tone, cyclopentanone and cyclohexanone; aliphatic and cyclic ethers such as diethyl ether, tetrahydrofuran, tetrahydropyrane anddioxane; and nitriles of saturated aliphatic monocarboxylic acids having a total of 1-6 carbon atoms, such as acetonitrile, propionitrile, methoxypropionitrile and butyronitrile.Aliphatic, cycloaliphatic and aromatic hydrocarbons are preferred, particularly alkanes having