Industrial Precipitated Tricalcium Phosphates V A R I . A N C E IN C H E M I C A L , S T R U C T U R A L , AND FERTILIZER PROPERTIES T h e over-all problem of precipitated tricalcium phosphates i s important t o t h e fertilizer industry, t o the chemist charged with water defluorination, and in chemical and biochemical investigations. Because of existing uncertainty in the composition and properties of commercial precipitated tricalcium phosphates, seven samples were obtained from dependable vendors and submitted t o chemical, optical, powder diffraction, Neubauer tests, and pot culture studies. Monocalcium phosphate, five purchased dicalcium phosphates, and three prepared tertiary products were included as controls. T h e dicalcium phosphates were virtually citrate-soluble and of uniform P2O6:CaO ratio. T h e tertiary precipitates varied
in composition, solubility, and reactivity toward calcium fluoride, i n optical properties, in x-ray powder diffractions, in Neubauer tests, in plant response, and in P,O6 recovery. Five precipitates were isotropes and t w e precipitates were anisotropes. Four precipitates were hydroxyapatites, and two were similar t o b u t not identical with 8-Ca3(PO&. T h e solubility varied from 34 t o 96%. Two lots from the same vendor varied 100% in solubility. Variance in Pz06uptake by Neubauer seedlings, in plant response, and in P20, recoveries were consonant with t h e values registered by chemical examinations of the precipitates. It i s proposed i n this paper t h a t a standardized and certified precipitated tricalcium phosphate be provided as a control in chemical and biochemical research.
HIRTY-five years ago Cameron W. H. Maclntire and S. H. Winterberg accounts for the relatively low and Bell (6) wrote: “The literaT H E UNIVERSITY O F TENNESSEE AORICULTURAL solubility of rock phosphate (16, ture of the phosphates is unEXPERIMENTAL STATION, KNOXVILLE 17). Either the removal or the inusually voluminous. . . perplexing activation of the fluorine comH. L. Marshall, George Palmer, and contradictory.” They conponent of apatite imparts fertitended that “no crystalline suband B. W. Hatcher h e r effectiveness, even beyond stance of the composition of the that possessed by Some Of the preTENNESSEE VALLEY AUTHORITY, KNOXVILLE, TENN. hypothetically neutral tricalcium cipitated tricalcium phosphates (7, phosphate--Cas(P04)~-has yet 8, been found in nature or recognized in the laboratory”. As reThe nature and fertilizer value of the several tertiary comcently as 1932 Buehrer (5) stated: “This phosphate is a hypopounds that develop during the ammoniation of superphosphates thetical compound whose existence in crystalline form as well a8 and by the admixing of either liming materials or powdery dein chemical composition, when prepared by precipitation from fluorinated rock phosphate (4,26) are of practical import. hlacsolution, has not yet been proved.” Intire and Hardin (37) demonstrated that superphosphates deWendt and Clarke (43) and Bassett (3) demonstrated that the rived from defluorinated rock phosphate can be ammoniated and normal tertiary phosphate is not attained by progressive addiotherwise processed without diminution in P20, availability. tions of Ca(0H)e to Hap04 iv aqueous systems. MacIntire and Keenen (20) concluded and Hardesty, Ross, and Adams (fa) Shaw (SI) likewise found incomplete reaction when solutiondemonstrated that the tertiary phosphates induced by the amsuspensions of monocalcium phosphate and limestone were agimoniation of superphosphate are apt to be less soluble than the tated and aspirated over long periods, and when moist mixtures reagent precipitates. MacIntire, Shaw, and Hardin (33) deterof dicalcium phosphate and limestone were aged 13 months (32). mined the solubilities of the secondary and tertiary phosphates in According to Bassett ( 3 ) , however, the “normal calcium phosmixtures that simulated occurrences in ammoniated superphate” precipitate is formed when a solution-suspension of monophosphatas. They noted also that two ammonium reagents can calcium phosphate is ammoniated above 80’ C. The formation be utilized to differentiate precipitates of tricalcium phosphate of tricalcium phosphate by the progressive ammoniation of an from generated fluorphosphate. aqueous solution of monocalcium phosphate was reported by No serious decrease in PzOs availability ensues when superLorah, Tartar, and Wood (a$). Ross and co-workers (38) dephosphate is ammoniated, unless tricalcium phosphates are scribed two procedures by which they obtained optically amorformed. The deleterious PoOatransitions that result from heavy phous tertiary precipitates. By x-ray examination, Hendricks ammoniation are accounted for by Keenen’s equation (20): et al. had found these compounds to be crystalline hydrates of 2CaHPOa CaSOa.+ 2NHa = (NH&S04 Cas(PO& tricalcium phosphate (15). Larson (21) and MacIntire ($3) subsequently obtained crystalline precipitates of tricalcium phosT h e indicated reaction is restricted, however, urhen temperature phate is held down during the ammoniation and storage of standard superphosphates, and is virtually obviated in the rational amTRlCALClUM PHOSPHATE FERTILIZERS moniation and chilling of concentrated superphosphates (11, 12, 13). Andrews ( 8 ) concluded that the development of tricalcium Variation in the fertilizer value of different forms of tricalcium phosphates in ammoniated superphosphates is reflected definitely phosphate was mainly of academic interest until the problem by decreases in the fertilizer effectiveness registered by plant rearose of tertiaries formed in the ammoniation of superphosphates. sponse. For many years both bones and rock phosphate were appraised The component fluorides of both ammoniated and limed superin terms of tricalcium phosphate or “bone phosphate of lime”. phosphates react with the generated tricalcium phosphates in Agricultural literature taught erroneously that the normal tervarying degree to form the exceedingly insoluble fluorphosphate tiary compound comprised the phosphate content of these nat(25-88,39, 44). Therefore, the ultimate teitiary calcium phosural materials (19). Now, however, a different composition is phate composition in processed fertilizers is variant and indeterascribed to bone (14,15, 37, 40), whereas constituent apatite
T
.
