By distillation of the ammonium salt glutarimide, CH 2 (CH 2 CP) 2 NH, is obtained; it forms small crystals melting at 151° to 152° C. and sublimes unchanged.
Terephthalic acid, formed by oxidizing para-diderivatives of benzene, or best by oxidizing caraway oil, a mixture of cymene and cuminol, with chromic acid, as almost insoluble in water, alcohol and ether; it sublimes without melting when heated.
By this method of distillation the arsenic sublimes into the receiver, leaving a residue of iron sulphide in the retort.
Realgar occurs native in orange prisms of specific gravity 3.5; it is prepared artificially by fusing together arsenic and sulphur, but the resulting products vary somewhat in composition; it is readily fusible and sublimes unchanged, and burns on heating in a current of oxygen, forming arsenic trioxide and sulphur dioxide.
It sublimes at about 310° C. Similar varieties of benzene hexabromide are known.