Thorium(IV) nitrate
Thorium nitrate is a chemical compound, a salt of thorium and nitric acid with the formula. A white solid in its anhydrous form, it can form tetra- and pentahydrates. As a salt of thorium it is weakly radioactive.
Preparation
Thorium nitrate hydrate can be prepared by the reaction of thorium hydroxide and nitric acid:Different hydrates are produced by crystallizing in different conditions. When a solution is very dilute, the nitrate is hydrolysed. Although various hydrates have been reported over the years, and some suppliers even claim to stock them, only the tetrahydrate and pentahydrate actually exist. What is called a hexahydrate, crystallized from a neutral solution, is probably a basic salt.
The pentahydrate is the most common form. It is crystallized from dilute nitric acid solution.
The tetrahydrate, is formed by crystallizing from a stronger nitric acid solution. Concentrations of nitric acid from 4 to 59% result in the tetrahydrate forming. The thorium atom has 12-coordination, with four bidentate nitrate groups and four water molecules attached to each thorium atom.
To obtain the anhydrous thorium nitrate, thermal decomposition of is required. The decomposition occurs at.
Properties
Anhydrous thorium nitrate is a white substance. It is covalently bound with low melting point of.The pentahydrate crystallizes with clear colourless crystals in the orthorhombic system. Each thorium atom is connected twice to each of four bidentate nitrate groups, and to three water molecules via their oxygen atoms. In total the thorium is eleven-coordinated. There are also two other water molecules in the crystal structure.The water is hydrogen bonded to other water, or to nitrate groups.
Thorium nitrate can dissolve in several different organic solvents including alcohols, ketones, esters and ethers. This can be used to separate different metals such as the lanthanides. With ammonium nitrate in the aqueous phase, thorium nitrate prefers the organic liquid, and the lanthanides stay with the water.
Thorium nitrate dissolved in water lowers it freezing point. The maximum freezing point depression is with a concentration of.
Reactions
When thorium nitrate pentahydrate is heated, nitrates with less water are produced, however the compounds also lose some nitrate. At a basic nitrate, is produced. When strongly heated thorium dioxide is produced.A polymeric peroxynitrate is precipitated when hydrogen peroxide combines with thorium nitrate in solution with dilute nitric acid. Its formula is.
The hydrolysis of thorium nitrate solutions produces basic nitrates and. In crystals of a pair of thorium atoms are connected by two bridging oxygen atoms. Each thorium atom is surrounded by three bidentate nitrate groups and three water molecules, bringing the coordination number to 11.
When oxalic acid is added to a thorium nitrate solution, insoluble thorium oxalate precipitates. Other organic acids added to thorium nitrate solution produce precipitates of organic salts with citric acid; basic salts, such as tartaric acid, adipic acid, malic acid, gluconic acid, phenylacetic acid, valeric acid. Other precipitates are also formed from sebacic acid and azelaic acid
Double salts
Hexanitratothorates with the generic formula or are made by mixing other metal nitrates with thorium nitrate in dilute nitric acid solution. can be Mg, Mn, Co, Ni, or Zn. can be Cs, or. Crystals of the divalent metal thorium hexanitrate octahydrate have a monoclinic form with similar unit cell dimensions: β=97°, a=9.08 b=8.75-8 c=12.61-3.Pentanitratothorates with the generic formula are known for being Na or K.
and are also known.