ffects of Fluorine in Tennes oils and Crops W. H. MACINTIRE A N D ASSOCIATES The University of Tennessee Agricultural Experiment Statl‘on, Knoxville, Tenn. T h e briefed findings are from 2O-year laboratory, lysimeter, and pot-culture experiments on the chemical and biochemical behavior and the fate of fluorine after i t reaches soils through insecticides, fertilizers, cryolite, rock phosphate, various fluorides and silicofluorides, slag, and rain waters, and from the atmosphere, and in particular the migration of the element from soil into vegetation. Through collaboration with TVA and two major manufacturing corporations, the experiments were elaborated to include studies of injurious effects upon plant and animal life purportedly resultant to fluoric effluents from two manufacturing operations in two widely separated locales in Tennessee. Soils were found to possess remark-
able retention of the fluorine carried by insecticides, fertilizers, and various fluoric compounds, while yielding abnormal concentration of fluorides to the rain water leachings from incorporations of electric furnace slap. Regardless of the nature and quantity of input of fluorides or native occurrence, or ingo from the atmosphere, vegetation effected virtually no enhancement in the uptake of fluorine from soils that possessed adequacy of calcium, either naturally contained or added. Comparative analyses of crops grown on soils, in place and after transportation to unaffected points, served to support the conclusion that abnormal incidence of fluorine in field vegetation is attributable to atmospheric contaminants.
H b utility of fiuoiine compounds ab dusts and sprays for insect control on field crops long has been under study at The University of Tennessee ( 5 2 ) . Virtually nothing was known, however, as to the behavior of those additives subsequent t o their inclusion in the soil. In particular, it appeared desirable to study the chemical and biochemical effects induced by incorporated barium silicofluoride, the use of which has been advocated for the eradication of larvae of Japanese beetle from golf-links soils in New Jersey and Pennsylvania (24, 33, 36). The behavior of that fluorine compound in the soil was the objective of a 4-year lysimeter study begun in 1929 in the Department of Chemistry, University of Tennessee Agricultural Experiment Station ( 4 7 ) . During the past 15 years the university and TVA have collaborated in extensive pot-culture studies of the uptake of fluorine by vegetation. Those studies have been integrated with lysimeter studies of chemical and biochemical effects that additive-fluorine materials induce in soils subject to rain-water leachings. I n those experiments, the fluoride incorporations were made b y means of insecticidal materials and fertilizers; as fluorides of sodium, potassium, calcium, and magnesium; and as cryolite, rock phosphate, and electric furnace slag. Recently, however, the experimental program was amplified objectively and augmented b y field studies, because of numerous complaints as t o injurious effects upon plant and animal life in certain locales in t x o widely separated counties in which are located two major industrial operations, both of which emit fluorine compounds to the atmosphere. As an “arm of the state,” The University of Tennessee accepted responsibility for determining whether conditions detrimental to plant and animal life have been induced b y larger emissions from the greatly expanded o2erations of those two essential industries, as well as from the more recent furnace operations of a federal agency, and whether claims of injurious effects upon crops, livestock, and farm values are justified. Moreover, the university is concerned directly, because its Experiment Station farm in Rlount County in east Tennessee is located near the Alcoa operation for the manufacture of aluminum and the experimental farm in Maury County in iniddle Tennessee is near several operations for the thermal processing of rock phosphate and slag, Therefore, the university inaugurated a comprehensive study of the problem through an Experiment Station project that is being conducted jointly by the Department of Chemistry and the Department of Animal Hus-
bandry and Veterinary Science. Subsequent to the initiatioii ot that study, its scope was euttinded through grants to the university by the Aluminum Company of America for further studipin Blount County and from Monsanto Chemical Company an( J-ictor Chemical Korks for additional investigations in Mam 1 County.
