CALCIUM SILICATE SLAGS
1) X 37
F X
E X 235
285, srosaed aicols
Properties of Quenched and Unquenched Slags and Effects of Their Admixtures with Phosphatic Fertilizers W. H. MACINTIRE, L. J. HARDIN, AND F. D. OLDHAM The Univemity of Tennemee Aqriaultural Experiment Station, Knoxvilie. Tenn. S 1914 a contribuution from this station
ernbodied in reports by Midgley (16) arid by Weiser ( Z g ) . The theoretical considerations have been discussed by Thomas @ I ) , and a recent joint contribution from the Tennessee and Virginia Agricultural Experiment Stations (IO)has sliown the conservation of and activities exerted by calcium silicate additions to soils, in comparisons with burnt lime, limestone, and dolomite, over an &year period.
(i6)showed that, as a liming material, calcium silicate (wollastonite) is equal, or even superior, to calcium carb0nat.e. Similar findings were obtained elsewhere in subsequent studies with certain specially processedfurnace slags and by-product silicates (1,4,7,8, $3). Cowles (6, 1)contended that the beneficial effects of calcium silicates are attributable to the effectiveness of their silica content in functions related to utilization OS phosphates by plant& During recent years this aspect has received eonsiderahle attention experinieotally in this country and abroad. In the several attempts to explain the beneficial effects of ca1ciuni silicate, it has been contended that tlie colloidal silica engeiidered from the added silicates functions as a partial replacemerit for P~OI;that it increases the availability of the PsOs content of the soil system; and that it enables the plant to utilize more effectively the quantities of P,Oj assimilated. It is certain that calcium silicate serves either as an activator or as a partial substitute for P20s. The literature has been
Objectives Because of the proved value of certain natural and syntlietic calcium silicates as a soil amendment (4,io, i6),as a biological activator (3, io), and as a source OS nutrient aalcium (8, 10, 19, i5, 123, 20, $2, 29, gh)? it was suggested that the particular typeof glassy slaRfrompI~osphate-reductionfurnaces could be used in lieu OS limestone for (a) the liming of soils, (h) "cutting" triple superphosphates and other concentrated phosphates to the ordinary P90sconcentration, and ( c ) furnish a mild but speedily effective form of calcium to offset the pot,cntial acidity of ammoniate contents of phosphatic 48
JANUARY. 1936
INDUSTRIAL AND ENGINEERING CHEMISTRY
fertilizers. It was intended to determine also whether, in mixtures containing potassic salts, the slag silicates and colloidal silica engendered by reactions within various mixtures would induce fixation that would preclude subsequent aqueous extraction of the potassium salts. Accordingly, the present contribution deals with the chemical properties of calcium silicate slags obtained from the phosphate-reduction furnaces at Wilson Dam and with the changes induced by their admixtures to triple superphosphates, with and without ammoniacal and potassic salts.
Properties and Analyses of Quenched and Unquenched Slags The two slags used were admixed in both dry and moistened condition. The unquenched slag was obtained by grinding the air-cooled crystalline mass, whereas the quenched material was obtained by direct delivery of the molten slag into water. In the tabulations they are designated, respectively, as “slag” and ‘‘slag-&.” The unquenched ground slag was a rocklike material that resembled a high-grade crystalline dolomite, whereas the quenched product showed a fibrous, glassy structure. The photomicrographs of the two products are shown in Figure 1. The unquenched material was of crystalline structure, orthorhombic system, and small axial angle, as shown in A and B. It registered strong double refraction between crossed nicols, as in C. The quenched material, D and E , was optically isotropic, with the exception of a few stray fragments. Its particles remained dark between the crossed nicols on rotation of the microscope stage, and a picture, F , corresponding to C showed solid black. The analyses of the two 100-mesh separates of the two products are given in Table I. The two samples were obtained from the same run and are considered to have been originally of near-identical composition. The quenching seemed to have exerted some slight hydration and also a hydrolytic effect, in that the quenched product showed an increased ‘free” lime content. The citrate-insoluble P z O content ~ was also affected by quenching and was decreased by about 75 per cent. In carbon-dioxide-free aqueous suspensions, both slags hydrolyze definitely but not extensively. The alkalinity of a 100-ml. carbon-dioxide-free water extraction of 2-gram charges a t the end of 1-hour agitation was equivalent to 1.7 ml. of 0.1 N acid for the quenched product and 2.2 ml. for the unquenched material. TABLEI. ANALYSESOF CALCIUM SILICATE-PHOSPHATE ROCK REDUCTION FURNACE SLAGS Unquenched Quenched Fluorine Sulfur 804 Free CaO PzOs Na Oxides of Fe, 4.10 4.12 Al, lLln KzO Sios: CaO ratio 1: 1 477 1: 1 . 5 1 8 CltCOa a = 89.09 a Basis of total Ca plus M g minus Fz and PzOs equivalence.
Si02
CaO MgO
37.31 05.10 0.80 1.40
35.80 54.33 0.70 1.38
87.49
The computed neutralizing values assigned to the two slags are based upon the lime and magnesia contents accounted for by silicates, aluminates, and ferrites. The minor occurrence of the phosphatic compounds is considered as neutral because of the protective effect of the approximately 50 per cent residues of lime present after correction for fluorine and P205equivalences. The PzOb content is probably present as tetracalcium phosphate, but in the computations to determine effective basicity, or calcium carbonate equivalence, the corrections for nonneutralizing calcium content were made on the basis of tricalcium phosphate and calcium fluor-
49
During recent years the pyrolytic methods for the production of phosphoric acid have been under study and development by both industrial and governmental agencies. Because of the advances made, it is probable that the furnace methods will come into more extended use, and with this development will arise the problem of the economical usage of the by-product calcium silicate slag of relatively high calcium fluoride content. In anticipation of this situation the present study was carried out to determine whether the slag could be used in lieu of limestone, as a basic supplement to concentrated superphosphates and their “complete” mixtures.
