The American Phosphorus Industry J
CHRISTIAN H. AALL M o m a n t o Chemical Co., Anniston, Ala. With present expansion, elemental phosphorus is rapidly becoming one of the more important electrothermal products made in this country. Power consumption equals thode of calcium carbide and ferrosilicon, and production units range among largest electric smelting furnaces ever built. The paper outlines the history of the American phosphorus industry from its humble beginning 60 years ago to the present giant smelting plants. Various processes and furnace types are discussed, as well as product and
market deveYopment6 The present importance of the element hinges on its conversion to phosphoric acid and salts, which find extensive use in the detergent and food industries. American phosphorus manufacturers are enumerated, with approximate data on furnace capacities and production. Special mention is made of the recent migration of industry into western phosphate fields and announced plans which will increase total production to more than 400,000,000 pounds of phosphorus per year.
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rosilicon. I n Figure 1 are shown the annual power consumptions of the phosphorus, carbide, and ferrosilicon industries for the past 10 years. It brings out the steady growth of the phosphorus industry as compared with the fluctuating curves for the two others. The dotted line extending into the future indicates the scheduled increase for phosphorus. The other consequence of the expansion of the phosphorus industry has been the development of large furnace units. Only a few years ago, in this country, unit loads of 10,OOO to 15,000kw. were considered sizable for any kind of furnace operation; today phosphorus is produced in furnaces double that size. These impressive furnace loads are supposedly the largest in existencea t least west of the Iron Curtain. Obviously, the construction of such large units involved much pioneering development and engineering, which have been useful t o other branches of the electrometallurgical industry. What is behind this rapid growth? Why has phosphorus, which after Brand’s discovery lay in a Sleeping Beauty trance for more than 200 years, become so important in our present lives? I n order to answer this question intelligently, let us go back some 50 or 60 years and follow the history of the phosphorus industry in this country.
NE evening in 1669, a German alchemist, Hennig Brand,
was impatiently searching for the stone of wisdom in his laboratory in Hamburg. He had been an unsuccessful merchant and was now trying to recover his lost fortune by converting base metals to gold. His clay retort stood on the fire heating a mixture of desiccated urine and sand. At white incandescence heavy vapors evolved from the mess, bursting into flames in the air and 6lling the room with white choking fumes. Such was man’s first encounter with phosphorus, the light bearer. To Brand the experiment must have been a disappointment, though he is known later to have sold the secret of his process for 200 thaler. Today, nearly three centuries after Brand’s discovery, we stand in the middle of a great expansion of the phosphorus industry in this country. One can hardly pick up a technical publication without finding some reference to new plants or addition of more capacity to those already in existence. This expansion is not merely a result of the quickened pace of the American industry as a whole following the outbreak of the Korean conflict. It reflects more the continuation of a growth that has marked the phosphorus industry since it came into its own in the early thirties. This increasing peacetime demand for phosphorus-or rather, for its derivatives-is best shown by the following production figures (including TVA) :
E.4R LY
1930 1935 1940 1945 1946 1947 1948 1949 1950
Million Pounds 21 43 97 160 167 185 224 276 307
Before 1940 part of the listed production was recovered as the anhydride or acid from both blast and electric furnaces; since then, however, all the phosphorus is produced as such by the electric furnace process. With the expansion plans already announced, it is estimated that another 130,000,000 pounds will be added to the present production by the end of 1953. This rapid growth has had two significant effects. First, it has brought elemental phosphorus into the limelight as one of the important electrothermal products made in this country. At a market price of 17 cents per pound, 1950 production was worth about $50,000,000;by the time it reached the consumers in the form of acid or salts, the value was several times this figure. To make this amount of phosphorus, 2.1 billion kilowatthours were expended, or approximately the same as was used in the production of such old-timers as calcium carbide and fer-
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DEVELOPMENTS
Elemental phosphorus was first produced commercially in America by the Oldbury Electro-Chemical Co. a t n’iagara Falls in 1896. This was only 8 years after Readman and Parker had taken out their patents on the electrothermal process in England, making the old retort process obsolete. The Oldbury plant, located at the then only source of cheap hydroelectric power, consisted of small single-phase furnaces of a total load of about 1500 kw., smelting a charge of phosphate rock, silica, and coke. At about 1500” C., the rock was reduced according t o the reaction:
+ 6SiOz + 1OC = 6CaSi03 + Pa + lOC0
