When cotton is immersed for three minutes in a mixture of nitric and sulphuric acids, five fluid ounces of each, then well washed, and dried upon a water-bath, it is converted into pyroxylon. The fibre does not alter in appearance, but is found to have acquired highly explosive properties, while its weight has increased 70 per cent. At a temperature of about 300°, pyroxylon inflames, explodes, and disappears. Yet by immersing in water, and being kept wet, the explosive power of the cotton is held in abeyance, and in this condition it may be carried any distance. The formula is C12H9(N04) + HO.