unloading line. The “drip” is 50 % NaOH 65 to 78
73 % NaOH 45 to 52
so timed as to collect the desired amount of sample uniformly
Anhydrous NaOH 32 to 40
during the time of unloading.
45 % KOH 100 to 120
7.3.2 Anhydrous Products: Anhydrous KOH 48 to 60
7.3.2.1 Commercial anhydrous caustic soda or caustic pot-
ash is packaged in drums in solid, flake, ground, or powdered
TABLE 2 Sample Size for Carbonate Analysis
forms. Sampling and handling of these materials must be done
Percent Na CO or Percent
with minimum atmospheric exposure. 2 3
Sample Size, g
K CO Expected
2 3
7.3.2.2 In the case of flake, ground, or powdered sodium or
0.01 to 0.10 8 to 10
potassium hydroxides, the top 75 or 100 mm of material in a
0.10 to 0.50 5 to 7
drumshouldfirstberemovedandasamplethentakenfromthe
0.50 to 1.00 2 to 4
center part of the drum. The sample should be placed imme-
diately in a suitable wide-mouth container then closed and
sealed with taps or wax.
11.2 Weigh the sample to the nearest 1 mg and transfer it to
7.3.2.3 Solid caustic shall be packaged by filling metal
a 1-L volumetric flask using several rinses of water to remove
drumswithmoltenanhydrousproductandallowingdrumsand
all traces of caustic from the weighing bottle. Dilute the
contents to cool before sealing air tight. On cooling and
solution to about 400 mL with water and cool to room
solidifying, impurities present in the caustic tend to segregate
temperature. After cooling, dilute to 1 L and mix thoroughly.
andconcentrateinthebottomsection.Tosamplesuchmaterial
11.3 Withavolumetricpipet,transfer50mL(seeNote1)of
properly, the metal drum must be opened at the vertical seam
the prepared solution to a 500-mLErlenmeyer flask and add 2
and removed. The solid cake may then be sampled either by
to 4 drops of modified methyl orange indicator solution (see
drilling at representative levels with a 19-mm auger bit (may
Note 2).Titrate this solution with standard 1.0 meq/mLacid to
cause metal contamination) or by splitting the cake in half
a gray end point (see Note 3) and record the volume and
vertically with hammer and chisel and chiseling off represen-
temperature of acid used. Correct the acid meq/mL for any
tative small fragments so that the total sample represents a
difference from the standardization temperature by use of the
vertical cross section through the cake. In either case, the
factor ∆N/°C=0.00035 between 20 and 30°C adding the
sample shall be promptly bottled and sealed in a wide-mouth
correctionwhentemperatureofuseisbelow(subtractingwhen
container. In the laboratory, the lumps shall be reduced to
above)thetemperatureofstandardization.(SeePracticeE200.)
convenient size by enclosing in several thicknesses of clean
cloth or kraft paper and pounding with a hammer.The crushed NOTE 1—If a 100-mLburet is to be used for this titration use a 100-mL
aliquot.
materialshallbebottledandthoroughlymixedbeforeanalysis.
NOTE 2—If desired, methyl orange indicator solution may be used.
NOTE 3—The analyst should attempt to end the titration at the same
TOTAL ALKALINITY
shade of color as was used for the end point in the standardization of the
acid.
8. Scope
8.1 This test method covers the determination of the total 12. Calculation
alkalinity of 50 and 73% liquid caustic soda, 45% liquid
12.1 Calculate the total alkalinity as % sodium oxide or
caustic potash, and anhydrous caustic soda and caustic potash.
potassium oxide as follows:
9. Summary of Test Method A 3 B 30.030990
Sodium oxide,% mass 5 3100 (1)
W
9.1 Total alkalinity is determined by titration with standard
A 3 B 30.047102
hydrochloric acid solution using methyl orange indicator
Potassium oxide,% mass 5 3100 (2)
solution or modified methyl orange indicator solution. W
where:
10. Reagents
A = acid required for titration of the sample, mL
10.1 Hydrochloric (or Sulfuric Acid), Special(1.0 meq/
B = corrected meq/mL of the acid, and
mL)—Prepare in accordance with Practice E200.
W = mass of sample in the aliquot, g.
10.2 Methyl Orange Indicator Solution—SeePracticeE200.
12.2 Calculate the total alkalinity as the respective hydrox-
10.3 Modified Methyl Orange Indicator Solution—SeePrac-
ide as follows:
tice E200.
