Period 6 element living organism. Tungsten interferes with molybdenum and copper metabolism, and is somewhat toxic to animal life. Rhenium is a chemical element with the symbol Re and atomic number 75. It is a silvery-white, heavy, third-row transition metal in group 7 of the periodic table. With an "estimated" average concentration of 1 part per billion (ppb), rhenium is one of the rarest elements in the Earth's crust. The free element has the third-highest melting point and highest boiling point of any element. Rhenium resembles manganese chemically and is obtained as a by-product of molybdenum and copper ore's extraction and refinement. Rhenium
Melting point a liquid phase only exists above pressures of and estimated (see ). Tantalum hafnium carbide (TaHfC) is a refractory compound with a very high melting point of 4215 K (3942 °C, 7128 °F). At the other end of the scale, helium does not freeze at all at normal pressure even at temperatures close to absolute zero; a pressure of more than twenty times normal atmospheric pressure is necessary. Many laboratory techniques exist for the determination of melting points. A Kofler bench is a metal strip with a temperature gradient (range from room temperature to 300 °C). Any substance can be