THE APPROACH Although the chemical atudics TI eir. plaiined to determiw source, nature, concentration, and behavior of gaseous and suspensoid effluents that may contaminate plant life, the initial approach was t o ascertain whether an abnormal content of fluorine is acquired by forage crops grown near the particular operationthat were known to emit fluorine compounds. With a background of findings obtained a t the Tennessee E\periment Station and domestic and foreign reports and bibliographies (1-1 1 , 1 5 , 17-23, 25-27, 29-32?, 34, 35,37,41-45,47-60,6860, 66, 66, 68, 71, 75-76, 77, 7 8 ) it was decided to investigate both soil and atmosphere as channels through which abnormal incidence of fluorine might prove deleterious to plant and animal lifr in the ta o designated locales. The piogiam calls for chemical examination of atmospheic,. soils, rain waters, and fluorine-polluted vegetation, for thr chemical control of admixed fluoric materials in the experimental feeding of small animals and livestock, and for analyses of their excrements and bones. Decisions as to admissible and critical levels of fluorine content in vegetation for livestock grazing and feeding and effects resultant from ingestions of various fluorint. additives b y animals are the responsibility and experimental objective of the Department of Animal Ilushandry and Veterinan Science. Deterininations of fluorine conteiit have been made upoii multiple samples of atmosphere, soils, I ain and river v aters, anti upon forage crops and hay collected periodically in Blount Count) in east Tennessee, in hfaury County in middle Tennessee, and iii unaffected locations. Analyses have been made also upon rainwater drainage from soils experimentally enriched in fluorinc, upon plants obtained from pot cultures of such soils, and upon the vegetation grown experimentally on soils of high native fluorine content, at points of their natural occurrence and at unaffected locations to which those soils had been transported. Exposed charges of chemical fixatives and glass plates also were examined 2466
November 1949
I N D U S T R I A L AND E N G I N E E R I N G C H E M I S T R Y
as to effects of atmospheric occurrences of fluorine. This paper embodies briefed findings that were obtained through such determinations in the earlier studies and through the recently integrated experiments. DISCOVERY AND PROPERTIES OF FLUORINE
‘*
*
Fluorine, the lightest of the four halogens, is rated by Mellor as the most chemically active element known (54). It is violently oxidative, potentially explosive upon contact with inorganic and organic compounds, and inert toward only argon, oxygen, and ozone. Fluorine combines directly with many metals. It attacks water vigorously, with resultant liberation of hydrogen, formation of hydrofluoric acid, and generation of ozone. The element does not occur as such in nature, with the possible exception of rare minute inclusions of molecular fluorine in geologital formations, and in volcanic eruptions. (In the text, “fluorine” connotes incidence of that element solely in componential forms.) Although the mineral, fluorspar, was recognized by Agricola in 1529, and hydrofluoric acid was generated and identified by Scheele in 1771, fluorine was not obtained in the gaseous phase until 1886 when Moissan achieved that result in the solving of “one of the most difficult problems in modern chemistry” (64). “Pike’s Peak” was reached in “Fickle Fluorine,” by Sumner T. Pike, vice chairman, Atomic Energy Commission (61). Fluorine has a really bad name among chemists. While it is probably the most friendly of all elements, in that it will insist on combining with almost anything handy, it is also one of the most fickle, and is always leaving one partner for another. If it sees a blonde on the other side of the street, it will instantly abandon the gal it is squiring a t the moment, and will cross over and pick her up only to forsake her also when something better turns up. I n the end, it ruins them all. OCCURRENCE OF FLUORINE
