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against discoloration by water that temporarily finds its way behind bevel siding and then seeps out between the overlapping boards to run down over the paint. ACKNOWLEDGMENT Acknowledgment is made of assistance of C. E. Hrubesky in supervision of the tests on western larch, of Don Brouse in supervision of the tests on Douglas fir and in the making of inspections, and of the following organizations in providing test fences for some of the experiments: Bureau of Standards, North Dakota Agricultural College, National Lead Company, W. P. Fuller Company, and Southern Pacific Railroad. LITERATURE CITED (1) Am. SOC.Testing Materials, Proceedings, 191, 384 (1919). (1A) Browne, F. L., Am. Paint Varnish Mfrs.’ Assoc., Sei. See., Circ. 317, 480 (1927). (2) Browne, F. L., Federation Paint Varnish Production Clubs, OfiCial Dkest 95, 106 (1930).
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Browne, F. L., IND.ENQ.CHEM.,22, 847 (1930). Ihid., 23, 290 (1931). Ihid., 25, 836 (1933). Browne, F. L., J. Chem. Education, 10, 529 (1933). Browne, F. L., PTOC. Am. SOC.Testing Materials, 30, Pt. 11, 852 (1930). Edwards, J. D., Paint, Oil Chem. Rev., 88, No. 13, 10 (1929). Edwards, J. D. and Wray, R. I., Federation Paint Varnish Production Clubs, Oficial Digest,122, 15 (1933). Edwards, J. D., and Wray, R. I., IND.ENQ.CHEM.,17, 639 (1925); 19, 975 (1927). Gardner, H. A., Am. Paint Varnish Mfrs.’ Assoc., Proc. Sci. Sec.. Circ. 412, 181 (1932). Gardner, H. A., Ibid., 428, 107 (1933). Gardner, H. A., and Hart, L. P., Ihid., 374 (1931). 406 (1932), 422 (1932). Hartwig, 0. R., Ibid., 355, 742 (1930). Am. Paint J.,15, N o . 28, 20 (1931). (15) Nelson, H. -4.. (16) Schmuta, F. C., Palmer, F. C., and Kittleberger, W. W., IND. ENQ.CHEM.,22, 855 (1930). (17) Walker, P. H., Ihid., 16, 528 (1924). RECEIVED October 2 4 , 1933.
New American Iodine Industry G. Ross ROBERTSON, University of California at Los Angeles
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Oil-well brines in southern California are now marine vegetation yielded first able to furnish the entire iodine requirementsof petroleum as an organic residue young petroleum chemist of S i g n a l H i l l , L o n g and iodide as an aqueous exthe United States at present business levels, with Beach, Calif., was s t r u g g l i n g tract. Districts lying outside some possibility for expansion when needed. with the problem of separating the supposed seaweed zone, such emulsified brine from the native The iodine present in very dilute solution as as a t Santa Fe Springs, of great crude oil of the local field. The iodide is separated either as the free element, adoil fame, do not show such high great resistance of this mixture to sorbed in or in the form of silver iodide, iodine content; the large oil c o n v e n t ion a1 demulsification fields t o t h e n o r t h a r e n o t f r o m which the desired element m a y readily be obtechnic led him to look for disDromisine. both from lack of water and” distance from the turbing substances among the marine location. The bromide ionic components of the aqueous phase, It was soon noted that the addition of an acidic oxi- content is not high, so that no special concentration of a predizing agent, such as nitrous acid, turned the brine slightly historic sea water is indicated. The iodine industry, always something of an uncertain yellow, and considerable quantities of iodine were revealed. Although iodine has been observed in oil-well brines of commercial quantity, is no more of a bonanza here than in other districts, such as Louisiana, the high content in the Chile, Japan, or other foreign production center. Production California wells was particularly encouraging. Later sur- costs are always substantial. Since Los Angeles County’s veys have shown, however, that only a few petroleum zones three iodine producers are now meeting the equivalent of the of the Far West have enough iodine content to warrant de- entire United States’ demand for iodine, a future potential revelopment. These lie in and near Long Beach, Calif., and source is recognized. At the present writing approximately include not only Signal Hill, of the 1922 boom-time oil fame, one-half ton per day of so-called “crude” iodine, of purity but the near-by Dominguez and Seal Beach fields which are above 99 per cent, is being manufactured. Even the high figure of 70 parts per million, while favorable, not far from the city limits of Los Angeles. I n these districts the day of flush oil production is long past, and the current naturally requires