Pewter is a chemical element with the symbol Sn (Latin: stannum) and atomic number 50. It is a silvery metal main group. Tin, one of the earliest discovered metals, was used for the manufacture of bronze, a copper-tin alloy. In 3500 BC. was already known that tin (as well as arsenic and nickel) had a hardening effect on copper. Therefore, it was used in tools and weapons. In the Bronze Age it was an indispensable metal as the prevailing technology was based on bronze. Even before the days of the Romans there was a thriving trade between the tin mines in Cornwall and the Mediterranean. The Egyptian pharaoh Pepi has around 2300 BC. let make a statue which was tin from the tin mines of Cornwall. In Assyrian trade settlements in Anatolia as rubber was already before 2000 BC. a lively trade in the metal, it probably came from what is now Afghanistan. From around the year 600 was tin also be applied in pure form. The word tin comes from the Germanic * TINA and state ablautend next toe that "twig" and in German (Zain) also "metal bar" means. The symbol Sn comes from the Neo-Latin stannum coming from the post-classical Latin Stagnum 'alloy of silver and lead. Tin is a flexible, malleable and highly crystalline silvery-white metal that upon bending gives a characteristic sound which is caused by the refracting crystals. The metal is resistant to sea and tap water, but is soluble in most acids. At standard pressure are two allotropes of tin. At low temperatures it occurs as a gray - alpha - tin with a cubic crystal structure similar to that of silicon and germanium. At temperatures above 13.2 ° C it changes to white - beta - tin. In this form, it has a tetragonal structure. On cooling, it again returns to the cubic shape. Previously, this process known as tin pest; it can be prevented by the addition of antimony or bismuth.