The element occurs widely and sparingly as a component of rocks, particularly those of volcanic origin (61),as fluorspar, as cryolite, and as a 4% component of rock phosphate. Clarke (12) gives 0.1% as the mean for incidence of fluorine in 73 specimens of igneous rocks and an occurrence of 0.1% of that element in the lithosphere. Clarke and Washington (18)computed 290 p.p.m. as the fluorine content in the upper 10-mile crust of igneous and sedimentary rocks. In Soils. Fluorine occurs as meager percentages in soils, other than those derived from rock phosphate. Until recent years, its
2467
occurrence in soils, as either a native or an additive, was virtually disregarded in relation to plant growth and animal life. Incidence of fluorine in the soil has been attributed to particles of biotite, muscovite, hornblende, tourmaline, and similar complex minerals (14, 16). Hilgard gave 0.02% as a representative soil content (28), and occurrences of the element in soils have been mentioned in several relativelyrecent reports (SS,J9,44, 47,57, 64, 7%). I n their comprehensive contribution, Robinson and Edington (64)reported occurrence of fluorine in soil profiles and showed that, in general, the percentages of the element are higher in t h e substrate. Dependable technique for complete analytical expulsion of fluorine from charges of soils to afford utilization of the Willard and Winter thorium nitrate titrative procedure (76) on the resultant distillates is of relatively recent origin (11, 25, 39, 40, 44). Incidence of substantial proportions of magnesium and imposition of unduly high temperature in the prefatory calcination of the limed charge of soil induce fixation of its fluorine content in forms that retain the element against perchloric acid distillation (40). In Tennessee and Kantucky Soils. Collections of samples of phosphatic soils were obtained in 1948 a t points on and near the Middle Tennessee Experiment Station farm. Nine such samples showed a mean of 0.059% fluorine content, with a corresponding mean of 0.60% phosphorus pentoxide content, a ratio of 1 t o 10, and a mean of o.0570 calcium carbonate content. Eight similar Maury County field soils registered a mean content of 0.053% of fluorine and 0.63% of phosphorus pentoxide, a ratio of 1 to 12, and a mean of 0.05% calcium carbonate content. One unusual soil from that county was found to contain 0.830/, of fluorine, 6.50% of phosphorus pentoxide, and 0.580/, of calcium carbonate, but those values were not included in obtaining the reported means. Those soils had been rated as highly productive of plant and animal life through decades prior to advent of the expanded phosphate operations and currently claimed injurioub effects. Six Kentucky soils of like derivation and fertility were supplied by the Kentucky station from survey samplings in locations where no phosphate processing has been done. The Kentucky soils registered mean percentage contents of 0.06 for fluorine and 0.60 for phosphorus pentoxide, a ratio of 1to 10,and a mean of 0.025% for calcium carbonate content. One such phosphatic soil was transported from Kentucky to Knoxville and then cropped in parallel with a corresponding Maury County soil and with two representative Tennessee soils from unaffected locales. In coxi-
West End of Greenhouse and Solarium, Lysimeter Installation in Foreground
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INDUSTRIAL A N D E N G I N E E R I N G C H E M I S T R Y
Uniformity i n Growth of Soybeans initial crop, after identical inputs of fluorine, 300 pounds per 3,000,000 pounds of limestoned Hartsells fine sandy loam (top row) and of limestoned Clarksville silt loam (bottom row) at Knoxville A. Magnesium fluoride B. Sodium fluoride @. Sodium silicofluoride D . Untreated Maury silt loam of high natural fluoride content from middle Tennessee (top row), from Kentucky (bottom row)
trast, the soils of Blount County have a relatively low contrnt( of Suorine and phosphorus pentoxide. I n Surface Waters. I n bugust, September, and October 1936 seven Tennessee streams were found to contain fluorine in the wige of from a trace in the rivers of the eastern section to a rriaxinium of 0.74 p.p.m. in the Duck River, which drains the area where rock phosphate is mined in middle Tennessee. Under present expanded mining and washing operations, however, the lrainage from that river may carry more fluorine. Some small ponds develop in the depressions resultant from the earlier practices in the mining of rock phosphate and the waters of these ponds may attain a fluorine concentration that might prove toxic n-hen imbibed b y livestock. Consideration of this point is tinder way because of observations made b y Gaud, Charnot, and ’ ~ induced in man and beast Langlais (19) as to “Le D a r m o u ~(737, ‘through the drinking of the drainage water in regions of highly Dhosphatic soils. INCREMENTS OF FLUORINE TO VEGETATION AND SOILS