+
+
INDUSTRIAL AND ENGINEERING CHEMISTRY
548
TABLEI. PARTIAL ANALYSESOF INDUSTRIAL TxIcALcIuni PHOSPWATES FROM SEVERAL SOURCES 4 N D O F CONTROL PHOSPHATES ,--
and s-ray powder patterns. The seven phosphates then were compared as to fertilizer values through the Neubauer biochemical test and by plant response and PzOecontent
PzOa---.
COMPOSITION OF PHOSPHATES
Pit-
Availainsol., bility, % Rn .0.05 99.9 0.10 99.7 0 . 0 8 99.8 0.30 99.4 0.05 99.9 0.90 98.0 100.0
PZO~ Total, CaO, per Unit Cu Phosphate Lab. No. % % of CaO F.. % ,.\IonoP-679 55:60 22’.h3 2.479 0.020 Di- (hydrated) S-972b 41.90 33,76 1.241 0.013 Di- (hydrated) 41.00 5-9816 32.94 1.245 0.013 Di- (anhydride) S-983b 50.90 41.04 1.240 0.013 Di- (no formula) S-985b 42.30 0.013 34 I94 1.211 Di- (hydrated) S-987b 44.02 0.013 36.20 1.216 CaF-IPOn Theoret. 52.19 41.19 1.267 CaHPOn.2H20 Theoret. 41.28 . .. 32.56 1.267 TriP-915 38.30 1.50 96.1 43.16 1.019d 0.014 Tri5-9036 0.014 38.70 25.30 34.6 51.12 0.757 TriS-973b 0 41.50 3.36 9 1 . 9 46.10 1.0436 7%S-982b 0 39.20 18.60 52.8 51.00 0.776f TriS-984b 1.80 95.6 44.90 1 . 0 8 1 ~ 0 40.90 Tri0 S-986 39.30 17.40 55.7 50.48 0.778 Tris-988 0.014 41.40 19.80 52.2 48,46 0,854 TriS-989b 39,230 25.90 34.7 51.50 0.773 0 Rone, fusedh 53-819 37.80 11.40 69.8 54.38 0.695 0.040 Tri-, fusedi S-855 45.40 12.40 72.7 51.84 0.876 0.008 Ca~(P0dn Theoret. 45.79 ... . 54.21 0.8447 Caio(POa)e(OH)z Theoret. 42.23 55.78 0.7571 By 1-hour digestion of I-gram charges with ammonium citrate of 1.09 sp. gr. and pH 7, and hand agitation a t 5-min. intervals. b Industrial products, purchased from different vendors. 2CaS01 f 4“: -* Made by reaction indicated by CaH4(POn)z.HzO 2(NHa)nSOa Cas(PO4)z He0, in a slurry a t 5’ C. d After correction for 10.07% content of CaSOa.2HeO. After correction for 11.4% content of CaCOa. I’ After correction for 0.89% content of CaCOa. After correction for 12.60% content of CaCOs. h Commercial steamed bone, fused in electric furnace. t Three moles CaO and one mole of PeOa supplied as marble and HsPOI, respectively, and fused. “e t;
... ...
. ..
. .. ..
.... ..