plant processes suited to huge flows of flow from wells shows a high percentage of saline water. brine. If the raw material were clean, one might hope to pa,y the expenses of concentration by running an adjunct salt These facts are to the advantage of the iodine producer. The brines in question, aside from iodine content, approxi- business. The contaniinstion of oil and mud, however, inmate sea water in general composition. The usual high per- troduces serious difficulties. Fortunately there are several characteristic properties of centage of sodium chloride, and substantial calcium and magnesium content, are found. Iodide ion, in amounts ranging iodine which offer aid in reclamation from extremely dilute solution. Chief among these are the ease of oxidation of iofrom 30 to 70 parts per million, is the unique feature. A reasonable explanation pictures a vast forest of seaweed in dide to volatile iodine, and the readiness and completeness of some past geological epoch in the southern part of what is precipitation as silver iodide. These two fundamental renow Los Angeles County. It is known that the whole actions are the basis of the present California processes and southern coast, running for many miles on either side of Long are discussed in detail below. Beach, has had comparatively recent elevation from subMINORPROCESSES marine levels. The entire lowland section adjacent to Los The classical experiment of extracting iodine from solution Angeles was under water during the Tertiary geological period. Not only ordinary kelpweed, but possibly deposits with the aid of chloroform or similar oil solvent led to considof diatoms and similar small plants may have accumulated. erable investigation of the application of the cheaper kerosene Presumably the decomposition of huge quantities of the to a large-scale method. Emulsion difficulties and fire hazBOUT seven years ago a
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ards, among other factors, have led to the abandonment of the plan, a t least temporarily. The blowing-out process, sometimes known as the Turrentine process, has been used in Louisiana ( 2 ) but has been shelved there and in California. By this scheme the iodide is first oxidized to the free state with any cheap oxidizing agent. The pH is necessarily adjusted, according to the patent claim, to a value not greater than 3.5. Air is now blown through the resulting dilute iodine solution. The efffuent air, laden with the halogen, passes into bubble towers where iodine is extracted with aqueous caustic alkali. Final isolation of the product may then proceed as discussed later. Precipitation of the native iodide as the cuprous salt seems feasible and has been tried. Unfortunately the necessary reduction or splitting of the cuprous iodide is not so readily accomplished as the like procedure for silver iodide, presumably because of the higher position of copper in the electromotive series. Oxidation of the cuprous ion may offer difficulty as well. Similarly the mercurous iodide process has not come into favor.
PRACTICAL METHODS Before any chemical process is started, a clean-up of the brines is an obvious necessity. Some of the umtttractive raw material comes from oil traps, settling tanks, and other containers where the petroleum was supposed to have been separated from the water. Other fractions come from rotary drill operations (during prosperous times when wells are being drilled) and still others from petroleum dehydration plants. The combined flow runs to several million gallons daily. The huge flow means the exclusion of such filter aids as charcoal or diatomaceous earth as being too expensive. Sand filters are employed. By a system of ponds, each emptying into the next through a submerged spillway, much of the gross accumulation of crude oil is left behind. Where rotary drill mud has entered, colloidal clay persists even in the presence of the salts and makes some trouble in later operations. Peculiarly, the effluent of the iodine plant is more attractive than its raw material, and hence cannot but be a benefit rather than a nuisance to the adjacent beaches, The clurzed brine is now subjected either to the silver iodide or the charcoal process, the two plans a t present favored.
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The latter method accounts for more than half of the recent Los Angeles output; two operators use the silver process. The following descriptions are representative of California technic, subject to interchange of operations and modification with rapidly changing conditions.