ide. The minor occurrences of monovalent bases were disregarded. On the basis of the lime-silica ratio, the negligible free lime value as registered by a sucrose solution, and the absence of suspended R203oxides, the glasslike materials may- be considered as being indeterminate mixtures of the several calcium silicates of variant lime-silica ratios, calcium aluminates, and calcium ferrites. In contact with water these components undergo hydrolysis, as typified by the equations: CaO.Si02 H2O = Ca(OH)I Si02 3Ca0.A120a 3Hz0= 3Ca(OH)* A1208
++
+ +
Reactivity of Slags toward Dilute Hydrochloric Acid The reactivities of the quenched and unquenched slags of 100-mesh fineness toward dilute hydrochloric acid were compared with corresponding values for high-calcic limestone and dolomite of the same fineness. One-gram charges of each material were agitated with a constant volume of one liter of 0.01 N hydrochloric acid for periods of 1, 4,and 24 hours, and then filtered. The solvent action of the dilute hydrochloric acid, as registered by the residual acidity of the filtrates, is shown in Table 11. The quenched slag seemed to be attacked to a slightly greater extent than the unquenched product. There was a striking difference between the values found for the two slags and those found for the two types of limestone at the end of one hour of agitated suspension. The values obtained at the end of the 20-hour period were comparable, for the four materials, but the speed of the neutralizing effect of each slag was decidedly greater than that of the limestone; and, in a comparison with dolomite, the difference was still greater. Calcium-Ammonium Exchange Activity The amounts of calcium extracted from the slags by a neutral 1 N solution of ammonium chloride through replacement of calcium for ammonium fall in the category of “exchangeable” soil calcium. The solubilities of the unreacted fractions of the admixed slags that would come to the soil through incorporation of phosphate-slag mixtures can be therefore evaluated on the basis of their response to extractions with the neutral normal reagent (19). The extent of replacement reactions between ions of calcium and ammonium in boiling 1N neutral ammonium chloride digestions, as determined by the
50
INDUSTRIAL AND ENGINEERING CHEMISTRY
VOL. 28, NO. 1
by the two limestones. In all four comparisons, both slags TABLE 11. SOLUBILITIES OF QUENCHED AND UNQUENCHED showed a reactivity somewhat greater than that registered by SLAGS,COMPARED WITH LIMESTONE AND DOLOMITE, IN 0.01 N dolomite. HYDROCHLORIC ACID I n ultimate values both limestone and dolomite show, CaCOn Dissolved from 1-Gram Charges within experimental error, their full calcium carbonate equivaPer cent-of Hours of Grams Per cent “effertive” lent values of 99.3 and 93.4 per cent, respectively. The of neutralizing Agitated Per charge valueb Materiala Digestion liter quenched product shows an ultimate replacement greater Quenched slag 1 0.440 44.0 49.4 than that shown by the unquenched material for the h e r 44.5 50.0 4 0.450 separates, but the values for the less finely divided separates 49.0 55.1 20 0.490 Unquenched slag 1 0.430 43.0 48.3 are concordant. In the case of the three finer separates, the 4 0.435 43.5 48.9 quenched product shows a replacement slightly in excess of 20 0.465 46.6 52.2 Limestone 1 0.240 24.0 24.2 the computed values for effective neutralizing power. This 4 0.440 44.0 44.3 is accounted for by a further replacement between the am20 0.490 49.0 49.4 Dolomite 13.5 14.3 1 0.135 monium chloride solution, which attains acidity, and the tri36.4 4 0.340 34.0 calcium phosphatic combinations that were not included in 20 0.460 46.0 49.3 the computed neutralizing values. The several comparisons a All materials through 100 mesh, rejected on 200 mesh. b Limestone, 99.3% CaCOs equivalence; dolomite, 93.4%; slags, 89% between the limestone and dolomite controls and the correby deducting Fz and PZOS equivalences. sponding slag separates demonstrate the ready availability of the calcium content of the slag. TABLE111. REACTIVITIES OF CALCIUM SILICATESLaas IN COMPARISON WITH LIMESTONH AND DOLOMITE, AS MEASURED Reactivity of Slags toward Carbonic Acid BY AMMONIAEVOLUTIONS FROM BOILING AMMONIUM CHLORIDW The effectiveness of calcium silicate as a source of nutrient Values from, S,uccessive DiRtillations until Negligih!e NHa Evolutions calcium and as a soil amendment, or ameliorant, is dependent -Initial diet.-Final disk-Totals of dist.Material Mesh Volume CaCOa Volume CaCOx Volume CaCOs upon its disintegration in the carbon-dioxide-impregnated Ml. Per cent MZ. Per cent MI. Per cent water of the soil. Table IV gives the values secured from Slag ... 50 59.0 50 0.2 883 84.4 agitation of 1-gram charges of each of the two slags, of limeSlag-Qb \ 325 50 62.0 77 0.6 824 93.8 Limestone0 ... 50 84.0 50 0.3 195 100.0 stone, and of dolomite; all of 100-mesh fineness, with carDolomite ... 50 52.0 50 0.3 250 93.8 bonated water for periods of 1 and 4 hours. The water was Slag 50 50 62 0.5 805 90.4 Slag-& 200-325 50 50 62 0.5 834 96.0 chilled to 9’ C. and saturated with carbon dioxide a t atmosLimestone ... 50 66.0 50 0.3 285 100.1 pheric pressure. The charges were introduced, the flasks Dolomite ... 50 34.0 50 0.3 330 96.4 Slag 0.4 84.0 . . . 50 50.0 60 901 were sealed, and the agitations were then carried out for the 50 93.5 50 60.0 759 Slag-& 0.3 200 stipulated periods. The carbonated water filtrates, obtained 50 Slag 0.5 86.1 55 39.5 806 770 40.0 88.6 55 Slag-Q l00~200 50 0.8 by rapid filtration at the end of each agitation period, were 50 50 41.0 0.3 98.8 Limestone ii4 ... 50 97.8 Dolomite 0.4 ... 26.0 3SO acidified with hydrochloric acid, boiled, and back-titrated. 50 26.0 63 0.6 1045 83.2 Slag The results for dissolved calcium carbonate thus obtained Slag-Q eolioo 50 30.0 47 0.6 1104 78.9 432 99.0 Limestone ... 50 26.2 50 0.4 register even greater differences in relative values than the 465 97.5 Dolomite ... 50 16.0 50 0.3 differences shown for hydrochloric acid and ammonium chloMethod of Shaw and MacIntire ( 1 9 ) . ride in Tables I1 and 111,respectively. b Q connotes quenched product. C Limestone and dolomite used were those of Tables I1 and IV, The transition of silicate to carbonate and the dissolving of the latter from the quenched product were especially marked during the first hour. The values registered by both slags a t ammonia evolutions, is shown for each of the five separates by the end of 4 hours were far in excess of those found for limethe data of Table 111. The values given are those for initial stone and for dolomite. Speed of the generation of the caldistillates, final distillates, and aggregate values that included cium bicarbonate solution came in the following order: the several intermediate distillates. The distillations were quenched and unquenched slags, limestone, dolomite. continued a t the average rate of 200 ml. per hour until the The values found for solubilities in carbonated water of distillate ammonia values corresponded with those of the amdefinite normality differ from those found for hydrochloric monium chloride control. The ammonia displacements were acid, because for each mole of calcium in solution as bicarcomputed to calcium carbonate values to give the curves of Figure 2 which shows the speed of the calcium-ammonium exchange. The values are for actual charges, a constant of TARLEIV. SOLUBILITIES OF QUENCHED AND UNQUENCHED SLAGS, COMPARED WITH LIMESTONE AND DOLOMITE, IN CHILLED 0.5 gram, rather than chemical equivalence. WATER^ CARBONATED As would be expected, the influence of the size of particles CaCOa Dissolved from was registered by