2Ca3(POa)z
and the evolved phosphorus was condensed under water. The operations were very modest by today’s standards, but for that time it was a good-sized installation and met the needs of the country. I n these early days the demand for phosphorus and its derivatives was limited. It is true that the fertilizer industry consumed large amounts of crude phosphoric acid for superphosphates, but this acid was produced by the wet process, and no attempts were made by the manufacturers of elemental phosphorus to encroach on that market. They confined their business t o the high-priced
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Phosphorus and Phosphate 3.0
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war in 1914, the demand for phosphorus inoreased rapidly. The element found use in munitions for incendiary bombs, in tracer bullets, and for smoke emission. Calcium phosphide was needed for marine signals, zinc phosphide for medicinals, and copper phosphides for bronzes, and phosphorus chlorides were used in the manufacture of acetic anhydride. For s a k t y matches alone, which appeared a t this time, nearly 1,OOO,O00 pounds of red phosphorus were consumed per year. More important than this, however, was the growing realization that phosphorus could be used as a source of phosphoric acid competitive with that obtained from the wet process. I n the wet process, phosphoric acid is produced by treating phosphate rock with dilute sulfuric acid and removing the gypsum formed by filtration. The crude acid is impure, containing nearly all the components of both the rock and the sulfuric acid. When the product is used for manufacture of fertilizera, this contamin& tion is not objectionable; however, if intended for foods and chemicals, the impurities must be removed. Some of these impurities are poisonous, such as arsenic, lead, and fluorine. The purification is a tedious and expensive process and-in the early dayswas not always too effective. I n addition, the acid was too weakapproximately 40% HaPO4-to be used directly in the production of most phosphates, and had to be concentrated by evaporation t o 70% phosphoric acid (50” Be.). It was thus no wonder that the producers turned t o the electrothermal phosphorus process in which a pure, concentrated acid could be obtained directly by oxidation of the volatilized element.
,
1940
1945
1950
Figure 1. Power Consumption of Phosphorus, Carbide, and Ferrosilicon Industries
compounds such as the sesquisulfide, then used for matches, the oxychloride, used for dyes, the anhydride, and medicinal and reagent grade phosphates. Very little phosphorus was oxidized to acid of the sirupy type. For a number of years this market, inherited from the old retort process, was practically controlled by a handful of manufacturers in this country, England, France, Germany, and Canada. The United States production, which amounted t o only 1,300,000 pounds of phosphorus a year by the time of World War I, was supplied exclusively by Oldbury, except for small amounts produced over a short period by the American Phosphorus Co. a t Harrisburg, Pa. The price was in the vicinity of $1 per pound. Two events brought an end to this state of affairs. With the
July 1952
FIRST ELECTROTHERMAL ACID PROCESSES
The &st effort to make “furnace phosphoric” was that by the Southern Electrochemical Go. a t Mt. Holley, N. C.,in 1914. Operating under the patents of Heckenbleikner, this plant consisted of a 4000-kw. furnace-incidentally, the largest phosphate smelting unit in existence a t that time-provided with multiple sloping electrodes. The furnace charge, preheated in a horizontal rotary kiln located immediately above the furnace, was fed down between the electrodes. The process differed from that
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used by Oldbury in that the furnace gases passing through the kiln were burned above the stock stream to carbon dioxide and phosphorus pentoxide, which in turn was recovered and hydrated to phosphoric acid in packed towers. The acid was thus produced in one single step, as distincb from the older process in which the evolved phosphorus was condensed in its elementary form, eventually to be oxidized to anhydride and acid in a separatp operation. Heckenbleikner’s undertaking was abandoned after 8 or 10 years of operation, presumably for lack of cheap power. By that time, however, he had demonstrated that the electrothermal process for directly producing phosphoric acid from rock was technically sound. As far m is known, Heckenbleikner’s acid was used only for manufacture of triple superphoqhate, where it competed successfully with the &-‘etprocess acid. There are no records of ita use in food grade products. An effort by the American Cyanamid Co. in 1920 to perfect the Heckenbleikner acid process by use of a special furnace was abandoned after 2 years of testing at Brewster, Fla. The unit used for this purpose was a combination shaft and electric furnace modeled on the Elecktro-Metal1 furnace of Swedish pig iron development. ANNISTON DEVELOPMENT