Fluorine reaches the soil through sprayings and dustings of in,ecticidal materials, through incorporations of superphosphate, raw rock phosphate, and electric furnace slag; and from dusts, soot, rain waters, and atmospheric effluents. Through Rain Waters. Six collections of rain waters were made by means of large asphaltum-coated elevated cones at the Blount County farm, equidistant from Xlcoa and Knoxville, between December 1947 and April 1948. The mean fluorine in those collections was 0.29 p.p.m., \\-hereas seventeen Knoxville collections also showed a mean content of 0.29 p.p.m. of fluorine, in the range of 0.06 to 1.23 p.p.ni. Incidence of so much fluorine in the rain waters at Knoxville is attributed to the large quantities of soot that are emitted through combustion of soft coal. Many soft coals contain as muck as 100 p.p.m. of fluorine (64). Maury County rain waters registered 0.30 p.p.m. as the mean fluorine content in the range between 0.14 and 0.74 p.p.m. in four collections. Occurrences of from 0 to 0.02 p.p.m. of fluorine were found in control collections of rain waters obtained at Crossville, M point approximately 100 miles equidistant from Blount and Maury Counties. T h e findings embodied in Table I record the pounds of fluorine per acre brought b y rain waters at the indicated points during
Vol. 41, No. 11
1948. The increments derived from the rain waters at the pointb adjacent to the two manufacturing operations, and in Knoxville, were six t o seven times those precipitated at the two control stations. Each of the four high increments n a s less, however, than the quantity imparted to the soil through a 500-pound ~ n corporation of superphosphate. Through Atmospheric Effluents, Superphosphate manufac‘curia has been blamed for fluoiine emissions purported to have caused detrimental effects upon plant and animal life (63, 66, YO). The writer has observed harmful effects upon vegetation at points near superphosphate operations. I n one instance, observed in 1920, the fluoric effluents caused complete decimation of a corn stand about 2 miles distant on a Davidson County farm, although an adjacent crop of soybeans was not injured. I n another instance. where a 2-day accidental and abnormal discharge of effluents reached a nearby farm, the grasses \cere spotted and the cornstalks had a midzone of deadened leaves. The leaves in the horizon betveen the unaffected upper and lowep loaves had ii fluorine content 44 times that found in the leaves that had developed on the stalks before and after the brief duration of the accidental discharge. The high content of fluorine occurred even after the affected leaves had been exposed to a 3-week periad of unusual rainy weather. About a fourth of the fluorine context of starting rock phosphate is evolved in the manufacture of superphosphate (63). ilccording to De Eds ( l 6 ) ,in 1933, superphosphate operations in the United States caused emission of 33,000 tons of fluorine per annum, whereas present operations probably emit 70,000 tons per annum. The emitted fluorine occurs as silicon tetrafluoride, which becomes silicofluoricacid and hydrofluoric acid upon contact with moisture. Atmospheric pollution from such emissions can be diminished greatly b y means of wash towers and absorbents, while rffecting conversion of the evolved fluoric gases into by-product solids. Under normal conditions, superphosphate operations should not become a menace to plant and animal life, even in locations relatively near. Fluorine emissions per ton of rock converted to superphosphate are much less percentagewise than the liberations induced through the thermal processings.
Table I .
Fluorine Present in Rain Waters Collected at Designated Points during 1948
(Pounds per acre) UT Farm, City of Blount ?&w-u’y County Knoxville County 4 B 0.71 0.56 2.106 0.86 1.38 0.79 0:71 0.52 0.11 0.53 0:34
UT Farm,
Month Jan.
Feb.
March April May June July Aug. Sept. Oct. Nov. Deo.
~.
