ASTM D1510-21

Standard Test Method for Carbon Black-Iodine Adsorption Number

SIGNIFICANCE AND USE
4.1 The iodine adsorption number is useful in characterizing carbon blacks. It is related to the surface area of carbon blacks and is generally in agreement with nitrogen surface area. The presence of volatiles, surface porosity, or extractables will influence the iodine adsorption number. Aging of carbon black can also influence the iodine number.
SCOPE
1.1 This test method covers the determination of the iodine adsorption number of carbon black.  
1.1.1 Method A is the original test method for this determination and Method B is an alternate test method using automated sample processing and analysis.  
1.2 The iodine adsorption number of carbon black has been shown to decrease with sample aging. Iodine Number reference materials have been produced that exhibit stable iodine number upon aging. One or more of these reference materials are recommended for daily monitoring (x-charts) to ensure that the results are within the control limits of the individual reference material. Use all Iodine Number reference materials from a set for standardization of iodine testing (see Section 8) when target values cannot be obtained.  
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 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.

General Information

• Status: Historical
• Publication Date: 30-Apr-2021
• ICS: 83.040.20 - Rubber compounding ingredients
• Technical Committee: D24 - Carbon Black
• Drafting Committee: D24.21 - Carbon Black Surface Area and Related Properties

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D1510 − 21
Standard Test Method for
Carbon Black—Iodine Adsorption Number
This standard is issued under the fixed designation D1510; 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 D1799 Practice for Carbon Black—Sampling Packaged
Shipments
1.1 This test method covers the determination of the iodine
D1900 Practice for Carbon Black—Sampling Bulk Ship-
adsorption number of carbon black.
ments
1.1.1 Method A is the original test method for this determi-
D4483 Practice for Evaluating Precision for Test Method
nation and Method B is an alternate test method using
Standards in the Rubber and Carbon Black Manufacturing
automated sample processing and analysis.
Industries
1.2 The iodine adsorption number of carbon black has been
D4821 Guide for Carbon Black—Validation of Test Method
shown to decrease with sample aging. Iodine Number refer-
Precision and Bias
ence materials have been produced that exhibit stable iodine
E969 Specification for Glass Volumetric (Transfer) Pipets
number upon aging. One or more of these reference materials
2.2 European Standards:
are recommended for daily monitoring (x-charts) to ensure that
ISO/EN/DIN 8655-3 Piston-operated volumetric apparatus -
the results are within the control limits of the individual
Part 3: Piston burettes
reference material. Use all Iodine Number reference materials
3. Summary of Test Methods
from a set for standardization of iodine testing (see Section 8)
when target values cannot be obtained.
3.1 In Test Method A, a weighed sample of carbon black is
treated with a portion of standard iodine solution and the
1.3 The values stated in SI units are to be regarded as
mixture shaken and centrifuged. The excess iodine is then
standard. No other units of measurement are included in this
titrated with standard sodium thiosulfate solution, and the
standard.
adsorbed iodine is expressed as a fraction of the total mass of
1.4 This standard does not purport to address all of the
black.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro- 3.2 In Test Method B, a weighed sample of carbon black is
priate safety, health, and environmental practices and deter- treated with a portion of standard iodine solution using an
mine the applicability of regulatory limitations prior to use. automated sample processor where the mixture is stirred,
1.5 This international standard was developed in accor- settled and aliquoted for automatic titration. The excess iodine
dance with internationally recognized principles on standard- is titrated with standard sodium thiosulfate solution, and the
ization established in the Decision on Principles for the adsorbed iodine is expressed as a fraction of the total mass of
Development of International Standards, Guides and Recom- black.
mendations issued by the World Trade Organization Technical
4. Significance and Use
Barriers to Trade (TBT) Committee.
4.1 The iodine adsorption number is useful in characterizing
2. Referenced Documents
carbon blacks. It is related to the surface area of carbon blacks
and is generally in agreement with nitrogen surface area. The
2.1 ASTM Standards:
presence of volatiles, surface porosity, or extractables will
influence the iodine adsorption number. Aging of carbon black
This test method is under the jurisdiction of ASTM Committee D24 on Carbon
can also influence the iodine number.
Black and is the direct responsibility of Subcommittee D24.21 on Carbon Black
Surface Area and Related Properties.
5. Apparatus
Current edition approved May 1, 2021. Published July 2021. Originally approved
in 1957. Last previous edition approved in 2019 as D1510 – 19a. DOI: 10.1520/ 5.1 Vials, glass, optically clear type, with polyethylene
D1510-21.
stoppers, 45 cm .
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on Available from International Organization for Standardization (ISO), 1, ch. de
the ASTM website. la Voie-Creuse, CP 56, CH-1211 Geneva 20, Switzerland, http://www.iso.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D1510 − 21
5.2 Gravity Convection Drying Oven, capable of maintain- 6.4 Potassium Iodate Solution, c(KIO ) = 0.00657 mol/
3 3
ing 125 6 5°C. dm (0.0394 N ) containing 45.0 g potassium iodide per dm .
5.3 Buret, either of the following may be used: 6.5 Potassium Dichromate Solution, c(K Cr O ) =
2 2 7
3 3 3
5.3.1 Digital Buret, 25-cm capacity, with 0.01-cm incre- 0.006567 mol/cm (0.0394 N), containing 1.932 g potassium
ment counter and zero reset control, or dichromate (certified/traceable primary standard) per dm .
5.3.2 Buret, glass 25-cm , Class A, side-arm filling, gradu- (Warning—Potassium dichromate is carcinogenic.)
ated in 0.05 cm and with automatic zero.
6.6 Sodium Thiosulfate Solution, c(Na S O ) = 0.0394 mol/
2 2 3
3 3 3 3
5.4 Repetitive Dispenser, 25-cm capacity, 60.1% repro- dm (0.0394 N), containing 5 cm n-amyl alcohol per dm .
ducibility and calibrated to within 60.03-cm accuracy.
6.7 Sulfuric Acid, 10 %.
5.5 Balance, analytical, with 0.1-mg sensitivity.
6.8 Soluble Starch Solution, 1 %, containing 0.02 g salicylic
5.6 Centrifuge, with minimum speed of 105 rad/s acid per dm .
(1000 r ⁄min).
