earth metal (this includes Mg(OH)2 (magnesium hydroxide) but excludes NH3 (ammonia)). Any base that is soluble in water and forms hydroxide ions or the solution of a base in water. (This includes both Mg(OH)2 and NH3, which forms NH4OH.) The second subset of bases is also called an "Arrhenius base". Alkali salts Alkali salts are soluble hydroxides of alkali metals and alkaline earth metals, of which common examples are: Sodium hydroxide (NaOH) – often called "caustic soda" Potassium hydroxide (KOH) – commonly called "caustic potash" Lye – generic term for either of two previous salts or their mixture Calcium hydroxide (Ca(OH)2) – saturated solution known as "limewater" Magnesium hydroxide (Mg(OH)2) – an atypical alkali since it has low solubility in water (although the dissolved portion is considered a strong base due to complete dissociation of its ions) Alkaline soil Soils with pH values that are higher than 7.3 are usually defined as being alkaline. These soils can occur naturally, due to the presence of alkali salts. Although many plants do prefer slightly basic soil (including vegetables like cabbage and fodder like buffalo grass), most plants prefer a mildly acidic soil (with pHs between 6.0 and 6.8), and alkaline soils can cause problems. Alkali lakes In alkali lakes (also called soda lakes), evaporation concentrates the naturally occurring carbonate salts, giving rise to an alkalic and often saline lake. Examples of alkali lakes: Alkali Lake, Lake County, Oregon Baldwin Lake, San Bernardino County, California Bear Lake on the Utah–Idaho border Lake Magadi in Kenya Lake Turkana in Kenya Mono Lake, near Owens Valley in California Redberry Lake, Saskatchewan Summer Lake, Lake County, Oregon Tramping Lake, Saskatchewan See also Alkali metals Alkaline earth metals Base (chemistry) References Inorganic chemistry