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lattice and thus reentrance of water and opening up of the crystal lattice, causing the potassium to become trapped in nonexchangeable form. Other cations, such as sodium and calcium, which are smaller than potassium, are not fixed or trapped in this manner. From a practical standpoint the question arises: How can this fixation in nonexchangeable form be lessened or prevented? Application of potash fertilizers a t a depth of several inches instead of a t the surface so as to lessen the influence of alternate wetting and drying suggests itself as a measure worthy of attention. Localized application of fertilizer and the use of granular forms should help considerably. Introduction of organic matter, which supplies organic base exchange material, should also be helpful, since entrance of
885
potassium in the organic exchange renders the potassium safe from fixation in nonexchangeable form for the time being.
Literature Cited 171 (1914).
(1) Fraps, G . S., Texas Agr. Expt. Sta., Bull.
(2) Hall, A. D., “Fertilizers and Manures,” 3rd ed., p. 180, New York, E. P. Dutton & Go., 1928. (3) Hendrick. J., and Welch, H. D., Proc. 1st Intern. Congr. Soil Sei., 2, 358-66 (1927). (4) Lyon, T. L., and Bizrell, J. A., Cornell Univ. Agr. Expt. Sta., Memoir 194 (1936). ( 5 ) Volk, G. W., Soil Sci., 45, 263-76 (1938). (6) Volk, N. J., Ibid., 37, 267-87 (1934). RECEIVED May 16, 1935. Published with the permission of the Director of the Wisconsin Agricultural Experiment Station. This work was supported by a grant from the -4merican Potash Institute, Inc.
POTASH IN PLANT METABOLISM Deficiency Symptoms as Indicators of the Role of Potassium G. N. HOFFER American Potash Institute, Inc., Lafayette, Ind.
T
HE importance of potassium in plant growth is being reflected in the increasing number of deficiency symptoms of various crops in many of the arable soils in the country. The symptoms are appearing in widespread areas, and much publicity is being given to cotton “rust” in the South and the “edge scorch” of the leaves and root rot of corn in the Midwest. Housewives are complaining because
Researches on the role of potassium show that it is intimately related with certain organic constituents in plants. I t is essential in all cell metabolic processes. It influences the rate of respiration. It operates in the synthesis of foods and their translocation in plants. Accordingly, when deficiencies in the soil supply of available potassium occur, changes in any one or all of these vital physiological processes may result, sooner or later, in definite outward manifestations, such as foliage discolorations, necroses of various kinds, and greater susceptibility to fungous diseases. These various injuries not only reduce the yields and quality of the plant products but emphasize the important role of potassium in plant metabolism and economy.
potatoes from certain areas turn dark and soggy when cooked; tobacco growers are producing lower quality leaf; and farmers in southern Illinois are finding it difficult to maintain the productivity of their soils with lime, phosphates, and legumes. These problems are being solved by supplying potash to these crops in the field, but how potassium functions in plants to produce these beneficial effects is not fully known. Eckstein, Bruno, and Turrentine (6) published a descriptive treatise on potash deficiency symptoms of practically all of the commercially important plants. This book is invaluable as a reference on the maladjustments of crops when growing with insufficient available potassium. The discussion of the role of potassium in this paper will refer to certain pertinent researches only to feature the relation that apparently exists between potassium and some of the vital processes in plant metabolism and growth. Our knowledge of deficiency symptoms is largely dependent upon the facts gained in biochemical investigations. By making comparative studies of potassium-starved and normal plants, both in the field and in controlled nutrient cultures, important facts are being discovered which doubtless will contribute to the more profitable use of potash salts in the control of these malnutrition difficulties. Up to the present time, even though many physiological studies have been made on this element, there seems to exist little definite evidence indicating the nature of the mechanism by which potassium functions. It has a specific role in influencing the absorption of certain other mineral elements, in assimilating carbon, in translocating sugars and forming starch, in regulating the rate of respiration, in affecting the rate of transpiration, and also in influencing the action of enzymes. Many researches on these subjects show that potassium is necessary in all protoplasmic activity, but the chief difficulty is to allocate the exact function of potassium to specific steps in the whole series of these interrelated physiological processes. A disturbance in any one affects the