6.9 Deionized Water.
5.7 Volumetric Flask, 2000-cm with standard taper stopper.
7. Standardization of Solutions
5.8 Funnel, large diameter, with standard taper joint to fit
the 2000-cm flask.
7.1 Sodium Thiosulfate, 0.0394 N (60.00008):
3 7.1.1 Use potassium dichromate solution as follows:
5.9 Glass Bottle, amber, 2000-cm , with standard taper
7.1.1.1 Measure approximately 20 cm of 10 % potassium
stopper.
iodide (see A1.4) solution into a small graduated cylinder and
5.10 Glass Jug, approximate capacity 20-dm . 3
transfer to a 250 cm iodine flask with a ground glass stopper.
5.11 Stirrer, approximately 300 by 300 mm for mixing. 7.1.1.2 Measure approximately 20 cm of 10 % sulfuric acid
solution (see A1.5) into a small graduated cylinder and add to
5.12 Stirrer, approximately 100 by 100 mm for titrating.
the KI solution in the iodine flask. The mixture should remain
5.13 Desiccator.
colorless.
5.14 Miscellaneous Class A Glassware, and equipment
NOTE 1—If a yellow color should develop, discard this KI solution.
necessary to carry out the test as written.
3 3
7.1.1.3 Using a 20 cm pipet, transfer 20 cm of standard
5.15 Mechanical Shaker, with at least 1 in. stroke length and
0.0394 N potassium dichromate solution (see A1.8) into the
a minimum of 240 strokes/min.
250 cm iodine flask, replace stopper, swirl, and place in the
dark for 15 min.
5.16 Automatic Titrator.
7.1.1.4 Titrate the contents of the iodine flask against the
5.17 Redox Electrode, combined platinum ring electrode
new sodium thiosulfate solution following 7.1.3 or 7.1.4.
with an Ag/AgCl/KCl reference electrode and a ceramic frit.
7.1.2 Use potassium iodate/iodide solution as follows:
5.18 Volumetric Flask, 500 cm with standard taper stopper.
7.1.2.1 Pipet exactly 20 cm of 0.0394 N potassium iodate/
iodide solution into a 250-cm iodine flask.
5.19 Flask, 250 cm with ground glass stopper.
7.1.2.2 Measure approximately 5 cm of 10 % sulfuric acid
5.20 Automatic Sample Processor and Titration Apparatus,
into a small graduated cylinder and add to the iodate/iodide
equipped with disposable filter.
solution.
7.1.2.3 Cap immediately and mix thoroughly.
6. Reagents and Solutions
7.1.2.4 Titrate the contents of the iodine flask against the
6.1 Purity of Reagents—Unless otherwise stated, all chemi-
new sodium thiosulfate solution following 7.1.3 or 7.1.4.
cals shall be of reagent grade.
7.1.3 Digital Buret:
7.1.3.1 Switch the digital buret to fill mode, fill the reservoir
6.2 The preparation of the solutions listed below is de-
with unstandardized sodium thiosulfate solution, and flush the
scribed in Annex A1. Pre-mixed 0.04728 N iodine solution and
inlet and delivery tubes.
0.0394 N sodium thiosulfate may be purchased from commer-
7.1.3.2 Change to the titrate mode and zero the counter.
cial sources. It is recommended that the normality of pre-mixed
7.1.3.3 Add sodium thiosulfate until the contents of the
solutions be verified before use.
3 iodine flask are a pale yellowish (potassium iodate) or pale
6.3 Iodine Solution, c(I ) = 0.02364 mol/dm (0.04728 N),
yellowish-green (potassium dichromate). Wash the buret tip
containing 57.0 g potassium iodide Kl per dm .
and the walls of the flask with water.
7.1.3.4 Add 5 drops of starch solution to the flask.
7.1.3.5 Continue adding sodium thiosulfate dropwise until
The sole source of supply of the apparatus known to the committee at this time
the blue or blue-violet color almost disappears.
is Brinkmann Instruments, Inc., One Cantiague Rd., PO Box 1019, Westbury, NY
7.1.3.6 Wash the tip and walls of the flask with water, then
11590-0207. The sole source of supply of the filter (disposable filter part #17594 K
5 µm Minisart with luer lock outlet) known to the committee at this time is Sartorius
advance the counter in 0.01-cm increments. Continue this
Stedim North America Inc., 131 Heartland Blvd., Edgewood, NY 11717. If you are
sequence until the endpoint is reached, indicated by a colorless
aware of alternative suppliers, please provide this information to ASTM Interna-
(potassium iodate) or sea-green (potassium dichromate) solu-
tional Headquarters. Your comments will receive careful consideration at a meeting
of the responsible technical committee, which you may attend. tion.
D1510 − 21
3 3
7.1.3.7 Record the titration value and repeat from 7.1.1 or (2.1 cm water per dm iodine solution for each 0.0001 N over
7.1.2 for a duplicate determination. 0.04728); if the solution is too diluted, add iodine (12.7 mg
7.1.3.8 Calculate the normality of the sodium thiosulfate iodine per dm iodine solution for each 0.0001 N under
solution as in 7.1.5 and proceed as in 7.1.6. If the titration is 0.04728). (This iodine may be more conveniently dispensed
made to standardize the iodine solution as described in 7.2 from a concentrated solution.)
calculate the normality of the iodine solution as in 7.2.1.2 and
8. Normalization Using Iodine Number Reference
proceed as in 7.2.1.3.
Materials
7.1.4 Glass Buret:
7.1.4.1 Using a conventional glass buret, fill the buret with 8.1 The SRB HT reference materials (previously known as
SRB HT Iodine Standards) are no longer commercially avail-
unstandardized sodium-thiosulfate solution and flush 2 to
3 cm through the tip. able but may still be in use in some laboratories. A new lot was
prepared by the same process as the SBR HT reference
7.1.4.2 Adjust to the mark and titrate to a pale yellowish
(potassium iodate) or pale yellowish-green (potassium dichro- materials and was designated as Iodine Number Reference
(INR) to be consistent with D24’s naming protocol for refer-
mate).
ence materials. The SRB HT and INR reference materials are
7.1.4.3 Wash the buret tip and the walls of the flask with
each a set of three materials with different reference values.
water.
