letters Nltratlon of Chlorobenzene-A
Warnlng
To the Editor: During a recent undergraduate laboratory experiment involving the nitration of chlorbenzene,' several students developed severe skin irritation. The dermatitis was due to the dinitration product 1-chloro-2,4-dinitrobenzene,a known skin irritant.= Fortunately, the irritation ceased after a few hours. A companion experiment for the mononitration of chlorobenzene worked satisfactorily, but since the dinitration product may form if the student does not carefully control the reaction temperature, it is recommended that these nitration experiments not be performed.
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Moorc, James A,. "Experimental Elementary Organic Chemistry." W. B. S.,unders Company, Philadelphia. Penns\lrsnia. 1974. p. 116. "The Merck Index," 8th ed., (Editor: G. Stecher, Paul) Merck & Co.,Inc., Rahway, N.J., 1968, p. 242.
Gary Trammel1 University of Hawaii Honolulu. 96822
Contamination in Wells To the Editor: J. G. Smith's article on "Chlorine in Your Water" [J. CHEM. EDUC., 52, 656 (1975)l was interesting and informative, but I feel one issue should be clarified. The statement that well water is not likely to be contaminated with chemicals is not entirely correct. In many rural areas, well water is unusable due to high concentrations (>45 mgll) of nitrate ions. In the digestive systems of infants nitrate is reduced to nitrite, which hinds to hemoglobin and reduces the oxygen-carrying capacity of the blood. Many cases of nitrate-caused methemoglohinemia, including some fatalities, have been reported in the United States. The principal sources of nitrates are believed to be feedlot wastes and fertilizers. (Reference: Manahan, S. E., "Environmental Chemistry," Willard Grant Press, Boston, 1972, p 30.) Wayne L. Smith Colby College Waterville. Maine 04901
To the Editor: The preceding comments of Wayne Smith on my article "Chlorine in Your Water" are well taken. As an organic chemist and one interested in the reactions of organic pollutants with active chlorine, the problems associated with organic compounds in water supplies were naturally emphasized in the article. Wayne Smith points out that there can be problems connected with inorganic ions in water supplies and these problems are not decreased by natural means in well waters as contrasted to suiface waters. J a m e s G. Smith University of Waterloo Waterloo. Ontario, Canada N2L 3GL
Nitrobenzene-Caustlc Alkall Hazards To The Editor: A recent accident report' describes a violently destructive incident involving the unexpected interaction of nitrobenzene and potassium hydroxide. Normally. preparation of a solution of flake 88% potassium hydroxide in excess methanol, followed by stirred addition of nitrobenzene caused an exotherm to 50°C in a 6000.1 vessel. Accidental omission of most of the methanol led to an explosively violent reaction which propelled the lid of the vessel over 100 m. It had been known that nitrobenzene would react violently a t 90-100DC with the very finely powdered and anhydrous base,2, hut this reference also states that nitrobenzene may he distilled from unpowdered technical (85% min.) potash a t 210°C without undergoing the conversion to potassium o-nitrophenolate. Presumably in the recent incident, the combination of largely undissolved solid base, and enough methanol to permit extensive mutual contact of the base and nitrobenzene, was equivalent in effect to the powdered anhydrous base. An earlier incident which involved the accidental use of nitrobenzene instead of aniline as dilueut in the fusion of henzanthrone with potassium hydroxide also led t u a violenr eu~losionand . vroiertim of the w s ~ elid l for fi5 m.3 . Heating a mixture of nitrobenzene, flake sodium hydroxide, and a little water in an autoclave led to an explosion, and the industrial practice of cleaning tarry residues from reaction vessels by heating with a little caustic alkali and water had been responsihle for a t least two violent explosions of this type some 30 years ago.4 In view of the absence of any reference to this hazard in the usual sources of information, you may care to bring it to the attention of your readers. L. Bretherick B P Research Centre, Sunbury-on-Thames, Middlesex, England Anon, Sichere Chemienrbeit, 27(11),89 (1975). Wohl, A. Ber., 62,3487 (1899). 3 Quart Safety Summ, 24, 42, (1953) Association of British Chemical Manufacturers. 'Hatton, J. P., private communication, 1976. 1
Chemistry: The Black Art? To the Editor: Most of our textbooks state that our modern term chemistry is derived from the Arabic term Alchemy, hut do not in turn explain the origin of the Arabic word. In a recent review of material on the history of ancient Egypt, I found that the Egyptian name for Egypt was Khem; furthermore, among ancient peoples, magic was commonlv termed the Emvtian Art-a tribute to their skill a t mumGfication. The literal meaning of the term Khem is Black: ancient E g w t was termed "the Black land". in recognition of the fertile black soil swept down annually by the Nile floods. I t would be interesting to determine for certain whether the Arabic term is, in fact, a reference to Egypt. Perhaps the historians of chemistry might have a word& two to say about this? James J. Glaekin 19%H F a i r Oaks Ave Pasadena, California 91103 Volume 53,Number 4. April 1976 / 267