Sodium hydroxide,% mass 5 1.2907 3 % mass Na O (3)
10.4 Water, Distilled, carbon dioxide-free (freshly boiled
Potassium hydroxide,% mass 5 1.1912 3 % mass K O (4)
and cooled).
12.3 If actual hydroxide content is desired, the carbonate
11. Procedure contentmustbedeterminedseparatelyasdescribedinSections
16–25 or Sections27–35. Then:
11.1 Transfer to a tared, covered weighing bottle a sample
of such size as determined from Table 1. Sodium hydroxide actual,% mass 5 A 2 B 30.755 (5)
~ ! ~ !
E291 − 18
Potassium hydroxide actual,% mass 5 C 2 D 30.812 SODIUM CARBONATE OR POTASSIUM
~ ! ~ !
CARBONATE (GAS-VOLUMETRIC TEST METHOD)
(6)
where:
16. Scope
A = % mass NaOH (total alkali),
16.1 Thistestmethoddescribesthegas-volumetricdetermi-
B = % mass Na CO ,
2 3
nation of sodium carbonate or potassium carbonate in caustic
C = % mass KOH (total alkali), and
soda or caustic potash respectively. The lower limit of deter-
D = % mass K CO .
2 3
mination is 0.001 g as carbon dioxide.
13. Report
17. Summary of Test Method
13.1 Reportthe%massofsodiumoxideorpotassiumoxide
to the nearest 0.01%.
17.1 Carbon dioxide is evolved by acid decomposition of
carbonate in the sample. The volume of CO is measured and
14. Precision and Bias
calculated as sodium carbonate or potassium carbonate.
14.1 The following criteria should be used in judging the
acceptability of results (Note 4):
18. Apparatus
14.1.1 Repeatability (Single Analyst)—The standard devia-
18.1 Carbon Dioxide Evolution, Measurement, and Absorp-
tion for a single determination has been estimated to be
tion Device, as illustrated in Fig. 1 and consisting of the
0.057% absolute at 144 DF. The 95% limit for the difference
following special parts:
between two such runs is 0.16% absolute.
18.1.1 Aspirator Bottle, J, 500-mL, used for leveling.
14.1.2 Laboratory Precision (Within-Laboratory, Between-
18.1.2 Compensator Tube, C, as shown in Fig. 1 and
Days Variability)—The standard deviation of results (each the
conforming to details shown in Fig. 2.
average of duplicates), obtained by the same analyst on
18.1.3 Gas Buret, B, 100-mL, modified as shown in Fig. 3.
different days, has been estimated to be 0.17% absolute at 72
18.1.4 Gas Pipet, K, preferably of the bubbler type.
df. The 95% limit for the difference between two such
18.1.5 Glass Condenser with Jacket, L, 12 in. (305 mm)
averages is 0.48% absolute.
long and 1 ⁄4 in. (32 mm) in outside diameter. The condenser
14.1.3 Reproducibility (Multilaboratory)—The standard de-
tube shall be of 8-mm outside diameter glass tubing.
viation of results (each the average of duplicates), obtained by
18.1.6 Tubing Assembly, D, as illustrated in Fig. 4.
analysts in different laboratories, has been estimated to be
0.25% absolute at 10 df. The 95% limit for the difference
19. Reagents
between two such averages is 0.70% absolute.
19.1 Hydrochloric Acid (sp gr 1.19)—Concentrated hydro-
NOTE 4—These precision estimates are based on an interlaboratory
chloric acid (HCl).
study on five samples comprising 45% KOH, 50% NaOH, 73% NaOH,
19.2 Methyl Orange Indicator Solution (1 g/L)—See Prac-
anhydrous NaOH, and anhydrous KOH. The number of laboratories
analyzing each sample ranged from seven to fifteen with one analyst in
tice E200.
each performing duplicate determinations and repeating one day later.
19.3 Potassium Hydroxide(35%Solution)—Dissolve350g
Practice E180 was used in developing these precision estimates.
of potassium hydroxide (KOH) in 650 mL of water.
14.2 Bias—The bias of this test method has not been
19.4 Sodium Carbonate (Na CO ), anhydrous.
determined because of the unavailability of suitable reference
2 3
materials.
19.5 Water, Distilled, carbon dioxide-free (freshly boiled
and cooled).
15. Quality Guidelines
15.1 Laboratories shall have a quality control system in
20. Preparation of Apparatus
place.
