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 spring (vernal) equinox will occur on Monday, March 20, 2018 at 16:15 UTC. In the United States, this translates to 12:15 pm EST, 11:15 am CST, 10:15 am MST, and 9:15 am PST. In the Southern Hemisphere, the equinox will mark their first day of autumn. The total duration of spring 2018 is 92 days, 17 hours, and 55 minutes.