(i
+
+
Vol, 36, No. 6
+
minate. The component calcium fluoride, and also that formed upon t,he addition of sodium fluoride to ordinary superphosphate, is much more reactive than incorporations of either pulverized fluorspar or the analagous reagent (12, 68), and the fluorphosphate transition may occur during analysis (I, 35.5). ,4 st>andardprecipitated tricalcium phosphate is essential for comparisons in the chemical evaluation and in the fertilizer rating of manufactured basic phosphates. Obviously, variance in tricalcium phosphate controls will vitiate the rating accorded industrial and experimental phosphates of fertilizer grade through chemical comparisons and integrated pot, culture studies. I n the development of analytical procedures for the appraisal of ferti!ixer phosphates (33, 54), samples of tricalcium phosphate of identical label and origin were found to differ markedly in chemical properties and also in effectiveness upon plant growth, especially on lirnestoned soils (29, 50). Several experiment stations have utilized an industrial precipitated phosphate as a yardstick in the evaluation of the tricalcium phosphate content of ammoniated superphosphates and in field comparisons with monoand dicalcium phosphates (9). This product, purportedly a tricalcium phosphate, was similar in composition and s~lubilit~y to two of the tertiary precipitates of the present study. The primary objective of this paper is to show that commercial precipitated tricalcium phosphates now obtainable are made by dijyerent processes, are not) true to form.ula and are variable in composition, reactivity, optical characteristics, and structure; therefore they are not trustworthy as controls in the chemical a.nd biochemical determination of the fertilizer value of basic phosphatic fertilizers. Another ob,iective was to ascertain whether an identical product is obtained when different lots are supplied by the same manufact,urer at different times. I t was anticipated that a proposal would be adva.nced to assure an indristrial tricalcium phosphate of uniform composit,ion and properties. I t was anticipated also that a simple and rapid chemical test would be proposed for the identification of industrial tertiaries. Seven lots of precipitated tricalcium phosphate were purchased from accredited vendors and subjected to comparisons as to composition, citrate solubility, react>ivity, optical properties,
Table 1 gives partial chemical analyses of the industrial products and of one made by the ammoniation of a chilled slurry of monocalcium phosphate and calcium sulfate. The industrial dicalcium phosphate controls were virtually citrate soluble, although the unstable dihydrate is rated as being more soluble than the anhydrous form (86). A monocalcium phosphate and two fused-quenched products were included in some of the studies. The industrial precipitated phosphates showed decided vaiiance in citrate solubility. (For brevity, “precipitate” will here connote an industrial precipitated tricalcium phosphate.) Precipitates 5-973 and 5-984 contained the least citrate-insoluble PzO~ and contained calcium carbonate in respective amounts of 11.4 and 12.60%. I n contrast, precipitate 5-982 had a high citrate-insoluble P206 content, a1though it also contained CaC03 These three lots and precipitate 5-986 were obtained from separate vendors in January, 1942. Four of the seven industrial precipitates show PsO5:CaO ratios that indicate hydroxyapatite Precipitates S-903 and S-984 were obtained from the same vendor but differed widely in properties. Moreover, the superior precipitate, 9-973, and the two decidedly less soluble precipitates, S-988 and S-989, were from the same vendor a t different times, Since three of the precipitates contained calcium carbonate and one product contained calcium sulfate, and since neither of these compounds was present in the other precipitates, it is obvious that the producers followed different procedures and used different ieactants. Hodge et al. (18) noted that the Pz06:Ca0 ratios in their tertiary phosphates, prepared by Lamon’s method @ I ) , were closer to true values than were the ratios found for industrial, products. They observed that “the composition of the precipitated phosphates is seen to depend upon the mode of precipitation rather than the amount of reactants”. In making tertiary precipitates in these laboratories, it has been found that composition is affected to marked degree also by the temperature of precipitation and drying It is evident that the composition of the bone was altered during fusion and that none of the phosphates had a fluoride content sufficient to induce a measurable decrease in citrate solubility. REACTIVITY O F PRECIPITATED PHOSPHATES W I T H CaFv
I n previous comparisons of the effectiveness of sand-diluted columns of calcium phosphates in the removal of fluorides during percolation, the basic phosphates registered valiant reactivity (94) Therefore, the present precipitates were tested for this property. A 2-gram charge of precipitate was introduced into 100 ml. of a 40.64 p.p.m. solution of calcium fluoride in a 250-ml stoppered flask. The solution-suspension was agitated continuously one hour a t 65” C. in an electrically heated chamber and allowed to clarify overnight. Aliquots of supernatant solution then were examined for changes in pH and analyzed for fluorine content by the technique of Hammond and MacIntire ( 9 ) ~~~
~
~
~~~
T.ARLE 11. VARIANCE I N EFFECTIVEXESS O F TSJK’IIAHY CALPIUM Pxiosm 4 PES IN DEFLUORINATION OF AQUEOUS SOLUTION OF CALCIL-M FLCORIDE Type of pH a t End Fluoride Lab. N o Tert. Phosphate of Digestion Removal, ’% 96.0 6.8 P-915 Lab. product 97.0 6.8 S-903 Industrial 46 0 186, Y I’I precipitates 9.4 9-973 ps.0 0.7 S-982 39.4[97 Ol’> 9.5 s-9S.I 97 0 6.8 s-980 99.0 6.2 s-988 W.5 6.6 s-989 After 24-hour agitated digestion in 2.5% NHIOH ~ o l u t i o nat room ten>perature.
.
lune, 1944
P-915
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
S-903
Figure 1.