The three materials from either SRB HT or INR reference
7.1.4.4 Add 5 drops of starch solution to the iodine flask.
materials should be used together for normalization. Do not
7.1.4.5 Continue adding sodium thiosulfate dropwise until
normalize using some materials from both sets.
the endpoint is reached, indicated by a colorless (potassium
iodate) or sea-green (potassium dichromate) solution.
8.2 When a laboratory cannot obtain target values for all
7.1.4.6 Record the titration value to the nearest 0.025 cm
three SRB HT or INR reference materials within established
and repeat from 7.1.1 or 7.1.2 for a duplicate determination.
control limits, the user should review recommendations found
in Guide D4821. If any one of the three SRB HT or INR
NOTE 2—To achieve maximum performance from a glass buret, it is
reference materials is still outside acceptable control limits, the
necessary to use a small magnifier and to read to the nearest 0.025 cm .
method described in 8.3 – 8.6 should be used to normalize all
7.1.4.7 Calculate the normality of the sodium thiosulfate
test results.
solution as in 7.1.5 and proceed as in 7.1.6. If the titration is
8.3 Test the three SRB HT or INR reference materials four
made to standardize the iodine solution as described in 7.2
calculate the normality of the iodine solution as in 7.2.1.2 and times each.
proceed as in 7.2.1.3.
8.4 Perform a regression analysis using the target value of
7.1.5 Calculate the normality of the sodium thiosulfate
the SRB HT or INR reference materials (y value) and the
solutions as follows:
individual measured value (x value).
N 5 20 0.0394 /T (1)
~ !
8.5 Normalize the values of all subsequent test results using
this regression equation:
where:
Normalized value5 measured value3 slope 1y 2 intercept (3)
N = normality, and ~ !
T = titration volume, cm .
8.6 Alternatively, a table of numbers may be generated
7.1.6 If N is not equal to 0.0394, adjust the solution in the based on the regression equation to find the correspondence
between a measured value and a normalized value.
following manner: if the solution is too strong, add water (2.5
3 3
cm water per dm sodium thiosulfate solution for each 0.0001
8.7 Reevaluate the need for normalization whenever re-
N over 0.0394); if the solution is too weak, add solid sodium
placement apparatus or new lots of iodine or sodium thiosulfate
thiosulfate (0.025 g solid sodium thiosulfate per dm sodium
solutions, or both, are put into use.
thiosulfate solution for each 0.0001 N under 0.0394).
9. Sampling
7.2 Iodine Solution 0.04728 N (60.00003)—This solution
9.1 Samples shall be taken in accordance with Practices
may be standardized against the secondary standard sodium-
thiosulfate solution (see A1.3) standardized as in 7.1. D1799 and D1900.
7.2.1 Use sodium thiosulfate solution as follows:
10. Blank Iodine Determination
7.2.1.1 Pipet exactly 20 cm of iodine solution into a
10.1 Method A—Blank Iodine Determination:
250-cm iodine flask and cap. Continue as in 7.1.3 or 7.1.4.
10.1.1 Make a blank iodine determination by pipeting 20
7.2.1.2 Calculate the normality of the iodine solution as
3 3
cm or dispensing 25 cm of 0.04728 N iodine solution into a
follows:
125-cm Erlenmeyer flask and titrating with 0.0394 N sodium
N 5 ~0.0394! T/20 (2)
thiosulfate as in 11.10.1, 11.10.2, or 11.10.3.
where:
10.1.2 A 25-cm blank must be multiplied by 0.8 for use in
the formula of 13.1.
N = normality, and
T = cm of 0.0394 N sodium thiosulfate solution. 10.1.3 Make a duplicate blank determination and use the
average of the two in the calculations.
7.2.1.3 If N is not equal to 0.04728 N, adjust solution in the
following manner: if the solution is too concentrated, add water NOTE 3—A duplicate blank determination need be run only once each
D1510 − 21
day, unless new solutions are introduced during the day.
10.2.8 Blank measurements may be made daily, especially
where small solution lots are prepared within a lab.
10.1.4 If both solutions are within acceptable limits, the
Alternatively, blanks may be measured once per solution lot or
blank will measure 24.00 6 0.09 cm . If not, the normalities of
other prescribed frequency, for large solution lots which are
one or both solutions should be rechecked. If, after the recheck
purchased, and where adequate measures are used to monitor
of solutions, normalities are still outside the acceptable limits
testing such as the daily use of x-charting HT or INR standards.
refer to 7.2.1.3 to adjust iodine solution. See Table 1 for blank
tolerance components.
NOTE 6—For daily blanks, a duplicate blank determination need be run
10.1.5 The blank tolerance for a 20 cm volume of iodine
only once each day, unless new solutions are introduced during the day.
solution is defined as the sum of (1) titration volume deviation
NOTE 7—When the particulate filter is changed adequate measures
should be taken to saturate the filter with iodine solution. An example of
for acceptable variation in both iodine and sodium thiosulfate
an adequate measure found to be satisfactory includes running a minimum
solution concentrations, and (2) dispenser tolerance for Class A
of five blanks. The fourth and fifth blank are then averaged for the final
20 mL pipet.
blank value and use the average of the two in the calculations. If the filter
10.1.6 The solution deviation is based on the maximum
has not been changed use the average of the first and second blanks for
variation in solution concentrations defined in 7.1 and 7.2.
calculations.
Tolerances for Class A volumetric pipets are from Specification
10.2.9 Blank tolerances are found in Table 2 for different
E969.
volumes of iodine solution. A blank tolerance is defined as the
10.2 Method B—Blank Iodine Determination:
sum of (1) titration volume deviation for acceptable variation
10.2.1 Make a blank iodine determination by placing a
in both iodine and sodium thiosulfate solution concentrations,
magnetic stir bar into an empty beaker and place the beaker
and (2) dispenser tolerance for a piston-operated volumetric
into the automated sample processor.
apparatus.
