Reaction of the anhydrous compound with sodium cyclopentadienide gives cobaltocene.

The anhydrous compound is a yellow solid.

HO and as the anhydrous compound.

The anhydrous compound hydrogen fluoride is more commonly used than its aqueous solution, hydrofluoric acid.

When water is then added to the anhydrous compound, it turns back into the pentahydrate form, regaining its blue color, and is known as blue copperas.

Some anhydrous compounds are hydrated so easily that they are said to be hygroscopic and are used as drying agents or desiccants.

As well as the anhydrous compound Co(NO), there are several hydrates of cobalt(II) nitrate.

Most common is the tetrahydrate Mn(NO) 4HO, but mono- and hexahydrates are also known as well as the anhydrous compound.

This anhydrous compound is a mauve-colored solid that rapidly absorbs water on exposure to air to form a purple-colored hexa hydrate, NdCl 6HO.