the speed of the ammonia evolutions in1-Gram Char ea Hours I e r cent duced by the slags and by the controls of limestone and doloof “effecmite. The most active initial reactivity of the finer separates of. Per tive“ AgiNormality of was registered by limestone. In a comparison of the two Carbonated Water cent of ising Material6 tion Initial Final liter charge value0 slags, the quenched product effected a more rapid exchange of Quenched slag 1 0,064 0.040 0.160 16.0 18.0 calcium for ammonium in the 325-mesh separate, but this 4 0.075 0.040 0.430 4.7.0 48.8 20 0,075 0.040 0.410 41.0 46.1 spread in reactivity values was not registered by the two Unquenchedslag 1 0.064 0.046 0.110 11.0 12.4 comparisons of coarser separates. The reactivities of the 4 0.075 0.047 0.430 43.0 48.8 20 0.075 0.044 0.450 45.0 50.6 two slags were comparable with the exchange effected by 12.0 12.1 0.048 0.120 Limestone 1 0.078 equal weight charges of the less basic precipitated calcium 33.0 33.3 4 0.050 0.034 0.330 20 silicate. In the initial distillations, the two finer limestone 4.5 4.8 0.030 0.045 Dolomite 1 0,040 separates were more active than the corresponding separates 4 0.050 0.042 0.090 9.0 9.6 of either of the slags, but this greater initial activity did not a Chilled to 9O C. and saturated with, COz gas. b All materials through 100 mesh rejected on 200 mesh. register for the 100-200 mesh and 60-100 mesh particles. c Limestone, 99.3% CaCOq equi;alenoe; dolomite, 93.4%: slags, 89% After displacements of about 40 per cent, the curves for the by deducting Fz and PzO6 equivalences. latter separates were more horizontal than those registered
8:;-
JANUARY, 1936
INDUSTRIAL AND ENGINEERING CHEMISTRY
bonate, 2 moles of carbonate were required, 1 mole for the conversion of each mole of silicate into carbonate and one to effect solution of the latter. On the other hand, the limestones utilize only 1 mole of carbonate to effect solution of each mole of calcium carbonate. Because of the relatively low final concentration of free carbon dioxide in the final solutions, these systems probably contained both calcium bicarbonate and carbonate. Frequently, in the analysis of lysimeter leachings it has been found that the free carbon dioxide is not sufficient to account fully for the carbonate solutes as being entirely in the bicarbonate form. But, solely on the basis of the amounts of bicarbonate in solution in the carbonated waters of stipulated normality, it is apparent that the two slags gave ultimate values far in excess of those for limestone. The spread is still greater in the comparison with dolomite. Although the extractions of the initial hour showed a greater solubility for the quenched product, comparable values were obtained for the two slags in the 4-hour and 20-hour digestion periods. The results are in harmony with those previously found at the Tennessee Station (9) for wollastonite and are accounted for most simply by the equations:
+ + +
+ +
CaSiOs HzO = Ca(0H)z Si02 and Ca(OH)z COa = CaC03 HzO or CaSiOs 2C02 2H20 = CaHZ(COJ2
+
51
IUV
60
60
dG
+ HSiOa
The extractions for the three periods of 1, 4, and 20 hours were verified by a 2-day extraction. Two-gram charges of each of the two slags were suspended in 100-ml. of distilled water, and carbon dioxide was bubbled through the suspension continuously for the 2-day period. The residues were then filtered and the filtrates analyzed for carbonates. Each slag registered a dissolved calcium carbonate content equivalent to 24.32 per cent of the calcium carbonate equivalence of the original slag. The aggregate transitions from silicates to carbonates, as accounted for by the totals of solid and solution phases of calcium carbonate, were determined in obtaining the data of Table V. One-gram charges of each of the four materials were suspended in 100 ml. of distilled water and kept in suspension by the rapid passage of carbon dioxide at a built-up pressure of 2 inches (5 cm.) of mercury for a period of 36 hours. The slag charges were of a fineness to pass 100-mesh sieve, with rejection by 200-mesh. Immediately at the end of the 36-hour period, the undissolved residues were filtered and washed with carbonated water. The filtrates were acidified with an excess of standard acid, boiled, and back-titrated t o determine the solute values. The residues of slag-calcium carbonate were then analyzed for carbonate carbon dioxide. The bicarbonate content of the solution from the quenched slag was 1.37 times that derived from the unquenched product, whereas the engendered solid-phase carbonate was 1.65 as great. The total carbonate conversion, the sum of the solute and solid phases of calcium carbonate, from the quenched product was practically one and one-half times the carbonate conversion from the ground unquenched material. The conversion of silicate into solute carbonate greatly exceeded the direct solvent action of the carbonated water upon limestone, with a still greater disparity for the dolomite.
Carbonate Conversion of Slags in Quartz
Media The data of Tables IV and V were further supplemented by a test more in accord with the conditions to be encountered by calcium silicate additions in soil media: Two-gram charges of each slag of 100-mesh Iineness were mixed with 100 grams of 50-mesh quartz. The silicate-quartz mixtures were moistened and placed in 4-cm. cylinders constricted t o an 8-mm. opening at one end. A current of carbon dioxide was passed into the constricted openings and upward through the moist mixtures at practically atmospheric pressure for approxi-
(00
80
60
40
OO-/OO MeJh
20
0
50
/CU
1.50
200
250
300
350
#
UO
Distihte Vo/ume -m.L
FIGURE 2. SPEEDOF REACTIVITY IN EXCHANGE OF CALCIUM FOR AMMONIUMBY QUENCHED AND UNQUENCHEDSLAGS O F VARIANT FINENESS, IN COMPARISON WITH LIMESTONE AND WITH DOLOMITE, AS MEASURED BY EVOLUTIONS OF AMMONIA FROM BOILING NEUTRAL 1 N SOLUTIONS OF AMMONIUM CHLORIDE Ammonia evolutions are charted against cumulations of auccessively timed diatillate volumes, average of 200 ml. per hour. x=Limestone, o = Dolomite, 0 =Quenched slag, A=Unquenched slag.
mately 24 hours. The hydration of the iron content of the slag was quite rapid, the white slag-silica mixtures being converted to a distinct reddish brown product during the f h t overnight period, or sooner. The mixtures were then removed, dried, and fractioned into charges that contained 0.5 gram of the admixed slag. Carbonate carbon dioxide determinations upon these fractions showed a calcium carbonate equivalence of 34.1 and 34.5 per cent for the quenched and unquenched slags, respectively. On attainment of those values the carbonation was practically static because of the protective coating effect of carbonate around the nuclei of slag. Such a pseudo-equilibrium is encountered with small particles of hydrated lime in the atmosphere. In the carbonated water of the soil, however, the solvent and
INDUSTRIAL AND ENGIIC’EERING CHEMISTRY
52
TABLEv.
CARBOXATE CONVERSIOK AND SOLUBIIlITY O F SLAGS IN
AQUEOL-sSUSPENSIONS AGITATEDBY
C41IBON
COMPARED WITH SOLUBILITIES OF LIMESTONE AND DOLOMITE -In
final s o h
-
As per cent of charge 17.50 12.75 8.25 4.70
CaCOs Values from 1-Gram Charges engendered solid phase--Total conversion-Per cent of neutralizing Gram per Per cent of neutralizing Gram per value charge charge value charge 19.61 0,1272 12.72 14.28 0.3022
--As
.is per cent of
Materiala Gram Quenched slag 0.1750 Unquenched slag 0.1275 14.31 0.0773 Limestonec 0.0825 8.31 .... .... Dolomite 0.0470 5.03 a Gas-flow agitation, 36 hours. b All materials through 100 mesh, rejected on 200 mesh, I-gram charges. C Limestone and dolomite used were those of Tables I1 to IV.
