Permeability of glass wool and other highly porous media

Abstract

2. Monobarium aluminate dissolves in barium hydroxide solutions with precipitation first of 7BaO.6Al 2 O 3 .36H 2 O, subsequently of BaO.Al 2 O 3 .-7H 2 O in the less basic and BaO.Al 2 O 3 .4H 2 O in the more basic solutions. 3. Tribarium aluminate is rapidly hydrolyzed by water, with precipitation of Ba(OH) 2 .8H 2 O, BaO.-A1 2 O 3 .7H 2 O, and, subsequently, 2BaO.Al 2 O 3 .5H 2 O. 4. All the hydrated barium aluminates dissolve in water and are hydrolyzed, with precipitation of hydrated alumina. 5. The hydrated barium aluminates dissolve in barium hydroxide solutions with eventual precipita-tion of the equilibrium solid phases, but frequently with preliminary separation of metastable inter-mediate solid phases. 6. The stable solid phases in the system BaO-Al 2 O 3 -H 2 O at 30° C are: (a) gibbsite (Ai 2 O 3 .3H 2 O) over a range from approximately zero concentration to about 52 g of BaO and 2.8 g of A1 2 O 3 per liter; (b) Ba(OH) 2 .8H 2 O from 52.9 g of BaO and zero A1 2 O 3 to about 55.5 g of BaO and 2.7 g of A1 2 O 3 per liter; (c) probably 2BaO.Al 2 O 3 .5H 2 O (but possibly BaO.-A1 2 O 3 .4H 2 O or gibbsite) over the short range from 52 BaO and 2.8 A1 2 O 3 to 55.5 BaO and 2.7 A1 2 O 3 . 7. 7BaO.6Al 2 O 3 .36H 2 O is a metastable phase, not sufficiently stable to permit an accurate determina-tion of its solubility. 8. BaO.Al 2 O 3 .7H 2 O is also metastable, but it may exist in contact with solution for several months. 9. BaO.Al 2 O 3 .4H 2 O is likewise metastable over the greater part, if not all, of its range, but its stability is greater than that of the higher hydrates. 10. 2BaO.Al 2 O 3 .5H 2 O resembles BaO.Al 2 O 3 .4H 2 O in its degree of stability in the metastable range. 11. No hydrate more basic than 2BaO.Al 2 O 3 .5H 2 O was found.