20.1 Assemble the apparatus as shown in Fig. 1 after
15.1.1 Confirm the performance of the test instrument or
preparing the various parts as follows:
test method by analyzing a quality control sample following
20.1.1 Compensator Tube, C—Warm the bulb slightly and
the guidelines of standard statistical qualify control practices.
place two or three drops of water in the tube. Then add
15.1.2 Aquality control sample is a stable material isolated
sufficientmercurysothatwhenthetubeisatroomtemperature
from the production process and representative of the sample
and normal atmospheric pressure the mercury columns are
being analyzed.
approximately level and are about 1 ⁄2 to 2 in. (38 to 51 mm)
15.1.3 When QA/QC protocols are already established in
in length. This is a trial and error operation. Manipulation by
the testing facility, these protocols are acceptable when they
alternately warming and cooling the bulb is helpful in making
confirm the validity of the test results.
this adjustment.
15.1.4 When there are no QA/QC protocols established in
20.1.2 Absorption Pipet, K—Fill this pipet with sufficient
the testing facility, use the guidelines described in Guide
caustic potash solution to fill the left bulb completely and to
D6809 or similar statistical quality control practices.
have about 1-in. (25-mm) depth in the right bulb. Protect the
solution from the atmosphere with a gas expansion bag, K .
6 2
Supporting data have been filed at ASTM International headquarters and may
20.1.3 Glass Water Jacket, O—Bore suitable holes in two
be obtained by requesting RR:E15-1040. Contact ASTM Customer Service at
service@astm.org. No.12rubberstoppers,asshowninFig.1,tosupporttheburet
E291 − 18
A—Water above mercury column of manometer. I—Three-way stop cock with TFE-fluorocarbon plug.
B—Gas buret, Fig. 3. J—Aspirator bottle.
C—Compensator tube, Fig. 2. K—Absorption pipet for KOH solution.
D—Capillary glass tubing with small bubble at D , Fig. 4.K —Gas expansion bag.
1 1
E—Filling funnel. L—Glass condenser.
F—Heavy rubber or plastic connectors. M—Rubber stopper.
G—Rubber tubing about 91 cm long. N—Sample receptacles.
H ,H , H—Two way glass stop cock. O—Glass water jackets, 63.5 mm in diameter.
1 2
FIG. 1 Carbon Dioxide Evolution, Measurement, and Absorption Device
and compensator tube. An additional hole in the top stopper volumetric pipet, determine the amount of carbon dioxide
will permit easy filling with water. (CO ) it contains by the evolution method as described in
20.1.4 Use a ring stand about 30 in. (760 mm) high with a
Section21.Atleastfivedeterminationsshouldbemadeandthe
heavy base to mount the various parts of the apparatus with
results averaged. The machine factor (F) is calculated as
suitable clamps. Arrange the parts so that glass tube connec-
follows:
tionsareascloseaspossibleandheldwiththerubberorplastic
0.2000 30.41523
tubing connectors, F.
F 5 (7)
A
20.1.5 Aspirator Bottle, J—Fill with a 20% solution of
sodium chloride (NaCl) or calcium chloride (CaCl ), acidify
where:
slightly, and add a few drops of methyl red indicator solution
A =CO found, mL.
to color the solution. Distilled water may be used in place of
the salt solution.
22. Procedure
21. Calibration of Apparatus (Machine Factor)
22.1 Have sample flask N clean and dry. Stopper the flask
with a rubber stopper or cork and weigh to the nearest 0.01 g.
21.1 Thefactormaybedeterminedtheoretically,butisdone
Transferthefollowingapproximatemassofcaustictotheflask,
more conveniently by a series of actual tests on a sample of
replace the stopper and reweigh to the nearest 0.01 g. After
known carbon dioxide content. Weigh 2.000 g of anhydrous
weighing, add a small piece of iron wire about the size of a
NaCO , dissolve in 25 mL of water, dilute to 100 mL in a
pinhead, 1 drop of methyl orange indicator solution, and water
volumetric flask at room temperature, and mix thoroughly.
Using 10-mL aliquot portions of this, measured by means of until flask N is about three quarters full. Replace the stopper.
E291 − 18
FIG. 4 Tubing Assembly
FIG. 2 Compensator Tube
22.2 Before connecting N to the apparatus, make the fol-
lowing adjustments:
22.2.1 Check the level of the potash solution in K with
relationtostopcock I.Thepotashliquorshouldfilltheentrance
tube up to a previously marked point approximately 1 cm
belowstopcock I.Ifsuchisnotthecase,close H ,open H,turn
I to connect J with K, and lower J to bring the level of the
potash up to the previously marked point. Turn three-way
stopcock I one-quarter turn to close all openings.