10.2.2 Initiate the automatic sample processor and titration
10.2.10 A blank tolerance can be calculated from the linear
apparatus.
equation as follows:
10.2.3 Dispense an appropriate volume of 0.04728 N iodine
Y 5 0.0056x10.0059 (4)
solution into the beaker. Treat the blank in the same manner as
the sample, refer to Section 12. where:
Y = tolerance 6, and
NOTE 4—For different size beakers, ensure stir bar covers the bottom
x = aliquot volume, mL.
surface of beaker for good mixing.
10.2.4 Measures should be taken to ensure adequate purging 10.2.11 Blank tolerances for Method B are also found in
of the entire system prior to delivering the final aliquot for Fig. 1. The function for solution deviation only and solution
titration (see Note 5). deviation plus dispenser tolerance are included for reference.
10.2.12 The solution deviation is based on the maximum
NOTE 5—An example of adequate purging of the system is achieved by
variation in solution concentrations defined in 7.1 and 7.2.
double rinsing with the current blank solution followed with a distilled
water rinse. This can be done in the following manner: (1) fill the dosing
Tolerances for piston-operated volumetric apparatus are from
device, which is equipped with a disposable filter, with an aliquot of the
ISO/EN/DIN 8655-3.
blank solution from the beaker, dispense the entire volume into titration
vessel, and pump out into the waste container; (2) repeat previous step one
11. Sample Preparation and Iodine Number
more time and fill the dosing device with the final aliquot of blank solution
(this aliquot should have an excess amount that will be used to flush the Determination—Method A
air bubbles, possibly formed during the two previous steps—the volume
11.1 Dry an adequate sample of carbon black for 1 h, in a
of aliquot used for titration can vary depending on user’s preference (7 to
gravity-convection oven set at 125°C, in an open container of
20 cm has been found satisfactory)); (3) dispense a small portion of the
blank solution into the reaction vessel, ensure that appropriate amount of
suitable dimensions, so that the depth of the black is no more
the solution is left for titration in the dosing device; and (4) clean the
than 10 mm. Cool to room temperature in a desiccator before
reaction (titration) vessel by rinsing with distilled water and pumping out
use.
waste repetitively.
11.2 Weigh a mass of the dried sample into a glass vial as
10.2.5 Dispense a final aliquot of the blank solution into the
shown by the following table. All masses must be to the nearest
reaction vessel for titration and wash the walls of the vessel,
0.001 g in case of iodine numbers from 0 to 520.9 and to the
stirrer, and redox-electrode with distilled water to ensure that
nearest 0.0001 g in case of iodine numbers from 521.0 and
any splashed iodine is washed into the mixture.
above.
10.2.6 Automatically titrate the iodine solution with 0.0394
N sodium thiosulfate.
10.2.7 Make duplicate blank determinations. The average of
two determinations is to be used in calculations.
TABLE 2 Blank Tolerances
Blank A. Solution B. Dispenser Blank
3 3 3 3
Volume cm Deviations cm Tolerance cm Tolerance cm
TABLE 1 Blank Tolerance Components
20.00 ±0.064 ±0.054 ±0.118
Blank A. Solution B. Dispenser Blank 10.00 ±0.032 ±0.027 ±0.059
3 3 3 3
Volume cm Deviations cm Tolerance cm Tolerance cm 6.00 ±0.019 ±0.024 ±0.043
20.00 ±0.06 ±0.03 ±0.09 1.00 ±0.003 ±0.007 ±0.010
D1510 − 21
FIG. 1 Blank Tolerances for Method B as a Function of Aliquot Volume
3 3
11.9 Pipet 20 cm of solution into a 250-cm Erlenmeyer
Iodine Number Sample Mass (g) Ratio I : Sample Mass
0–130.9 0.500 50:1
flask and titrate with standardized 0.0394 N sodium thiosulfate
131.0–280.9 0.250 100:1
solution using either the digital or glass buret as described in
281.0–520.9 0.125 200:1
11.10.
521.0 and above 0.0625 400:1
11.3 Use the sample mass determined by the expected
11.10 Titration of Iodine Solution:
iodine number. If the result falls either above or below the
11.10.1 Using a Digital Buret:
range shown for that sample size, retest using the sample mass
11.10.1.1 Switch to the fill mode, fill the buret reservoir
specified in 11.2 for the range into which it has fallen.
with solution, and flush the inlet and delivery tubes.
NOTE 8—Unagitated, unpelleted carbon black may be densified, if 11.10.1.2 Change to the titrate mode, zero the counter, and
desired, before drying, prior to weighing.
clean the tip with tissue.
11.4 The sample mass table given in 11.2 pertains to the 25 11.10.1.3 Add sodium thiosulfate until the solution is pale
cm iodine solution as given in 11.5. Different volumes of yellow. Wash the buret tip and walls of the flask with water.
iodine solution and of sample masses are permissible only if
11.10.1.4 Add 5 drops of starch solution.
the iodine solution to sample mass ratio is kept the same as that
11.10.1.5 Continue adding sodium thiosulfate dropwise un-
given by the table in 11.2. The sample mass must be kept to
til the blue or blue-violet color almost disappears.
1.000 g maximum. Should the sample mass and corresponding
11.10.1.6 Wash the tip and walls of the flask with water and
volume of iodine solution be increased, then a glass vial with
then advance the counter in 0.01-cm increments. Continue this
a volume that is at least two times the amount of iodine
sequence until the endpoint is reached as indicated by a
solution used for the test should be used in order to preserve the
colorless solution.
efficiency of the shaking. 3
11.10.1.7 Record the buret reading to the nearest 0.01 cm .
11.5 Pipet (or dispense from a calibrated repetitive dis-
11.10.2 Using a Conventional Glass Buret:
penser) 25 cm of 0.04728 N I solution into the glass vial
2 11.10.2.1 Remove any adherent drop on the tip of the buret
containing the sample and cap immediately.
by gently toughing the drop with the wall of a clean flask. The
flask may be used several times by toughing a clean part of the
11.6 Secure the vial in the mechanical shaker and shake for
wall to remove further drops prior to titration. Add sodium
1 min at a minimum of 240 strokes/min.
thiosulfate until the solution is pale yellow. Wash the buret tip
11.7 Centrifuge immediately for 1 min for pelleted black
and walls of the flask with water.
and 3 min for loose black.
