Activated Alumina: Aluminium Trihydrate Heated at 350 °C While Hot Air Carries the Steam Away (Derr, Alcoa, US 2,015,593)

Heating aluminium trihydrate drives out its water and leaves a porous alumina that soaks up moisture. Alcoa's Derr found it works much better when the steam is carried away at once, by a stream of hot air or by a vacuum, instead of lingering in the bed. Result: activated alumina that takes up 14 % of its weight in water from air (8 % made the old way), up to 16 % if washed first in 3 % sulphuric acid. Source: Derr, US 2,015,593 (Alcoa, 1935). Not given: times, bed depth, air rate, amounts. Picture drawn by Youblob.