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whole series, and thus it is difficult to limit the interpretation of the results of research on potassium to any one physiological action in the plant. POTASSIUM apparently does not enter into any permanent organic combinations in the plants. It is not found in the chlorophyll molecule, in sugars, in starch, in cellulose, in protein derivatives and proteins, in oils or fats, or in the supporting tissues of plants. Furthermore, it is capable of being leached completely from plant tissues ( 2 3 ) . It is essential, however, for the production of all of these plant products. This fact points to an intimate relation of potassium to
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salts by plants is dependent to a large extent upon respiration and ceases when sufficient oxygen is lacking. The relation between salt accumulation and the growth of the plant is complicated. I n the Iaboratory experiments where not only the mineral nutrient supply is controlled, but where light intensities and quality, temperature, humidity, and other factors are measured, information on the probable role of all of the various nutrients is obtained. At least sixteen elements are absolutely necessary for plant growth and possibly ten or fourteen more. They are required in different amounts by various plants. The potassium ion, however, is absorbed in larger quantities than any other mineral element. Bartholomew and Janssen (8) stated that the absorption of potassium takes place a t a maximum rate throughout the life of the plant, and consequently any symptom of a deficiency becomes very important. The absorption of salts seems to be determined by the general level of respiration. This requires favorable temperature, oxygen supply, and sugar content for the cells active in the process of accumulating salts. Respiration activity releases energy and sugars disappear,; a relation of potassium to these actions was shown by Gregory and Richards (11). So little is known definitely, however, regarding the relation between salt accumulation and respiration that it is almost a virgin field for biochemical investigation.
ALL plants begin their growth from seeds or vegetative parts containing a limited supply of foods and mineral nutrients. Growth becomes manifest with the vacuolar expansion of the meristematic cells. The ionic content of the vacuolated cytoplasm and the energy released in the cells of these tissues in respiration bear a fundamental relation to subsequent salt POTASH Is NEEDEDTO FILLOUT THE RADISH(NP-); PHOSPHORUS (N-K) AND NITROGEN (-PIC) ARENEEDED FORFOLIAGEaccumulations. Berry and Steward (3) called attention to the GROWTH importance of potassium in this phase of growth. James and Penston (21) recognized the close connection between an abundance of potassium and active growth. There is need of evidence to show whether potassium in these tissues preprotoplasmic functioning in comparison to some of the other cedes active growth or whether actively growing tissues inelements. For example, nitrogen is combined in all protein crease their capacity for potassium absorption. derivatives. Phosphorus enters into the composition of Alten and Goeze ( I ) , working with young wheat plants in nuclear materials. Magnesium constitutes a part of the sand cultures, found that the intensity of the assimilation of chlorophyll molecule. Calcium compounds are found in carbon dioxide is dependent upon the amount of potassium various tissues. Other elements, such as iron, copper, and supplied t o the plants. Under conditions of potash starvaboron, have important roles, but potassium is the only eletion the leaves tend to age quickly and become incapable of ment of the radioactive series found in plants. Certain assimilating carbon dioxide. These decreased areas of foliage antagonisms between potassium and calcium (as),iron (7,18), result also in lessened assimilation. Consequently, plants and magnesium (16) have been noted. These antagonisms with ample potassium keep a healthier foliage and this results may be manifestations of the interaction of these various in a higher assimilation rate. elements with the colloids of protoplasm, and when balanced Richards (34) showed that there is an intimate relation the protoplasm functions normally. between the rate of respiration and the potassium content of Potassium ions affect the colloidal cytoplasm and regulate, the tissues. Working with barley leaves, he demonstrated in a measure, the degree of swelling. I n contrast to this that respiration increased as the level of potassium concentraeffect is that of calcium which tends to inhibit the swelling tion was lowered. He suggested that the high amino acid Both of these elements, therefore, have a controlling influence content of potassium-deficient leaves may influence the loss on the processesrdfecting the water economy of the plant. It of water in transpiration. is believed that in this property of potassium resides its proSnow (40) reported a decrease in the transpiration rate of tective action in increasing resistance of the plant to frost and sunflowers, tobacco, and bean plants when grown in nutrient to the conditions induced by droughts, both of which have a solutions deficient in potassium. The greatest decrease ocdehydrating effect on the cell colloids (44, 40'). curred under the highest