. . . "As the solvent, a hydrocarbon solvent such as hexane, benzene, toluene or xylene, a halogenated hydrocarbon solvent such as dichloromethane or chloroform, an ether solvent such as diethyl ether, tetrahydrofuran or 1,4-dioxane, an ester solvent such as methyl acetate or ethyl acetate, a ketone solvent such as acetone or methyl ethyl ketone, an aprotic polar solvent such as N,N-dimethylformamide, N," . .