In the meantime another development, which was to prove of more lasting success, was under way in Anniston, Ala, A ferroalloy firm, the Southern Manganese Corp., had been making ferromanganese for munitions during the war. I n 1918, with a decreming market for this alloy, the company changed t o the production of ferrophosphorus which wm in demand by the steel industry, especially for the manufacture of sheets for automobiles. The ferrophosphorus was made in open electric furnaces from a charge of iron ore, phosphate rock, silica, and coke. Inevitably, a certain amount of phosphorus would escape from the furnaces to the atmosphere, forming dense, white fumes of phosphoric anhydride and acid which were an annoyance to the neighborhood. As a means of nuisance abatement, the plant installed electrostatic precipitators on the furnaces t o collect the acid. Before long, however, i t was found that the “nuisance” could be marketed very profitably and that, in fact, there was more to be gained by producing phosphoric acid than the ferroalloy. The Anniston operations expanded rapidly. If the company had entered into the phosphoric acid market by accident, it knew how to make the best of it. One of the furnaces used for making ferrophosphorus was converted to the manufacture of acid in 1921, followed by three additional acid units by 1924. Salt production facilities were first installed locally, and later expanded by the acquisition of the Provident Chemical Works a t Carondelet, Mo., the Iliff-Bruff Chemical Co. a t IIoopeston, Ill., and Wilkes Martin and Wilkes at Camden, N. J. Parallel with this technical development, which we are told had its headaches, an intensive market development was undertaken. Theodore Swann, founder of Southern Manganese, fully realized the potentialities of his pure electrothermal acid for foods and detergents, and quickly made his bid for these markets previously supplied by the wet acid process. Existing outlets such as phosphoric acid for soft drinks and jellies, disodium phosphate for silk weighting, trisodium phosphate for cleansers, and monocalcium phosphate for baking powders and self-rising flours were further exploited. In addition, new outlets were developed for products, many of which were produced for the first time commercially. Typical examples of the latter are sodium acid pyrophosphate, which appeared in 1925 as a leavening agent, followed by sodium metaphosphates for water softening and tetrasodium pyrophosphate for detergent applications. For nearly 10 years, until Victor Chemical Works started their blast furnace operation in 1929, the Anniston organization, then reorganized under the name of the Swann Corp., was practically the sole supplier of the 1522
superior furnace grade acid. The production costs were well within competitive values of the wet process acid for manufacturc of products other than fertilizers. TWO-STEP ACID PROCESS
The fortuitous beginning of the Anniston acid operations had led to the adoption of the one-step process. As thepurity standards of phosphoric acid and phosphates in the food and chemical industry were raised, increasing consideration was given to the two-step acid process. By separating the oxidation of phosphorus from the electric furnace operation, a higher degree of punty could be obtained for this acid, and at the same tin-e the concentration could be raised from 80 to 85% phosphoric acid to pure phosphorus pentoxide (equivalent to 138% phosphoric acid) if so required. An expanding market and higher freight rates also favored the two-step process as the transportation of elemental phosphorus, in tank cars, was predicated as of lower cost than that of phosphoric acid. After extensive testing, the first acid furnace in Anniston was converted to phosphorus in 1931, with plans for the others to follow. At this time, however, it was also decided to move the entire phosphate smelting operations to the Tennessee phosphate fields, from which the company already had been drawing most of its ore supply and which, for this purpose, had been widely prospected. The move was delayed by the depression and corporate changes-the merger of the Swam C o p . into the Blonsanto Chemical eo.-until 1935, when a sinter plant was erected near Columbia, Tenn., followed in 1937 by the installation of three 8000-kw. furnaces for elemental phosphorus. This plant has since developed into the largest phosphorus operation in existence with an installed furnace capacity of over 100,000 kw. -4fourth furnace unit was added in 1941, followed by a fifth in 1948 and, finally, by a sixth in 1950. The phosphorus is shipped for conversion to acid and salts to the company’s facilities a t Anniston, Carondelet, East St. Louis, Ill., and Trenton, Mich. Except for technical perfections necessitated by the magnitude of the operations, the electrothermal process developed by Monsanto for its Tennessee plant xas essentially the same as the original Oldbury procedure and as eventually to become the only furnace acid process of commercial importance in this country. American Agricultural Chemical Co. had already adopted this procedure in 1935, when it initiated a small electric furnace ,peration for chemical and food grade phosphorus products a t south Amboy, N. J. I n 1938, the Phosphate Mining Co. built a 5000-kw. furnace a t L\JiChols,FIa., producing phosphorus from local phosphates. This company as later absorbed by the Virginia-Carolina Chemical CO., which expanded the phosphorus operations by a 12,000-kw. furnace a t its Charleson, S. C., plant in 1950. The two-step electric furnace process was also the one embraced by Victor in 1938 after a 10-year effort to make phosphoric acid in blast furnaces, and by Westvaco when it initiated the westward migration of the phosphorus industry in 1948. BLAST FURNACE ACID
