Cerium(III) sulfate, also called cerous sulfate, is an

inorganic compound In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as ''inorganic chemistr ...

with the formula Ce₂(SO₄)₃. It is one of the few salts whose solubility in water decreases with rising temperature. Cerium (III) sulfate (

anhydrous A substance is anhydrous if it contains no water. Many processes in chemistry can be impeded by the presence of water; therefore, it is important that water-free reagents and techniques are used. In practice, however, it is very difficult to achie ...

) is a

hygroscopic Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption or adsorption from the surrounding environment, which is usually at normal or room temperature. If water molecules become suspended among the substance ...

white solid, which begins to decompose above 600°C. It has a monoclinic crystal structure. Cerium (III) sulfate tetrahydrate is a white solid that releases its

water of crystallisation In chemistry, water(s) of crystallization or water(s) of hydration are water molecules that are present inside crystals. Water is often incorporated in the formation of crystals from aqueous solutions. In some contexts, water of crystallization i ...

at 220 °C. It has (like the white octahydrate) a monoclinic crystal structure with the space group ''P''2₁/''c'' (

space group In mathematics, physics and chemistry, a space group is the symmetry group of an object in space, usually in three dimensions. The elements of a space group (its symmetry operations) are the rigid transformations of an object that leave it unch ...

14). The nonahydrate has a hexagonal crystal structure with the space group ''P''6₃/''m'' (space group 176). Hydrates of this compound are known with 12, 9, 8, 5, 4 and 2 parts of water of crystallisation.

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