Compatibility of Fused Rock PhosPhate with Superphosphates W. H. MACINTIREAND L. J. HARDIN1 The University of Tennessee Agricultural Experimental Station, Knoxville, Tenn.
Although superphosphates and calcined rock phosphate have the common property of supplying Pz06in highly available forms, mixtures of the tw-o phosphatic products suffer substantial losses in P7.06 availability. Reversion in such mixtures has been attributed to the formation of fluorphosphate, through reaction between the fluorides of the superphosphate and the tricalcium phosphate of the substantially defluorinated calcine (6). It is demonstrated, however, that the partly defluorinated fused rock phosphate is compatible with superphosphates under ordinary conditions. No
appreciable decrease of Pa06 availability occurred in mixtures of the two materials during aging under conditions somewhat more severe than those to be expected in practice. Some citrate insolubility developed when mixtures of fused rock and fluoride-bearing superphosphates were aged with imposition of abnormal humidity and temperature, whereas none developed upon similar treatment of mixtures that contained fluoride-free superphosphates. Films of basic phosphates developed upon the surface of the particles of the fused rock and tended to condition the cured mixtures.
HE PzOs content of defluorinated ground rock phosphate has a high “availability” by chemical analysis. The phosphatic calcine is distinctly basic and reacts vigorously with acidic phosphates. It would seem logical, therefore, to admix the calcine to build up the available P205 content of ordinary superphosphates and t o condition concentrated superphosphates. Beeson and Jacob (2) found, however, that certain mixtures of superphosphate, calcined ground rock phosphate, and ammonium sulfate suffered loss of ammonia and marked decrease in available P206content The work of Beeson and Jacob was repeated, and their findings were verified by the present authors (6). The corroborative study was amplified, however, to include mixtures of a special fluoride-free concentrated superphosphate with a substantially fluoride-free calcined rock phosphate from a commercial semiworks operation. No decrease in P206 availability developed in the aged mixtures of these two materials of meager fluoride content (6). Development of citrate-insoluble P2Oa in mixtures of the type used by Beeson and Jacob has been attributed by the present authors to the formation of fluorphosphate (6, 6). That formation constitutes true reversion through reaction between the component fluorides of the superphosphates and the tricalcium phosphate of the admixed phosphatic calcine (6). This conclusion was prompted by related findings from mixtures of concentrated superphosphates with high-calcic limestone and with calcium silicate slag (7). The present study was planned to determine the compatibility of fused rock phosphate with superphosphates, and their mixtures with certain fertilizer salts, as influenced by humidity and temperature. The primary objective was to ascertain whether the properties imparted to rock phosphate through fusion would obviate the tricalcium phosphate-fluoride reversion that developed in the previous mixtures of cal-
T
In cooperation with the Department of Chemical Engineering, Tennessee Valley Authority. 1
574
cined rock phosphate and commercial superphosphates. The behavior of processed rock phosphates toward superphosphates in aqueous suspensions also was determined. Characteristics of Fused Rock Phosphate The fused rock phosphate was a material similar physically to the product of lower fluorine content described by Curtis, Copson, Brown, and Pole (3). The dense glassy material carried about one third of the fluorine content of the raw rock and was decidedly different from the unfused substantially defluorinated rock phosphate calcines used in the studies by Beeson and Jacob (9) and in previous studies by the present authors (6). Granulation of water-quenched fused rock phosphate2 is shown in Figure 1. Microscopic examination of the fused rock indicated absence of uncombined calcium fluoride, and the material then was submitted to S. B. Hendricks, of the United States Bureau of Agricultural Chemistry and Engineering for x-ray study. He wrote: ‘lX-ray diffraction patterns showed that the principal phases were of the alpha modification of tricalcium phosphate. We checked your microscopic observations. I should estimate that the sample contains roughly two thirds alpha tricalcium phosphate and one third apatite.” Quenching of the molten rock produces fragments with corrugated surfaces readily discernible under magnification, as Figure 2 shows. Experimental Procedure Analyses of the several phosphatic ANALYTICALMETHODS. materials were made by A. 0. A. C. methods (1) and are given in Table I. Fluorine determinationswere made by the Willard and Winter procedure (8),modified by use of steam current distillation and in the titration procedure (4). Decreases in watersoluble Pz06content of experimental mixtures and suspensions 9 For brevity the term “fused rock” will be used in lieu of “fused rook phosphate”, and “calcine” to designate the calcined and substantially defluorinated rock phosphate.