Victor Chemical Works’ blast furnace operation was the result of a long development. The blast furnace had first been suggested for the production of phosphoric acid by the U. S. Bureau of Soils in 1917 as an alternate to the electric furnace process. The study was carried on until 1923, when Victor, which had been in the phosphoric acid and salts business for some time, became interested in the new process. The following year a pilot investigation was initiated at the company’s Chicago Heights plant, finally culminating in the erection of a full scale blast furnace a t Nashville, Tenn., in 1929. This furnace, thought to be the only one of its kind in continuous commercial production of
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phosphoric acid, was rated a t 250,000 pounds of phosphorus pentoxide per day, equivalent to the capacity of a 26,500-kw. electric furnace. It wa9 coke fired, producing the acid in a single operation by burning the evolved phosphorus in a n excess of air and recovering the product by electrostatic precipitation. While fuel economy made the blast furnace appear more attractive than the electric furnace, the large amount of gas evolved proved to be a serious drawback. It reduced the concentrations of phosphoric acid t o a point where it was difficult t o recover economically and, finally, led Victor t o abandon the process in 1939. I n the meantime (1938) the company had built a n electric furnace plant a t Mt. Pleasant, Tenn., for the production of elemental phosphorus. The plant went into operation with one furnace in 1938, followed by two more in 1939, and, finally, a fourth unit was added in 1940. The phosphorus is shipped for conversion t o acid and salts at the company’s Chicago Heights, Ill., Nashville, Tenn., Morrisville, Pa., and South Gate, Calif., plants. hnother, considerably more short-lived, outcome of the Bureau of Soils’ investigation of the blast furnace production of phosphorus and phosphoric acid was a unit built by the Coronet Phosphate Co. at Pembroke, Fla., in 1931. This blast furnace was of the regular pig iron type with regenerative stoves and modern auxiliaries smelting a charge of phosphate sinter and coke. The evolved phosphorus was condensed from the reducing gases which were burned in the stoves for perheating the blast. This apparently unprofitable operation was discontinued after a few years. The furnace was later dismantled and reassembled a t Rusk, Tex., for production of charcoal pig iron. WESTERN EXPANSIONS
Until recently, most of the commercial phosphorus produced in this country was derived from the Tennessee phosphate deposits. Both Monsanto’s and Victor’s operations, accounting for about 90% of the total output, were located on these deposits and depended on local ore, the so-called matrix, and cheap hydroelectric power, for their production, With the increased production during the war and the years immediately following, July 1952
this put a heavy strain on the Tennessee reserves. T o alleviate this condition, Victor decided to expand its operations t o Florida where phosphate rock still was available in ample supply, with the erection of a furnace plant a t Tarpon Springs. This plant went into operation in 1947 with one furnace unit. I n the meantime, considerable interest was focused o n the large phosphate rock deposits in the West, especially in Idaho. These deposits had so far been exploited only for fertilizer use and great quantities of low-grade ore, well suited for phosphorus smelting, were readily available, with reasonable power costa. Westvaco Chemical Division of Food Machinery and Chemical Corp. was the first to take advantage of these conditions. I n 1947 this company, which until then had been supplied with phosphorus by Monsanto and others, announced the construction of a furnace plant at Pocatello, Idaho, consisting of two units rated at approximately 15,000 kw. each. These first furnaces, placed in operation a year later, were followed a few months ago by a third and larger unit, with a fourth unit now under construction and scheduled for operation by July 1952. When completed, the plant will have an estimated capacity of 85,000,000pounds of phosphorus per year. The product is converted t o acid and salts a t the company’s plants a t Newark, Calif., Lawrence, Kan., and Carteret, N. J. Victor followed Westvaco’s example in 1950 when it started construction of a phosphorus plant at Silver Bow, Mont. T h e first furnace will go into operation shortly, while a second unit is scheduled for completion late in 1952. The expansion is estimated t o cost approximately $9,000,000and will increase the company’s over-all phosphorus and phosphate capacity by more than two thirds. Finally a few months ago, Monsanto, which until then had centralized its phosphorus production at the plant in Tennessee, joined in the western migration, announcing the construction of a new plant a t Soda Springs, Idaho, some 70 miles southeast of Pocatello. The first phosphorus unit is scheduled for completetion late in 1952. Today, there are six commercial producers of phosphorus in this country. The following table gives an approximate idea of the size of their operations. The figures represent yearly
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production capacities, taking into account announced expansion during 1951. Monsanto Chemical Co. Victor Chemical Works Weatvaco Chemical Corp. Virginia-Carolina Chemical Co. Oldbury Electro-Chemical Co. American Agricultural Chemical Co.
