used for substituting water contained in the aqueous sol include aromatic hydrocarbons, such as toluene and xylene; alcohols, such as ethanol and n-butanol; polyhydric alcohols, such as ethylene glycol and propyleneglycol; glycol derivatives, such as butylcellosolve, ethylcellosolve, butylcellosolve acetate, propylene glycol monoethyl ether and propylene glycol monopropyl ether; aliphatic hydrocar