S-982
S-986
S-988
549
s.989
Powder Dlffraotion Patterns for Tertiary Precipitates of Table I
The m u l t s in Table I1 show that the laboratory-prepared precipitate of high citrate solubility and the five commercial precipitates of low citrate solubility effected fluorine removals beyond 95%, with attendant rise in pH from below 4.0 to a maximum of 6.8. I n contrast, the two commercial precipitates of high citrate solubility effected removals of less than 50%, and elevations to pH values of 9.4 and 9.5. But after 2-gram charges of these two precipitates of low fluoride reactivity had been agitated 24 hours in a 2.5%, solution of ammonium hydroxide and filtered, fluorine removals of 86.9 and 97.0% were found. These results suggested that the five commercial precipitates of low Bitrate solubility and the highly soluble laboratory product, P-915, were hydroxyapatites, the hydroxyl of which was replaced by the Fa of the solute fluoride in the formation of fluorphosphate, and that the more soluble precipitates, 5-973 and 5-984, were converted to hydroxyapatites during digestion in the dilute solution of ammonium hydroxide. MICROSCOPICAL DISTINCTIONS
Examined in white light, the five precipitates of high citrate insolubility and laboratory product P-915 were found to be isotropic. Examination with crossed Nicols showed the more soluble precipitates, S-973 and 5-984, of high PZOSavailability and CaCOa content, to be anisotropic; precipitate 5-982, of low PzOs availability and small carbonate content, was isotropic. ISOTROPES. P-915 was comprised chiefly of subangular to subrounded colorless particles of the order of 0.006 X 0.006 mm., with some rods of 0 002 x 0.02 mm. and with q = 1.578. The particles of 5-903 were, like those of P-915, from 0.04 X 0.04 down to 0.002 X 0.002 mm., with q = 1.610. The particles of 5-982 were, like the two foregoing precipitates, principally 0.012 X 0.012 mm. and smaller, although many particles were of 0.030 X 0.030 and some as large as 0.120 X 0.160 mm., with q = 1.610. The particles of 5-986 were subrounded and colorless, some with black inclusions. Most were 0.01 X 0.02 mm. and smaller, although some were 0.06 X 0.04 mm., and others were rectangular, anistropic, 0.005 x 0.01 mm., with 7 = 1.610. Precipitate 5-988 was similar t o 5-986, with 1) = 1.595. The particles of S989 were subrounded to rounded and colorless, with some dark inclusions, 0.02 X 0.02 mm. and smaller, and others up to 0.08 X 0.05 mm. with 1) = 1.615. ANISOTROPES.Precipitate 5-973 comprised particles mostly rhombic and roughly rectangular, uniaxial, and colorless, with dimensions of 0.02 X 0.02 mm., and 0.015 X 0.020 and smaller, although some were 0.03 x 0.05 mm. Interference colors were of the 6 r s t order, with qa = 1.610, q-, = 1.615, and qy qa = 0.005, a weak birefringence. Precipitate 5-984 was virtually
-
identical with S-973: ‘la = 1.605, v-, = 1.613, and
tlV
- vcr =
0.008. X-RAY POWDER DIFFRACTION
The diffraction patterns (Figures 1 and 2) were obtained with a Machlett copper target tube, operated 4 hours at 35 kilovolts and 13 milliamperes in a Hayes unit. A nickel filter was employed t o obtain the characteristic Ka radiation, A = 1.539 A. Duplitized nonscreen Agfa film was used in a circular type camera of 7 cm. radius, calibrated against known spacings of sodium chloride and of calcite. The five optically amorphous industrial precipitates gave the typical pattern of hydroxyapatite and indication of minute particle size. Although seven patterns of 5-903 were made, none exhibited the line intensities registered by the patterns of the other industrial hydroxyapatites. There was no indication of dicalcium phosphate, and hydroxyapatite identification was in accord with the conclusions of Roseberry et al. (37) and Hodge et al. (18). When these five precipitates were ignited one hour a t 1000” C. and cooled slowly, four suffered no change in pattern other than crystal growth and, therefore, were unquestionably hydroxyapatites. Apparently, however, S-988 was a hydrated tertiary, since it yielded p-Cas(POd)z. The laboratory-prepared tertiary registered a crystalline pattern, and its microcrystallinity was indicated by the diffuseness of the lines. Incidence of CaS04.2H20also was registered by the respective spacings of 7.6, 4.22, 3.01, and 2.88 A. forlthe &st, second, sixth, and seventh lines. As shown, by Hill and Hendricks (16)and as indicated by the Hanawalt table (IO), the pattern of CaS04.2H0 is similar t o that of CaHPOr.2H20, but a 10.07% residue of the reactant sulfate and absence of dicalcium phosphate was established by the analysis of Table I. The two precipitates that contained more than 11% CaCOs yielded identical patterns, similar to but not identical with the spacings for @-Ca3(POa)a,a s given by Hanawalt (IO). The P2Oa:CaO ratios indicate that these two precipitates were derived from concentrated solutions. Hodge, LeFevra, and Bale, observed that “during precipitation, if the solution is rich in phosphate, many multipolar phosphate ions are drawn around the tiny crystals, attach themselves weakly with only a partial loss of their attractive forces for the water shell, and constitute, together with the crystal, coacervated particles” (18). They also concluded that “commercial tertiary calcium phosphates are probably hydroxylapatite with more or less adsorbed phosphate ions to give empirical formulas approaching the theoretical”. Upon ignition for 3 hours a t 950’ C., dessicated charges of precipitates 5-973 and S-984, containing carbonate, suffered re-
‘
INDUSTRIAL AND ENGINEERING CHEMISTRY
550
TABLE 111. AVAILABILITY O F DI- AND TRICALCIUM PHOSPHATES ON HARTSELLS AND FULLERTOX SOILS AS IXDICATED B y PZo5 UPTAKEIN KEUBAUER CULTURES PSOSUptake per 100 Grains Soil, Hartsells fine sandy loam PhoWhate lncorporationa U s d b , L i r n e d C Type Lab. No. pH 4.8 pH 6.7 None 0.2 1.3 MonoP:6?9 5.8 6.7 DiS-972 6.4 6.9 6.4 8.0 Dis-981 DiS-983 7.5 7.2 BiS-985 7.6 10.5 Di5-987 5.7 7.7 Tri P-915 5.2 3.7 Tri5-903 4.7 1.1 Tri s-973 6.6 8.5 Tri5-982 5.2 1.o TriS-984 5.2 8.7 TriS-986 5.3 0.9 Tris-988 4.7 1.1 Tris-989 5.2 0.9 Bone, fused S-819 6.4 1.9 Tri-, fused S-855 6.5 5 .3
JIg.
