Typical inorganic water soluble salts suitable for use herein include alkali metal salts and the like such as potassium and ammonium salts e.g. potassium chloride, tetramethyl ammonium chloride and ammonium chloride; alkaline earth metal halides such as calcium chloride, calcium bromide and magnesium chloride; transition metal salts such as zinc halide salts, aluminium salts, zirconium salts and t