Because representative, reliable sampling is the key to effective analytical control of bayer alumina plants, Alcan is completing a comprehensive sampling improvement program at its Vaudreuil Works alumina plants in Quebec. Automatic, continuous samplers have been developed and installed for solids such as dry bauxite, wet alumina trihydrate, and calcined alumina; for hot, supersaturated sodium aluminate liquors; and for high-solids slurries in the hydrate-precipitation and mud-washing circuits. In most cases, operation has been highly reliable, with an average downtime of less than 5% and good representative. Analytical process control has been substantially improved.