iMillion Pounds 120 90 60 28 12
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TENNESSEE VALLEY AUTHORITY
This narrative of the development of the phosphorus industry in this country would not be complete without mention of the Tennessee Valley Authority. Though essentially noncommercial this governmental institution has been producing phosphorus and its derivatives on a large scale since the early thirties a t Wilson Dam, Ala., as p a r t of its fertilizer development program. At the same time, thanks t o generous research funds, it has contributed significantly t o the technical development of phosphorus processing. TVA entered the phosphorus field in 1934 by converting two 5300-kw. calcium carbide furnaces, handed down in operating stand-by condition from World War I, t o the manufacture of phosphoric acid. One of the converted furnaces was modeled on those then in use in Anniston; the other was of a new design. They were initially built as one-step acid units, but in 1936 elemental phosphorus collection equipment was tentatively installed on one unit and subsequently this modification was adopted for all succeeding furnaces. This change later proved fortunate, since during World War I1 TVA was called upon to supply the major part of the 200,000,000 pounds of elemental phosphorus needed by the military. A third furnace of the same capacity was added in 1937, followed by a fourth unit of 6500 kw. in 1939, a fifth of 12,000 kw. in 1942, and finally a sixth of 13,000 kw. in 1945. Over the years the first four units have been modified, if not completely rebuilt, so that today TVA’s installed furnace capacity is 58,500 kw. with a n estimated yearly output of about 65,000,000 pounds of phosphorus. Most of the production is converted t o phosphoric acid used in the manufacture of triple superphosphate. Technical contributions made by TVA include a furnace design using a specially shaped refractory roof with the three electrodes in line. This design, which gives an economical and effective smelting unit, has been adopted by most of the commercial producers other than Monsanto, which prefers the triangular electrode arrangement for its large units. Recently TVA has pioneered the adaptation to phosphorus smelting of a new electric furnace type, the so-called rotating furnace. This type, in which the crucible rotates or oscillates on a turntable, is being tested with promising results on an 8500-kw. unit. A new agglomeration process-pelletizing followed by shaft kiln calcination-for the phosphatic furnace charge is also under development a t the Wilson Dam plant. The process utilizes the natural plasticity of the raw ore and compares favorably with sintering. For the conversion of phosphorus to phosphoric acid, TVA uses a graphite burning unit of simple and ingenious design. Lately several new processes have been developed and demonstrated for the production of fertilizers such as calcium metaphosphate and defluorinated phosphate rock. THE WHYS OF EXPANSION
If one should t r y t o summarize the factors that have contributed to the growth of the electrothermal phosphorus industry in this country, two things, or rather a combination of the two, stand out: the simplicity of the process, and special market conditions. In spite of all technical advances, electric phosphate smelting is still a simple, almost crude, process. The ore blended with silica and coke is charged continuously to the furnace in which the reaction takes place; the phosphorus is distilled, dedusted, and condensed under water, while a calcium silicate slag with 1524
some by-product ferrophosphorus is tapped out a t intervals. Practically all the impurities in the raw materials are eliminated in the process, giving a 99.9% pure product which can be easily converted to high-grade, concentrated acid. This means that almost any type of phosphate ore can be processed, including low-grade rejects from fertilizer mining, without the costly purification and concentration steps required by the wet acid process. This simplicity has not only made the electrothermal process economically attractive, but has also favored growth by the ease with which the production can be expanded. A good illustration of this flexibility is supplied by the large furnace recently completed by Monsanto, which in one year alone produces more phosphorus than the entire United States production from 1896 through World War I. The special-and highly f a v o r a b l e m a r k e t conditions refer