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.
The eclipse will cross America, from Oregon to the Carolinas. (Courtesy of NASA) The last total solar eclipse visible from the continental United States was in 1979, and it was only over a corner of the Pacific Northwest.