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.
Need to know the exact date of of the First Day of Spring this year? On the equinoxes the Sun shines directly on the equator and the length of day and night is nearly equal â but not quite. The March or Vernal Equinox is when the Sun crosses the celestial equator, moving from south to north. This date is considered to be the first day of Spring. Here's a chart that shows what day of the week the First Day of Spring is celebrated in Northern Hemisphere from 2016 - 2027: Year Day First Day of Spring Falls on