Mixtures of these basic solvents with other solvents, including alcohols such as methanol and ethanol, ethers such as tetrahydroguran and dioxane, amides such as dimethylformamide and dimethylacetamide, aromatics such as toluene and benzene, haloalkanes such as chloroform and dichloromethane, ketones such as acetone and methylethylketone, and esters such as ethyl acetate, are also useful.