Fullerton silt% Unlimedb, Lirnedc. pH 5.0 pH 6..5 0.2 1.2 10.6 11.3 11.5 11.2 10.7 12.3 12.7 14.6 12.1 14.6 10.7 12.0 11.4 7.7 10.2 4.8 11.7 11.0 10.6 3.8 11.9 12.8 11.9 4.8 12.5 4.4 10.6 4.8 9.5 7.0 11,4 10.9
Constant charge of 25 mg. PZOSper 100 grams soil. At rate of 5000 Ih. CaCOa per 2,000,000 Ib. soil. At rate of 2600 Ib. CaCOs per 2,000,000 lb. soil: aged moist 10 days before phosphate incorporation. a
b
c
Vol. 36, No. 6
Table 111 shows that, in general, the Pz06uptake from the tertiary forms was somewhat less than that from the dicalcium phosphate controls in the acidic Hartsells soil. The previous moderate incorporation of CaCOs did not repress the uptake from either the mono- or dicalcium phosphate controls or the di-Ca precipitates, 5-973 and S-984, with citrate solubilities above 90%. I n contrast, the liming treatment did repress the uptake from the five industrial tertiary precipitates that registered citrate solubility in the range between 34 and 55%. As in the case of the Hartsells soil, moderate liming of the Fullerton soil caused no repression in the P2O6 uptake from either mono- or dicalcium phosphate, or from the two di-Ca precipitates, 8-973 and 8-984; liming did repress the uptake from the other industrial precipitates. From the P206 uptake by rye seedlings it is evident that the availabilit,y of di-Ca precipitates S-973 and 5-984 was not affected adversely as an immediate effect of moderate liming, whereas the availability of the other industrial precipitates was affected adversely. This disparity in extent of P,O, uptake accords with the indications from the preceding chemical, optical, and x-ray examinations. EVALUATION BY PLANT RESPONSE AND PaOS RECOVERY
spective water losses of 6.49 and 7.60%, and gave patterns identical with the @Cas(PO4)ncalcine obtained by Hendricks ( I @ and by Hanawalt on anhydrous tricalcium phosphate (10). Although sold as tertiaries, both of these precipitates proved to be CaHP04 which reacted with oomponent CaCOa to form @-Ca3(P04)~. . The lines observed for the fused-quenched bone were similar to those of hydroxyapat,ite in some respects, but the intensities of the interference maxima mere lower and the lines were finer and fewer than those of the hydroxyapatites. Apparently the major constituent of the fused-quenched bone is the phase designiated “Bredig’s X” by Hill et al ( l 7 ) , whereas the quenchea melt of the limestone-H3POc mixture gave a pattern similar to a-Caa(POa)a pattern given by Hill et al. (17 ) . FERTILIZER EVALUATION BY NEUBAUER TEST
The tertiary phosphates were compared as to availability by the Neubauer biochemical test (41) on Hartsells fine sandy loam and Fullerton silt loam, soils that occur extensively in Tennessee.
s-973 -
Before ignition
~
Figure 2.
5-984
s-973
The precipitates were compared further as to fertilizer value through the response by four successive crops-red clover, soybean, Sudan grass, and red clover-in pot cultures. To a5sure growth of clover, the Hartsells and Fullerton soils had been moderately limestoned to a 6-inch depth at the respective rates of 4500 and 2500 pounds per acre. After one month of aging, KzS04was incorporated at the rate of 100 pounds KzO a d again to each of the three subsequent crops. The phosphate incorporations, however, were restricted to the upper 3-inch zone, a t the rate of 40 pounds Pz06 per acre surface. All pots received boron, copper, zinc, manganese, and magnesium in appropriate quantities. Crop weights and PZOs recoveries are given in Table IV. The responses to the five dicalcium phosphate con‘trols on the Hartsells soil were uniform and greater than the responses to the tertiary precipitates. The response to di-Ca precipitates reflected their superiority as shown by the chemical comparisons and Neubauer tests. In spite of the pulverulence of the industrial precipitates, S973 and S984 were the only ones to give responses equal to those of the two fused materials of much larger particle size. The mean of t,herecoveries of P,O, from these two precipitates wm
After ignition
S-984
5-819 Fused
Bone
Powder Diffraction Patterns for Purported Tertiaries and Fusions of Table I
5-855 Fused Mix. of L.S. and HsPO
INDUSTRIAL AND ENGINEERING CHEMISTRY
June, 1944
551
TABLE IV. PLANT RESPONSEAND P2OsRECOVERY FROM DI-ANDTRICALCIUM PHOSPHATEB BY FOUR SUCCESSIVE CROPSIN POTCULTURES Phosphate Incorporation Lab. No. Type None P:6;9 Mono-
Red clover, gramaa 0.6
11.1
DiDiDiDiDi-
hydrated hydrated] anh drous) no &mula) (hydrated)
i
5-972 8-981 8-983 8-985 S-987
10.1 10.5 13.6
TriTriTriTr/-
(pptd.) pptd.) {pptd.) (pptd.
