The Most Expensive Liquids In The World Mercury is the only metal that remains liquid at room temperature. It is mainly used in the production of thermometers. However, chemical industries, metal production, and agriculture find it useful too. 8. Mercury — $2,966 per gallon « Previous Page Next Page » Pages: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 2017-11-01 news