Historical Use of Chlorinated Solvents and Their Stabilizing Compounds - Environmental Investigation and Remediation - page 46

TABLE 1.24
Common Metal-Inhibitor Compounds Used in Chlorinated Solvents

Solvent and Trade Name and List
of Metal-Inhibitor Compounds Quantity (vol%) References

Methylene chloride
1,4-Dioxane

World Health Organization (1984b),
Beckers (1973)

<1
0.8

Cyclohexane Present Rowe and Cawley (1977)

1,3-Dioxolane ~ 2 Beckers (1973)

Stabilized trichloroethylene
Isoamyl alcohol Petering and Aitchison (1945)

Perchloroethylene
Cyclohexane

Stevens (1955)

<1

Ethyl acetate 0.1-0.5 Stevens (1955), Copelin (1959)

Methyl chloroform
1,4-Dioxane

2-2.7 Occidental Chemical Corporation (1989)

1,4-Dioxane 3 Ashland Chemical Company (1995)

1,4-Dioxane 0-4 Unocal (1989)

1,3-Dioxolane 2 Great Western Chemical Company

(1990)

1,3-Dioxolane 1-5 Ashland Chemical Company (1996)

Formaldehyde dimethyl hydrazone Present Tarrer et al. (1989)

2-Methyl-3-butyn-2-ol Present Ishibe and Metcalf (1982)

before arriving at the right chemical to reliably stop solvent breakdown. Far from trial and error,
industrial chemists applied sophisticated methods to select from thousands of candidate stabilizers.
A number of patents claim groups of three or more stabilizer chemicals that work synergistically,
such that the absence of one compound precludes the stabilizing action of the others. The extensive
list of more than 500 stabilizer compounds named in the patent literature and presented in Appendix
1 testii es to the enormous effort carried out by industrial chemists since 1914 to enable use of the
major chlorinated solvents in demanding applications.
In the early decades of solvent stabilization, some inventors made claims for single additives to
solve several stabilization problems. As the art of solvent stabilization evolved, industrial chemists
developed solvent stabilizer packages commonly consisting of four or more chemicals to address
the multiple reactions contributing to solvent breakdown. In recent decades, solvents were sold with
stabilizer packages customized for very specii c applications particular to each solvent, such as
vapor degreasing parts with iron and zinc but not aluminum or magnesium.
As with any endeavor involving organic chemistry, compiling lists of chemicals can be difi -
cult because of the many acceptable synonyms for organic compounds as well as the larger list
of trade names for some compounds. Appendix 1 lists some of the stabilizers claimed in the
selected patents cited.
A number of articles, product fact sheets, and other sources provide numerous nonspecii c lists
of stabilizer compounds that name the class of compounds used or provide a longer list of chemicals
that might have been used. Some listings of stabilizers for a given solvent include all the stabilizer
formulations used by the leading solvent producers, giving the incorrect impression that one manu-
facturer's grade of solvent might contain all the listed compounds. These listings are useful to obtain
a sense of which classes of compounds were required to neutralize acid, inhibit acid formation, and