Ammonium polyphosphate
Ammonium polyphosphate commercially produced by Clariant (former business area of Hoechst AG), is an inorganic salt of polyphosphoric acid and ammonia containing both chains and possibly branching. Its chemical formula is [NH4 PO3]n showing that each monomer consists of an orthophosphate radical of a phosphorus atom with three oxygens and one negative charge neutralized by an ammonium cation leaving two bonds free to polymerize. In the branched cases some monomers are missing the ammonium anion and instead link to three other monomers.