With a sharp knife wetted, cut into thin slices 1 oz. of pure Para rubber. Place it in a wide-mouthed bottle, cover it with carbon bisulphide or benzene (coal-tar naphtha), and cork down. Next day the rubber will have swollen considerably and have absorbed most of the liquid; pour on more liquid, and continue the addition until a thick fluid is obtained. One ounce of rubber will make about lpt.of solution, which is used as a cement for rubber goods.