11.10.2.2 Add 5 drops of starch solution.
NOTE 9—Make sure that the carbon black is separated from the iodine
11.10.2.3 Continue adding sodium thiosulfate dropwise un-
solution in such a way that enough carbon black free iodine solution is
til the endpoint is reached as indicated by a colorless solution.
available for the titration. In case that carbon black particles are still
11.10.2.4 Record the titration volume to the nearest 0.025
visible in the iodine solution to be titrated, repeat the sample preparation
and increase the centrifugation speed.
cm .
11.10.3 Using an Auto-titrator:
11.8 Decant immediately. If more than one sample is being
analyzed, the solution should be decanted into small flasks or 11.10.3.1 Two redox equivalence point titration methods
clean, dry vials and capped immedi
...

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: D1510 − 19a D1510 − 21
Standard Test Method for
Carbon Black—Iodine Adsorption Number
This standard is issued under the fixed designation D1510; 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 This test method covers the determination of the iodine adsorption number of carbon black.
1.1.1 Method A is the original test method for this determination and Method B is an alternate test method using automated sample
processing and analysis.
1.2 The iodine adsorption number of carbon black has been shown to decrease with sample aging. Iodine Number reference
materials have been produced that exhibit stable iodine number upon aging. One or more of these reference materials are
recommended for daily monitoring (x-charts) to ensure that the results are within the control limits of the individual reference
material. Use all Iodine Number reference materials from a set for standardization of iodine testing (see Section 8) when target
values cannot be obtained.
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 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:
D1799 Practice for Carbon Black—Sampling Packaged Shipments
D1900 Practice for Carbon Black—Sampling Bulk Shipments
D4483 Practice for Evaluating Precision for Test Method Standards in the Rubber and Carbon Black Manufacturing Industries
D4821 Guide for Carbon Black—Validation of Test Method Precision and Bias
E969 Specification for Glass Volumetric (Transfer) Pipets
2.2 European Standards:
ISO/EN/DIN 8655-3 Piston-operated volumetric apparatus - Part 3: Piston burettes
This test method is under the jurisdiction of ASTM Committee D24 on Carbon Black and is the direct responsibility of Subcommittee D24.21 on Carbon Black Surface
Area and Related Properties.
Current edition approved Aug. 15, 2019May 1, 2021. Published September 2019July 2021. Originally approved in 1957. Last previous edition approved in 2019 as
D1510 – 19.D1510 – 19a. DOI: 10.1520/D1510-19A.10.1520/D1510-21.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Available from International Organization for Standardization (ISO), 1, ch. de la Voie-Creuse, CP 56, CH-1211 Geneva 20, Switzerland, http://www.iso.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D1510 − 21
3. Summary of Test Methods
3.1 In Test Method A, a weighed sample of carbon black is treated with a portion of standard iodine solution and the mixture
shaken and centrifuged. The excess iodine is then titrated with standard sodium thiosulfate solution, and the adsorbed iodine is
expressed as a fraction of the total mass of black.
3.2 In Test Method B, a weighed sample of carbon black is treated with a portion of standard iodine solution using an automated
sample processor where the mixture is stirred, settled and aliquoted for automatic titration. The excess iodine is titrated with
standard sodium thiosulfate solution, and the adsorbed iodine is expressed as a fraction of the total mass of black.
4. Significance and Use
4.1 The iodine adsorption number is useful in characterizing carbon blacks. It is related to the surface area of carbon blacks and
is generally in agreement with nitrogen surface area. The presence of volatiles, surface porosity, or extractables will influence the
iodine adsorption number. Aging of carbon black can also influence the iodine number.
5. Apparatus
5.1 Vials, glass, optically clear type, with polyethylene stoppers, 45 cm .
5.2 Gravity Convection Drying Oven, capable of maintaining 125 6 5°C.
5.3 Buret, either of the following may be used:
3 3
5.3.1 Digital Buret, 25-cm capacity, with 0.01-cm increment counter and zero reset control, or
3 3
5.3.2 Buret, glass 25-cm , Class A, side-arm filling, graduated in 0.05 cm and with automatic zero.
3 3
5.4 Repetitive Dispenser, 25-cm capacity, 60.1% reproducibility and calibrated to within 60.03-cm accuracy.
5.5 Balance, analytical, with 0.1-mg sensitivity.
5.6 Centrifuge, with minimum speed of 105 rad/s (1000 r ⁄min).
5.7 Volumetric Flask, 2000-cm with standard taper stopper.
5.8 Funnel, large diameter, with standard taper joint to fit the 2000-cm flask.
5.9 Glass Bottle, amber, 2000-cm , with standard taper stopper.
5.10 Glass Jug, approximate capacity 20-dm .
5.11 Stirrer, approximately 300 by 300 mm for mixing.
5.12 Stirrer, approximately 100 by 100 mm for titrating.
5.13 Desiccator.
5.14 Miscellaneous Class A Glassware, and equipment necessary to carry out the test as written.
5.15 Mechanical Shaker, with at least 1 in. stroke length and a minimum of 240 strokes/min.
5.16 Automatic Titrator.
D1510 − 21
5.17 Redox Electrode, combined platinum ring electrode with an Ag/AgCl/KCl reference electrode and a ceramic frit.
5.18 Volumetric Flask, 500 cm with standard taper stopper.
5.19 Flask, 250 cm with ground glass stopper.
5.20 Automatic Sample Processor and Titration Apparatus, equipped with disposable filter.
6. Reagents and Solutions
6.1 Purity of Reagents—Unless otherwise stated, all chemicals shall be of reagent grade.
6.2 The preparation of the solutions listed below is described in Annex A1. Pre-mixed 0.04728 N iodine solution and 0.0394 N
sodium thiosulfate may be purchased from commercial sources. It is recommended that the normality of pre-mixed solutions be
verified before use.
