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.
The first day of Spring is in 2016 on March 19 (according to the astronomical definition). It is also called the spring quinox. Spring is one of the four temperate seasons, the transition period between winter and summer. Spring and springtime refer to the season, and broadly to ideas of rebirth, renewal and regrowth.