Heavy metals is improved with the addition of thorium. Tellurium is added to copper and steel alloys to improve their machinability; and to lead to make it harder and more acid-resistant. The biocidal effects of some heavy metals have been known since antiquity. Platinum, osmium, copper, ruthenium, and other heavy metals, including arsenic, are used in anti-cancer treatments, or have shown potential. Antimony (anti-protozoal), bismuth (anti-ulcer), gold (anti-arthritic), and iron (anti-malarial) are also important in medicine. Copper, zinc, silver, gold, or mercury are used in antiseptic formulations; small amounts of some heavy metals are used to control algal growth in, for example,
Heavy metals differences become less clear at the boundaries. Light structural metals like beryllium, scandium, and titanium have some of the characteristics of heavy metals, such as higher melting points; post-transition heavy metals like zinc, cadmium, and lead have some of the characteristics of light metals, such as being relatively soft, having lower melting points, and forming mainly colourless complexes. Heavy metals are present in nearly all aspects of modern life. Iron may be the most common as it accounts for 90% of all refined metals. Platinum may be the most ubiquitous given it is said to be found in, or used