Abstract: A mixed gas consisting of carbon dioxide and nitrogen is separated into the component gases by a method which comprises treating sepiolite with nitric acid, subjecting the treated sepiolite to an ion-exchange treatment thereby exchanging the cationic metal present in the treated sepiolite with Mg ions, heating the sepiolite resulting from the ion-exchange treatment, and exposing the ultimately prepared sepiolite to the mixed gas.

Abstract: Separation of nitrogen and carbon dioxide is accomplished by a method using as a separating material one member selected from the group consisting of sepiolite in the unmodified form, sepiolite which has been heat-treated, and sepiolite which has had part or the whole of the exchangeable cation thereof replaced with zinc ion and which has been subsequently subjected to a heat treatment.

Abstract: A high-strength sintered article of chemical substances having the .beta.-silicon nitride type crystal structure is produced by blending 50 to 99.9 weight percent of a .beta.-silicon nitride and/or .beta.'-Sialon and 50 to 0.1 weight percent of a mixture, as a sintering aid, consisting of BeO, Ga.sub.2 O.sub.3, and Al.sub.2 O.sub.3 in respective amounts such as to have a Ga.sub.2 O.sub.3 /BeO ratio in the range of from 2.8 to 9.4, an Al.sub.2 O.sub.3 /BeO ratio in the range of from 0.0 to 2.6, and an Al.sub.2 O.sub.3 /Ga.sub.2 O.sub.3 ratio in the range of from 0.0 to 1.1, all ratios being ratios by weight and sintering the resultant blend.