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,
Taxation of precious metals same "intra-community transaction" rules to all of Europe on a bilateral basis resulting in legally tax-free silver coin availability throughout all of Europe. Precious metals are subject to tax as collectibles, with any profit being taxed at the collectibles capital gains rate. This is normally the standard income tax rate, with metal held over 1 year is subject to a maximum of 28%. Note that many people unfamiliar with the collectibles tax rates (including some well-known websites) incorrectly think that precious metals are taxed at a flat 28% (because they interpret the word "maximum" in "maximum 28% rate"). Taxation of