APRIL, 1940
INDUSTRIAL AND ENGINEERING CHEMISTRY
and increases in citrate insolubility were used as respective indexes of the formation of dicalcium phosphate and the develop ment of fluorphosphate. pREPARATloN M ~ The super ~ hosphates ~ were ~ brought to a moisture content of 7 per cent anrfsieed to 40 mesh before being mired with the other phos hatic materials. I n comparisons of nrixtures that contained orRnar? super hosphak with mixtures that contained the concentrated su erpgoaphates initial the latter diluted by qmfia to give compara[b eentratians of water-soluble P,O,. Each mixture then was divided into six 25-gram rtians, each portion being compaetegn B separate glass container and placed in a tempcraturehumidity control chamber. One cont,ainer of each mixture w&s withdrawn from the chamber after each aging period, and loss in neight was determined. The contents were con. rhtioned b y light grinding, sizing to 35-mesh, and remixing immediately before weiehinz 1-%ram chmees for analysis, 'ivhicb \;ere correGed far chctnics in weight. The superphosphates used in all mixturea WBPP aeed senaratelv at 30" and a t 45" C. and in r$at,ive hrimidities of 70.2 and 90.5 per. cent to establish the fact t,hat imposition of these conditions would induce no aonreeiable increase in citrate-insoluble p&, in the abscnee of additive tlaatrnenb. No decrease in the water-soluble PzOacontent oecurred, except for a slight and ignored diminution found for the triple superphosphate nged at 45" (;. The imposed conditions indored n o apprecfable changes in values found for citrateinsoluble P&.
575
phates upon thin coatings of any engendered tertiary phosphate and upon fused tricalcium phosphate on the surface of the ~ fused ~rock particles. . The amounts of P20saccounted for jointly by engendered dicalcium and tertiary phosphates and the alpha component of the fused rock appeared well within the solvent capacity of the oitratc solut.ion. The fluoride effeet, therefore, did not appear in the mixtures that contained t.he concentrated superphosphates.
Effect of Temperature upon Mixtures during Aging DECREASEI N WATER-SOLUBLE PrOj. The mixtures of superphosphates and fused rock of Table 11, aged at 30" and 45" C . in prevailing humidity, were analyzed immediately and after periods of 28, 56, and 84 d a y s . To p a r a l l e l t h e p r e v i o u s studies as to the behavior of the calcine (2, 6 ) , tho fused rock was mixed with each of the three superphosphates in proportions corresponding to 5, 2, and 1 of fused rock FICWRE 1. WATER-QUENCHED FUSED ROCK PEOSPHAZE ( X 25) I-MM. SCALE DIV~SZON to 1 of ordinary superphosphate. Decreases in watersoluble P,O, content during t h e aging p e r i o d of 28 days at 30" and at 45" C. in prevailing humidity Figure 2A shows the characteristic fractures and corrugated were, in general, relatively small, and no marked effect of surface of the particles of the fused rook. Aqueous washings temperature was reflectad during further aging. Decreases caused no observable change in the appearance of the parfound for the mixtures of commercial superphosphates aged at ticles. Basic phosphat,e coating, acqnired by the fused rock 45" C. were somewhat greater, however, than those aged at particles after one-month contact with a fluoride-free triple 30". This did not hold, however, for the mixtures of the spesuperphosphate, is evident in B. This coating had withstood cial superphosphate. The mean of percentage decreases in removal by aqueous washing. C shows absence of the acwater-soluble P,O, WES 20.6. quired coating which had been dissolved by a brief digestion FORMATION OF BASICPHOSPBATES. Initial and final values with diluted ammonium citrate for available P,O, were comparable for seventeen of the eighEffect of Humidity diiring Aging teen mixtures of Table IT. Respective means of 17.98 and 17.82 per cent for initial and final available P,O, content The phosphatic materials and proportions of Table I11 were demonstrate absence of reversion. comparable, respectively, with those oE Table 11, but inclusion Restricted reaction between the acidic