light intensities and temperatures Noack (%Q),in discussing the laws governing the penetraused in his experiments. The wilting and dehydration of the tion of ions and of water into the cells of living roots, pointed tissues of these plants lead to the development of the characout that the absorption of a salt of a given ion is impeded by teristic symptoms of potash deficiency under such conditions. the presence of a salt of other cations in the following order: Gassner and Goeze (9) pointed out that the effect of potaspotassium, sodium, lithium, magnesium, barium, calcium. sium on nitrogen assimilation in the barley plant is dependent He also showed that certain ions can influence considerably upon the light and nitrogen supply and age of the plant. It the swelling of the colloidal proteins, a process of vital imis their belief that nitrogen and potassium must be considered portance to plant life. Noack and Schmidt (SO) showed that together and that their respective effects are fundamental a differential absorption of ions is induced by changes in the in protein synthesis. High potassium and low nitrogen prointensity of light falling on the plants. Steward (41) and duce similar results in the protein content, chlorophyll conHoagland (14) recently pointed out that the absorption of
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INDUSTRIAL AND ENGINEERING CHEMISTRY
tent, and assimilation and transpiration rates. It is the element in ((relative excess” which predominates. A high assimilation rate in young leaves with comparative potassium deficiency may also be regarded as due to “relative nitrogen excess.” Richards and Templeman (35) believed that the synthesis of proteins is not dependent directly on potassium, but that it is in some way essential for the maintenance of the protoplasmic complex. I n its absence the protoplasm breaks down rapidly, leading to a rapid hydrolysis of the proteins and the formation of simpler amino and amide nitrogen compounds which accumulate in the plant. JAMES (20) demonstrated that potassium forms a bicarbonate buffer in the cytoplasm of potato leaves and aids in increasing the supply of carbon dioxide for assimilation. Starch formation shows a significant increase per unit leaf area in response to potassium. Potassium stimulates catalytic activity, and the loss of potassium is a causal factor in the aging and death of the tissues. Senescence is delayed in plants well supplied with potassium. This function may explain the development of leaf scorch symptoms found in plants when transpiration losses cannot possibly be the cause of their occurrence. Warne (50) believed, however, that the scorching of apple leaves was related to water supply and t h a t under potassium-deficient conditions the water-retention capacity of the foliage was lessened and a drying of the tissues resulted. Hoagland and Chandler (15) reported on the control of leaf scorch by potassium. Davis and Hill (5) described the incidence of potassium-starvation effects on apple foliage as follows: ‘(Thefoliage gradually became dull, losing its luster, and by the end of the fruiting season the leaves began to curl considerably and exhibited a bronzing with considerable purple on the underside of the leaf. By late summer this color had spread to the upper surface and occupied the entire margin of most leaves, with only the center showing green.” Garner (8) described leaf scorch as being associated with unthriftiness and lack of vigor. The conditions favoring leaf scorch are those of excess nitrogen and deficient potassium. Garner pointed out that the liberal use of nitrogenous fertilizers increases the need for potassium. Gildehaus (10) also showed that the leaf scorch symptom is controlled with potassium. The addition of potash to the soil eliminated all tendencies for the trees to develop this trouble. The relation of nitrogen to potassium in the fertilizers used was established, and when wide nitrogen-potassium ratios were used, scorching of the foliage resulted. Wallace (48), Hoblyn (17), Murneek (28),Shaw (SQ),and others studied this leaf scorch symptom and pointed out the nitrogen-po tassium relation which favors its incidence. I n general, it is found that with relatively low nitrogen availability, the potassium supply may be adequate for normal leaf growth, but as the nitrogen-potassium ratio widens, the conditions affect the metabolism processes and leaf scorch takes place. WORKING with kale, brussels sprouts, cauliflower, kohlrabi, and winter cabbage, Vogel (47) described the effects of potassium deficiency as a pale color and complete absence of the characteristic waxy layer on the surface of the leaves. Potassium deficiency resulted in excessive transpiration and the consequent tendency of the plants to wilt when exposed to intensive sunlight. This resulted in the typical edge scorch of the foliage in this group of plants. Tottingham and his associates (46) found that the darkening of boiled potatoes was negligible when the plants were grown in soils where potassium was available a t the rate of 400 poupds per acre. Potatoes with more than 1.8 per cent of potassium in the dry matter were free from darkening.
