Superoxide forms salts with alkali metals and alkaline earth metals. It oxidizes chemicals such as hydrides, alkali metals, and some alkaline earth metals. The permanganates of alkali and alkaline earth metals are powerful oxidizers. Pure water has a pH close to 7 (neither alkaline nor acidic). Lithium iron disulfide batteries are intended for use in equipment compatible with alkaline zinc batteries. Phosphate is another inhibitor which competitively inhibits alkaline phosphatase. Sodium silicates are stable in neutral and alkaline solutions. Aqueous solutions should be neutral to slightly alkaline. The chemistry of calcium is that of a typical heavy alkaline earth metal. EMD is commonly used in zinc manganese dioxide rechargeable alkaline (Zn RAM) cells also. Prismatic cells were made available in both alkaline and lithium designs. It requires light, often alkaline soils. Manganates are unstable towards disproportionation in all but the most alkaline of aqueous solutions. Capacity of NiMH batteries is close to that of alkaline batteries. Dissolution of weak acids in alkaline media is similarly important.