SOLVENTS AND DILUENTS

207

Solvents, evaporation rate. The volatile part of a paint or varnish film is
necessary at the time of application and largely escapes or evaporates after the
film is spread. This escape is a movement of molecules through the surface and

100

Time in Hourly

FIGURE i. Evaporation rate curves of fast to intermediate liquids, adapted from those
of A. K. Doolittle, 'Lacquer Solvents in Commercial Use,' Industrial and Engineering
Chemistry, XXVII (1935), p. 1171, fig. 3- According to number, these are as follows:

1. Methyl acetate

2. Acetone

3. Benzene

4. Ethylene dichloride

5. Ethyl acetate

6. Methanol (anhydrous)

7. Methyl ethyl ketone

8. Ethanol (anhydrous)

9. Petroleum naphtha

10. Toluene

11. 7?-Butyl acetate

12. Xylene

13. Amyl acetate (mixed isomers)
into the surrounding air where they mix with the gaseous components of the air
and become part of them. Escaping molecules exert a pressure called * vapor
pressure/ The rate of escape differs greatly in different liquids. To some extent.