887
While the control of the darkening occurs with applications of potassium salts to the soil, the exact functions involved are not definitely associated with the potassium ion as yet. Wallace (48), Merkenschlager (27), and Raper (3.2) reported on the enzymatic reactions which produce the darkening of the tissues. These workers also found a reduction in the darkening when potassium was applied to the soil. I n 1903 Loew (25) had already called attention to the role of potassium in condensing amino acids, and it was his work which suggested the possibility that this trouble was due to deficient potassium in the potato plant. Rohde (36) stated that potassium acts as a catalyst in the synthesis of proteins and carbohydrates in tobacco. It aids in the process of cell division, decreases transpiration, and maintains the outer cytoplasm layer in the root cells in a condition which favors the optimum intake of available water. I n dry weather, plants amply supplied with potassium resist wilting and dehydration better than those which are potashstarved. Haley (12) found that the potassium content of tobacco leaves affected the curing of the leaves. If the ratio of nitrogen to potassium is narrow, the desired bacterial type of fermentation takes place. But if the ratio is wide, molds bring about an undesired type of fermentation and produce a leaf of lower quality.
EARSOF CORNPRODUCED ON POTASH-STARVED PLANTS ARE C H a F F Y AND OF LOW VALUE FOR FEED
Gregory and Richards (11) showed in their studies with barley that a deficiency of potassium decreases the assimilation rate of carbon and increases respiration. The transport of carbon dioxide into the chloroplast is dependent upon potassium, forming potassium carbonate, and the subsequent assimilation of carbohydrates may begin with this compound. I n potassium-starved plants the breakdown and death of the older leaves set free potassium which is translocated to the younger portions of the plant, according to these workers. POTASSIUM functions in producing a balance in the quantities of the chlorophyll components. Wlodek (52) showed that a lack of potassium resulted in an absolute and relative lessening of chlorophyll b and an increase of chlorophyll a in potato leaves. Remy and Liesegang (33) found that the leaves of potassium-starved potato plants contained more chlorophyll per unit weight than plants receiving sufficient potash, but these latter plants possessed the power to assimilate carbon dioxide for a longer time. A change to a darker bluish green color of the foliage is one of the initial symptoms of potassium starvation in this crop. Later, when other physiological activity is affected by a lack of potassium, these darker green tissues suffer from necrosis.
