The notation  hydrated compound ânH2O , where n is the number of water molecules per formula unit of the salt, is commonly used to show that a salt is hydrated. The n is usually a low integer, though it is possible for fractional values to occur. For example, in a monohydrate n is one, and in a hexahydrate n is 6.
When does spring start? How you define the first day of spring depends on whether you follow the astronomical or meteorological seasons. This year, spring will take place between March 20 and June 21, if you use the astronomical method. But it starts slightly earlier, between March 1 and May 31, if you follow the meteorological calendar.
CLEVELAND, Ohio -- The first day of spring 2017 will be March 20, with winter officially ending at 6:28 a.m. that day. Summer 2017 will begin on June 21, fall on Sept. 22 and winter on Dec. 21. The first day of spring and fall each year marks the point when the length of days and nights are approximately equal everywhere on Earth. In Cleveland, day and night will each last very close to 12 hours a little ahead of the start of spring, on March 17, according to the U.S. Naval Observatory.