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
Drinking water supply and sanitation in the United States water quality that are of some concern in the United States, including Cryptosporidium, disinfection by-products, lead, perchlorates and pharmaceutical substances. However, in almost all cases drinking water quality is in conformity with the norms of the Safe Drinking Water Act, which requires EPA to set Maximum Contaminant Levels for pollutants. In addition, the EPA's Consumer Confidence Rule of 1998 requires most public water suppliers to provide consumer confidence reports, also known as annual water quality reports, to their customers. Each year by July 1 anyone connected to a public water system should receive in the mail an annual water quality