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 1st day of spring marks the spring equinox, a time of renewed passion, transformation and rebirth. This year on the 20th March at 04.30am GMT, the sun shines directly on the equator. This day is the 1st day of spring on our calendar and known as the spring equinox.