Cellulose or its organic esters are dissolved or caused to swell up in concentrated aqueous solutions of metallic perchlorates, e.g. perchlorates of beryllium, aluminium, magnesium, zinc, and calcium. Acetone soluble cellulose acetate is dissolved in the cold in concentrated aqueous solutions of perchlorates of beryllium, aluminium, magnesium, calcium, lead, copper, zinc, strontium, barium, and lithium. Cellulose triacetate is first dissolved in methyl formate and the solution mixed with the solution of the perchlorate, and the methyl formate then removed. The solutions thus obtained may be coagulated in water or saline or acid baths in the form of filaments or films. Solutions may be obtained containing mixtures of diacetyl cellulose, triacetyl cellulose, and cellulose, for example, and cellulosic solutions may contain also nitrogenous substances such as gelatine, fibroin, and natural silk. The latter may be employed to make products having dyeing properties resembling those of wool and silk. The following examples are given: (1) Paper or wood pulp is dissolved in a saturated solution of beryllium perchlorate. (2) Cotton lint is dissolved in a solution of aluminium perchlorate obtained by adding hydrated aluminium chloride to a 20 per cent perchloric acid solution, and dissolving the crystals formed in water. (3) Commercial cellulose acetate is dissolved in a saturated solution of magnesium perchlorate. (4) Cellulose diacetate and gelatine are dissolved in a saturated solution of magnesium perchlorate and the solution used in the manufacture of artificial textiles. (5) Cellulose formate is dissolved in a solution of magnesium perchlorate. The solutions may be employed, for example, in the preparation of ultra-filter membranes by impregnating a vegetable or metallic woven fabric with the solution and coagulating in water. Paper or filter paper similarly treated gives a parchment paper or a reinforced filter paper. Again, wood-pulp, paper-pulp, or the like may be dipped into the solutions of metallic perchlorates and compressed into a coherent mass usuable in electrical insulations and mountings. The cellulose, whether in solution, or after precipitation is sensitive to the action of chemical reagents, physical agents (catalysis, electrolysis, radiation), and dyestuffs, the latter forming lakes with the cellulose.ALSO:Aluminium perchlorate is obtained by adding hydrated aluminium chloride to a 20 per cent perchloric acid solution, and dissolving the crystals formed in water.ALSO:Cellulose or its organic esters are dissolved or caused to swell up in concentrated aqueous solutions of metallic perchlorates, e.g. perchlorates of beryllium, aluminium, magnesium, zinc, and calcium. Acetone soluble cellulose acetate is dissolved in the cold in concentrated aqueous solutions of perchlorates of beryllium, aluminium, magnesium, calcium, lead, copper, zinc, strontium, barium, and lithium. Cellulose triacetate is first dissolved in methyl formate and the solution mixed with the solution of the perchlorate, and the methyl formate then removed. Solutions may be obtained containing mixtures of diacetyl cellulose, triacetyl cellulose, and cellulose, for example, and cellulosic solutions may contain also nitrogenous substances such as gelatine, fibroin, and natural silk. The following examples are given:-(1) Paper or wood pulp is dissolved in a saturated solution of beryllium perchlorate. (2) Cotton lint is dissolved in a solution of aluminium perchlorate obtained by adding hydrated aluminium chloride to a 20 per cent perchloric acid solution, and dissolving the crystals formed in water. (3) Commercial cellulose acetate is dissolved in a saturated solution of magnesium perchlorate. (4) Cellulose diacetate and gelatine are dissolved in a saturated solution of magnesium perchlorate and the solution used in the manufacture of artificial textiles. (5) Cellulose formate is dissolved in a solution of magnesium perchlorate. The solutions may be employed, for example, in the preparation of ultra-filter membranes by impregnating a vegetable or metallic woven fabric with the solution and coagulating in water.