mobile effects would cause the carbonation t o proceed to true equilibria. From the several experiments relative to the conversion of the slag into calcium carbonate by the action of carbon dioxide in the presence of moisture, it can be concluded that any part of a silicate supplement not altered in the prior phosphate mixture can be considered as though it were an equivalent Iimestone incorporation. One of the important considerations in the use of calcium silicate as a soil amendment is the function of colloidal silica liberated in the hydrolytic disintegration of the silicate in the soil system. When suspended in distilled water and in ammonium citrate solution, the quenched and unquenched slag had been observed to act differently in the liberation of silica. The two slags in variant charges (1, 5 , and 10 grams) were therefore suspended in distilled water and simultaneously subjected to carbon dioxide gas-flow agitation for 40 hours. The residual suspensions were then filtered through Buchner filters, washed with carbonated water, dried, and analyzed for carbonates. The filtrates were analyzed for dissolved silica, and also calcium carbonate content. The results are given in Table VI. TABLEVI. CARBONATE CONVERSIONS OF QUENCHEDAND UNQUENCHED SLAGS& IN RELATION TO SOLUBLE SILICA ENGENDERED BY CARBONATED WATER SUSPENSIONSa -Slag-
VOL. 28, NO. 1
Type Charge 1 Quenched Unquenched 1 Quenched 5 Unquenched 5 Quenched 10 10 Unquenched a 100-mesh Droducts. b Gas-flow agitation, 40
(In grams) -CaCOa EngenderedSolute Solid phase Total 0.208 0.220 0.180 0.209 0.187 0.179
0.236 0.075 1.860 0.6S6
2.230 2.420
0.444 0,295 2.040 0.895 2,417 2,599
Dissolved Si02 0.0143 0.0452 0.0157 0.0393 0.0167 0.0926
hours.
In each case, the dissolved silica derived from the ground unquenched slag greatly exceeded the value found for the quenched slag of the corresponding charge for the constant period of agitated suspension. The quantity of soluble silica from the quenched product was uniform for the three charges, 1, 5, and 10 grams. The same held for the unquenched material in the case of the l- and 5-gram charges, but approximately twice as much silica was present in the solution from the 10-gram charge. It is of interest to note a parallel effect that was later registered by a neutral solution of ammonium citrate (1.09 specific gravity). I n a study of the reactions that take place between the two slags and the citrate solvent, it was found that the amount of silica dissolved from a 1gram charge of slag by 100 ml. of solution during 1-hour digestion a t 65’ C. was 4.03 per cent for the quenched and 4.62 per cent for the unquenched. The quenched material, however, gave a more pronounced gel effect. The carbonate values of Table VI were in contrast with the silica values. The solute calcium carbonate concentrations were fairly concordant for the three charges. On the other hand, the solid-phase calcium carbonate values, and hence the totals, were considerably greater for the quenched product
7.73
8.68
...
, . .
...
...
0.2048
.... ....
--CaSlOa Per cent of charge 30,22 20 4 s . I .
...
DIOXIDE.^ t o CaCO?---
Per cent of neutralizing
value
33.95 23.01
...
.
.
I
in the case of the 1- and 5-gram charges, whereas comparable totals were obtained from the 10-gram charges of the two slags. Hence, as was found in the related carbonated Jyater extractions, the reactivity of the quenched product was greater than that of the unquenched material. The divergent effects registered by the silica liberated in the hydrolytic disintegration of the slags cannot be explained by variant concentrations of calcium bicarbonate, since these values were uniform for the six systems. Neither can the differences be explained by assuming an occlusion of silica by the calcium carbonate that was precipitated during the digestion, since the highest value for dissolved silica was obtained in the system that gave the greatest value for solidphase carbonate. The sole explanation appears to he that the quenching induced an alternative effect upon silica content as a result of the sudden chilling and crystallization.
Reactivity between Calcium Silicate Slags and Phosphates in Dry Mixtures Pzo5 TRAXSITIONS. The foregoing studies relate to the soil reactivities to be expected from those fractions of admixed slag that do not enter into reaction with the free acid and acid salts of superphosphates. The reactivities of the ground slag in dry mixtures of two parts of slag and one part of superphosphate were then measured by PeOs transitions, as determined by the A. 0 .A. C. methods which were intended solely for acidic materials. All phosphatic materials passed a 35mesh sieve and the slag was of 100-mesh fineness. Mixtures of the dry, unquenched slag were made with two triple superphosphates and potassium sulfate. The product listed in the tables as CaHd(P04)2 contained 56 per cent PZOScontent and was made from the acidulation of limestone with H3P04. The other, a 48 per cent product, was from acidulation of phosphate rock. The total P& content of each product was also “available.” A similar mixture was made with monoammonium phosphate and potassium sulfate. In still another mixture, 2 parts each of triple superphosphate and diammonium phosphate were mixed with 8 parts of dry slag. The dry superphosphates and dry slag were mixed thoroughly by means of large spatulas and rolling upon oil cloth, and the resultant mixtures were immediately sealed in tared fruit jars to assure constancy of the initial total weights. After 35 days of storage, the mixtures were analyzed for total, water-soluble, and citrate-insoluble PzOsiand the analyses were compared with the computed values derived from the separate analyses of the several components, as shown in Table VII. The diminution in water-soluble Pz05in each of mixtures A , B, C, and D demonstrates that dicalcium phosphate was formed to the extent of 31.4 and 28.0 per cent for the two superphosphates with admixtures of K2S04, 24.6 per cent for the superphosphate-ammonium phosphate mixture, and only 9.6 per cent for the one with only monoammonium phosphate. The decidedly greater reactivity of the two monocalcium products, as compared with monoammonium phosphate, is therefore registered. The transitions are indicated by the equations:
INDUSTRIAL AND ENGINEERING CHEMISTRY
JANUARY, 1936
+
+
+
H3POn CaSiOs = CaHPOI Si02 HsO CnH4(P0& CaSiOa = 2CaHP04 Pi02 H20 26H4H2POa CaSiOa = CaHPOI (NH&HPOo
+ +
+ +
+
Si02
+ + HSO
(1)
(2) (3)
Reactions 1 and 2 were involved in mixtures A and B , whereas only reaction 3 was involved in mixture C. In the case of mixture D all three reactions were in effect. The analyses of mixtures A and D of Table VI1 indicate that some increase in citrate-insoluble P20s took place. In the light of previous experiments with admixtures of standard superphosphates with limestone and with dolomite ( I C ) , it seemed probable that the increase was due, not to formation of triphosphates in the dry mixture, but to the vitiations that occur when analytical procedures are used with basic mixtures. When introduced alone into the solution of neutral ammonium citrate, the slags were partially dissolved. This was especially true of the unquenched product. The solvent capacity of the neutral ammonium citrate for basic phosphates is materially affected by its reaction with calcium silicates and the resultant formation of calcium citrate and free ammonia. But, in spite of such an effect, the well-buffered solution undergoes only slight changes in p H values, as shown in Table VII. It is recognized that the neutral ammonium citrate digestion was developed for use with standard superphosphate, an acid material, and its mixtures. The method was not intended for use in the analysis of products containing supplements of liming materials. Moreover, when the method was developed, treble superphosphates were not a commercial product. The calcium-depleted residues from one digestion were therefore redigested with a fresh solution of neutral ammonium citrate. If the increase registered for citrate-insoluble P%Ojby a single digestion were due to engendered tricalcium phosphate, the second digestions should show values corresponding to those computed from the analyses of the separate materials. The several values thus obtained, and shown in Table VII, are in accord with the initial values computed for the mixtures from the analysis of the separate components. It is therefore concluded that the “reversion” indicated by the single digestions was due to diminished solvent action of the ammonium citrate upon insoluble PzOj formed during analytical manipulation and that no formation of citrate-insoluble Pz05occurred in any of the four dry mixtures, transitions being arrested a t the diphosphate stage. Hence, it is apparent that triple superphosphates can be mixed with dry calcium silicate slag in the proportions used, 1 2, without causing any change for which commercial penalty would be justifiable. INFLUENCE OF SLAGS UPON STABILITY OF AMMONIATE SUPPLEMENTS. There was no nasal indication of liberation of ammonia from either of the ammonium phosphate mixtures
+
53
C and D. The averages for initial and final nitrogen content were 4.40 and 4.3i per cent. Previous experiences (11) and practical bagging tests had demonstrated that even a definite odor of ammonia from such mixtures will often not be registered by chemical analysis. The extent of the reaction between the monoammonium phosphate and slag (Equation 3) that results in the formation of di-forms of calcium and ammonium phosphates was apparently only about one-third the equivalence of that found for the two calcium superphosphates. Because of the low initial moisture content of the mixtures and the hydration effect induced by the formation of the diphosphates and by the capacity of the liberated colloid silica effectively to tie up the water liberated by reactions, the mixtures remained exceedingly dry and consequently no hydrolysis of the ammoniates took place. This same negative result was found by MacIntire and Sanders (11) for dry mixtures of dolomite and limestone with five types of synthetic ammoniates, and by Beeson and Ross (6) for mixtures of ammonium phosphates with dolomite. Moreover, the final ammonia contents of the ammoniate mixtures showed a close agreement with the ammonia values computed from the separate components. Although the dry mixtures generated practically no heat and lost no ammonia on mixing, the acid salts effected a liberation of hydrogen sulfide from the.slag: a distinct odor of this gas was noted for each mixture immediately after mixing. PHYSICAL EFFECT.The dry mixtures A , B, C, and D were transferred to jar containers immediately after mixing and then thoroughly compacted by uniform tamping, to simulate the compaction and heating that would be expected to take place in piles. At the end of 35 days the well-compacted mixtures were free of lumps and could easily be restored to the original physical state by gentle rubbing. From the foregoing observations and analyses it is evident that the dry admixing of the two types of slag, quenched and unquenched, of 100-mesh fineness with the several concentrated phosphatic materials of 38-mesh fineness can be practiced without objectionable physical effects and without chemical changes that would be commercially penalisable for contents of either Pz06or XH4,in mixtures similar to those made in the present study.
