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.
Answer Wiki. A2A. There are several interpretations of Spring. Astronomically, it begins on the Vernal Equinox, which is on or around March 21st, and ends on the Summer Solstice, on or about June 21st. Then there is Meteorological Spring, which begins on March 1st and ends on May 31st.