Barium carbonate as a flux, a matting and crystallizing agent and combines with certain colouring oxides to produce unique colours not easily attainable by other means. Its use is somewhat controversial since some claim that it can leach from glazes into food and drink. To provide a safe means of use, BaO is often used in fritted form. In the brick, tile, earthenware and pottery industries barium carbonate is added to clays to precipitate soluble salts (calcium sulfate and magnesium sulfate) that cause efflorescence. Barium carbonate Barium carbonate (BaCO), also known as witherite, is a chemical compound used in rat poison, bricks,
Sterling silver Royal Mint in 1843. It bears the royal stamp "ENRI. REX" ("King Henry") but this was added later, in the reign of Henry III. The first legal definition of sterling silver appeared in 1275, when a statute of Edward I specified that 12 Troy ounces of silver for coinage should contain 11 ounces pennyweights of silver and pennyweights of alloy, with 20 pennyweights to the Troy ounce. This is (not precisely) equivalent to a millesimal fineness of 926. In Colonial America, sterling silver was used for currency and general goods as well. Between 1634 and 1776, some 500 silversmiths created