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.
Using these two annual events the year was divided into in 24 equal parts, each forming the 24 solar terms. The month with its first day nearest the Beginning of Spring (the first solar term) is the first lunar month, and on that day the Spring Festival is held and this varies between January 20th and February 20th.