3 3
6.3 Iodine Solution, c(I ) = 0.02364 mol/dm (0.04728 N), containing 57.0 g potassium iodide Kl per dm .
3 3
6.4 Potassium Iodate Solution, c(KIO ) = 0.00657 mol/dm (0.0394 N ) containing 45.0 g potassium iodide per dm .
6.5 Potassium Dichromate Solution, c(K Cr O ) = 0.006567 mol/cm (0.0394 N), containing 1.932 g potassium dichromate
2 2 7
(certified/traceable primary standard) per dm . (Warning—Potassium dichromate is carcinogenic.)
3 3 3
6.6 Sodium Thiosulfate Solution, c(Na S O ) = 0.0394 mol/dm (0.0394 N), containing 5 cm n-amyl alcohol per dm .
2 2 3
6.7 Sulfuric Acid, 10 %.
6.8 Soluble Starch Solution, 1 %, containing 0.02 g salicylic acid per dm .
6.9 Deionized Water.
7. Standardization of Solutions
7.1 Sodium Thiosulfate, 0.0394 N (60.00008):
7.1.1 Use potassium dichromate solution as follows:
7.1.1.1 Measure approximately 20 cm of 10 % potassium iodide (see A1.4) solution into a small graduated cylinder and transfer
to a 250 cm iodine flask with a ground glass stopper.
7.1.1.2 Measure approximately 20 cm of 10 % sulfuric acid solution (see A1.5) into a small graduated cylinder and add to the
KI solution in the iodine flask. The mixture should remain colorless.
NOTE 1—If a yellow color should develop, discard this KI solution.
3 3 3
7.1.1.3 Using a 20 cm pipet, transfer 20 cm of standard 0.0394 N potassium dichromate solution (see A1.8) into the 250 cm
iodine flask, replace stopper, swirl, and place in the dark for 15 min.
The sole source of supply of the apparatus known to the committee at this time is Brinkmann Instruments, Inc., One Cantiague Rd., PO Box 1019, Westbury, NY
11590-0207. The sole source of supply of the filter (disposable filter part #17594 K 5 μm Minisart with luer lock outlet) known to the committee at this time is Sartorius
Stedim North America Inc., 131 Heartland Blvd., Edgewood, NY 11717. If you are aware of alternative suppliers, please provide this information to ASTM International
Headquarters. Your comments will receive careful consideration at a meeting of the responsible technical committee, which you may attend.
D1510 − 21
7.1.1.4 Titrate the contents of the iodine flask against the new sodium thiosulfate solution following 7.1.3 or 7.1.4.
7.1.2 Use potassium iodate/iodide solution as follows:
3 3
7.1.2.1 Pipet exactly 20 cm of 0.0394 N potassium iodate/iodide solution into a 250-cm iodine flask.
7.1.2.2 Measure approximately 5 cm of 10 % sulfuric acid into a small graduated cylinder and add to the iodate/iodide solution.
7.1.2.3 Cap immediately and mix thoroughly.
7.1.2.4 Titrate the contents of the iodine flask against the new sodium thiosulfate solution following 7.1.3 or 7.1.4.
7.1.3 Digital Buret:
7.1.3.1 Switch the digital buret to fill mode, fill the reservoir with unstandardized sodium thiosulfate solution, and flush the inlet
and delivery tubes.
7.1.3.2 Change to the titrate mode and zero the counter.
7.1.3.3 Add sodium thiosulfate until the contents of the iodine flask are a pale yellowish (potassium iodate) or pale
yellowish-green (potassium dichromate). Wash the buret tip and the walls of the flask with water.
7.1.3.4 Add 5 drops of starch solution to the flask.
7.1.3.5 Continue adding sodium thiosulfate dropwise until the blue or blue-violet color almost disappears.
7.1.3.6 Wash the tip and walls of the flask with water, then advance the counter in 0.01-cm increments. Continue this sequence
until the endpoint is reached, indicated by a colorless (potassium iodate) or sea-green (potassium dichromate) solution.
7.1.3.7 Record the titration value and repeat from 7.1.1 or 7.1.2 for a duplicate determination.
7.1.3.8 Calculate the normality of the sodium thiosulfate solution as in 7.1.5 and proceed as in 7.1.6. If the titration is made to
standardize the iodine solution as described in 7.2 calculate the normality of the iodine solution as in 7.2.1.2 and proceed as in
7.2.1.3.
7.1.4 Glass Buret:
7.1.4.1 Using a conventional glass buret, fill the buret with unstandardized sodium-thiosulfate solution and flush 2 to 3 cm
through the tip.
7.1.4.2 Adjust to the mark and titrate to a pale yellowish (potassium iodate) or pale yellowish-green (potassium dichromate).
7.1.4.3 Wash the buret tip and the walls of the flask with water.
7.1.4.4 Add 5 drops of starch solution to the iodine flask.
7.1.4.5 Continue adding sodium thiosulfate dropwise until the endpoint is reached, indicated by a colorless (potassium iodate) or
sea-green (potassium dichromate) solution.
7.1.4.6 Record the titration value to the nearest 0.025 cm and repeat from 7.1.1 or 7.1.2 for a duplicate determination.
NOTE 2—To achieve maximum performance from a glass buret, it is necessary to use a small magnifier and to read to the nearest 0.025 cm .
7.1.4.7 Calculate the normality of the sodium thiosulfate solution as in 7.1.5 and proceed as in 7.1.6. If the titration is made to
standardize the iodine solution as described in 7.2 calculate the normality of the iodine solution as in 7.2.1.2 and proceed as in
7.2.1.3.
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7.1.5 Calculate the normality of the sodium thiosulfate solutions as follows:
N 5 20 0.0394 /T (1)
~ !
where:
N = normality, and
T = titration volume, cm .
7.1.6 If N is not equal to 0.0394, adjust the solution in the following manner: if the solution is too strong, add water (2.5 cm water
per dm sodium thiosulfate solution for each 0.0001 N over 0.0394); if the solution is too weak, add solid sodium thiosulfate (0.025
g solid sodium thiosulfate per dm sodium thiosulfate solution for each 0.0001 N under 0.0394).