0.33 0.41
0.28 0.28
0.11
0.04 2.4 1.1 9.66
0.18
0.92 0.17 0.29 0.55C 0.13
0.94
1.15 - .6.65
1.19 0.31
0.50 0.11
0.54 0.12
1.10
0.20 0.45 0.1s 0.67 0.28
.. .. 3.00
2.00
Croswille Springfield 0.07“ 0.07u 0.03 0.12 0.12 0,2I
0.01
0.06 0.05 0.03 0.12 0.07
7.01 5.22 0.81 (0.92)~’ (7.79)Q (7 83)n Locations A and B findings computed to 12-month basis. b Precipitation of 6.5 inches for month. Average of 11 months inserted. d Parenthetical valuc computed t o 12-month basis. I
0:03 0.09 0.06
0.15
I.
~. ~,
.. 0.33 (0.9i)d
e
Fluorine discharges come also from the fluorspar used as a flux in the steel and metal industries through iron refining-in Thomas Siemens-Martin, in Bessemer, and in cupola operations-as well as in the manufacturing of lead, copper, and nickel, the resultant emissions of fluorine being attributable to silicon tetrafluoride. It is estimated that such usage accounts for 80% of the world production of fluorspar (67). T h e injurious effects upon farming and livestock operations in certain sections of Blount County have been attributed to discharges of fluorine compounds in the production of aluminum.
November 1949
I N D U S T R IA L A N D E N G I N E E R I N G C H E M I S T R Y
I n the reduction of alumina to aluminum, the passage of an electric current through the molten cryolite in a carbon-lined cell induces an emission of fluorine as hydrogen fluoride that is hardly noticeable at the cell, yet the aggregate of the emissions from a largely increased installation of cells has created an unhappy economic situation a t certain points in a county of extensive livestock farming. Apparently, effects induced by fluorine emissions are attributable to gaseous phases. There was no determinable difference in the fluorine present in filtered and unfiltered samples of atmosphere of abnormal fluorine content that were collected on the university farm, some 5 miles distant from the aluminum plant. Moreover, Medenbach stated that “fluorine compounds have been sought for over the open melting baths, but without success” (69). Expulsion of cryolite during the reduction of refined bauxite therefore can be disregarded as a factor in atmospheric pollution. Thermal processings of rock phosphate are being conducted in extensive operations a t several points in Maury County. These operations effect substantial percentage expulsions of the rockcontained fluorine and large aggregate discharges of that element into the atmosphere. When rock phosphate is sintered for inclusion in the “burden” of the electric furnace, 30 to 35% of the contained fluorine is driven off. I n the fusion of rock phosphate for its conversion to tricalcium phosphate fertilizer, however, at least 90% of the fluorine content, or 70 pounds per ton of rock, is dispelled to the atmosphere, chiefly as hydrogen fluoride, the most virulent form whereby the element may reach vegetation. LYSIMETER STUDIES ON INPUTS OF FLUORIDES IN
FALLOW SOILS Additive Barium Silicofluoride. Soils acquire fluorine directly from incorporations of superphosphate and insecticides and indirectly through application of fluorine dusts and sprays to vegetation. The objectives of the initial lysimeter experiment were to determine the fate of barium silicofluoride (BaSiFe) after its incorporation into the sail (94, 33, 36) and to ascertain resultant chemical and biochemical effects. The fluoride was incorporated into a brown silt loam in 1/20,000-acre lysimeters a t the rate of 1500 pounds per acre and also through three annual replications to aggregate 6000 pounds. The 4-year findings registered a near-complete retention of the fluorine of the added barium silicofluoride against the leaching action exerted by an over-all rainfall of 200 inches. This prompted the reasoning that calcium fluoride is engendered in the soil when fluorine is incorporated in any other form. The findings also were interpreted as assurance of a low concentration of fluorine in soil water and to “obviate any cumulative toxic effect from increments derived from dusts and sprays of fluorine materials from calcium