Historical Use of Chlorinated Solvents and Their Stabilizing Compounds - Environmental Investigation and Remediation - page 29

TABLE 1.14
Purity of Solvents Sold for Industrial Uses

Solvent Grade Purity (%) References

Methyl chloroform Degreasing 95 Ashland Chemical Company (1995)

Technical 96.5 Dow Chemical Company (1990)

Technical 94-98 Unocal (1989)

Dichloromethane Technical 98 Vulcan Chemicals (1987)

Technical 99.5 Dow Chemical Company (1995)

Technical 99.9 Dow Chemical Company (1999a)

Aerothene MM™ 99.4 Dow Chemical Company (2006a)

Trichloroethylene Neu-Tri™ 99.4 Dow Chemical Company (1981, 2006a)

Technical, O-T-634 Dow Chemical Company (1985a)

> 95

Perchloroethylene Perchloroethylene-SVG™ 99.5 Dow Chemical Company (1986)

DOWPER CS solvent™, 1985 97 Dow Chemical Company (1985b)

DOWPER solvent™, 2006 99 a Dow Chemical Company (2006a)

Perclene™ dry-cleaning grade 99-100 Occidental Chemical Corporation (1991)

SVG double-stabilized 99 b Dow Chemical Company (2006a)

a

1% stabilizer.

b

0.1% stabilizer.

The relative stability of the major solvents can be inferred from the quantity of stabilizers
required. Material Safety Data Sheets (MSDSs) and other documents indicate the purity of solvents
sold for industrial applications in recent years, as presented in Table 1.14.
Solvent purity listed in Table 1.14 rel ects both the addition of stabilizers and impurities from
manufacturing. Technical grade TCE (also called “industrial grade”) has been known to include
about 0.15% carbon tetrachloride as the major chlorinated hydrocarbon impurity (Willis and
Christian, 1957). The compound 1,1,2-trichloroethane can be an impurity in the manufacture of
methyl chloroform and is more reactive than methyl chloroform (World Health Organization, 1990).
Solvent impurities may also be introduced from cross-contamination in unclean tank cars,
tank trucks, drums, piping, and hoses. Mixtures of chlorinated solvents, even if stabilized, may
have substantially reduced stability when in contact with aluminum, compared to the stability of
the individual solvents. For example, stabilized TCE can become unstable in the presence of as
little as 2% of stabilized dichloromethane. When replacing one chlorinated solvent with another,
it is therefore necessary to remove all traces of the i rst solvent before using the new solvent
(EuroChlor, 2003). Most facilities would not frequently change solvents. However, solvent-recy-
cling facilities that use the same distillation equipment for different solvents must clean out drum-
i lling pipes between batches. Several anecdotes describe drum-i lling pipes that were l ushed to
the ground or storm drain sumps between batches of solvents at a solvent recycler in Silicon
Va l ley, Ca l i for n ia .

1.2.3.1 Performance Criteria for Solvent Stabilizers in Various Applications
The industrial chemists who worked to solve the solvent-breakdown problem overcame a major
challenge of solvent stabilization through much experimentation. Additives were needed that would
inhibit a variety of reactions with the aggressive substances found in industrial processes, especially
where physically destructive conditions are present. The chemists' pursuit was to i nd stabilizers
that would meet most of the following criteria (Levine and Cass, 1939; Klabunde, 1949; Kauder,