7.2 Iodine Solution 0.04728 N (60.00003)—This solution may be standardized against the secondary standard sodium-thiosulfate
solution (see A1.3) standardized as in 7.1.
7.2.1 Use sodium thiosulfate solution as follows:
3 3
7.2.1.1 Pipet exactly 20 cm of iodine solution into a 250-cm iodine flask and cap. Continue as in 7.1.3 or 7.1.4.
7.2.1.2 Calculate the normality of the iodine solution as follows:
N 5 ~0.0394! T/20 (2)
where:
N = normality, and
T = cm of 0.0394 N sodium thiosulfate solution.
7.2.1.3 If N is not equal to 0.04728 N, adjust solution in the following manner: if the solution is too concentrated, add water (2.1
3 3
cm water per dm iodine solution for each 0.0001 N over 0.04728); if the solution is too diluted, add iodine (12.7 mg iodine per
dm iodine solution for each 0.0001 N under 0.04728). (This iodine may be more conveniently dispensed from a concentrated
solution.)
8. Normalization Using Iodine Number Reference Materials
8.1 The SRB HT reference materials (previously known as SRB HT Iodine Standards) are no longer commercially available but
may still be in use in some laboratories. A new lot was prepared by the same process as the SBR HT reference materials and was
designated as Iodine Number Reference (INR) to be consistent with D24’s naming protocol for reference materials. The SRB HT
and INR reference materials are each a set of three materials with different reference values. The three materials from either SRB
HT or INR reference materials should be used together for normalization. Do not normalize using some materials from both sets.
8.2 When a laboratory cannot obtain target values for all three SRB HT or INR reference materials within established control
limits, the user should review recommendations found in Guide D4821. If any one of the three SRB HT or INR reference materials
is still outside acceptable control limits, the method described in 8.3 – 8.6 should be used to normalize all test results.
8.3 Test the three SRB HT or INR reference materials four times each.
8.4 Perform a regression analysis using the target value of the SRB HT or INR reference materials (y value) and the individual
measured value (x value).
8.5 Normalize the values of all subsequent test results using this regression equation:
Normalized value 5 ~measured value 3slope!1y 2 intercept (3)
8.6 Alternatively, a table of numbers may be generated based on the regression equation to find the correspondence between a
measured value and a normalized value.
D1510 − 21
8.7 Reevaluate the need for normalization whenever replacement apparatus or new lots of iodine or sodium thiosulfate solutions,
or both, are put into use.
9. Sampling
9.1 Samples shall be taken in accordance with Practices D1799 and D1900.
10. Blank Iodine Determination
10.1 Method A—Blank Iodine Determination:
3 3 3
10.1.1 Make a blank iodine determination by pipeting 20 cm or dispensing 25 cm of 0.04728 N iodine solution into a 125-cm
Erlenmeyer flask and titrating with 0.0394 N sodium thiosulfate as in 11.10.1, 11.10.2, or 11.10.3.
10.1.2 A 25-cm blank must be multiplied by 0.8 for use in the formula of 13.1.
10.1.3 Make a duplicate blank determination and use the average of the two in the calculations.
NOTE 3—A duplicate blank determination need be run only once each day, unless new solutions are introduced during the day.
10.1.4 If both solutions are within acceptable limits, the blank will measure 24.00 6 0.09 cm . If not, the normalities of one or
both solutions should be rechecked. If, after the recheck of solutions, normalities are still outside the acceptable limits refer to
7.2.1.3 to adjust iodine solution. See Table 1 for blank tolerance components.
10.1.5 The blank tolerance for a 20 cm volume of iodine solution is defined as the sum of (1) titration volume deviation for
acceptable variation in both iodine and sodium thiosulfate solution concentrations, and (2) dispenser tolerance for Class A 20 mL
pipet.
10.1.6 The solution deviation is based on the maximum variation in solution concentrations defined in 7.1 and 7.2. Tolerances for
Class A volumetric pipets are from Specification E969.
10.2 Method B—Blank Iodine Determination:
10.2.1 Make a blank iodine determination by placing a magnetic stir bar into an empty beaker and place the beaker into the
automated sample processor.
10.2.2 Initiate the automatic sample processor and titration apparatus.
10.2.3 Dispense an appropriate volume of 0.04728 N iodine solution into the beaker. Treat the blank in the same manner as the
sample, refer to Section 12.
NOTE 4—For different size beakers, ensure stir bar covers the bottom surface of beaker for good mixing.
10.2.4 Measures should be taken to ensure adequate purging of the entire system prior to delivering the final aliquot for titration
(see Note 5).
NOTE 5—An example of adequate purging of the system is achieved by double rinsing with the current blank solution followed with a distilled water rinse.
This can be done in the following manner: (1) fill the dosing device, which is equipped with a disposable filter, with an aliquot of the blank solution from
the beaker, dispense the entire volume into titration vessel, and pump out into the waste container; (2) repeat previous step one more time and fill the
dosing device with the final aliquot of blank solution (this aliquot should have an excess amount that will be used to flush the air bubbles, possibly formed
TABLE 1 Blank Tolerance Components
Blank A. Solution B. Dispenser Blank
3 3 3 3
Volume cm Deviations cm Tolerance cm Tolerance cm
20.00 ±0.06 ±0.03 ±0.09
D1510 − 21
during the two previous steps—the volume of aliquot used for titration can vary depending on user’s preference (7 to 20 cm has been found satisfactory));
(3) dispense a small portion of the blank solution into the reaction vessel, ensure that appropriate amount of the solution is left for titration in the dosing
device; and (4) clean the reaction (titration) vessel by rinsing with distilled water and pumping out waste repetitively.
10.2.5 Dispense a final aliquot of the blank solution into the reaction vessel for titration and wash the walls of the vessel, stirrer,
and redox-electrode with distilled water to ensure that any splashed iodine is washed into the mixture.
10.2.6 Automatically titrate the iodine solution with 0.0394 N sodium thiosulfate.
10.2.7 Make duplicate blank determinations. The average of two determinations is to be used in calculations.
10.2.8 Blank measurements may be made daily, especially where small solution lots are prepared within a lab. Alternatively,
blanks may be measured once per solution lot or other prescribed frequency, for large solution lots which are purchased, and where
adequate measures are used to monitor testing such as the daily use of x-charting HT or INR standards.