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and potassium chloride for 72 hours, and found an appreciable effect on g e r m i n a t i o n . H e s u g g e s t e d that potassium in the living plant is present as one of its isotopes with a higher atomic weight and a greater radioactivity than the form stable under ordinary conditions, Brewer (4) found that the radioactive isotope K4‘ is found in kelp and potato plants. The highest concentration was found in kelp where the abundance ratio was 7.33 per cent K4I. As potato vines mature, the K4I content increases to 6.96 per cent. This is 6.3 per cent greater Alfalfa than the content of the original White clover Alsike clover Pulp. WHITE SPOTSINDICATE POTASH STARVATIOX Pohl and Pringsheim ( S I ) a t t r i b u t e d t h e energy releases t o the photoelectrical effect when electrons having properties The importance of potassium in carbohydrate production similar to those of cathode rays are converted into kinetic was demonstrated experimentally by Hellriegel ( I S ) and by energy. These may influence the mechanism of chemical Wilfarth and Wimmer (51),who found that sugar beet plants reactions in the assimilation of carbon dioxide. Up to the assimilated 25 grams of sugar for each gram of potassium present, the results of the physical investigations of the photooxide taken up. I n this process light energy is converted electrical effect of potassium do not justify us in regarding into chemical energy, and potassium was shown to have an it definitely as the role of potassium, nevertheless further important role in this relation. Warburg (49) attempted to systematic work on this function in the utilization of light explain this relation of potassium to sugar production on the energy should be carried on. Should it be established that basis of the quanta of energy in light but could not account a definite relation holds between this effect of potassium for the reactions which continue without the influence of and the supply of light energy, it would then be feasible to light. He assumed that the assimilation of carbon dioxide regard potassium not as a mere constituent of the plant cell takes place in stages involving activated molecules of chlorobut rather the source or transformer of light energy which the phyll. Holluta (19) accepted Warburg’s hypothesis and plant uses in its many interlocking vital processes. believed that carbon dioxide is reduced under the influence of radiant energy accumulated in activated chlorophyll, and THE large number of different kinds of symptoms shown by that the resulting compound is decomposed by light into potassium-starved plants indicate that this element has an formaldehyde which is converted into carbohydrate under the important function in many of the vital physiological procinfluence of a catalyst. esses, and i t is suggested that potash-starved and healthy Russell (37) reported on the observed effect of potassium plants be the source material for intensive biochemical and in the growth of potatoes during years of unfavorable climatic physicochemical research. conditions, With little sunshine during the growing season, the plants receiving the larger amounts of potash produced Literature Cited higher yields. He concluded that potash is somehow capable of compensating the plant for lack of sunshine. In any case, Alten, F., and Goeze, G., Ernah. Pflanze, 33,21 (1937). this phenomenon indicates that the function of potassium in Bartholomew, R. P., and Janssen, G., Ark. Agr. Expt. Sta., Bull. 265 (1931). the processes of plant growth is closely related to the effects Berry, W. E., and Steward, F. C., Ann. Botany, 48, 395 of light. The plants with the higher potassium contents are (1934). able to utilize the energy of sunlight to a greater degree. Brewer, A. K., J. Am. Chem. SOC.,58, 365 (1936). Scharrer and Schropp (58) reported similar results with Davis, M. B., and Hill, H., Can. Dept. Agr., Pamphlet 96, new series (1934). potato plants. Eckstein, O., Bruno, A., and Turrentine, J. W., “Potash Other workers (22) have demonstrated that potassium Deficiency Symptoms,” New York, B. Westermann & Co., influences the assimilation of carbon dioxide. Stoklasa (42) 1937. Eckstein, O., and Jacob, A., 