Reactivity between Calcium Silicate Slags and Phosphates in Moistened Mixtures PREPARATIOK OF MIXTURES. If only a silieate slag, aircooled and ground, were to be used, it would not be important to determine the activity of the same slag in a moistened condition. The granulated, quenched product is distinctly moist initially, although it readily dries out when in small piles. The necessity of grinding the hard slag is obviated, however, by the quenching treatment unless a finely divided product
REACTIVITY BETWEEN DRYADMIXTURESO F ~OO-MESHCALCIUM SLAG FROM PHOSPHATE ROCKREDUCTION FURYaCE TRIPLESUPERPHOsPHATES‘ WITH AND WlTHOUT AMMONIUMPHOSPH.4TES AND POTASslUM SULFATE
TABLEVII.
AND
7 -
Series A
B
Mixturesb Component
-Pros Values Computed fromAnalyses of Components WaterCitrateTotal sol. insol.
Parts
Slag CaHa(PO4)r 0 &SO4 Slag Triple superphosphate/
&so4
Q
Moisture
7
65 65
1
i
16.00
E: :
PzOs Values Found after 35 D a y s WaterCjtrate- Citratesol. insol. insol. C Transitiond
Total Per cent
7
16 95
0 92
0.23
18 20
11 63
13.03
0.92
0.28
15,75
9.38
0.92
0.08
20.10
17.38
Slag 20.10 19.23 NHaHzPOd D Slag CaH4PO4)z 19.10 16.89 200 (NHdzHPO4 N o citrate-insoluble PzOs in either triple superphosphate. b All phosphatio materials passed 35 mesh; slag passed through 100 mesh. 0 Residues from single “official” digestion subjected to a second digestion u-ith ammonium citrate.
C
-
1 49
(uH 6 9) 0.89
(pH 7.1) 0.97
(pH 7.1)
0.9
31.4
0.8
28.0
0.8
9.6
( u H 7.0) (pH 7.1) (pH 6.9)
1.69 0.9 24.6 (pH 7.1) (pH 7.1) d Per cent of water-soluble PZOK converted t o diphosphate, a8 registered by “official” method. e Made from limestone HaPOa. / Made from phosphate rock H3PO4.
0.92
0.48
19.10
+ +
12,73
INDUSTRIAL AND ENGINEERING CHEMISTRY
54
VOL. 28, NO. I
TARLBVTII. REACTIVITY BETWEEN MOISTENED ADMIXTURESOF 100-MESHCALCIUM SILICATE SLAGS“FROM PNOSPHATE ROCK REDUCTION FURNACE AND TRIPLESUPERPHOSPHATES,~ WITH AND WITHOUT AMMONIUM PHOSPHATES AVD POTASSIUM SULFATE
Componentc Series A’ Slag CaH1(P04)z KzSOc B’ Slag Triple superphosphate
&so4
C‘
D’
E‘
U
!E4 0 . 6 500 250 40.6
1
5.2
50.9
6.1
4.3
5.4
15.00
11.90
0.81
15.10
2.75
0.80
1.13
6.10
Trace
7.88 (4.88)
7.1
7.2
53
6.2
5.7
5.6
18.87
17.40
0.80
18.85
10.88
0.96
8.05
2.35
7.35
2.48 (0.91)
7.1
7.0
48
6.0
4.5
3.6
7.00
2.15
1.04
7.05
None
1.64
None 3 . 2 3
0
3.20 (0.92)
7.1
7.0
45
5.6
6.5
6.3
18.00
16.80
0.88
18.40
9.63
0.80
7.40
2.73
6.88
7.1
7.0
39
5.0
1.9
2.9
18.30
17.20
0.89
18.30
2.38
0.20’
1.00
3.30
Trace
3.05 (0.81) 7.05 (2.90)
7.1
7.3
48.4
} 1
15
(NHSaHPO4
500 125 125
?%%?04)*
!E f
F
4.6
Moistened Mixtures Parts -MoistureHzO Ini35 75 Parts added tial days days
Slag 500 250 NH~H~POI 55 &SO4 Slag Ammoniated triple superphosphate 500 250
:%‘(Po&
5.8
PtOa Values Computed from pH Values of Analyses of CPsOs Values Found by Analysis Citrate r 48 hours 35 daysd -75 daysdDigestions Components CitCltCltCitof 75-Day Water- rateWater- rate- Water- rate- Water- rateMixtures Total sol. insol. Total 801. insol. sol. insol. sol. insol.” First Second Per cent 17.20 16.06 0.84 17.00 4.75 0.50’ 1 . 1 0 6 . 8 5 Trace 9.S; 6.9 7.3
,---
--
.
(5.50)
Slag-Q 500 2.8 4.5 16.00 1 3 . 0 0 0 . 8 8 16.26 1.500.28’0.754.04 5.0 Tri le superphos&ate 250 1 - 4 2 H 6 . 3 6 . 0 2 0 . 0 0 1 9 . 1 2 0 . 8 8 2 0 . 4 0 1 0 .130.80 8.032.58 46 5 . 7 Slq-Q NH~HZPOI I Sla Q 6.6 6.2 18.00 16.83 0 . 8 8 18.35 10.70 0.16’ 7 . 1 3 1.57 44 5.5 Cafi-4(POa)* (NHdsHPOk 125 a S l a g ground rock slag. slag-& same d a g quenched by delivery into water. b Ca r(PO4)t connotes dmestone’ HsPO4 product; triple superphosphate, rock phosphate Hap04 product. e All phosphatic materials passed 35-mesh sieve. d Tptal PlOs in sealed containers identical with initial and 48-hpur values.. Citrate-insoluble values in parentheses are results of second digestion with ammonium citrate. f Decrease from original values verified.