NOTE 6—For daily blanks, a duplicate blank determination need be run only once each day, unless new solutions are introduced during the day.
NOTE 7—When the particulate filter is changed adequate measures should be taken to saturate the filter with iodine solution. An example of an adequate
measure found to be satisfactory includes running a minimum of five blanks. The fourth and fifth blank are then averaged for the final blank value and
use the average of the two in the calculations. If the filter has not been changed use the average of the first and second blanks for calculations.
10.2.9 Blank tolerances are found in Table 2 for different volumes of iodine solution. A blank tolerance is defined as the sum of
(1) titration volume deviation for acceptable variation in both iodine and sodium thiosulfate solution concentrations, and (2)
dispenser tolerance for a piston-operated volumetric apparatus.
10.2.10 A blank tolerance can be calculated from the linear equation as follows:
Y 5 0.0056x10.0059 (4)
where:
Y = tolerance 6, and
x = aliquot volume, mL.
10.2.11 Blank tolerances for Method B are also found in Fig. 1. The function for solution deviation only and solution deviation
plus dispenser tolerance are included for reference.
10.2.12 The solution deviation is based on the maximum variation in solution concentrations defined in 7.1 and 7.2. Tolerances
for piston-operated volumetric apparatus are from ISO/EN/DIN 8655-3.
11. Sample Preparation and Iodine Number Determination—Method A
11.1 Dry an adequate sample of carbon black for 1 h, in a gravity-convection oven set at 125°C, in an open container of suitable
dimensions, so that the depth of the black is no more than 10 mm. Cool to room temperature in a desiccator before use.
11.2 Weigh a mass of the dried sample into a glass vial as shown by the following table. All masses must be to the nearest 0.001
g in case of iodine numbers from 0 to 520.9 and to the nearest 0.0001 g in case of iodine numbers from 521.0 and above.
TABLE 2 Blank Tolerances
Blank A. Solution B. Dispenser Blank
3 3 3 3
Volume cm Deviations cm Tolerance cm Tolerance cm
20.00 ±0.064 ±0.054 ±0.118
10.00 ±0.032 ±0.027 ±0.059
6.00 ±0.019 ±0.024 ±0.043
1.00 ±0.003 ±0.007 ±0.010
D1510 − 21
FIG. 1 Blank Tolerances for Method B as a Function of Aliquot Volume
Iodine Number Sample Mass (g) Ratio I : Sample Mass
0–130.9 0.500 50:1
131.0–280.9 0.250 100:1
281.0–520.9 0.125 200:1
521.0 and above 0.0625 400:1
11.3 Use the sample mass determined by the expected iodine number. If the result falls either above or below the range shown
for that sample size, retest using the sample mass specified in 11.2 for the range into which it has fallen.
NOTE 8—Unagitated, unpelleted carbon black may be densified, if desired, before drying, prior to weighing.
11.4 The sample mass table given in 11.2 pertains to the 25 cm iodine solution as given in 11.5. Different volumes of iodine
solution and of sample masses are permissible only if the iodine solution to sample mass ratio is kept the same as that given by
the table in 11.2. The sample mass must be kept to 1.000 g maximum. Should the sample mass and corresponding volume of iodine
solution be increased, then a glass vial with a volume that is at least two times the amount of iodine solution used for the test should
be used in order to preserve the efficiency of the shaking.
11.5 Pipet (or dispense from a calibrated repetitive dispenser) 25 cm of 0.04728 N I solution into the glass vial containing the
sample and cap immediately.
11.6 Secure the vial in the mechanical shaker and shake for 1 min at a minimum of 240 strokes/min.
11.7 Centrifuge immediately for 1 min for pelleted black and 3 min for loose black.
NOTE 9—Make sure that the carbon black is separated from the iodine solution in such a way that enough carbon black free iodine solution is available
for the titration. In case that carbon black particles are still visible in the iodine solution to be titrated, repeat the sample preparation and increase the
centrifugation speed.
11.8 Decant immediately. If more than one sample is being analyzed, the solution should be decanted into small flasks or clean,
dry vials and capped immediately.
3 3
11.9 Pipet 20 cm of solution into a 250-cm Erlenmeyer flask and titrate with standardized 0.0394 N sodium thiosulfate solution
using either the digital or glass buret as described in 11.10.
D1510 − 21
11.10 Titration of Iodine Solution:
11.10.1 Using a Digital Buret:
11.10.1.1 Switch to the fill mode, fill the buret reservoir with solution, and flush the inlet and delivery tubes.
11.10.1.2 Change to the titrate mode, zero the counter, and clean the tip with tissue.
11.10.1.3 Add sodium thiosulfate until the solution is pale yellow. Wash the buret tip and walls of the flask with water.
11.10.1.4 Add 5 drops of starch solution.
11.10.1.5 Continue adding sodium thiosulfate dropwise until the blue or blue-violet color almost disappears.
11.10.1.6 Wash the tip and walls of the flask with water and then advance the counter in 0.01-cm increments. Continue this
sequence until the endpoint is reached as indicated by a colorless solution.
11.10.1.7 Record the buret reading to the nearest 0.01 cm .
11.10.2 Using a Conventional Glass Buret:
11.10.2.1 Remove any adherent drop on the tip of the buret by gently toughing the drop with the wall of a clean flask. The flask
may be used several times by toughing a clean part of the wall to remove further drops prior to titration. Add sodium thiosulfate
until the solution is pale yellow. Wash the buret tip and walls of the flask with water.
11.10.2.2 Add 5 drops of starch solution.
11.10.2.3 Continue adding sodium thiosulfate dropwise until the endpoint is reached as indicated by a colorless solution.
11.10.2.4 Record the titration volume to the nearest 0.025 cm .
11.10.3 Using an Auto-titrator:
11.10.3.1 Two redox equivalence point titration methods should be programmed into the autotitrator:
(1) A method to store two blank determinations as an average blank value, and
(2) A method to analyze samples for iodine number.
NOTE 10—Follow the recommendations of the manu
...