Heavy metals only mercury, lead and bismuth meet all of them. Despite this lack of agreement, the term (plural or singular) is widely used in science. A density of more than 5 g/cm is sometimes quoted as a commonly used criterion and is used in the body of this article. The earliest known metals—common metals such as iron, copper, and tin, and precious metals such as silver, gold, and platinum—are heavy metals. From 1809 onwards, light metals, such as magnesium, aluminium, and titanium, were discovered, as well as less well-known heavy metals including gallium, thallium, and hafnium. Some heavy metals are either
Permanente Metals short tons of goop-filled bombs were used in World War II (approximately eight percent of the total tonnage of incendiaries that were dropped during that conflict). Permanente ranked 42nd among United States corporations in the value of World War II military production contracts. Permanente Metals Permanente Metals Corporation (PMC) is best known for having managed the Richmond Shipyards in Richmond, California, owned by one of industrialist Henry J. Kaiser's many corporations, and also engaged in related corporate activities. These four of the seven west coast Kaiser Shipyards were known for their construction of Liberty ships. The company was also a