ASTM D2420-91(2001)

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An American National Standard
Designation: D 2420 – 91 (Reapproved 2001)
Standard Test Method for
Hydrogen Sulfide In Liquefied Petroleum (LP) Gases (Lead
Acetate Method)
This standard is issued under the fixed designation D 2420; 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 they come in contact and the measurement of hydrogen sulfide
2 is important. In addition, in some cases the odor of the gases
1.1 This test method covers the detection of hydrogen
must not be objectionable. (See ASTM Specification D 1835
sulfide in liquefied petroleum (LP) gases.The sensitivity of the
and GPA Standard 2140)
test is about 4 mg/m (0.15 to 0.2 grain of hydrogen sulfide per
100 ft ) of gas. Methyl mercaptan, if present, produces a
5. Apparatus and Materials
transitory yellow stain on the lead acetate paper which,
5.1 Apparatus for Detecting Hydrogen Sulfide in Liquefied
however, fades completely in less than 5 min. Other sulfur
Petroleum Gas, as shown in Fig. 1 or commercially available
compounds present in liquefied petroleum gas do not interfere
apparatus.
with the test.
5.2 Lead Acetate Test Paper—Commercially available test
1.2 The values stated in SI units are to be regarded as the
paper is satisfactory. Alternatively, the test paper can be
standard.
prepared by dipping strips of smooth filter paper in 5 % lead
1.3 This standard does not purport to address all of the
acetate solution and removing the excess solution with a clean
safety concerns, if any, associated with its use. It is the
blotter. The strips of paper shall be approximately 50 mm long
responsibility of the user of this standard to establish appro-
and 10 mm wide and containa3mm hole near one end so they
priate safety and health practices and determine the applica-
will hang freely vertical in the test apparatus.
bility of regulatory limitations prior to use.
5.3 Flow Indicator—Awet test meter or a rotameter, which
2. Referenced Documents measures flow rates in the range of 2 to 3 L of gas per minute.
2.1 ASTM Standards:
6. Sampling
D 1835 Specification for Liquefied Petroleum (LP) Gases
6.1 Caution—Because of the chemical activity and physi-
2.2 Other Document:
4 cal adsorptive properties of hydrogen sulfide, it is highly
GPA Standard 2140
desirable to connect the test apparatus directly to the sample
3. Summary of Test Method source and perform the test on the spot, rather than transferring
sample into a sample cylinder for testing in the laboratory.
3.1 The vaporized gas is passed over moist lead acetate
Experience has demonstrated that the hydrogen sulfide concen-
paper under controlled conditions. Hydrogen sulfide reacts
tration in liquefied petroleum gas by use of scrupulously clean
with lead acetate to form lead sulfide and thus produces a
sample cylinders is depleted even though the cylinder is made
coloration on the paper which will vary from yellow to black,
of stainless steel. The exact opposite, an increase in sulfide
depending upon the amount of hydrogen sulfide present.
concentration, has been found to occur when samples of
4. Significance and Use liquefied petroleum gas containing no hydrogen sulfide are
transferred into sample cylinders that have not been properly
4.1 Liquefied petroleum gases and the products of combus-
cleaned and which have been in use with samples containing
tion must not be unduly corrosive to the materials with which
hydrogen sulfide. This points out the fact that
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