SILVER IODIDE PROCESS To the clarified brine, in a wooden tank, is added the exact theoretical requirement of silver nitrate in a 1 to 2 per cent solution. Mechanical stirring facilitates the immediate and complete precipitation of silver iodide without trouble from localized formation of silver chloride. A small quantity of ferric chloride is added, and this hastens the subsidence of the desired silver precipitate. Within 2 to 4 hours the settlkg is complete, and most of the supernatant liquid is run out to waste. The mixed silver iodideferric hydroxide precipitate, with some residual brine, is pumped out as a thin sludge. A second settling and further elimination of brine may take place in a second tank. Concentrated hydrochloric acid is now added; this of course dissolves the ferric hydroxide. The resulting acidic slurry of silver iodide is now mixed with clean new steel scrap (punchings, wire, etc.). If the brine is clean, transformation to metallic silver and ferrous iodide is complete in an hour. With oil contamination, several hours may be required. The material for the container in this reaction has been something of a problem, neither wood nor iron being entirely satisfactory. The reclaimed silver, in a finely divided state, is readily converted into silver nitrate and sent back for repeated duty. The ferrous iodide filtrate is now treated with whatever oxidizing agent is favored by the manufacturer or the market. Chlorine, or sodium dichromate and sulfuric acid, or nitrite and acid, are employed. Granular iodine is a t once precipitated. This is melted, while still wet and fresh from filtration, under concentrated sulfuric acid. The resulting slightly diluted acid is of such high boiling point that iodine can be directly melted under its surface. The liquid iodine phase can be tapped off or otherwise separated in a condition relatively free from acid. After the materia1 has cooled, the cake of iodine is cracked up, washed free of acid, and dried over calcium chloride in drying chambers. The product, while
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termed “crude” iodine, is often of 99.8 per cent purity and has been purer than much of the more beautiful resublimed iodine known in ordinary commerce. The final product is shipped in 200-pound kegs. No attempt is made in California to prepare either the resublimed flake iodine or any of the salts. Further details of this method are discussed in the patent literature ( 3 ) . CARBON PROCESS The brine, partially cleansed of its oil and mud, is treated with the amount of sulfuric acid needed for the oxidation reaction which soon follows. The change in acidity causes some further clarification, and accordingly this operation is conducted in a pond where deposition of solids offers no complications. Just as the acidified water is about to reach the main tank, the proper quantity of sodium nitrite solution is added. 10dide is oxidized to iodine, and presumably the nitrite is reduced to nitric oxide. In view of the exposed condition of the solution, we may also presume that atmospheric oxygen may cause the formation in turn of nitrogen dioxide, fresh nitrous acid, and thus start a new cycle in reduced quantity. The resulting yellow solution, carrying free iodine, is treated with Nuchar or equivalent activated carbon, and the whole is thoroughly stirred with a battery of vertical-shaft individually motored agitators. Iodine and some clay and oil are caught in the carbon. After the carbon has settled in the reaction tank, most of the clear mother liquor is run to waste. Successive batches, up to twelve or fifteen in number, of new oxidized brine are introduced, aad the charcoal is eventually loaded with iodine to the limit of efficiency. The mixture is then thickened to a sludge with appropriate drainage of the worthless mother liquor.
EXTRACTION OF IODIXE The sludge passes t~ a large rectangular vacuum filter, suggestive of an immense Riichner funnel, with a canvas filter bed. The residue from filtration is treated with caustic soda solution until the latter acquires about 3 per cent of sodium iodide. Apparently the iodate, which should appear in the familiar ratio of 1 iodate to 5 iodide, is a t least partially reduced. Possibly the carbon catalyzes the reduction. This is of course a disadvantage in view of the oxidizing agent required soon thereafter. The iodide solution is now treated in a conical precipitating vessel with chromic-sulfuric acid mixture. Iodine collects as
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a dull granular lumpy m a s I t is either melted under sulfuric acid, as previously described in the other process, or steamsublimed. By the latter procedure the crude iodine is melted in a large metal vessel. Steam is blown through the material, and the vapors pass to a long vitrified stoneware pipe line wrapped in cloth over which water constantly pours. Since the steam is completely condensed, less loss of iodine is experienced than would occur in a conventional air-sublimation process. The latter technic, however, yields a more beautiful product. The wet iodine sublimate is dried on trays in the presence of calcium chloride in a heated room. Fortunately this place which is thoroughly saturated with iodine can be out of doors.
IODINEMARKET Thanks both to the California producers and the Japanese kelp iodine industry, the old pegged price level of $4.68 per pound seems to have been abandoned indefinitely. This question has been taken up in detail by Holstein (1) who discusses in particular the Chilean situation. Roman (4) has given an elaborate review of the economics of iodine over a period of several decades, with world-wide consideration. An extended bibliography is given with his paper. The old standard price of iodine, maintained without regard to general business conditions, apparently was based to some extent on the observation that no one person or company seems to need a large quantity of the material. Iodine does not make up a large part of the cost of any major world product. At the same time a great many customers need small amounts. In case6 where iodine would seem to be requisite in quantity, usually its brother bromine, or perhaps chlorine, can be drafted into service without serious difficulty. Accordingly the traffic in iodine, like that in diamonds, has been able to bear a price not directly related to production costs. Under present-day competitive conditions, however, the price of iodine is approaching manufacturing costs, or does SO in regions of respectable living standards. Unless some new and important use for iodine is discovered, we may expect comparatively little expansion of the California industry. LITERATURE CITED (1) Holstein, P. F., Chem. & M e t . Eng., 39, 422 (1932). (2) Jones, C. W., U. S. Patent 1,853,621 (1932). (3) Ibid., 1,837,777 (1931). (4) Roman, W., Z.angew. Chem., 44, 9 (1931). RECEIVED February 12, 1934.
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