It's generally described with the formula Al(OH)a Cl bwith a+b=3, combined with small amounts of other substances. This is a highly stable yellowish solution.
The Aluminium Polychloride is used for water and wastewater treatment either in normal or situations where large amounts of water with high colloidal concentration must be purified, such as in a flood.
Aluminium Polychloride efficiently coagulate suspended solids in the water, producing flakes that settle quickly, which accumulate as a deposit that can be easily filtered.
Several chemical, organic and inorganic, products are used as flocculation additives, but Aluminium Polychloride does not usually require any other substance to improve its performance and the necessary amount of alkalis is lower than with other flocculation agents, since the water pH is only moderately even in an overdose situation.