Aluminium nitrate most commonly exists in its hydrated crystal form, aluminium nitrate nonahydrate, Al(NO3)3·9H2O. It is a white crystalline, water-soluble salt with a molecular weight of 375.15 g/mol. It melts at 73oC and decomposes at 150oC. It is an odourless material and will react explosively upon contact with organic compounds. Its solution is acidic and is a strong oxidising reagent. It can easily dissolve in water and ethanol but not in acetic acid and ethyl acetate.
Contrary to aluminium chloride, it cannot be synthesised just by adding nitrates containing compounds (such as nitric acid) to aluminium metal. This is because aluminium will form a passivation layer, where there will be a creation of an outer layer on the metal to prevent further chemical reactions from occurring. Hence, aluminium nitrate is typically prepared by the addition of nitric acid to aluminium chloride. Nitrosyl chloride is generated as a byproduct which oozes out of the solution as a gas.
Aluminium nitrate can also be produced by mixing solution of lead nitrate with aluminium sulfate via a metathesis reaction. Insoluble lead sulfate precipitates out of the solution, giving a solution with aluminium nitrate.
Aluminium nitrate works as a tanning agent that helps to stabilise the collagen structure in the leather skin. It develops bacteria-resistant properties along with hydrothermal stability in which the tanned collagen is able to remain stable at high temperature.
Aluminium nitrate is a strong oxidizing agent and it can have a lot of applications in various industries. Other than working as a tanning agent, it can be used for petroleum refining, dyeing agent for cotton industry, uranium extraction, and corrosion inhibitor.