2. Pflanzenerntlhr., Dungung showed microchemically that potassium is concentrated in Bodenk., 14A, 205 (1929). close proximity to the chloroplastids in the cells, and attribGarner, H. V., J. Ministry Agr. (Engl.), 36, 991 (1930). uted its effectiveness in photosynthesis to the radio acGassner, G., and Goeze, G., Z.Botan., 27,257 (1934). tivity of this element. He based this opinion on the fact Gildehaus, E . J., Botan. G u z . , 92,384 (1931). Gregory, F. G., and Richards, F. J., Ann. Botany, 43, 119 that he was able to produce effects corresponding to those o? (1929). potassium by using radium emanations on sugar beets. The Haley, D. E., Przybylski, H., and Olson, O., paper presented hypothesis, however, does not explain why photosynthesis before Div. of Fertilizer Chemistry a t 94th Meeting of in plants occurs only under the incidence of light energy. Am. Chem. SOC., Rochester, N . Y . . Sept. 6 to 10, 1937. Hellriegel, F. H., and Wilfarth, H., Arb. deut. Landw. GeseEl., If the energy from potassium radiations, feeble a t best, were 34, 1 (1898,. wholly operative in this process, it should proceed in darkness. Hoagland, D. E., and Brayer, T. L., paper presented before Loew (24) ascribes the specific action of potassium to the symposium of Am. Assoc. Advancement Sci., Berkeley, fact that potassium compounds in protoplasm emit P-rays Calif.., 19%. ---Hoagland, D. R., and Chandler, W. H., Proc. Am. S O ~ Hort. . and give rise to the physiological oxidation processes and Sci., 29, 267 (1932). thus promote the generation of energy in the living cell. It Hoagland, D. R., and Martin, J. C., Soil Sci., 36, 1 (1933). follows that potassium is essential to the building up of Hoblyn, T. N., J . Pomology Hort. Sci., 9, 303 (1931). protein bodies. Stoklasa (43) subjected seeds of various Hoffer. G. N., Purdue Univ. Agr. Expt. Sta., Bull. 298. rev. (1930). plants to the beta and gamma radiations from pure potassium
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INDUSTRIAL AND ENGINEERING CHEMISTRY
Holluta, H., “Die neueren Anschaugen uber die Dynamik und Energetik der Kohlensaure-Assimilation,”Stuttgart, 1926. (20) James, W. O., Ann. Botany, 44, 173 (1930). (21) James, W. O., and Penston, N. L., Ibid., 47, 279 (1933). (22) Johnston, E. C., and Hoagland, D. R., Soil Sci., 27, 89 (1929). (23) Kostytschew, W. S., and Eliasberg, P., 2. physiol. Chem., 111, 228 (1920). (24) Loew, O., E r t l h . Pflanze, 30, 141 (1934). (25) Loew, O., U. 5.Dept. Agr. Plant Ind., BUZZ.45, 34 (1903). (26) Lundegardh, H., Soil Sei., 40, 89 (1935). (27) Merkenschlager, F., Erndh. Pflanze, 25, 275 (1929). (28) Murneek, A. E., and Gildehaus, E . J., Mo. Agr. Expt. Sta., Bull. 310 (1931). (29) Noack, K., Ern&h. Pflanze, 32, 353 (1936). (30) Noack, K., and Schmidt, O., Z . Botan., 30, 290 (1936). (31) Pohl, R., and Pringsheim, P., “Die lichtelectrischen Erscheinungen,” Braunschweig, F. Vieweg & Sohn, 1914. 132) Raper, H. S., Biochem. J.,20, 735 (1927). (33) Remy, Th., and Liesegang, H., Landw. Jahrb., 64, 213 (1926). (34) Richards, F. J., Ann. Botany, 48, 515 (1934). (35) Richards, F. J., and Templeman, W. G., Ann. Botany, 50, 367 (1936). 119)
(36) (37) (38) (39) (40) (41) (42) (43) (44) (45) (46) (47) (48) (49) (50) (51) (52)
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Rohde, G., 2. Pjlanzenernahr Dtingung Bodenk., 44, 1 (1936). Russell, E. J., “Soil Conditions and Plant Growth,” 6th ed., p. 90, New York, Longmans, Green & Co. 1932. Scharrer, K., and Schropp, W., Erntlh. PRanze, 32, 312 (1936). Shaw, J. K., Mass. Agr. Expt. Sta., Bull. 305, 50 (1934). Snow, A. G., Jr., Plant Physiol., 11, 583 (1936). Steward, F. C., Protoplasma, 18, 208-42 (1933). Stoklasa, J., Biederinanns Zentr., 61, 161 (1932). Stoklasa, J., Erndh. Pflanze, 30, 299 (1934). Ibid., 32, 2 7 (1936). Stoklasa, J., Z . Zandw. Versuchsw., 11, 52 (190%). Tottingham, W. E., Am. Potato J . , 13, 297 (1936). Vogel, F., Ernah. P R a n z e , 29, 457 (1933). Wallace, T., Univ. Bristol, Ann. Rept. Agr. Hort. E r p t . Sta., 1921, 136. Warburg, O., Riochem. Z., 100, 230 (1919). Warne, L. G. G., Ann. Botany, 48, 57 (1934). Wilfarth, H., and Wimmer, G., Arb. deut. Landw. Gesell., 68 (1902). Wlodek, J., Bull. acad. polonaise sei. lettres, classe sci. math. nut., [ B ]1921, 19.
