Context and question: Mercury has been smelted from cinnabar for thousands of years. Mercury dissolves many metals, such as gold, silver, and tin, to form amalgams (an alloy in a soft paste, or liquid form at ambient temperature). Amalgams have been used since 200 BC in China for plating objects with precious metals, called gilding, such as armor and mirrors. The ancient Romans often used mercury-tin amalgams for gilding their armor. The amalgam was applied as a paste and then heated until the mercury vaporized, leaving the gold, silver, or tin behind. Mercury was often used in mining, to extract precious metals like gold and silver from their ores.
Since when have Amalgams been used?
Answer: 200 BC
Context and question: A multilateral treaty is concluded among several countries. The agreement establishes rights and obligations between each party and every other party. Multilateral treaties are often regional.[citation needed] Treaties of "mutual guarantee" are international compacts, e.g., the Treaty of Locarno which guarantees each signatory against attack from another.
What is a treaty concluded among several countries?
Answer: A multilateral treaty
Context and question: DST has mixed effects on health. In societies with fixed work schedules it provides more afternoon sunlight for outdoor exercise. It alters sunlight exposure; whether this is beneficial depends on one's location and daily schedule, as sunlight triggers vitamin D synthesis in the skin, but overexposure can lead to skin cancer. DST may help in depression by causing individuals to rise earlier, but some argue the reverse. The Retinitis Pigmentosa Foundation Fighting Blindness, chaired by blind sports magnate Gordon Gund, successfully lobbied in 1985 and 2005 for US DST extensions.
What vitamin does sunlight help the human body absorb?
Answer:
vitamin D