to the period in the early twenties when the electrothermal phosphorus industry made its bid for the phosphoric acid market. Up to that time, phosphorus had been produced on a limited scale as a commodity with relatively few and special uses. With the developments in Anniston, horn-ever, by which the phosphorus was converted to the acid on an economical basis, this picture was completely changed. To the consumers, especiallg in the food industry, “furnace phosphoric”-through its greater purity and higher concentration-was much more attractive than t,he wet process acid they had been getting. With the tightening purity control, laid down in state and federal pure food laws, this fact was further emphasized. Soon the new acid and its salts had invaded the market, supplanting the products of the wet process and taking over, seemingly without much resistance, outlets that had taken years of previous development. This ready, almost eager market for the electrothermal acid was obviously a pofferful impetus to the growing phosphorus industry; however, this fact alone does not explain the development to follow, which has given the industry its present significance. T h a t is the story of intensive chemical research and market development. Existing outlets, inherited from both the wet process acid and the early days of the electrothermal process, have been further expanded, new markets have been developed for products already manufactured, and a host of new productswith interesting properties and applications--have been brought to light, many of which have assumed great importance. Excluding fertilizers, the main outlet for the phosphorus derivatives-today, as 30 years ago-is in the detergent field as sodium phosphates. When used as detergent synergists or soap builders, these salts exert the combined beneficial actions of softening the water by precipitating or sequestering lime and magnesia, emulsifying or dispersing solids in the detergent solutions, and augmenting the inherent detergent properties of soaps and synthetic surface active agents (surfactants). The first to be used for this purpose and for many years the large-tonnage chemical of the phosphate group was trisodium phosphate (TSP). The salt is still used in many household cleaning and washing powders; however, the demand for lo\T-er alkalinity and sequestering properties, by which heavy metal ions in the water are tied up in the form of soluble complex salts without precipitation, has led to a preference for tetrasodium pyrophosphate (TSPP) and sodium tripolyphosphate (STP). The latter salt has undergone an especially phenomenal development. Brought on the market in significant quantities for the first time in 1945, it has become the most important of all phosphate salts. It is estimated that approximately half of the present phosphorus output is converted into tetrasodium pyrophosphate and sodium tripolyphosphate and t h a t the production of these two salts exceeds 500,000,000pounds per year. Other sodium salts, mch as mono and disodium phosphates (MSP and DSP) and metaphosphate (Calgon) also have watersoftening properties and are used extensively for boiler water conditioning. The acid pyrophosphate enters into the formula-
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,-,Phosphorus tion of self2rising flours and baking powders as a baking acid reacting with sodium bicarbonate when heated. I n addition, the sodium salts find application a~ emulsifiers in making process cheese, for conditioning oil well drilling muds, and in the preparation of enamels, glazes for pottery, and many more. The three calcium orthophosphatesmonocalcium (MCP), dicalcium(DCP), and tricalcium ( T C P ) phosphates-are the next most important phosphate salts. Monocalcium p h o s p h a t e i s used extensively in flours and baking powders and for leavening purposes in breads, biscuits, etc. Dicalcium and tricalcium phosphates are used in the composition of tooth paste and powders with varying alkalinities, where they are preferred for their mild polishing power. Other uses of the calcium salts are as mineral supplements in foods, for pharmaceuticals, and as anticaking agents of table salt, sugar, and powdered dusting sulfur. Sizable amounts of mono- and diammonium phosphate (MAP and DAP) are consumed in yeast culture and fermentation, supplying both the phosphoric anhydride and nitrogen required in the growth and propagation of yeast cells. The ammonium salts are also effective