22.2.2 With stopcock H open, turn stopcock H to the open
position, level the mercury columns by manipulation of level-
ing bottle J and close H .
22.2.3 Now open stopcock I to connect B with the tube
leading to N, fill the buret and tube with the retaining solution
by raising J, and close H when the condenser tube is filled.
22.2.4 Openstopcock H andrinsethefunnel Eandstopper
with water.
22.3 Connect Ntotheapparatusandclosestopcock H .Into
E pour an amount of concentrated HCl slightly more than
enough to neutralize the sample. Now open stopcock H and
then H sufficiently to let the acid drop slowly into N until the
solution is acid, and close H .
22.4 Fill E nearly full with water, heat the contents of N to
boiling, and continue boiling very gently for at least 2 min.
Remove the burner, open stopcock H and lower J (if neces-
sary)untilthewaterfrom Efills Nandtheconnectingtubejust
up to I. Give three-way cock I one-quarter turn to cut off all
NOTE 1—Dimensions of tubing diameters are approximate.
openings.
FIG. 3 Gas Buret
22.5 Raise J until its liquid level is approximately the same
asthewaterintheburet,open H ,andraiseorlower Juntilthe
E291 − 18
mercury columns in the compensator are level; then close H Table3attheindicateddegreesoffreedom.The95%limitfor
and H and read the buret. Record this buret reading as A. thedifferencebetweentwosuchaveragesisalsogiveninTable
3.
22.6 Holding J slightly above the liquid level in B, open H
25.1.3 Reproducibility (Multilaboratory)—The standard de-
and turn I to connect with the absorption pipet K. Raise
viation of results (each the average of duplicates), obtained by
leveling bottle J to force the gas into potash pipet K until the
analysts in different laboratories, has been estimated to be the
liquidin Breachesaheightapproximatelyequivalenttothatof
valuegiveninTable3attheindicateddegreesoffreedom.The
Stopcock I.Atthispointlower Jtoreturnthegastoburet Band
95%limitforthedifferencebetweentwosuchaveragesisalso
bring the potash level up to the previously marked point. This
given in Table 3.
procedure should be repeated at least twice more to absorb the
carbon dioxide completely.After three passes into K, bring the
NOTE 5—These precision estimates are based on an interlaboratory
potash liquor level up to the previously marked point and turn
study on six samples with carbonate contents as follows:
I one-quarter turn. Hold J at the approximate water level of B,
Approximate
open H ,levelthemercurycolumnsasbefore,andclose Hand
1 Percentage of
Sample Carbonate
H and read the buret. Record this buret reading as B.
45 % KOH 0.01
22.7 The difference (A− B), represents the millilitres of
50 % NaOH 0.20, 0.05, 0.13
73 % NaOH 0.08
CO evolved and absorbed. This difference, multiplied by a
Anhydrous NaOH 0.35
machine factor, gives the mass of CO in the sample.
One analyst in each of fourteen laboratories performed duplicate
23. Calculation
determinations and repeated one day later. Practice E180 was used in
developing these precision estimates.
23.1 Calculate the % mass solution carbonate or potassium
carbonate present as follows:
25.2 Bias—The bias of this test method has not been
determined because of the unavailability of suitable reference
~A 2 B! 3 2.4083
Sodium carbonate,% mass 5 3100 (8)
materials.
W
A 2 B 3 F 33.1405
~ !
Potassium carbonate,% mass 5 3100 26. Quality Guidelines
W
(9) 26.1 Laboratories shall have a quality control system in
place.
where:
26.1.1 Confirm the performance of the test instrument or
A = buret reading before KOH addition,
test method by analyzing a quality control sample following
B = buret reading after KOH addition,
the guidelines of standard statistical quality control practices.
F = machine factor, and
26.1.2 Aquality control sample is a stable material isolated
W = sample used, g.
from the production process and representative of the sample
24. Report being analyzed.
26.1.3 When QA/QC protocols are already established in
24.1 Report the % mass of sodium carbonate or potassium
the testing facility, these protocols are acceptable when they
carbonate to the nearest 0.01%.
confirm the validity of the test results.
