Superoxide forms salts with alkali metals and alkaline earth metals. Disposal by using dilute solution of alkali hydroxide is recommended. Tungsten trioxide can form intercalation compounds with alkali metals. The permanganates of alkali and alkaline earth metals are powerful oxidizers. Upon reacting with oxygen, alkali metals form oxides, peroxides, superoxides and suboxides. Saltiness is the taste of alkali metal ions such as sodium and potassium. Consequently, it forms complexes even with alkali metal cations. It is often stored in the form of alkali metal salts. Hydrogen, like some of the alkali metals, reacts explosively with fluorine. Fluorine reacts explosively with hydrogen in a manner similar to that of alkali metals. The toxicity of this compound is comparable to that of soluble alkali cyanides. PCBs have also been destroyed by pyrolysis in the presence of alkali metal carbonates. Addition of an alkali produced an oxide. And an amine by hoffman degradation of the amide in the presence of alkali hypoclorites. Hygroscopic, though less than other alkali halides usable for UV windows.