188 ) ;;! 1
+
Traoe 7.73 6.90
9.00 (4.80) 2.90 (0.43)
7.1
7.2
7.1
6.9
2.13 (0.57)
7.2
7.2
+
’
is sought. If the damp condition of the slag were to induce and KzO contents, when detrimental effects upon P205,“4, used for admixtures or for “cutting” a t the quenching location, it would be necessary to dry the moist slag by aeration for protracted periods, or by heat. Moreover, it was necessary to anticipate the possibilities to be encountered by extended storage of the mixtures under humid conditions, or in case unforeseen interreactions of supplemental components were to produce deliquescence. Accordingly, a series of nine mixtures was prepared by mixing the several dry fertilizer components with moistened slag. To the dry 100-mesh slag was added 11 per cent water, which addition gave a condition slightly below saturation. The conditioms imposed were intentionally severe. Quenched slag would not require grinding if a finely divided material were not demanded, and a coarser product would carry much less water than that which was added to the 100-mesh product. Each fertilizer salt, or combination of salts, was thoroughly mixed with a constant charge of 500 grams, dry basis, of moistened slag and placed in a sealed container, the increase in the final weight of the sealed mixture being reported as “water added,” Table VIII. Some water vapor was lost from the mixtures, which were in variant degree of dampness, during mixing and thereafter. The value “water added” therefore represents the aggregate of the amount of water that remained as moisture, that assimilated as water of hydration by the engendered diphosphate dihydrate, and that held by the liberated silica The totals, recorded as “HzO added,” were therefore in variant amounts and always less than the actual additions. Loss OF AMMOKIA.A rise in temperature was noted in every mixture of wetted slag, except series H and I , the two ammonium phosphates without potassium sulfate, which remained somewhat damp. The minimal temperature attained by the mixtures within 1.5 hours was 60” C. The maximal temperature reached was 70” C. a t the end of 2 hours in the monoammonium mixture with quenched slag, series H. In some instances considerabIe lag occurred before maximal
temperatures were noted. Ammoniacal odor was noted in each of the series that included ammonium salts. The odor was particularly strong in the case of the mixture that contained the previously ammoniated superphosphate and, hence, diammonium phosphate, when the slag admixtures were made. The final nitrogen content of this initially alkaline mixture was 0.91 per cent, or only 50 per cent of the original. There was only a faint odor of ammonia to be noted in the acid monophosphate mixture with the ground slag during the first 24 hours, but a more marked effect was noted after 48 hours. In the mixture of the monoammonium salt with the quenched slag, the ammoniacal odor was noted much sooner and was more intense. This would be expected, because of the previously noted fact that the quenched slag hydrolyzes much more readily. The average initial nitrogen content of the four mixtures, C’, E‘, H , and I , of Table VIII, that contained ammonium phosphate was 4.21 per cent, whereas the average final content was 4.03 per cent, a loss of 0.18 per cent. The diphosphate transition therefore proceeded to the next step that involved formation of tricalcium phosphate and liberation of ammonia as indicated by the equation:
PHYSICAL EFFECT.The combined effects of “drying out” induced by the dry materials that were added to the moistened slag and chemical transitions to salts of greater hydrate content resulted in products of fairly dry and loose condition, immediately after mixing, and good condition at the end of 35 days, with little further change. Only the monoammonium phosphate mixtures C‘ and H showed any tendency to cake and require regrinding. As previously noted, the conditions imposed were intentionally far more rigorous than those that would be encountered through long exposure under humid conditions. This was done not only to ascertain whether the quenched slag could be used without drying, but also to determine whether a near-complete transition of P20G from mono- to di-forms
JANUARY, 1936
INDUSTRIAL AND ENGINEERING CHEMISTRY
55
could be induced, if desired, and without loss of ammonia solvent power of the citrate solution was shown by the followfrom those phosphatic concentrates fortified with ammoniing procedure: The standard digestion by 100 ml. for 1 hour was carried out upon 0.6-gram charges of slag, alone, or apates. The PzOj transitions that took place proximately the slag content in a 1-gram charge of the 2 to 1 PzOs TRANSITIONS. during periods of 48 hours, 35 days, and 75 days are shown mixtures. The extracts were then filtered quickly by suction, ~ all mixtures deand, without dilution, were used in making digestions of 1in Table VIII. The water-soluble P z O of creased decidedly within 48 hours and disappeared from the gram charges of the four mixtures A’, B’, C’, and G. monocalcium mixtures before the end of the 35-day period. The results given in Table IX demonstrate that the presThe water-soluble content of the ammonium phosphate mixence of dissolved calcium citrate in the ammonium citrate tures disappeared less rapidly and the 35-day and 75-day solution and alkalinization of the solution materially repressed values were fairly concordant at about 7 per cent. The four the capacity of the ammonium citrate solution to dissolve PzOS.It is evident that the reactivity of the silicate is such triple superphosphate mixtures A’, B’, F , and G showed no increases, and even decreases, in citrate-insoluble P z O during ~ as to give a pH value decidedly different from prescribed neutrality. As indicated by the high citrate-insoluble values of the 48-hour period. This observation, not explained, was carefully verified. The free acid content of the four super13.95, 12.55, 10.03, and 11.30 per cent for A’, B‘, C’, and G, phosphates possibly served to increase the availability of the respectively, and by the uniform pH value of 8.0 for the filinsoluble P,O5 content of both slags before the subsequent trates of the second digestion, the hydrolytic effect upon the marked decrease in water-soluble P205. At the end of 35 ammonium citrate generated free ammonia. This forced the Pz06 transition to the more basic forms that register as citcontents of the four mixtures A’, days the water-soluble PzOs B’, F, and G were still lower, whereas after 75 days no deterrate-insoluble or causes the same effect that obtains when minable amounts remained. As a corollary effect, marked standard superphosphates are subjected to undue ammoniaincreases in citrate-insoluble P z O were ~ found for the two petion. It is now generally recognized, however, that the less riods of 35 and 75 days. As had been done in the case of the dry mixtures of Table VII, the citrate-inso1ub1e were determined by T l B L E I x . EFFECT OF SLAG COMPONENT I N MOISTENED SLAG-PHOSPHATE both single and repeated ammonium citrate digesMIXTUREUPON SOLVENT CAPACITY OF AMMONIUM CITRATE IN EXTRACTIONS OF CITRATE-SOLUBLE P206 tions. The bracketed figures of Table VI11 show Values from 1-Hour Digestions of 1-Gram Charges that the digestions of the residues from the first of 75-Day Mixture6 digestions caused the citrate-insoluble averages Using ammonium oitrate soln. that had to drop from 8.45 to 4.52 per cent for the four been digeated with 0.6-gram charge of superphosphates without ammoniates (mixtures -By standard procedureslag and filtered A’, B‘, F , and G). These data indicate the -100 ml-200 m1.