25. Precision and Bias
26.1.4 When there are no QA/QC protocols established in
the testing facility, use the guidelines described in Guide
25.1 The following criteria should be used for judging the
D6809 or similar statistical quality control practices.
acceptability of results (see Note 5):
25.1.1 Repeatability (Single Analyst)—The standard devia-
tion for a single determination has been estimated to be the
SODIUM CARBONATE OR POTASSIUM
valuegiveninTable3attheindicateddegreesoffreedom.The
CARBONATE (GRAVIMETRIC TEST METHOD)
95% limit for the difference between two such runs is also
given in Table 3.
27. Scope
25.1.2 Laboratory Precision (Within-Laboratory, Between-
Days Variability)—The standard deviation of results (each the 27.1 This test method covers the gravimetric determination
average of duplicates), obtained by the same analyst on of carbonate in caustic soda or caustic potash. The lower limit
different days, has been estimated to be the value given in of determination is 0.001 g as carbon dioxide.
TABLE 3 Precision for Carbonate (Gas-Volumetric Method)
Repeatability Laboratory Precision Reproducibility
Standard Degrees of 95 % Range, Standard Degrees of 95 % Range, Standard Degrees of 95 % Range,
Level %
Deviation Freedom Percent Absolute Deviation Freedom Percent Absolute Deviation Freedom Percent Absolute
0.01–0.02 0.0034 24 0.01 0.0062 13 0.02 0.0093 5 0.03
0.04–0.08 0.0069 28 0.02 0.0145 14 0.04 0.021 6 0.06
0.12–0.35 0.017 28 0.05 0.019 14 0.05 0.034 6 0.10
E291 − 18
28. Summary of Test Method 31. Preparation of Apparatus
28.1 Carbon dioxide is evolved by acid decomposition of
31.1 The apparatus shall be assembled as shown in Fig. 5
the carbonate in the sample and is absorbed on sodium
and should conform to the description given. It shall consist of
hydrate-asbestos absorbent. The increase in mass is a measure
a 250-mLextraction flask F in which the CO is evolved.Acid
of the carbonate present.
is admitted through the stopcock D from separatory funnel C
which should be of at least 80-mL capacity. The acid delivery
29. Apparatus
tube entering F should be bent upwards at the end to prevent
the escape of CO . To the top of C shall be attached a similar
29.1 Fig. 5 illustrates the analytical train required. The
tube Bcontainingsodiumhydrate-asbestosabsorbentprotected
principal parts are as follows:
byglasswool,topurifythecarrierairwhichentersatstopcock
29.1.1 Separatory Funnel, C, 100-mL capacity.
A. The flask shall be heated directly by a bunsen burner and
29.1.2 Flask, F, 250-mL extraction.
shall be protected from drafts by shield E, either of metal or
29.1.3 Condenser, G, 8-in. (203-mm) modified Liebig.
asbestos. The gases escape from F through an 8-in. (203-mm)
29.1.4 Drying Tubes, H and J, Schwartz, glass-stoppered, 6
water-cooled condenser G. All of this part of the apparatus
in. (152 mm).
shall be conveniently mounted on one large ring stand,
29.1.5 Drying Tubes, L, N, O, P, Schwartz, glass-stoppered,
facilities being arranged for removing the flask F and guard
4 in. (101.6 mm).
tube B for each determination.All stoppers and joints must be
29.1.6 Bubbler Bottle, Q, 4-oz (0.056-L) capacity.
absolutely airtight.
29.1.7 Siphon-Vacuum Bottle, 1-gal (3.6-L) capacity.
31.2 The U-tubes shall be hung individually from hooks by
30. Reagents
copper wire loops securely fastened to the necks of the tubes.
H is a 6-in. (152-mm) U-tube containing glass beads and a
30.1 Barium Perchlorate (or Magnesium Perchlorate),
solution of silver arsenite Ag AsO in dilute H SO . Its
anhydrous, granular.
3 3 2 4
functionistoremovealkaligases,sulfides,chlorides,chlorine,
30.2 Perchloric Acid(1+2)—Mix 1 volume of 60% per-
andotheroxidizinggases. Iisaplugofglasswooltoretainany
chloric acid (HClO ) with 2 volumes of water and boil for 10
reagent entrained in the gas. J is a 6-in. U-tube containing
min in a large Erlenmeyer flask. Cool and bottle.