water-soluble fireproofing agents for paper, wood, and textiles. This property results partly from the formation of a fused, inactive protective layer on the combustible surface. Other phosphate salts that have assumed commercial importance are the potassium phosphates for medicinal purposes and in special detergent applications, the aluminum salts used in the manufacture of glasses and ceramic refractories, and the copper compounds, which have fungicidal properties. Recent years have seen the marketing of certain organic derivatives such as the tricresyl and triphenyl phosphates as plasticizers, and alkyl alkali phosphates used as nonflammable hydraulic fluids and humectants. With an eye to the future, it seems fitting to close this story of the American phosphorus industry with a few words on phosphoric acid, the “furnace phosphoric” that has played such an important part in the development of the industry. The importance of the electrothermal acid resides primarily in its use as an intermediate in the preparation of phosphate salts, with limited applications besides those mentioned for foods and pharmaceuticals. Except for TVA’s large scale experiments, there are no outlets for the electrothermal acid as an acidulating agent in fertilizer manufacture. This field is completely preempted by sulfuric acid, whether the end product is superphosphate, formed by direct action on the phosphate rock, or triple superphosphate, for which the phosphoric acid required is obtained by the wet process. Recent trends may change this picture. Dwindling supplies of natural sulfur-the source of cheap sulfuric acid-and an increased demand for this acid for other purposes may ultimately make it too costly for use in the fertilizer industry, especially for triple superphosphate. Coupled with this development is the trend toward higher freight rates favoring the manufacture of this highly concentrated fertilizer over that of regular superphosphate. It may take years before breaking point is reached, but if and when it happens, it will open up a tremendous new market for the electrothermal phosphoric acid. It is hardly an overstatement to say that the phosphorus industry follows this development with great interest. July 1952
and Phosphate,-
SELECTED BIBLIOGRAPHY
(1)Aall, C. H.,Chemistry & Industry, 1950, 830-40. Electrothermics and electrothermal processes. Castner Memorial Lecture, Nov. 21,1950. (2)Aall, C. H., Industrie chimique, 37, No. 401, 329-31 (December 1950). L’Industrie chimique am6ricaine. (3) Almond, L. H., and Steinhiss, H. K., Chem. Eng., 55, No. 10, 106-9 (1948). Phosphorus combustion system. (4) Callaham, J. R.,Ibid., 58, No. 4, 102-6 (1951). How VirginiaCarolina makes phosphorus by sound engineering, one unit process, four unit operations. (5) Carothers, J. N., Chem. Ilnds., 42, 523, 825, 827-8 (1938). Phosphoric acid, 1918-38. (6) Chem. Inds., 66,8234 (1950). Twice as much phosphorus. (7) Chem. I n d . Week, 68, No. 18, 11-12 (May 19, 1951). Phosphorus moves west. (8) Easterwood, H. W., Trans. Am. Inst. Chem. Engrs., 29, 1-20 (1933). Manufacture of phosphoric acid by the blast furnace method. (9) Gray, A. N., “Phosphates and Superphosphate,” 2nd ed., London, International Superphosphate Manufacturers’ Association, 1943; New York, Interscience Publishers, 1946. (10) Hignett, T.P.,Chem. Eng. Progress, 44, 753-64, 821-32, 895904 (1948). Development of blast-furnace process for production of phosphoric acid. (11) Skeen, J. R.,Chem. Eng. News, 26, 2436-7 (1948). Furnace phosphorus. (12)Striplin, M. M., Jr., “Development of Processes and Equipment for Production of Phosphoric Acid,” Tennessee Valley Authority, Chem. Eng. Rept. 2 (1948). (13) Striplin, M. M., Jr., McKnight, David, Megar, G. H., and Pates, J. M., Chem. Eng., 58, No. 7, 108-10 (July 1951). This phosphorus furnace rotates. (14) Waggaman, W.H.,IND. ENG.CHEM.,24,983-8 (1932). Present status and future possibilities of volatilization process for phosphoric acid production. (15) Waggaman, W. H.,“Phosphoric Acid, Phosphates and Phosphatic Fertilizers,” New York, Chemical Catalog Co., 1927. (16) Waggaman, W. H., and Bell, R. E., Ibid., 42, 269-92 (1950). Western phosphates. R E C D I V ~for D review September 10, 1951. ACCEPTED February 25, 1952. Presented before Section 8, Industrial and Engineering Chemistry, a t the X I I t h International Congress of Pure and Applied Chemistry, New York, N. Y., September 10 t o 13,1951.
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