A substance is anhydrous if it contains no water, for example, salts lacking their water of crystallisation. The way of achieving the anhydrous form differs from one substance to another.
A partial solar eclipse at its peak at 3:37 p.m. in Mesa on Oct. 23, 2014. The eclipse was visible over most of North America and covered 44 percent of the Arizona sun. Michael Chow/The Republic.
Like the supermoon eclipse, the total eclipse on August 21, 2017, will also be a rare event for the United States. The last time a total eclipse of the sun was visible in the United States was in 1979. After 2017, it will not occur again until 2024, according to EarthSky.org.