% PZOS PH % PZOS PH % PZOS pH Mixtures” formation of a calcium phosphate more basic than 10.28 7.1 8.95 7.0 13.95 8.0 A’ Slag CsH4(P04)z K260r tricdcium p h o s p h a t e , probably the hydroxy B’ Slag’tri l e s u erihosphate,KaSOa 9.58 7.2 8 48 7.1 12.55 8.0 5.1 7.1 4 65 7.1 10.03 8.0 a p a t i t e 3Ca (P04)z.Ca(OH)2,d u r i n g the hot $ ~ ~ ~ ~ ~ ~ ~ ~ t r ~ ~ ~ u p e , p h o s digestion with ammonium citrate rather than phate 10.65 7 . 1 8.98 7.1 11.30 8 . 0 ‘S*m*asthoSeofTableVIII. during the period w h e n t h e solid m i x t u r e s were aging. Interference by iron and aluminum c a n n o t be postulate-d b e c a u s e of the soluble phosphates thus formed are not to be considered as similarity of the results from the high-concentration 56 per possessing only the limited value assigned to the citrate-incent superphosphates of series A’ and F and those from the soluble residues of apatite not decomposed in the phosphatesuperphosphates B’ and G of much higher iron and alumirock acidulation process. num content. The effect of wet mixtures of slag would be to draw a On the other hand, when the ammonium phosphate mixpenalty for “reversion,” were the mixtures to be evaluated tures C’ and H with the unquenched and quenched slags, reon the basis of state control analysis. The conditions imspectively, the two mixtures E’ and I that contained amposed were, however, not expected to be applied to largemonium phosphates with monocalcium phosphate, and also scale commercial operations. The intent was to determine the previously ammoniated superphosphate of mixture D’ the changes that would occur when the concentrated superwere subjected to a second digestion and concomitant dephosphates are transported as such to the point of usage and crease in dissolved calcium content of the digestant, the there cut to the “standard” concentration by admixtures of values obtained were in accord with those computed and also slag. Under these conditions there would be no official samthose determined a t the end of 48 hours. It appears that the pling and control analysis. The main point would be to deinclusion of the ammonium phosphates in series C’, E’, H , and termine whether the decrease in chemical availability would be I , served to maintain the water-soluble PZO5 a t a higher level, registered by the crop. An additional point is to be considto give lower citrate-insoluble values for single digestions, and ered. The large proportionate addition of colloidal silica to register no increase in citrate-insoluble values against a would influence the utilization of the PzOS,but this known second digestion a t the end of the 75-day period, in contrast value is not registered by the chemical analysis. to the reverse effects for calcium phosphates alone. The final products of mixtures A‘, B’, C‘, and G were also Influence of Slags upon Solubility of Potash digested with a double volume, 200 ml., of neutral ammonium Supplements citrate (1.09 specific gravity). The double-volume digestions Substantial additions of potassium sulfate were included registered 8.95, 8.48, 4.65, and 8.98 per cent citrate-insoluble in two of the dry mixtures of Table VI1 and in three of the P106, as against corresponding values of 10.28, 9.58, 5.1, and moistened-slag mixtures of Table VIII. Those five mixtures 10.65 per cent for the simultaneous single digestions with 100 were analyzed to determine whether the admixed slag afml., 30 days subsequent to the analyses of Table VIII. The fected the recovery of potash by aqueous extractions. pH values of the single and double volumes of the wellIt is difficult to effect a full recovery of added potash from buffered citrate solution were, however, practically identical. the conventional types of fertilizers by means of the A. 0. The effect that the reaction between the ammonium citrate A . C. method. This subject has been considered by referees solution and the unchanged residues of slag exerts upon the
INDUSTRIAL AND ENGINEERING CHEMISTRY
56 TABLE
x.
FIXATION O F WATER-SOLUBLE
TRATED
a
b
POTASSIUM Fly DRYAND MOISTENED SLAGS ADMIXED PHOSPHATIC FERTILIZERS
ADDITIONSOF
VOL. 28, NO. I WITH
CONCnN-
2.5-gram charges of 75-day mixtures. Computed from analysis of componenta.
over a period of years. At the 1934 meeting of the Association of Official Agricultural Chemists, results by Kraybill and Thornton and by Ross and associates demonstrated that the siliceous impurities induced a fixation of potash in forms “exchangeable,” as registered by ammonium oxalate extractions. It was further demonstrated that the potash that becomes fixed in fertilizers is nevertheless utilizable by plants, although no credit for such potash content is given on the basis of the control analysis. It was therefore decided to determine whether either the liberated silica or the silicates of the slags would show the same effect that is attributed to the argillaceous content of acidulated phosphate rock. The five mixtures of Tables VI1 and VI11 were therefore used to obtain the data of Table X. From the results obtained by ammonium chloride and concentrated hydrochloric acid digestions of the water-extracted residues, it is apparent that no appreciable fixation took place in the dry mixtures. There was, however, a considerable fixation registered in the moistened mixtures A ’ , B’, and C’, but the normal ammonium chloride digestions showed that most of the potash fixed was still “available.” Because of the absence of appreciable fixation in the aged dry mixtures and the definite absorptions shown by the ammonium chloride extractions of the mixtures that included the moistened slags, it is evident that the potash fixations in the moist mixtur‘es took place during aging, rather than during the analytical manipulations.
Calcium Fluoride Content of Slags Since the slags contained 3.17 per cent fluorine, or 6.51 per cent calcium fluoride, the mixtures were quite high in fluorine content. Of itself and alone, calcium fluoride is not toxic to germination, but a recent contribution by Morse (17) has shown that the joint presence of “free” Hap04 and calcium fluoride induces toxicity when unaltered superphosphates come in close proximity to seed. In the slag mixtures the “free” acid was killed off by the excess of calcium silicate. A recent contribution by MacIntire, Shaw, and Robinson (1.2) demonstrated that calcium fluoride occurrences in soils are rendered exceedingly insoluble by additions of limestone. Hence, premixing of calcium silicate slags would induce a basicity that would eliminate the toxic effect that the fluorine content of the triple superphosphate might otherwise exert upon germination. This is an additional justification for the premixing of superphosphates with liming materials, prior to incorporation with soils. PRACTICAL CONSIDERATIONS. It was concluded that calcium silicate slags can be used effectively as a soil aniendment and that cured triple superphosphates and their mixtures with monoammonium phosphate and potassic salts can be “cut” with dry calcium silicate slags, in lieu of limestone, to give dry, noncaking, and nonhygroscopic products, without decrease in Pz05 availability, without loss of ammonia, and without appreciable decrease of available potash. Because of the ready availability of their calcium content, the slags are equal in value to equivalent quantities of high-calcic limestone as a soil corrective and as a fertilizer supplement, with
an additional value residing in the slags because of their PzOa residues and yield of colloidal silica in the soil system. The partial conversion of water-soluble phosphates to dicalcium phosphate by the admixed slag retards the fixation of P205 by soils of high-fixation capacity. The proposed “cutting” is not considered as a manufacturing operation but as means of increasing the effectiveness of the concentrated product after its delivery to the place of usage.