P-915 8-903 8-973 8-982 S-984 5-986 8-988 5-989
6.8 1.8
% : g:ji Tri- (pptd.) Tri- (pptd.)
10.1
11.6
10.1 2.5 13.0 2.3 2.7 2.7
Hartaells Fine Sandy Loam Sudan Red Tota1i4croPs bean, grass, olover Dry wt., P z Ore~ gramab gramsc gramab grama covery, %
Fullerton Silt Loam Sudan Red crops grass. clover, Dry wt., PeOs regramsc gramad grams covery,%
Red clover, grams“ 6.0
Soybean grrtmib
11.9
18.5 25.8
7.6 11.1
5.4 16.2
37.5 66.0
39:7
65.1
25.5 26.2 28.6 26.7 30.3
10.6 12.8 15.2 11.9 11.6
22.0 21.8 23.6 21.5 22.7
12.5 12.9 13.8 13.2 13.9
16.8 16.6 17.4 16.5 17.7
61.9 64.1 70.0 65.1 65.9
28.3 28.3 27.8 31.0 29.5
49.5 29.2 61.2 32.4 67.4 40.0 38.9 34.2
22.5 13.2 27.4 13.1 27.4 17.0 17.9 12.4
10.1 5.8 11.7 3.7 13.1 5.2 6.7 5.4
22.3 18.2 24.4 19.7 24.7 19.0 21.2 19.8
16.2 13.3 16.4 11.0 15.2 15.1 17.0 12.5
16.4 14.8 18.4,
65.0 52.1 70.9
20.4 20.4 28.7
16.’5 16.8 16.5 15.7
6Q:5 55.6 61.4 53.4
30:O 23.5 24.2 18.9
17.8 15.8
67.4 60.4
32.2 29.1
Soy-
12.8 20.0
5.6 10.3
2.9 14.2
21.9 55.6
21.1 22.1 22.0 22.1 25.7
9.2 10.3 11.5 11.0 12.5
14.4 13.9 18.6 15.4 15.3
54.8 56.8 65.7
15.3 12.6 22.2 13.2 26.4 15.0 15.0 13.9
9.1 5.6 11.7 5.2 12.4 7.6 6.8 7.5
18.3 9.2 17.2 11.5 16.6 15.1 14.4 10.1
68.6
25:s
5-819 19.4 11.5 15.3 56.0 25.7 12.6 Bone, fused 9.8 21.9 15.1 8-855 23.4 12.6 15.4 62.6 28.1 11.7 11.1 19.3 13.6 Tri-, fused *Initial incorporation was a t the rate of 40 lbs. of PzOa er acre surface. aRespective removals of PzOa by initial crop (red clover7 were restored with 40 lbs. additional before seeding of soybeans. CNeither restoral nor addition of phosphate was made before sleeding of Sudan grass. dAdditions t o supply PZOO a t 40-lb. rate were made to the fourth crop, red clover. ‘Pots were lost.
identical with that from the incorporations of five industrial dicalcium phosphates, and almost twice the mean of the recoveries from the other five precipitates. I n the fourth harvest the responses to the dicalcium and tricalcium groups were more comparable, probably as a cumulative effect of the P206residues from the three 40-pound-per-acre incorporations. On the lightly limestoned Fullerton soil, the responses to the five tertiaries by the initial crop of red clover were far less than the responses to the dicalcium phosphates. Subsequent responses to the secondary and tertiary phosphates were more nearly equal. The mean aggregate plant response to the five dicalcium phosphate controls was identical with the response from the monocalcium phosphate and the laboratory-prepared tertiary, and 1.17 times the mean of the responses to the hydroxyapatites. The P20srecoveries from the hydroxyapatites were also considerably below the recoveries from the dicakium phosphate controls on the Fullerton soil. Again the recoveries from the fused grainy tricalcium phosphates were equal to or beyond the recoveries from the dicalcium phosphates and still farther beyond those from the five tertiaries. The maximal recovery of P#& was from the addition of monocalcium phosphate. The distinctions shown in Table IV are in accord with those indicated by the Neubauer test and by the modes of appraisal of the phosphates outside the soil.
growth. It was anticipated that successive lots of precipitated tricalcium phosphate from the same source, identically labeled, would be of identical composition and properties and presumably made by the same procedure. On the contrary, successive products of identical designation were found to be decidedly different in structure, solubility, reactivity, and fertilizer effectiveness. Of the seven industrial precipitates labeled “tricalcium phosphate” two proved to be dicalcium carrying CaC08, four were hydroxyapatite, and one was a Caa(PO& hydrate of low availability. It is obvious that the use of precipitates X973 and S-984 as controls in comparisons of PZOS availability would result in fertilizer appraisals different from those arrived a t through similar use of any of the other five industrial precipitates. An accepted permanent reference and control should be obtainable. This would facilitate the integration of laboratory studies, authenticate classification through optical and x-ray examinations, and serve as a standard in Neubauer tests and in pot culture comparisons. The use of the same and declared mode of procedure and technique by the several producers undoubtedly would result in a more uniform and dependable output of tricalcium phosphate. One outcome of the present study will be the proposal of a chemical test by which the hydrated precipitate can be differentiated from the hydroxyapatite and obviate the need for x-ray identification.