H SO and glass beads to absorb most of the water from the
2 4
30.3 Silver Arsenite in Sulfuric Acid—Dissolve2gof
gas. It is also protected by a plug of glass wool I in the outlet
pulverized arsenious oxide (As O ) in the least amount of
2 3 tube. K is a bulb containing clean mossy zinc which serves to
potassium hydroxide (KOH) solution (100 g/L) that will effect
catch any trace of acid carried over from J. L is a 4-in.
solution.Diluteto250mLandadddilutesulfuricacid(H SO ,
2 4 (102-mm) U-tube containing anhydrous barium perchlorate
1+9) until neutral to litmus. Add silver nitrate (AgNO )
(Ba(ClO ) ) or anhydrous magnesium perchlorate (Mg-
4 2
solution(50g/L)aslongasayellowprecipitateforms,keeping
(ClO ) ).Thetubeshallbepreparedinthreesectionsseparated
4 2
the solution neutral by dropwise addition of KOH (100 g/L)
by glass wool to eliminate channeling by the gases.
solutionwhennecessary.Stiruntilcoagulated,settle,andwash
31.3 N and O are 4-in. U-tubes for the absorption and
by decantation. Dissolve the precipitate in an excess of H SO
2 4
weighing of the CO , each prepared with two sections of
(1+9), dilute to 150 mL, and filter out any precipitated silver
sodium hydrate-asbestos absorbent and one of anhydrous
chloride (AgCl).
Ba(ClO ) or anhydrous Mg(ClO ) separated by glass wool,
4 2 4 2
30.4 Sodium Hydrate—Asbestos Absorbent, 12 to 20 mesh.
the desiccant being nearest the outlet end.These tubes shall be
30.5 Zinc Metal, clean, mossy. connectedtothesystemandeachotherbytheshortglasstubes
FIG. 5 Analytical Train
E291 − 18
M, and the tubes shall be disconnected and weighed with their 33. Calculation
rubber tubing connections attached.
33.1 Calculate the percent sodium carbonate or potassium
31.4 P is a 4-in. U-tube filled with desiccant to prevent any
carbonate as follows:
accidental back draft from containing any weighable moisture.
A 32.4083
Q is a bubbler bottle containing concentrated H SO.Ifthe Sodium carbonate,% mass 5 3100 (10)
2 4
W
bubbler tube is of 6-mm bore and the tip is placed 1.9 cm
A 33.1405
below the surface of the acid, one bubble per second will
Potassium carbonate,% mass 5 3100 (11)
W
indicate about 20-mL/min gas flow.
where:
31.5 R is a 1-gal (3.6-L) siphon vacuum bottle. It provides
sufficient vacuum for the flow required, and its capacity is a A = total grams increase in the mass of U-tubes O and N,
good measure of the time required for an analysis. The siphon and
W = sample used, g.
can be closed by pinchcock S and the rapidity of emptying
regulated by screw clamp U.
34. Report
31.6 A freshly prepared train should be conditioned with a
0.2-g sample of Na CO carried through the analysis to
34.1 Report the % mass of sodium carbonate or potassium
2 3
saturate the reagents with CO . Before the train is ready for a
carbonate to the nearest 0.01%.
series of determinations, successive weighings of the tube N
must agree within 0.0002 g before and after the passage of one
35. Precision and Bias
halfofthevolumeofairrepresentedbythecapacityof R,when
35.1 The following criteria should be used for judging the
no sample is in place. Tube O shall be used as a precautionary
acceptability of results (see Note 6):
measure. At the indicated gas flow, N will be found to absorb
35.1.1 Repeatability (Single Analyst)—The standard devia-
all the CO until its capacity is nearly depleted.Tube O should
tion for a single determination has been estimated to be the
always be weighed as a check for any CO not absorbed in N.
valuegiveninTable5attheindicateddegreesoffreedom.The
95% limit for the difference between two such runs is also
32. Procedure
given in Table 5.
32.1 Weigh into a tared evolution flask F to the nearest 0.1
35.1.2 Laboratory Precision (Within-Laboratory, Between-
g, a sample of size determined from Table 4. Connect the flask
Days Variability)—The standard deviation of results (each the
F to the analytical train as shown in Fig. 5.
average of duplicates), obtained by the same analyst on
32.2 Open all stopcocks and adjust screw clamp U for a
different days, has been estimated to be the value given in
flow of 60 to 80 mL/min corresponding to 3 to 4 bubbles/s
Table5attheindicateddegreesoffreedom.The95%limitfor
when the bubbler Q is built as described in 31.4. Close
thedifferencebetweentwosuchaveragesisalsogiveninTable
stopcock Dandpinchcock S.Remove Bandaddatleast75mL
5.
of the diluted HClO into C and replace tube B. Open
4 35.1.3 Reproducibility (Multilaboratory)—The standard de-
pinchcock S and then stopcock D carefully to admit the acid.
viation of results (each the average of duplicates), obtained by
When all the acid has entered, begin heating with a 25-mm
analysts in different laboratories, has been estimated to be the
bunsen flame. When the heating has progressed to the point
valuegiveninTable5attheindicateddegreesoffreedom.The
where the flow of air through the acid delivery tube seems to
95%limitforthedifferencebetweentwosuchaveragesisalso
stop and the liquid shows a tendency to back up in the tube,
given in Table 5.
close D.
