SOLVENTS AND DILUENTS 193
there are some indications of toxicity. Oil-soluble dyes dissolve in dioxane, but
those which are usually spirit- or water-soluble are only partially affected by it.
Distillate. This name, given to a liquid that is condensed from its vapors,
covers most of the organic solvents. In distillation a liquid is purified by being
heated to the boiling point, the vapors then being condensed and collected.
Fractional distillation is the slow distillation of a mixture of substances and the
separate collection of distillates at each boiling point or after definite temperature
intervals. The low-boiling fractions are collected first. The distilling range is the
recorded thermometer range at which a liquid is distilled. Destructive distillation
is the heating with exclusion of air of complex organic matter like wood or coal
until it is decomposed or split into a number of liquid and solid substances.
Steam distillation is the passage of steam through a liquid whereby the liquid
vapor is carried off with the steam and, on condensation, the liquid and water
are separated by their immiscibility. Vacuum distillation is done under reduced
pressure; it is usually carried out with high-boiling materials which decompose at
their atmospheric boiling points. Most organic solvents are distilled in processes
of preparation or purification (see Alcohol, Petroleum Thinner, and Turpentine).
Essential Oil, a volatile oil, with characteristic odor, derived from plants.
Esters (see Solvents, classification).
Ether (ethyl ether [^HgOCaHs]). Since the XVI century this clear, volatile,
and highly flammable fluid has been made by the dehydration of ethyl alcohol
with sulphuric acid. The solvent action is very wide, including oils, resins, fats,
and waxes. High vapor pressure (442 mm. Hg at 20°C.), with danger of explosion,
make it hazardous to use as a studio or laboratory solvent. The boiling point is
34.5°C. The vapors are heavy and tend to creep. Because of its rapid evaporation,
it has little use as a commercial solvent for lacquer. It is completely miscible with
alcohol and with most organic solvents, but with water only to the extent of 7.42
per cent at 2o°C. It has some use as an extraction solvent in the analysis of paint
samples, and either alone or in mixtures for the removal of resin and wax.
Ethyl Acetate (CHsCOC^Hs). Action of acetic acid on alcohol forms this
ester. It is a colorless liquid, with faint odor, and the pure, anhydrous form boils
at 78°C. Being hygroscopic, it reacts with absorbed water by hydrolysis to form
acetic acid and alcohol. It is miscible with alcohol and with most organic solvents,
but only partially with water. Its acidity and the tendency to cause blush, the
result of rapid evaporation, are factors against its use as a solvent.
Ethylene Bichloride (i,2-dichlorethane [CH2C1CH2C1]), a clear, volatile
liquid, has an odor somewhat like that of chloroform and boils at 83.5°C. (It may
be confused with dichlorethylene, C2H2Cl2.) Dutch chemists discovered it in 1795,
making it one of the earliest organic compounds to be isolated. Only in recent
years, however, has it become commercially available. Direct chlorination of the
ethylene gas is the method of manufacture. This is an excellent solvent for oils,
fats, and waxes, and for certain resins, but serves only as a diluent for cellulose