fluoride introduced by additions of phosphatic fertilizers” (47). The near-complete retention of the incorporated fluorine against rain-water leachings seemed attributable to the relatively low solubility of calcium fluoride and to the sorptive and reactive capacities of the aluminum complexes in the soil, with possible formation of CasAIFa ( 4 ) . The mechanism of such retention will be considered further in relation to later findings as to the specific behavior of fluorine supplied through repetitive inputs of precipitated calcium fluoride, fluorspar, and slag. Additive Calcium Fluoride. The second lysimeter experiment was of 10 years’ duration and dealt with effects postulated for annual inputs of precipitated calcium fluoride upon the availability of the phosphorus in variously phosphated soils (48). I n one series, fluorine inputs were restricted to rock phosphate incorporations, which were a t the rate of 2 tons per acre, with and without calcium, magnesium, and dolomitic supplements. The raw rock in these systems yielded only nugatory quantities of fluorine in the rain-water leachings. The other series, the phosphated soils, received annual inputs of fluorine which aggregated 2400 pounds, or 4932 pounds of calcium fluoride per acre. As total outgo in the 10-year drainage caused
2469
by a 51-inch per annum rainfall, the largest leaching of fluorine amounted to merely 2.5% of the 2400-pound input. Only after 7 years did any drainage water content show as much as 1p.p.m. of fluorine. The quantities of fluorine retained by the phosphated soils were far beyond the amounts that the several additive calcium phosphates could have accounted for as having been due to engendered fluorophosphate, which had been shown t o develop in mixtures of superphosphate with limestone, slag, or powdery defluorinated rock phosphate, in mixtures outside the soil (41-43). Near-complete retention of the incorporated fluorine through the development of calcium-aluminum-fluorine compounds in the limestoned soil is a possibility suggested by the demonstrated reaction between calcium hydroxide and hydrated alumina and the succeeding uptake of calcium sulfate, with resultant formation of the tertiary 3Ca0.A120a.3CaS04.33H20 in high-calcic soils, as reported by MacIntire and Shaw (46). Another postulation is the development of a ternary calcium-aluminum-fluorine compound, the possibility of which is suggested by the reaction between the fluorides of monovalent bases and hydrated alumina as demonstrated by Baud ( 4 ) . Obviously, the added calcium fluoride undergoes some hydrolytic dissociation in the soil system. This was evidenced by the fact that the outgo of calcium from the incorporated calcium fluoride was many times the equivalence of the small enhancements in the concomitant outgo of fluorine. Moreover, Sherman, McHargue, and Hageman (6.9) found that calcium fluoride effected the oxidation of manganous oxide to manganic form in the soil, whereas such transition was not induced by the salts of the other halogens. Addition of Fluorine a s Component of Slag. I n still another lysimeter study (48), now of nearly 9 years’ duration, an objective was to ascertain whether rain-water leachings from incorporations of the quenched slag of the electric rock phosphate reduction furnace induce a fluorine enrichment in the ground waters and thus might create a health hazard. The incorporated slag supplied inputs of fluorine a t rates between 152 and 1523 pounds per acre. I n distinct contrast to the near-complete retention of the fluorine that was incorporated as precipitated calcium fluoride, in limestoned and in dolomited soils, the slagged soils released up to 674 pounds of fluorine per acre to rain-water leachings in 8 years The maximal outgo of fluorine was from the 1523-pound input, that was carried by relatively coarse slag through four annual incorporations of 5 tons per acre. That outgo represented a 44% leaching of the input of fluorine and amounted to more than 10 times the recovery from the 2400-pound input that was made through