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 dates for the next three total eclipses are Oct. 8, April 4, 2015 (also the first night of Passover), and Sept. 28, 2015. The last time four total lunar eclipses occurred in a row - called a tetrad - was in 2003-2004, and there will be seven more this century.