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NEW ENGLAND ASSOClATlOlY of CHEMISTRY TEACHERS Vital Materials from Sea Water1 A. A. LAWRENCE Dow Chemical Company, Boston Massachusetts
ethyl lead, when used alone, fouled sparkplugs, valves, and piston rings, a difficulty which it was found could the sphere we live on has been one of the most dominant be eliminated by the addition of a small amount of factors in the d e v e l o ~ e n tof civilization, it is some- ethylene dibromide to the mixture. Chemists realwhat remarkable that so little has been written upon the ized the inadequacy of existing sources of bromine and chemical composition of the waters themselves, and set about looking for new ones. In spite of the fact that so few recorded attempts have been made to ex- that bromine is found in sea water to the extent of less thau 70 parts per million, this source was seriously ploit them as a natural resource. The first really comprehensive analysis was made considered because i t obviously represented an inby Dittmar in 1884. Dittmar's analysis listed more exhaustable supply. In 1924 the Ethyl corporation than 30 elements and more recent investigations have began the operation of a small Atlantic coast plant which produced trihromoaniline, a substance which brought the total up to 50. Aside from uncovering a number of "new" elements, could be used for the motor fuel treatment. After Dittmar's analysis proved one very interesting and several months they set up another extraction plant on important fact-that the composition of sea water is hoard a boat, the SS Ethyl. However, neither unit was commercially profitable and the project was essentially constant in all parts of the world. For most practical purposes we may consider that sea abandoned. Meanwhile Dow chemists were becoming interested water contains the elements chlorine, sodium, magnesium, calcium, potassium, bromine, boron, and fluor- in the problem, believing that i t might well be possible ine, chiefly in the form of various soluble salts, with to extract pure bromine from sea water using a process the other elements in concentrations too small to he similar to that which they had perfected for obtaining given serious consideration a t this time. These range, the element from the Midland, Michigan, brines. Howin order, from chlorine a t 19,000 parts per million down ever, the Midland brines contained some 1300 parts of bromine per million as against 65 to 70 parts per million to fluorine a t 1.4 parts per million. Until very recent years few attempts had been made in the case of sea water. Because of the slight alkalinity to extract any of the oceans' impressive array of chem- of sea water it was first found necessary to add sulfuric ical elements and compounds. The notable exception acid, as well as chlorine, to the raw material, a disis, of course, common salt. From the earliest days of covery which proved to be the real key to successful salt making, the extraction of sodium chloride from bromine extraction. A search was begun for a suitable ocean water has been, and still is, accomplished chiefly ocean site which was subsequently found near Wilmington, North Carolina, a t the mouth of the Cape through solar evaporation. Of comparatively recent origin is the use of the Fear River. In 1931, a pilot plant was erected on this bitterns from this process for further chemical reduc- site. In July of 1933, the Ethyl-Dow Chemical Comtions. Notable in this field is the Westvaco Company pany was incorporated, and less thau six months later of San Francisco which uses this concentrated liquor a plant having a capacity of 15,000 pounds of bromine from the salt beds for the production of bromine, per day was in operation. Thus in 1933 did science magnesium chloride, hydroxide, and oxide, and calcium accomplish the first commercially profitable extraction of an element from this extremely dilute and complex sulfate or gypsum. The trend toward high-compression gasoline engines chemical solution. The Dow Chemical Company first became interested in the early 20's made necessary the treatment of motor in magnesium during the early years of World War I fuels with tetraethyl lead to prevent "knock." Tetraas one of several American concerns which went into Abstract of an address presented at the Sixth Annual Summer Conference. New England Association of Chemistry Teachers, the business when supplies of the metal from Germany, then the sole producer, were cut off. As might be exNew London. Connecticut, August 24.1924. 620
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N VIEW of the fact that the tremendous mass of water which covers something l i e 71 per cent of
