ASTM D5776-99

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.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:D5776–99
Standard Test Method for
Bromine Index of Aromatic Hydrocarbons by Electrometric
Titration
This standard is issued under the fixed designation D 5776; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope* 2.2 Other Document:
OSHA Regulations, 29 CFR paragraphs 1910.1000 and
1.1 This test method determines the amount of bromine-
1910.1200
reactive material in aromatic hydrocarbons and is thus a
measure of trace amounts of unsaturates in these materials. It is
3. Terminology
applicable to materials having bromine indexes below 500.
3.1 Definition:
1.2 This test method is applicable to aromatic hydrocarbons
3.1.1 bromine index—the number of milligrams of bromine
containing no more than trace amounts of olefins and that are
consumed by 100 g of sample under given conditions.
substantially free frommaterial lighter than isobutane and have
a distillation end point under 288°C (550°F).
4. Summary of Test Method
1.3 The following applies to all specified limits in this
4.1 The specimen dissolved in a specified solvent is titrated
standard: For purposes of determining conformance with this
with standard bromide-bromate solution. The end point is
standard, an observed value shall be rounded off “to the nearest
indicated by a fixed end-point electrometric titration apparatus,
unit” in the last right hand digit used in expressing the
when the presence of free bromine causes a sudden change in
specification limit, in accordance with the rounding off method
the polarization voltage of the system.
of Practice E 29.
1.4 This standard does not purport to address all of the
5. Significance and Use
safety concerns, if any, associated with its use. It is the
5.1 This test method is suitable for setting specification, for
responsibility of the user of this standard to establish appro-
use as an internal quality control tool, and for use in develop-
priate safety and health practices and determine the applica-
mentorresearchworkonindustrialaromatichydrocarbonsand
bility of regulatory limitations prior to use. For a specific
related material. This test method gives a broad indication of
hazard statement see Section 8.
olefinic content. It does not differentiate between the types of
aliphatic unsaturation.
2. Referenced Documents
2.1 ASTM Standards:
6. Apparatus
D 1159 Test Method for Bromine Number of Petroleum
6.1 Fixed End Point Electrometric Titration Apparatus—
Distillates and Commercial Aliphatic Olefins by Electro-
Any fixed end-point apparatus may be used incorporating a
metric Titration
high resistance polarizing current supply capable of maintain-
D 1193 Specification for Reagent Water
ing approximately 10 to 50 µA across two platinum plate
D 3437 Practice for Sampling and Handling Liquid Cyclic
electrodes or a combination platinum electrode and with a
Products
sensitivity such that a voltage change of approximately 50 mV
E 29 Practice for Using Significant Digits in Test Data to
at these electrodes is sufficient to indicate the end point (see
Determine Conformance with Specifications
Note 1).
E 691 Practice for Conducting an Interlaboratory Study to
Determine the Precision of a Test Method
NOTE 1—The reagents and techniques may be checked by determining
the bromine index of a 100 mg/kg cyclohexene in heptane. This is
expected to give a bromine index of 18 to 20 mg/100 g sample. Refer to
Table A2.1 of Test Method D 1159.
This test method is under the jurisdiction of ASTM Committee D16 on
Aromatic Hydrocarbons and Related Chemicals and is the direct responsibility of
6.2 Titration Vessel—A tall form glass beaker of approxi-
Subcommittee D16.04 on Instrumental Analysis.
mately 250-mL capacity or a water jacketed titration vessel of
Current edition approved June 10, 1999. Published August 1999. Originally
published as D 5776 – 95. Last previous edition D 5776 – 98.
Annual Book of ASTM Standards, Vol 05.01.
Annual Book of ASTM Standards, Vol 11.01.
4 6
Annual Book of ASTM Standards, Vol 06.04. AvailablefromSuperintendentofDocumentsU.S.GovernmentPrintingOffice,
Annual Book of ASTM Standards, Vol 14.02. Washington, DC 20402.
*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.
D5776–99
approximately 250-mL capacity connected to a refrigerated flask, remove the flask from the ice bath and allow the KI
circulating water bath controlling the temperature at 0 to 5°C. solution to slowly flow into the flask by removing the stopper.
Apairofplatinumelectrodesspacednotmorethan5mmapart, Shake vigorously, transfer to a chilled beaker and rinse the
shall be mounted to extend well below the liquid level. Stirring flask including stopper with 100 mL of water. Immerse the
shall be by a mechanical or electromagnetic stirrer and shall be electrodes into the solution, titrate with standard sodium
rapid but not so vigorous as to draw air bubbles down to the thiosulphate (Na S O ) to an end point indicated by a
2 2 3
electrodes. significant change in potential that persists for 30 s (see Note
6.3 Iodine Number Flasks, glass-stoppered, 500-mL capac- 2).
ity.
NOTE 2—With commercial titrators, a sudden change in potential is
indicated on the meter or dial of the instrument as the endpoint is
7. Reagents and Materials
approached. When this change persists for 30 s it marks the end of the
titration. With each instrument, the manufacturer’s instructions should be
7.1 Purity of Reagents—Reagent grade chemicals shall be
followed to achieve the sensitivity achieved in the platinum electrode
used in all tests. Unless otherwise indicated, it is intended that
circuit.
all reagents shall conform to the specifications of theAmerican
Chemical Society where such specifications are available. 7.5 Potassium Iodide Solution (150 g/L)—Dissolve150gof
potassium iodide (KI) in water and dilute to 1.0 L.
Other grades may be used, providing it is first ascertained that
the reagent is of sufficiently high purity to permit its use 7.6 Sodium Thiosulphate, Standard Solution (0.10 N)—
Dissolve 25.0 g of sodium thiosulphate pentahydrate (Na
without lessening the accuracy of the determination.
7.2 Purity of Water—Unless otherwise indicated references 2S O ·5H O) in water and add 0.02 g of sodium carbonate
2 3 2
(Na CO ) to stabilize the solution. Dilute to 1.0 L and mix
to water shall be understood to mean reagent water conforming
2 3
to Type III of Specification D 1193. thoroughly by shaking. Standardize by any accepted procedure
that determines the normality with an error not greater than 6
7.3 Bromide-Bromate Standard Solution (0.10 N) —
Dissolve 10.1 g of potassium bromide (KBr) and 2.8 g 0.0002. Restandardize at intervals frequent enough to detect
changes of 0.0005 in normality.
potassium bromate (KBrO ) in water and dilute to 1.0 L.
Standardize to four significant figures as follows: Place 50 mL 7.7 Starch Solution—Mill5gof arrow-root starch with 3
to 5 mL of water. Add the suspension to 2 L of boiling water.
of glacial acetic acid and 1.0 mL of concentrated hydrochloric
acid (HCl, sp gr 1.19) in a 500-mL iodine number flask. Chill As a preservative, 5 to 10 mg of mercuric iodide (H I)or0.2
g 2
g of salicylic acid can also be added. Boil for 5 to 10 min, then
the solution in an ice bath for approximately 10
...