incorporations of calcium fluoride in the earlier 10-year lysimeter study. The fluorine concentration in the drainage waters from the slagged soils was up to nine times the concentration attained when distilled water was saturated with precipitated calcium fluoride, and five times the concentration attained when carbon dioxideimpregnated water was saturated by means of either precipitated calcium fluoride or fluorspar, even though the rain-water leachings showed a high concentration of calcium as neutral salts and as calcium bicarbonate. Obviously, the enrichment of fluorine in the leachings from the slagged soils is not to be attributed t o a passage of solute calcium fluoride. The high content of fluorides in the drainage waters from the slagged soils was accompanied by considerable quantities of solvated silica, the occurrences of which were almost nil in the leachings from the limestoned soils. However, similar quantities of the silica were present also in the drainage waters from the soil that had received incorporations of fluorine-free wollastonite. Nevertheless, occurrences of solvated silica in the rain-water drainages from the slagged soils and from those wollastonited are distinctive, for suspensions of the two silica materials imparted no significant quantities of silica to their carbonated water extracts in the laboratory (46). Hence, it is yet to be established
INDUSTRIAL AND ENGINEERING CHEMISTRY
2470
Vol. 41, No. 11
Huorine materials were incorporated together with rationalrate incorporations of high-calcic Hartsells Fine Sandy Loam ~Clarksville Fine Sandy Loan-limestone. Blkahlkalinityb, Ka, Cab, SiOZC, Fluorined, linitgb, Na. Cab, SiOzb, Fluorined, The rain-water dminages of the \Isterisls Added mg./l. mg./l. mg./l. mg./l. mg./lb. mg./l. mg./l. mg./l. mg./l. mg./lb. initial year showed only meager None 20 I.O 16 2.4 5 . 6 (11.0) 33 0.9 24 2.4 2 . 6 (5.0) 108 . 3 . 5 (7 .0) 96 . . 89 .. 4 . 0 (8.0) enhancementsinthefluorineout 99 2i 28 .. S.O(l6.0) 38 . 32 . i.O(l4.0) go per acre from either cropped or 28 10:6 10 S.O(l6.0) 42 R:4 16 .. 9 . 5 (19.0) 83 94 ., 4 . 5 (9.0) IC19 . . ~ 100 .. S.O(l6.0) fallowed soils. Moreover, the FC + C ~ C O ~ 102 i:, 112 4.0 ‘8.0) 11.5 10.3 L60 92 14;:8 content of fluorine in the large 89 96 i:2 9 . 5 (i0,O) 170 2 4- NazSiOsipQ 130 fiS:O 1 32.8 4 . 5 (9.0) 217 100.0 22 46.4 7 . 5 (15.0) crops of soybeans was not enCa.Fz + CaSiOrg.6 59 69 12.4 6 . 0 (12.01 112 .. . 114 25.2 7 . 0 (14.0) hanced percent’agewiseby the inCaFz +: CaCOa + SazSlOaf! 0 202 91.5 44 32.0 2.5 (6.0) 245 99.0 63 34.3 6 . 0 (12.0) put from any fluorine carrier, in’‘ *After 10 days’ aging in iiioist condition. Fluorine additions at rate of 10 mg. of F per 100 granis of soil. or c]uding roclr phosphate. ~ h :n 1 l i t w of extract, or a s 200 pounds of F per 2,000,000 pounds of soil. h CaCOa additions a t rates of 3 and 2 t o n s for Hartsells and Clarksville soils. again, the fluorine carried by in5 Carried 12.1 mg. of Pia per 100 grams of soil. corporated fluorides was found to (7 Bracketed figures express pounds of element per acre (2,000,000 pounds). a I n p u t of 8880 pounds supplied fluorine a t 200-pound rate. have been retained almost comi Carried 129.2 mg. of N a pep 100 grams of soil. ‘/ Siliceous materials were applied a t rate of 0.1631 gram of Si02 per 100 grams of soil. pletely against rain-water lcachFused wollastonite, through 100-mesh. Silica equal to t h a t of slap. irigs from Tennessee soils in which there was reasonx1)le ca1cium content. The ready leachability of the fluorine supplietl through incorwhether the high coiiceti trdtion of fluorine in the drainages from porations of quenched calcium silicate slag had been found to be i,he slagged soil is attributable to calcium silicofluoride, or t o an outstanding exception to the retention of fluorine supplied wpersaturation of calcium fluoride imparted through its “nasotherwise. Yet this exception to fluoride mobility does not extend cency” in state of submicrocrystallinity at the moment when that tJo an increase in migration