The Environmental Chemistry of Felt Manufacture Using Mercury (Hg) By Kelechi Isiugo CUNY School of Public Health at Hunter College 17-12-12
Objectives This presentation will shed light on: • Mercury • Process of felt manufacture using mercury • Chemistry of felt manufacture using mercury • Health effects - toxicology • Environmental effects • References
Mercury • Mercury is a naturally occurring element that is found in air, water and soil. It is the only metal which is liquid at normal temperature. • Mercury has the symbol Hg and atomic number 80. It is commonly known as quicksilver and its scientific name is hydrargyrum • Mercury exists in various forms: elemental (or metallic) and inorganic (to which people may be exposed through their occupation); and organic (e.g., methylmercury, to which people may be exposed through their diet).
Felt manufacture Felt is a kind of cloth or non-woven fabric made by rolling and pressing wool or another natural fiber while applying moisture or heat, and other processes to form a dense fabric of permanently interlocking fibers. Felt can be made out of wool from sheep, rabbit, beaver’s fur, and any other natural fiber. felt is used in musical instruments (to wrap bass drum), to make hats, etc.
mercury in felt manufacture A process called carroting was used. Carroting is the process of treating hatters' fur with mercury(II) nitrate or any other solution or material for the purpose of rendering the hatters' fur suitable in the manufacture of hats. Beaver’s fur was widely used for making hats although other natural fibers were sometimes used. Beaver’s fur was shaved off from the body, and was treated with a dilute solution of mercury nitrate. The skins were then dried in an oven where the thin fur at the sides turned orange, thus the name carroting.
Carroting continuation the fur was immersed in a boiling acid solution to thicken and harden it. The acid treatment decomposed the mercury nitrate to elemental mercury. Finishing processes included steaming the hat to shape and ironing it Mercury nitrate caused the fibers of the fur to separate from the pelt and to mat together more readily. It gave the finished product a metallic sheen appearance.
Chemistry of mercury in felt manufacture During carroting, when mercury nitrate solution is poured on the beaver’s skin, the mercury bonds with sulphur from the acid treatment, and denatures the sulphur molecule to produce felt with mercury sulphide attributes (orange-ish brown/cinnamon) Hg + S Hgs The steaming process: heat applied on the prepared felt increased the kinetic energy of molecules in felt and released some molecules as gases into the atmosphere where the manufacturing process was taking place. Thus producing vapors of mercury(II) nitrate
Health effects - Toxicity Fumes of toxic mercury nitrate was inhaled during felt manufacture using mercury. Mercury poisoning attacks the nervous system, causing drooling, hair loss, uncontrollable muscle twitching, a lurching gait, and difficulties in talking and thinking clearly. It could cause stumbling about in a confused state with slurred speech and trembling hands, giving rise to the expression “Mad as a hatter”.
Environmental significance when elemental mercury is released into the environment, bacteria in rivers and lakes may convert the metal into methylmercury (the organic form). Methylmercury is assimilated by larger organisms (e.g fish) when they consume the bacteria. The concentration could be high in older predatory fish that eat other fish e.g King mackerel, sword fish. This is because mercury accumulates in the body. This causes mercury poison to humans if they eat these fish that have high mercury concentration.
Mercury ban United States Public Health Service banned use of mercury in the felt industry in 1941
References • Wikipedia. Mercury(II) nitrate. http://en.wikipedia.org/wiki/Mercury%28II%29_nitrate • Anthony Carpi. Matter & Energy. http://web.jjay.cuny.edu/~acarpi/NSC/2-matter.htm • Corrosion doctors. Mad as a hatter. http://corrosion-doctors.org/Elements-Toxic/Mercury-mad-hatter.htm • World Health Organization. Mercury and health. World Health Organization. http://www.who.int/mediacentre/factsheets/fs361/en/index.html. Published April 2012. Accessed December 14, 2012. • Google answers. The use of mercury in hat making. http://answers.google.com/answers/threadview/id/763004.html • University of Connecticut. The mad hatter mercury mystery. http://digitalcommons.uconn.edu/cgi/viewcontent.cgi?article=1023&context=wracklines • CAS chemistry. The Not-So-Mad Hatter: Occupational Hazards of Mercury. http://www.cas.org/news/insights/science-connections/mad-hatter • Health effects of mercury in humans and the environment. http://www.p2pays.org/mercury/tryon/art2.pdf
Youtube videos • Youtube. Mercury in hat. http://www.youtube.com/watch?v=9SbP2hkLfME • Youtube. Vapor pressure. http://www.youtube.com/watch?v=hA5jddDYcyg