Environmental Engineering Reference
In-Depth Information
Consequently, testing is needed for both reserve alkalinity and acid acceptance (Dow Chemical
Company, 1999c).
Other acid tests and related solvent tests include the following:
•
ASTM D 21-6-78—an amine acid acceptance method that measures the concentration of
an amine (basic) inhibitor by titration with standard acid.
ASTM D 2942-74—a test that determines the total AAV and measures the total concentra-
•
-epoxide) inhibitors in a solvent.
ASTM D 1364-90—a test that measures the water content of volatile solvents. The presence
tion of an amine and neutral-type (
α
•
of water promotes corrosion of metals and hydrolysis of the chloride-carbon bond. The
hydrolysis releases hydrogen chloride, which immediately combines with water to form
hydrochloric acid. This test uses an analysis of Karl-Fischer type, which involves placing
a sample into a drying oven at a predetermined temperature for a predetermined period of
time. The water in the sample is vaporized and carried into a reaction vessel with methanol.
The methanol traps the water, which is titrated to an endpoint with a Karl-Fischer reagent
to determine the amount present.
1.2.5.2 Aluminum Scratch Test
The aluminum scratch test, ASTM D 2943-76, determines whether sufi cient metal inhibitor
(a compound that inhibits the catalyzing action of metal surfaces) is present to prevent reaction
between aluminum and methyl chloroform. The test involves holding a clean coupon (a coupon is
the metallurgical term for a thin strip of metal used for testing metal properties) of aluminum
beneath the surface of the liquid solvent and scratching away the protective oxide coating. If the
metal stabilizers in methyl chloroform (most commonly 1,4-dioxane) are depleted, a reaction will
ensue that produces a blood-red color emitted from the metal surface. The color and bubbling are
attributed to the complex formed between aluminum chloride and methyl chloroform, following
dehydrochlorination and the production of hydrogen chloride gas. The degree of solvent discolor-
ation, the amount of dark residue material formed, and the presence or absence of hydrogen chloride
bubbling are used to gauge the inhibitor strength (Archer, 1984; Tarrer et al., 1989).
Other tests for inhibition of solvent breakdown by metals are as follows:
•
The National Institute of Cleaning and Dying Standard 3-50 tests for an 18 mg or smaller
loss in three uniformly sized copper strips (Skeeters, 1960b)
Federal Specii cation OT-634A, “Trichloroethylene, Technical, 4/17/56” tests quantitatively
•
for the extent to which metal-catalyzed oxidation decomposition of TCE has progressed
1.2.6 I
DENTIFYING
S
OLVENT
S
TABILIZERS
U
SED
IN
C
HLORINATED
S
OLVENTS
Determining the right mix of additives that will successfully stabilize a chlorinated solvent for a
particular application was the subject of intensive research by industrial chemists working for the
major solvent producers. Obtaining a successful formulation was a dei nite advantage in a competi-
tive market. Proprietary formulations were therefore held as trade secrets, making difi cult the task
of establishing which stabilizers were used in commercial formulations of the major chlorinated
solvents. Nevertheless, there are several ways of determining the identity and composition of stabi-
lizers in commercial solvent formulations. The presence of specii c stabilizer compounds in com-
mercial solvent formulations may be documented in the following:
•
MSDSs
•
Chemical Safety Data Sheets from the Manufacturing Chemists Association (predating
MSDSs)
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