Abstract: Flowing an ozone-containing gas through one passage which is either the space between an outer tube and an inner tube disposed in the outer tube or the space in the inner tube, and flowing an aqueous liquid through the passage, which the ozone-containing gas is not flowing through, provides aqueous ozone solutions of high concentration and purity provided that the inner tube possesses a number of pores with an average diameter of 2 to 4 microns.

Abstract: A process for producing a porous glass which comprises forming a shaped product of borosilicate glass having a predetermined shape, heat-treating the shaped product for phase separation to form a silica rich insoluble phase and an alkali and boric oxide rich soluble phase, leaching out the soluble phase from the insoluble phase with an acid or an alkali to obtain a porous glass, wherein said shaped product of borosilicate glass is composed essentially of from 45 to 67% by weight of SiO.sub.2, from 0.5 to 10% by weight of Al.sub.2 O.sub.3, from 10 to 30% by weight of B.sub.2 O.sub.3, from 0.5 to 8% by weight of Na.sub.2 O, from 0.1 to 8% by weight of K.sub.2 O+Li.sub.2 O+Cs.sub.2 O, from 0.5 to 7% by weight of CaO, from 0.5 to 15% by weight of MgO+BaO+SrO, from 0 to 10% by weight of ZrO.sub.2 +TiO.sub.2 and from 0.03 to 3% by weight of F+SO.sub.3 +Cl+As.sub.2 O.sub.3 +Sb.sub.2 O.sub.3.