of ca.lcium fluoride into the plant, for quoride is liberated into the soil system through the hydrolytic no slag input has induced a significant percentage increase i n the t iisintegration of the incorporated slag. fluorine content of experimentally grown forage crops. Additive Potassium and Calcium Fluorides. I n yel another It may be that the near-complete retention of the fluorine of iyhimeter experiment, objectives n-ere the fate of potassium and calcium fluoride (eit’herthat added as such or that engendered) by fluorine in relation to possiblc anion and cation fixations through the several soils of Tennessee would not be effected by the light exchange reactions and postulated reaction between potassium sandy soils of low content of colloidal matter, such as those in the fluoride and hydrated aluminum compounds native to the soil. Coastal Plain regions of comparable rainfall. The corollary posT h e initial inputs of the two fluorides were supplied to distinctive sibility is that vegetation on the sandy soils might effect a higher w i c k soils, with and without light and heavy incorporations of percentage uptake of fluorine. limestone, fused-quenched wollastonite, and quenched calcium vilicate slag, made a month prior t o the incorporations of the two LABORATORY EXTRACTIONS OF EXPERIMENTALLY ituorides. The quantities of fluoiine in the early collections of FLUORINATED SOILS drainage waters were small; the largest outgo was less than 4 A laboratory experiment was conducted to elucidate the findpounds per acre. The small leachings of fluorine from the added ings as to ready outgo of fluorine in the rain-wat,cr leachings from rhorides were diminished still further by the inputs of calcium t,he incorporated electric furnace slag, in contrast to t.he nearith limestone and as wollastonite. The input of calcium also decomplete retention of the fluorine from incorporations in other creased the recovery of the potasbium of the potassium fluoride forms (Table 11). qdditione to the soil that WRP highly aridic initially. TKOsoils were fortified with sodium fluoride alone; with calMIGRATIONS OF ADDITIVE FLUORIDES FROM c:ium fluoride, alone and jointly with calcium carbonate; with calcium fluoride and sodium silicate; with calcium fluoride and CROPPED SOILS calcium silicate, jointly, with and without calcium carbonate. The foregoing finding* ab to Huoiide migration from incorporitAfter 10 days’ aging in moist condition, the several soil systems were brought to equilibrium in carbon dioxide-saturated aqueous rims of different materials ‘(VAPP obtained from soils devoid of suspensions through 16 hours’ agitation a t room t,emperature. plant growth. I n a more recenl lysimeter experiment, however. The resultant, extracts contained small and identical recoveries of retentions of additive fluorine by the fallow soils and by those Huorine from the sodium and calcium fluorides that had been cropped were determined simultaneously. Soybeans were grown aged in t.he unlimed soils. The extract,s from the soil ~ l u calcium s fluoride plus sodium silicate systems coiitained solvated silica i n two soils that received fluorine a t the rate of 200 pounds pel nearly thrice the silica, content of the extracts from the fused cal-%ere,through incorporations as sodium fluoride, sodium silicocium silicate, yet the concomitant fluorine recovery was even less ‘-tuoiide, magnesium fluoride c1 wlite, and rock phosphate The than t,he qua.ntity recovercd in the extracts from t h e untrcated soil. Table 11.
Alkalinity and Calcium, Sodium, Silica, and Fluorine Recoveries through Carbon Dioxide-Water Extracts of Fluoride-Treated Soils“. ~
,
~
!::(i!:tj
Table 111. Solubility of Calcium Fluoride i n Carbon Dioxide-Charged Water, with and without Wollastonite“ CompoPition of Extracts. -Solute _._I___ ~.. ~
CaCOa, p. p. in.
‘aFy, precipitateclb iyollastonite, 100-meuhp
CaFn a n d wollastonite6
Son?
158
,!
&,Fz and wollastonitcb~ c * *
197
146
Fluorinr, p.p. In. 10 van?
4 6 3 3
Charges suspended in 100 IUI. arid system aspiratod vigorously with
