ASTM D7704-11

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Designation:D7704–11
Standard Test Method for
Total Aldehydes in Styrene Monomer by Potentiometric
Titration
This standard is issued under the fixed designation D7704; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3. Summary of Test Method
1.1 This test method covers the wet chemical determination 3.1 An alcoholic solution of hydroxylamine hydrochloride
of aldehydes in styrene monomer. Aldehydes are calculated is added to a specimen of styrene monomer. Active aldehydes
and reported as benzaldehyde. The range of concentration for present react in accordance with Eq 1:
this test method is 0.001 mass % to 0.030 mass %.
RCHO 1 NH OH·HCl→ RCHNOH 1 H O 1 HCl (1)
2 2
1.2 In determining conformance of the test results using this
The amount of hydrochloric acid released, which is equiva-
methodtoapplicablespecifications,resultsshallberoundedoff
lent to the aldehyde present in the sample, is titrated with
in accordance with the rounding-off method of Practice E29.
standard alcoholic potassium hydroxide solution.
1.3 The values stated in SI units are to be regarded as
standard. No other units of measurement are included in this
4. Significance and Use
standard.
4.1 This test method is suitable for determining the quantity
1.4 This standard does not purport to address all of the
of aldehydes, both for quality control and quality assurance of
safety concerns, if any, associated with its use. It is the
the product.
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
5. Interferences
bility of regulatory limitations prior to use.
5.1 Ketones, if present, interfere by partially reacting with
the reagent.
2. Referenced Documents
5.2 Methanolusedinthisproceduremaypartiallyreactwith
2.1 ASTM Standards:
aldehydes to form (hemi)acetals.
D1193 Specification for Reagent Water
D3437 Practice for Sampling and Handling Liquid Cyclic
6. Apparatus
Products
6.1 Titration Vessel, 150 mL.
D6809 Guide for Quality Control and Quality Assurance
6.2 Combined pH – Glass Electrode, dedicated for non-
Procedures for Aromatic Hydrocarbons and Related Ma-
aqueous liquids.
terials
6.3 Stirring Bar,30mm.
E29 Practice for Using Significant Digits in Test Data to
6.4 Titration Stand with stirrer.
Determine Conformance with Specifications
6.5 Pipets,25mL.
2.2 Other Documents:
6.6 Volumetric Flasks, 100 mL.
OSHA Regulations, 29 CFR paragraphs 1910.1000 and
6.7 Burets, 5 mL. (Microburets are preferred.)
1910.1200
6.8 Exchange Unit, 5 mL.
6.9 Thermometers, capable of differentiating 1°C at ambi-
This test method is under the jurisdiction of ASTM Committee D16 on ent.
Aromatic Hydrocarbons and Related Chemicals and is the direct responsibility of
Subcommittee D16.07 on Styrene, Ethylbenzene and C and C Aromatic Hydro-
9 10
carbons.
Current edition approved March 1, 2011. Published March 2011. DOI: 10.1520/
D7704–11.
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D7704–11
7. Reagents and Materials while stirring. Titrate with the 0.02 N KOH/methanol solution,
dispensed from a 5-mL buret, until the first equivalence point,
7.1 Purity of Reagents—Reagent grade chemicals shall be
and record the volume used.
used in all tests. Unless otherwise indicated, it is intended that
10.3 Since methanol may contain aldehydes, run a blank
all reagents conform to the specifications of the Committee on
determination on 25 mL of methanol (7.4), record the volume
Analytical Reagents of the American Chemical Society where
used.
such specifications are available. Other grades may be used,
10.4 Since styrene may contain acids, run a blank determi-
provided it is first ascertained that the reagent is of sufficiently
nation by repeating 10.2 without adding the neutralized hy-
high purity to permit its use without lessening the accuracy of
droxylamine hydrochloride solution, record the volume used.
the determination.
7.2 Purity of Water—Unless otherwise indicated, references
11. Calculation
to water shall be understood to mean reagent water as defined
11.1 Calculate the percentage of aldehydes as benzaldehyde
by Type III of Specification D1193.
as follows:
7.3 Hydroxylamine Hydrochloride Solution—Dissolve 20 g
of hydroxylamine hydrochloride (NH OH·HCl) in 1 L of
Aldehydes, mass % 5 [~~A 2 B 2 C!/N 3 0.106!/25 3 D] 3 100
methanol. Take a portion of this volume (for example, 50 mL) (2)
and neutralize (to the first equivalency p
...