pected, the end of the war dropped the bottom out of the American market for this metal which few people in this country then regarded as having structural possibilities. The price, which was $5.00 a pound in 1915, was down to $1.30 by 1921, and only two companies carried on with the work-American Magnesium Corporation and The Dow Chemical Company. Through the discovery of new uses for the metal a t home and sales abroad the demand increased and in 1937 the program was expanded. Guided by our experience with the successful extraction of bromine from the ocean a t Wilmington, we naturally turned to the sea again as a potential source of magnesium. Sea water contained magnesium chloride as did the natural brines a t Midland, and while the compound was found in much smaller concentration in the sea than in the Midland brines, still this concentration in sea water was approximately 20 times that of bromine. After careful consideration. the conclusion was reached that - ~~-~ it was cheaper to pump water than to mine rock. In addition to sea water, the requirements included an abundance of cheap power, limestone, and salt. A site embodying all these requirements was found a t Freeport, Texas, and plans were laid calling for facilities capable of handling 300 million gallons of water a day, and on January 21, 1941, the first ingot of magnesium was poured-the first metal, of any consequence, in the history of the world to be taken from the waters of the oceans. The sea water is drawn from a ship canal through large grid and rotary screens well below the surface and through a flume to the plant. Oyster shells, dredged from Galveston Bay, are received a t the plant by barge and unloaded over a conveyor belt to primary storage. The shells are then put through a rotary screen washer and conveyed to a 300-foot rotary kiln where they are burned to lime. The lime is sent directly from the kiln to rotary slakers and emerges as a thick slurry of milk of lime. The lime slurry from the slakers is piped into a Dorr thickener 150 feet in diameter in which it is dewatered to a thick sludge. This thickened sludge drawn from the bottom of the thickener is sent into six launders on the surface of a flocculating tank where i t meets the incoming sea water. The resulting magnesium hydroxide floc suspended in sea water is then distributed to four 200-foot Dorr thickeners from which the hydrate is pumped to the filters. Suction is applied through the leaves until a cake an inch or more in thickness is built up on the leaves. The unit is then moved to an adjoining compartment where the cake is loosened by air pressure. This material is then mixed with magnesium chloride brine and pumped to the neutralizing unit where i t is treated with crude hydrochloric acid and reconverted into magnesium chloride. The dilute solution is concentrated in direct-fired cylindrical furnaces, and the resulting concentrate further filtered and evaporated until it emerges as practically anhydrous magnesium chloride to be fed ~~
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into the electrolytic cells. The fused metal rising to the top of the cell bath is removed by hand ladles and poured into pigs having an average purity greater than 99.9 per cent. In the past 20 years men with determination and vision have accomplished a t least two miracles in mastery over the sea which would doubtless have been scoffed down by the preceding generation. Having witnessed these achievements, our job is not to scoff, but rather to impart, as best we can, that same vision and determination to the generation of scientists to come.
OFFICIAL BUSINESS 227th Meeting-October 21, 1944 Phillips Exeter Academy Exeter, New Hampshire
THE 227th meeting of the N.E.A.C.T. was held a t Phillips Exeter Academy, Exeter, New Hampshire, on 0ctober 21, 1944, with the following program: "Apple growing in New England," James W. Elton, Exeter, New Hampshire; "Experiences in chemistry instruction in the Army Specialized Training Program," Edward R. Atkinson, University of New Hampshire; Demonstrations by Charles L. Bickel, Judson B. Cross, Richard L. Dunnell, and Donald H. Miller, Phillips Exeter Academy; "Industrial engineering problems in New Hampshire," Datiiel S. Eppelsheimer, Engineering Experiment Station, University of New Hampshire; "Technical services of the Marine Biological Laboratory a t Woods Hole," Elbert P. Little, Phillips Exeter Academy. Notes The 229th meeting of the N.E.A.C.T. will be held at Providence College, Providence, Rhode Island, on February 3, 1945, and the 230th meeting a t Smith College, Northampton, Massachusetts, on March 17, 1945. Film Reviews' Aluminum, Mine to Metal: Shows the processes in the producti& of aluminum, including the dynamiting of a bauxite mine and the various stages through which the ore passes, until "alumina" finally reaches the electrolytic cells and the aluminum is ladled out and poured into ingots. Photography is good and details very clear. Recommended for high-school, lay, and elementary college groups. lfimm., sound. 17 min. Free except for transportation. Distributor: Aluminum Company of America, Motion Pictures Department, 801 Gulf Building, Pittsburgh 19, Pennsylvania. Masters of Molecules: A very good picture in color of the process of petroleum refining. A complete script is available, showing some of the pictures in a booklet of the same name, which may be used for further study. Recommended for high-school, lay, and collexe 16mm., sound. 40 min. Free except . groups. . -
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Contributed by Marjory R. Fenerty, Lincoln School, Providence. Rhode Island, and Millard W. Boaworth, Vermont Academy, Saxtons River. Vermont.