APPLICATIONS
ACKNOWLEDGMENT
These comparisons reveal variabilities in the composition and properties of precipitated tricalcium phosphates distributed by reputable vendors. The results show that a t least three processes were employed in the manufacture of the precipitates. Obviously, manufacturers of tricalcium phosphate either follow variant technique in a common precipitative procedure or employ different reagents and methods of precipitation. Moreover, a precipitate obtained from a vendor may be decidedly different from one obtained from the same vendor a t another time. It is evident that stoichiometric exactness in CaO:PzOa ratio will not assure a true tricalcium phosphate. Investigators and users, in general, should be able t o obtain a standardized and certified precipitated tricalcium phosphate. Verification of composition should not be necessary; in many cases, it is not feasible for the user to establish discrepancies between label and product. It is apparent, however, that industrial precipitates can be expected to vary markedly in their several inherent characteristics and in their effectiveness on plant
Acknowledgment is accorded R. C. Shank, H. W. Dunham, and L. B. Clements for assistance in the experimental work. LITERATURE CITED
(1) Adams, J. R.,and Ross, W. H., J . AS80C. Oflcial Agr. C h m . , 21,
268-73 (1938). (2) Andrewa, W.B., Ibid., 25,499-509 (1942). (3) Bassett, H., J . Chent. SOC.,111, 627 (1917). (4) Beeson, X. C.,and Jacob, K. D., IND.ENG.CEBM., 30, 304-8 (1938). 16) Buehrer, T. F., Univ. Ariz, Agr. Expt. Sta., Tech. Bull. 42, 162 (1932). (6) Cameron, F. K.,and Bell, J. M., U. 8. Dept. Agr., Bur. Soils, Bull. 41, 190 (1907). (7) Curtis, H. A,, Copson, R. L., Brown, E. H., and Pole, G. R., IND. ENQ.CHIM., 29,766-70 (1937). (8) Elmore, X.L., Huffman, E. 0.. and Wolf, W.W., Ibid., 34,404 (1942). (9) Hammond, J. W.,and MacIntire, W. H., J . Assoc. Oflcial AUT. Chem., 23, 398-404 (1940). (IO) Hanawalt, J. D., Rinn, H. W., and Frevel, L. K., IND.ENQ. CHIM., ANAL.ED., 10,457-512 (1938). .----I
INDUSTRIAL AND ENGINEERING CHEMISTRY Hardesty, J. O., and Ross, W.H., IND. ENG.CHEM.,29, 1283-90
(29)
MacIntire, W. H., and Hatcher, B. W., J . Am. SOC. Agron., 34,
(30)
MacIntire, R. H., and Hatcher, B. W., Soil Sci., 53, 43-54
(31)
MacIntire, W. H., and Shaw, W. M., IND. ENG.C H E M .24, , 1401-
(32)
MacIntire, W. H., and Shaw, W.H., J . Am. SOC. Agron., 26,
Hendricks, S. B., Hill, W. L., Jacob, K. D., and Jefferson, M. E., IND. ENG.CHEM.,23, 1413 (1931). Hill, W. L., and Hendricks, S. B., Ibid., 2 8 , 4 4 0 (1936). Hill, W. L., Hendricks, S. B., Jefferson, M. E., and Reynolds,
(33)
Maohtire; W.
(34)
MacInCire, W. H., Shaw, W. M., and Hardin, L. J., J . A m .
D. S., Ibid., 29, 1299-1304 (1937). Hodge, H. C . , Le Fevre, M. L., and Bale, W. F., IND.ENG. CHEM.,ANAL.ED.,10, 156 (1938). Hopkins, C . G . , and Whiting, A. L., Ill. Agr. Expt. Sta. Bull. 190, 395 (1916). Keenen, F. G., IND. ENQ.C H E M .22, , 1378 (1930). Larson, H. W. E., IND. ENG.CHEM.,ANAL.ED., 7 , 4 0 1 (1935). Lorah, J. R., Tartar, H. V., and Wood, L., J . Am. Chem. Soc., 51, 1097 (1929). MacIntire, W. H., U. S. Patent 2,095,994 (1937). MacIntire, W. H., and Hammond, J. W., IND. ENQ.C H E M .30, ,
(35) (36) (37)
Rader. L. F., Jr., and Ross, W. H., Ibid., 22, 400-8 (1939). Rindell, A,, Comp. rend., 134, 112-14 (1902). Roseberry, H. H., Hastings, H. B., and Morse, H. X., J . Bid.
