i p,o PAINTING MATERIALS
and have a toxic effect if inhaled for any considerable period. They are com-
bustible but not highly flammable.
Butyl Cellosolve (see Ethylene Glycol Monobutyl Ether and Glycol Ethers).
Butyl Lactate. This solvent (CH3-CHOH-COO-C4H9), an ester of butyl
alcohol and lactic acid, is very slow to evaporate and, for that reason, has certain
special uses. Herbert E. Ives and W. J. Clarke (' The Use of Polymerized Vinyl
Acetate as an Artist's Medium/ Technical Studies, IV [1935], pp. 36-41) suggest
it as a solvent for vinyl acetate when that is used as a painting medium. When
pure, it is colorless, but commercial varieties have a brown tint. It is only slightly
miscible with water (3.4 per cent at 25°C.) but is miscible with most organic
solvents. Toch says (p. 91) that butyl lactate added in small amounts to tur-
pentine acts as a good cleaning agent for old paintings.
Carbon Bisulphide (carbon bisulphide [CSa]). The only important industrial
solvent of this type containing sulphur, this is a volatile liquid which boils at
46.3°C. and is heavy (sp. gr. 1.263). ^ was discovered in 1796. The commercial
product, made by the direct union of carbon and sulphur at dull red heat, is
slightly yellow in color and has a disagreeable odor caused by impurities of other
organic sulphur compounds. It mixes with most organic solvents but only slightly
with water. The flash point is — 2o°C.; it is highly flammable and forms explosive
mixtures with air. It can be spontaneously ignited by contact with objects at
I5O°C.; even contact with a warm steam pipe or electric lamp bulb may be suffi-
cient to cause ignition of the vapor. Because of this, it is about the most dangerous
solvent in commercial use. Its vapors, moreover, are strongly toxic. Although it is
a good solvent for oils, fats, waxes, rubber, and a number of resins, safer materials
are now taking its place.
Carbon TetracMoride (tetrachlormethane ^CCl^J) may be regarded as meth-
ane, in which all the hydrogen atoms have been replaced by chlorine. Prepared
by the chlorination of carbon disulphide, this is a clear liquid with an odor similar
to that of chloroform, a high specific gravity (1.629), and a boiling point ofjy°C.
Because it is non-flammable, it has a unique place among organic solvents and is
miscible with most of them. Solvent action on oils and soft resins is good and it is
frequently mixed with other solvents to cut down the fire hazard. A disadvantage
is that at slightly elevated temperatures it reacts slowly with water to form
hydrochloric acid. At moderate temperatures it is stable to water and to light.
Cellosolve is a trade name for ethylene glycol monoethyl ether, and the name
is used with qualifying adjectives like methyl, butyl, etc., to designate several
other closely related derivatives of ethylene glycol (see Glycol Ethers).
Cellosolve Acetate (see Ethylene Glycol Monoethyl Ether Acetate and Glycol
Ethers),
Chlorinated Hydrocarbons (see Solvents, classification).
Chloroform (trichlormethane tCHCy), a clear, colorless liquid, with a charac-
teristic sweetish odor, and a boiling point of 6i°C., is prepared by the action of