Troy weight Troy weight Troy weight is a system of units of mass customarily used for precious metals and gemstones. One troy ounce (abbreviated "t oz" or "oz t") is equal to exactly , (or about 1.0971 oz. avoirdupois, the "avoirdupois" ounce being the most common definition of an "ounce" in the US). There are only 12 troy ounces per troy pound, rather than the 16 ounces per pound found in the more common avoirdupois system. The avoirdupois pound has 7000 grains whereas the troy pound has only 5760 grains (i.e. 12 × 480 grains). Both systems use the same grain defined
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,