(38)
Ro;s,-W: H.‘, Jacdb, K: D., and Beeson, K. C., J . Assoc. Oficial
(39)
Ross, W. H., Rader, L. F., Jr., and Beeson, K. C . , Ibid., 21, 258-
(40) (41) (42)
Shear; M. J., and Kramer, B., J . Biol. Chem., 79, 125-60 (1928). Thornton, S. F., Ind. (Purdue) Expt. Sta., Bull. 3 9 9 (1935). Walthall, J. H., and Bridger, G. L., IND. ENG.CHEM.,35, 774-7
(43)
Wendt, G . L., and Clarke, ,4.H., J . Am. Chem. SOC.,45, 881
(44)
Whittaker, C . W., Rader, L. F., Jr., and Zahn, K. V., Am. Fertilizer, 91, NO. 12, 5-8 (1939).
(1937).
Hardesty, J. O., Ross, W. H., and Adams, J. R., J . Assoc. O& cial Agr. Chem., 26, 203-11 (1943). Hartford, E. P.,and Keenen, F. G., IND. ESG. CHEaf., 33, 508-12
1010-15 (1942). (1942).
(1941).
Hendrioks, S. B., and Hill, 7.77. L., Science, 96, No. 2489, 255
9 (1932).
(1943).
656-61 (1934).
160-2 (1938).
MacIntire, W. H., and Hardin, L. J., Ibid., 32, 88-94 (1940). Ibid., 32,574-9 (1940).
MacIntire. W. H., and Hardin, L. J., J . Assoc. OAicial Agr.
, (28)
Vol. 36, No. 6
Chem., 23, 388-98 (1940).
MacIntire, W, H., Hardin, L. J., Oldham, F. D., and Hammond, J. W., IND. ENQ.CHEM.,29, 758-66 (1937).
k,Shaw, M. hl., and Hardin, L. J., IND.ENG.
CHEEM., ANAL. ED., 10, 143-53 (1938).
as so^. Agr. Chem., 21, 113-21(1938).
C h m . . 90. 395 (1931).
Agr. Chem., 15, 227-65 (1932). 68 (1938).
(1943). (1923)
PRESENTED before the Division of Fertilizer Chemistry a t the 106th Meeting of the AMERICAN CHEMICAL SOCIETY, Pittsburgh, Pa.
Moisture Absorptive Power of
STARCH HYDROLYZATES
T
HE absorption of moisture by various materials may be desirable or undesirable according t o the specific use of the material. Thus the use of glycerol in smoking tobacco t o keep the product moist and of invert sirup in cake and cookie icings to extend the freshness are commonplace and desirable properties from the standpoint of moisture absorption. Examples of undesirable moisture absorption are most familiar in the caking of salt, fertilizers, and sugars. This property of moisture absorption which occurs readily under normal atmospheric conditions is commonly termed “hygroscopicity”. Strictly speaking, any dry crystalline solid which is soluble in water and does not form a crystalline hydrate will, when exposed to the atmosphere, tend to absorb moisture, with the formation of a saturated solution. If surface absorption is neglected, such absorption can occur only when the vapor pressure of the saturated solution is lower than the partial pressure of the water vapor in the atmosphere t o which the solid is exposed. Since the vapor pressure of any aqueous solution is lower than that of pure water, any solid will absorb moisture when exposed to saturated aqueous water vapor and is therefore hygroscopic Lo some extent (8). This paper covers the moisture absorption of starch hydrolyantes under equilibrium conditions in atmospheres of various relative humidities. Starch hydrolyzates are here considered as the 1
Present address, Clinton Company, Clinton, Iowa.
A method of obtaining absorption and desorption moisture
equilibrium data for sugars and sirups has been developed. Starch hydrolyzates are effective materials for absorbing water. The amount of absorbed water increases with dextrose equivalent and with increasing relative humidity. Starch hydrolyxates are compared with two common materials used as humectants, invert sirup and glycerol. The water content of each material, when a t equilibrium a t any relative humidity between 20 and 7870, is defined. When, adequately dispersed, each material reaches a characteristic water content which is at equilibrium with an atmosphere of given humidity (or relative vapor pressure) a t the same temperature. Hence, precise measurement of the vapor pressure should accurately define the water content.
J. E. CLELAND AND W. R. FETZER’ Union Starch and Refining Company, Granite City, 111. products of the acid hydrolysis of starch with the usual commercial refining without removal of dextrose. This definition includes the various corn sirups and crude corn sugars. One dualconversion corn sirup (acid hydrolysis followed by enzyme hydrolysis) was included. Corn sirups (noncrystallieing starch hydrolyaates) are largely used in the confectionery and baking industries. Confectioners’ corn sirup, of 42 dextrose equivalent (D.E. = percentage of reducing sugars as dextrose on a dry basis) is used universally in the manufacture of hard candy and contributes to the moisture absorption in the finished goods. The baking industry employs the higher conversion sirups (50-55 D.E.) in the manufacture of icings and coatings, particularly in areas of low relative humidity, because the moisture absorption of these sirups is greater and products result which do not dry out so rapidly. Although these properties are well known among users, no data exist other than empirical tests, which in most cases are not generally available.