NOTE 6—These precision estimates are based on an interlaboratory
32.3 After 5 min of brisk boiling, remove the flame, open
study on six samples with carbonate contents as follows:
stopcock D,andcontinuedrawingairthroughthetrainuntilthe
Approximate
water in bottle R has been siphoned off almost entirely. Close Sample Percentage of
Carbonate
S, the last stopcock in P, both stopcocks in O and in N, the last
45 % KOH 0.01
stopcock in L, and the first stopcock in H.
50 % NaOH 0.02, 0.05, 0.13
73 % NaOH 0.10
32.4 Remove Nand Oandallowtostandinthebalancecase
Anhydrous NaOH 0.41
for at least 10 min. Open the stopcocks momentarily to attain
atmospheric pressure, wipe gently with tissue, and weigh One analyst in each of twelve laboratories performed duplicate deter-
minations and repeated one day later. Practice E180 was used in
accurately to 0.1 mg.
developing these precision estimates.
35.2 Bias—The bias of this test method has not been
determined because of the unavailability of suitable reference
TABLE 4 Sample Size for Carbonate Analysis
materials.
Percent Na CO or Percent Sample
2 3
K CO Expected Size, g
2 3
36. Quality Guidelines
0.01 to 0.10 15 to 20
0.10 to 0.50 10 to 15
36.1 Laboratories shall have a quality control system in
0.50 to 1.00 7 to 10
place.
E291 − 18
TABLE 5 Precision for Carbonate (Gravimetric Method)
Repeatability Laboratory Precision Reproducibility
Standard Degrees of 95 % Range, Standard Degrees of 95 % Range, Standard Degrees of 95 % Range,
Level, %
Deviation Freedom Percent Absolute Deviation Freedom Percent Absolute Deviation Freedom Percent Absolute
0.01–0.02 0.0034 20 0.01 0.0025 10 0.01 0.0054 4 0.02
0.04–0.08 0.0068 20 0.02 0.0058 11 0.02 0.0018 5 0.05
0.12–0.15 0.0095 10 0.03 0.014 6 0.04 0.031 5 0.09
Apprx. 0.40 0.016 10 0.04 0.025 5 0.07 0.043 4 0.12
36.1.1 Confirm the performance of the test instrument or 40.2 If the approximate chloride content is unknown, make
test method by analyzing a quality control sample following atrialdeterminationwithasampleof10g.Ifnecessary,repeat
the guidelines of standard statistical quality control practices.
with a proper size sample for the actual determination.
36.1.2 Aquality control sample is a stable material isolated
40.3 Weigh the sample, in a tared and covered weighing
from the production process and representative of the sample
bottle, to the nearest 0.001 g for smaller samples (nearest 0.01
being analyzed.
g for larger samples). Transfer the sample quantitatively to a
36.1.3 When QA/QC protocols are already established in
500-mL Erlenmeyer flask using about 100 mL of water to
the testing facility, these protocols are acceptable when they
effect transfer and solution. Add 1 mL of ferric indicator and
confirm the validity of the test results.
(slowly) sufficient HNO (sp gr 1.42) to dissolve the reddish-
36.1.4 When there are no QA/QC protocols established in
brown precipitate formed with the ferric indicator. Cool to
the testing facility, use the guidelines described in Guide
room temperature.Add 0.1 meq/mLAgNO solution (Note 7)
D6809 or similar statistical quality control practices.
in an excess of 5 to 10 mLover that required to react with the
CHLORIDE, TITRIMETRIC
chloride, agitating continuously while adding. The total
amount added will depend on the average chloride content of
37. Scope
the particular grade of caustic being analyzed.