Conclusions From microscopical examinations and chemical studies of two ground calcium silicate slags, air-cooled and waterquenched, in several systenis, it was concluded that the slags were more reactive than limestone and dolomite, as soil amendments. The slags readily reacted with triple superphosphate and monoammonium phosphate, producing uniformly good mechanical condition. Admixtures of two parts of the dry slags with one part of triple superphosphates of calcium and of ammonium, induced about 30 per cent transitions of P z O to ~ the di-forms for the calcium compounds and about 10 per cent in the case of the ammonium phosphate, with no formation of citrate-insoluble P z O when ~ measured by two citrate extractions at the end of a 36-day period. No ammonia was evolved from the dry mixtures, nor was there an appreciable fixation of the potash content of “complete” mixtures. Similar admixtures of wetted slag to triple calcium superphosphates effected, in time, complete disappearance of watersoluble PzOsand considerable formation of citrate-insoluble PzOS. Partial disappearance of water-soluble Pzo5, negligible formation of citrate-insoluble PzOs, some loss of ammonia, and definite potash fixation were registered in the wetted ammonium phosphate mixtures. The influence of the slags in vitiating solvent power and pH values of citrate solvent, the factors of fluorine content and silica value, and the inapplicability of the “official” method for such mixtures were pointed out. The admixtures were proposed for cutting triple superphosphates to “standard” concentration at or near the point of usage to improve drillability and to eliminate acidity and fluorine toxicity.
Acknowledgment Thanks are due W. M. Shaw, associate soil chemist, for the photomicrographs of Figure 1.
Addendum Subsequent to the completion of the foregoing studies, certain related work suggested that the fluorapatite molecule might be formed during the aging of the wet mixtures. The residue from a citrate digestion of the wet mixture was therefore subjected to a second digestion, and the second residue was submitted along with the slag to S. B. Hendricks of the Bureau of Chemistry and Soils who kindly made the requested x-ray examination and stated : “The material marked ‘residue from double digestion with ammonium citrate’ gave a typical apatite-like diffraction pattern. The sample labeled
JANUARY, 1936
INDUSTRIAL AND ENGINEERING CHEMISTRY
‘original slag’ gave a different type of diffraction pattern. Copper K radiation was used in both examinations.” This further indicates the undesirability of aging a premixture of triple superphosphate with a wetted slag of high fluorine content. Plant culture studies are planned to determine whether the fluorine content of such mixtures exerts any influence upon assimilation of the P206content of the mixtures, identical mixtures of fluorine-free slags being used as controls. The authors believe it desirable to restrict the slag additions to the latter type until conclusive plant response evidence is obtained relative to the use of the slags of high fluorine content.
Literature Cited (1) Ames, J. W., Ohio Agr. Expt. Sta., Monthly Bull. 1, 359-62
(1916). Barnette, R. M., Soil Sci., 18, 479 (1924). Ibid., 21, 463 (1926). Ibid., 22, 459 (1926). Beeson, K. C., and Ross, W. H . , IND.ENG. CHEW, 26, 992 (1934). (6) Cowles, A. H., M e t . & Chem. Eng., 17,,664-5 (1917). (7) Cowles, A. H., and Scheidt, A. W., paper pub. by Electrical Smelting and Alum. Co., Sewaren, N. J.. 1917.
(2) (3) (4) (5)
57
(8) Hartwell, B. L., and Pember, F. R., Soil Sci., 10, 57-60 (1920).
(9) MaoIntire, W. H . , Univ. Tenn. Agr. Expt. Sta., Bull. 115, 19 (1916). (10) MacIntire, W. H., Ellett, W. B., Shaw, W. M., and Hill, H. H., Ibid., 152 (1934); Va. Agr. Expt. Sta., Tech. Bull. 54 (1934). (11) MacIntire, W. H., and Sanders, K. B., J. Am. Soc. Agron.. 20, 764-70 (1925). (12) MacIntire, W. H., and Shaw, W. M., Ibid., 26, 656-61 (1934). (13) MacIntire, W. H., Shaw, W. M., and Robinson, B., Univ. Tenn. Agr. Expt. Sta., Bull. 155 (1935). (14) MacIntire, W. H., and Shuey, G. A., IND. ENQ.CHEM.,24, 93341 (1932). (15) MaoIntire, W. H., and Willis, L. G . ,Ibid., 6, 1005-8 (1914). (18) Midgley, A. R., J. Am. SOC. Agron., 24, 822-35 (1932). (17) Morse, H. H.. Soil Sci., 39, 177-97 (1935). (18) Sohollenberger, C. J., Ibid., 14, 347-62 (1922). (19) Shaw, W. M., and MacIntire, W. H., Ibid., 39, 369-75 (1935)., (20) Shedd, 0. M., Ibid., 14, 233-46 (1922). (21) Thomas, W., Science, 71, 422-3 (1930). (22) Weiser, V. L., Univ. Vt. Agr. Expt. Sta., Bull. 356 (1933) (23) White, J. W., Pa. Agr. Expt. Sta., Bull. 220 (1928). (24) Wianoko, A. T., Walker, G . P., and Conner, S. D., Ind. (Purdue) Agr. Expt. Sta., Bull. 329 (1929).
RECEIVED June 1, 1935. This paper is a contribution of The University of Tennessee Agricultural Experiment Station in collaboration with the Chemical Engineering Division of T . V. -4.
CHEMISTRY ’ofthe ACETYLENES 111. Cracked Gasoline as Source of Alpha-
Olefins for Preparation of Acetylenes’ HOMER J. HALL* AND G. BRYANT BACHMAN The Ohio State University, Columbus, Ohio
T
HE development of the chemistry of the higher acetylenes has long awaited a cheap source of these highly reactive hydrocarbons. The so-called alpha-acetylenes in which the triple bond is located a t the end of the carbon chain are especially interesting because of the labile hydrogen atoms they contain. By substitution or addition reactions it is possible to proceed from alpha-acetylenes to aldehydes, ketones, acids, olefins, hydrocarbons, and a great variety of other derivatives. A number of methods of synthesizing the higher acetylenes have been developed, and a few of them start withthe relatively cheap acetylene (C2Hz)itself; but for the most part dehalogenation of suitable chlorinated or brominated hydrocarbons is utilized. All of these methods have failed, however, to make commercially available a t a low price any one of the alpha-acetylenes, usually because of the high cost of the starting materials. In attempting to find a cheap source for some one higher acetylene for purposes of research, the possibility was considered that cracked gasoline might be fractionated to yield For the first two articles i n this series see J . Am. Chem. Soc., 56, 2730 (1934); 57, 2167 (1935). Present address, Standard Oil Development Company, Elizabeth, N. J.
’
olefins of the type RCH=CH2 which on treatment with halogens and then with alkalies would give the corresponding acetylenes, RC=CH. A few instances of the fractionation of cracked gasoline have already been summarized in the literature ( 5 ) . These reports, however, point uniformly to the absence of alpha-olefins of the desired type in any considerable quanti&, and indeed theoretical reasons have 1 - P e n t y n e and been advanced to explain the 1 - h e x y n e are predominant formation of conveniently obdisubstituted and branchedchain olefins in the cracktained in a pure ing units. However, certain form from the preliminary i n f o r m a t i o n c orresponding which we obtained indicated olefins distilled that gasoline from the Gyro from Gyro procprocess probably contained considerable amounts of 1ess gasoline. pentene a n d 1-hexene. The olefins, 1Wagner (1%) h a s a l r e a d y pentene, and 1pointed out that the Gyro hexene are presprocess produces a different type of gasoline from that ent to the extent obtained in most other crackof about 5 and 4 ing processes. per cent, respecA t a b l e was first contively, in t h e structed showing (a)the boilo r i g i n a l mateing points of all known hydrorial. carbons boiling below 80’ C.,
