Water of crystallization degree of hydration can be critical to the resulting chemical properties. For example, anhydrous RhCl is not soluble in water and is relatively useless in organometallic chemistry whereas RhCl•3HO is versatile. Similarly, hydrated AlCl is a poor Lewis acid and thus inactive as a catalyst for Friedel-Crafts reactions. Samples of AlCl must therefore be protected from atmospheric moisture to preclude the formation of hydrates. Crystals of hydrated copper(II) sulfate consist of [Cu(HO)] centers linked to SO ions. Copper is surrounded by six oxygen atoms, provided by two different sulfate groups and four molecules of water. A fifth water resides elsewhere
Water crisis in the Democratic Republic of the Congo that they require only minimal investment to install and maintain. However, springs are often exploited without adequate protection and development. Another important source of water supply in rural areas are shallow wells, using hand and machine pumps. Other rural water supply sources include boreholes, small piped distribution systems and rainwater harvesting systems. Generally, charges for rural water systems do not cover operational costs. Furthermore, almost no water quality testing is conducted. Current investments in the rural water sector aim at the expansion of borehole drilling and small piped networks in large villages, which each serve between 2,000 and 5,000 people