37.1 This test method covers the volumetric determination
40.4 Filter off the precipitated silver chloride using semi-
ofchlorideincausticsodaorcausticpotashbytheVolhardtest
quantitative paper and only one 5-mL portion of wash water.
method. The lower limit of determination is 0.001 g as
Leave the filtrate in the receiver flask and back-titrate the
chloride.
excessAgNO with 0.1 meq/mL NH SCN solution to the first
3 4
reddish-browncolorlastingforaminimumof15s.Recordthe
38. Summary of Test Method
volumes of titrants used to the nearest 0.02 mL.
38.1 The sample is diluted, acidified, and treated with a
small excess of standard silver nitrate solution. The precipi-
NOTE 7—It is sometimes preferred to add 0.5 to 1.0 mLof 0.1 meq/mL
tated silver chloride is removed by filtration and the excess
NH SCNsolutionbeforeaddingAgNO whichisthenaddedinanamount
4 3
2 to 5 mL in excess of that required to cause the disappearance of the
silver nitrate is titrated with standard ammonium thiocyanate
brown color.Any NH SCN so added must be included in the calculation.
solution using ferric ammonium sulfate indicator.
The sample is then back-titrated in accordance with 40.4.
39. Reagents
41. Calculation
39.1 Ammonium Thiocyanate, Standard Solution (0.1 meq/
mL)—See Practice E200. 41.1 Calculate the % mass of chloride as follows:
A 3 N 2 B 3 N 30.035453
39.2 Ferric Ammonium Sulfate Indicator Solution—See @~ ! ~ !#
1 2
Chloride,% mass 5 3100
Practice E200. W
(12)
39.3 Nitric Acid (sp gr 1.42)—Concentrated nitric acid
(HNO ).
where:
39.4 Silver Nitrate, Standard Solution (0.1 meq/mL)—See A = AgNO solution added, mL,
Practice E200. B =NH SCN solution added, total mL,
N = meq/mL of AgNO solution used,
1 3
40. Procedure
N = meq/mL of NH SCN solution used, and
2 4
W = sample used, g.
40.1 If the approximate chloride content of the sample is
known, take a sample of size as indicated in Table 6.
41.2 Calculate the % mass of sodium chloride or potassium
chloride, if desired, as follows:
TABLE 6 Sample Size for Chloride Analysis
Sodium chloride,% mass 5 chloride, wt % 31.6485 (13)
Percent NaCl or Percent Sample
Potassium chloride,% mass 5 chloride, wt % 32.1029 (14)
KCl Expected Size, g
1to2 5
42. Report
0.5 to 0.9 10
0.01 to 0.49 20
42.1 Report the % mass of chloride to the nearest 0.01%.
E291 − 18
43. Precision and Bias 47. Apparatus
43.1 The following criteria should be used for judging the
47.1 Automatic Titrator or pH Meter, switched to millivolt
acceptability of results (Note 8):
mode.
43.1.1 Repeatability (Single Analyst)—The standard devia-
47.2 Buret, 20-mL automatic delivery type or 25-mL
tion for a single determination has been estimated to be
manual type.
0.0071% absolute at 56 df. The 95% limit for the difference
between two such runs is 0.02% absolute.
47.3 Silver Billet, combination electrode.
43.1.2 Laboratory Precision (Within-Laboratory, Between-
47.4 Magnetic Stirrer and Stir Bars.
Days Variability)—The standard deviation of results (each the
average of duplicates), obtained by the same analyst on
48. Reagents
different days, has been estimated to be 0.0036% absolute at
28 df. The 95% limit for the difference between two such
48.1 Nitric Acid—(sp gr 1.42)—concentrated nitric acid
averages is 0.01% absolute.
(HNO ).
43.1.3 Reproducibility (Multilaboratory)—The standard de-
viation of results (each the average of duplicates), obtained by 48.2 Phenolphthalein Indicator Solution (10g/L)—Dissolve
analysts in different laboratories, has been estimated to be
1 g of phenolphthalein in 100 mL of ethanol (95%) as
0.0069% absolute at 6 df. The 95% limit for the difference prescribed in Practice E200.
between two such averages is 0.02% absolute
48.3 Silver Nitrate, Standard Solution (0.1 meq/mL)—
NOTE 8—These precision estimates are based on an interlaboratory
Prepare in accordance with Practice E200, but standardize
study on four samples covering the range from 0.15 to 0.8% chloride in
using the potential (end point) break obtained using an auto-
potassium hydroxide and sodium hydroxide. One analyst in each of seven
matic titrator or pH meter in the millivolt mode.
laboratories performed duplicate determinations and repeated one day
later. Practice E180
...