PARKES, ALEXANDER

born Dec. 29, 1813, Birmingham, Warwickshire, Eng. died June 29, 1890, West Dulwich, near London British chemist and inventor noted for his development of various industrial processes and materials. Much of Parkes's work was related to metallurgy. He was one of the first to propose introducing small amounts of phosphorus into metal alloys to enhance their strength. One of his most significant inventions was a method of extracting silver from lead ore (1850). This procedure, commonly called the Parkes process, involves adding zinc to lead and melting the two together. When stirred, the molten zinc reacts and forms compounds with any silver and gold present in the lead. These zinc compounds are lighter than the lead and, on cooling, form a crust that can be readily removed. Another of Parkes's important contributions was the discovery of the cold vulcanization process (1841), a method of waterproofing fabrics by means of a solution of rubber and carbon disulfide. Parkes also produced a flexible, durable material called Parkesine (c. 1855) from a mixture of chloroform and castor oil that led to the development of the first plastic, celluloid.