RECEIVED May 4, 1938.
POTASSIUM SALTS A S CHEMICAL RAW MATERIALS J. W. TURRENTINE American Potash Institute, Inc., Washington, D. C. LTHOUGH the economic and social significance of potash salts in the channels of world commerce is commonly associated with their value as essential ingredients of commercial fertilizers, they are equally essential as raw material of the more strictly designated chemical industries. Potassium chloride may be considered the parent salt from which all other potash salts of commerce are derived. While this comprehensive statement is subject to some modification, it, will serve as the starting point from which to trace the source of potash salts as chemical raw materials. Potash refineries produce potassium chloride predominantly and, in this country, practically exclusively. In Germany where magnesium sulfate is a constituent of the raw materials processed, potassium sulfate and the double salt (potassium magnesium sulfate) are also produced through the interaction of potassium chloride and magnesium sulfate. I n the plants of affiliates, potassium nitrate is yielded from potassium chloride and nitric acid, and potassium carbonate by way of the Engel salt reaction. In France potassium sulfate is manufactured from potassium chloride and sulfuric acid. The potash industry, therefore, may be said to provide the chloride, sulfate, nitrate, and carbonate of potassium as raw materials of, or as primary materials for, the chemical and process industries.
A
THE extent to which potassium salts enter these industries within the United States is shown by citing the sales of the chemical grades, of domestic and foreign origins during the calendar year 1937-namely, 32,400 short tons, made up principally of 30,700 tons of high-grade muriate (chloride) of 98100 per cent purity. If considered alone, this figure appears fairly impressive, but when compared with the total of potash salts sold and delivered within the United States during 1937 (1,100,000 short tons) the former oategory, representing only 3.2 per cent of the total, appears rather insignificant.
The sales of chemical grades of potash salts since 1929 (in short tons) were as follows: 1929 1930 1931
9,437 12,070 8,713
1932 1933 1934
8,467 13,824 13,734
1935 1936 1937
29,074 29,335 32,358
Potassium chloride finds a diversity of uses in minor quantities, but its major consumption is in the electrochemical industries for conversion principally into caustic, a considerable part of which is, in turn, converted into potassium carbonate. According to the 1935 census of chemical manufactures (the latest figures available), potassium hydroxide of 88-92 per cent concentration produced for sale amounted to 9600 tons, and potassium carbonate amounted to 5860 tons. During the same year 1540 tons of caustic and 1850 tons of the carbonate were imported, representing a domestic market in that year of 11,000 tons of caustic and 7700 tons of cartonate. During 1937 imports of these two commodities were 1136 and 787 tons, respectively. This decline in imports, considered in the light of an increase in sales of chemical grades of muriate and a probable increase in the use of caustic and carbonate, would indicate a corresponding increase in the domestic production of each. CAUSTIC potash is produced as the finished product in the solid, flake, broken, and ground forms of 88-92 per cent concentration, and in solution form of 45-50 per cent concentration. Increasing amounts of caustic are being delivered in the form of solution in 8000-gallon tank car lots; on delivery they are discharged directly into storage tanks, to be drawn off as needed. Thus, economies are effected in evaporation, redissolving, handling, and containers to offset the increase in bulk. Perfection in manufacturing process and in tank car construction, particularly linings, makes possible the delivery of such solutions uncontaminated by impurities such as iron, copper, sulfates, and chlorides.