phosphates and the of the ammonium sulfate constant used in the earlier related fused rock formed a thin coating of dicalcium phosphate upon studies (2, 6 ) decreased total P,Os content. to the range of 17 the surface of the glassy particles, and the mechanical and to 22 per cent. desiccative effects of this coating tended to minimize further Compatibility of calcine with included ammonium sulfate reaction; therefore only meager quantities of tricalcium phoswas not E primary objective, bnt pvtential resctions between phate were formed. Development of fluorphosphate was the two materials affect P,O, availability materially in mixrestricted to rcnction of component Ruovides of the superphostures with superphosphates that carry calcium sulfatc. No
INDUSTRIAL AND ENGINEERIKG CHEMISTRY
576
Combined Effect of Humidity and Temperature during Aging
T.4BLE I. PERCENTAGE AKALYSESO F FUSED K O C K PHOSPHATE .4KD OTHER PHOSPHATIC MATERIALS USED I N MIXTURESAND
SUSPEN~IONE
P?OS Water- CitrateTotal sol. insol. 29.80 ... 12.70/
7
Material
VOL. 32, S O . 4
Since no marked P205transitions and no appreciable decreases in the available P205content of t'he mixtures of Tables I1 and I11 resulted from variation of temperature in prevailing humidity or from variation in humidity with constant temperature of 30' C., the joint influence of higher humidity and elevated temperature was imposed upon the mixtures of Table IV. Behavior of the partially defluorinated fused rock also was compared with behavior of a similar product that had been defluorinated completely. Diminution of water-soluble P ~ O content' Z and derelopment of citrate insolubility were accelerated by higher humidity a t both temperatures in the mixture of triple superphosphate XVith bot11 types of fused rock. Tv th humidity constant, the higher temperature caused greater change in both watersoluble and citrate-insoluble P20jcont'ent. Each unit that contained triple superphosphate and the fused rock devoid of aDatite showed citrate insolubilitv beyond that of the correspoilding unit that contained triple superphosphate and the fused rock that contained apatite. The joint effect of higher humidity and elevated temperature apparently mas t o accelerate reaction between the fused tricalcium phosphate and the fluorides of the triple superphosphate and to engender greater quantities of tertiary phosphate for localized reaction with the fluorides of the concentrated superphosphate. Effect of the higher humidity upon decreases in watersoluble P,Os was pronounced in the last two groups that contained the special fluoride-free t'riple superphosphate. There was, however, no indicat'ion of developmelit' of citrate insolubility in the mixtures of this special product with either the fluoride-free fused rock or the fused rock that contained residual apatite. The reactant fluorides of the superphosphates, therefore, were responsible for the development of fluorphosphate in the first eight mixtures of Table IV.
7
Avail- Fluorine able Contents
Fusedbron-nrockphobphateh 17.10 0.67 Special fused brown rock 27,50 , , , 2,j0 23,00 0,003 phosphateC Calcined rock phosphated 36.80 5 , 0 0 31.80 0 . 1 ; ~ Standard superphosphate 21,00 18:23 0.20 20,70 2 . 0 5 Triple superphosphate (T. S. P.) 46.40 34.40 3.50 42.90 1.60 Special triple superphosphatee 55,60 54.00 None 53.60 0.02 a Analyses b y J. IT. Hammond. Semiworks Dam g r o u n d t o pass mesh: referred t o in text as ordinary iused rock. c A specially selected experimental material, 80 mesh; designated in text as fluoride-free fused rock. rl h semiworks product supplied bJ7 Darling and Company and not in production, 80 mesh. e Made by reaction between Appalachian marble and HzP04: referred t o in text as fluoride-free superphosphate. / By 1-gram charge; 12.4 per cent by 0.5-gram charge.
,
I
odor of ammonia was noted, however, in any of the mixtures of Table 111 a t any stage and no nitrogen determinationswere made, since conventional analyses will not register ammonia losses not detectable by odor. In each of the three series, higher humidity induced greater decrease in water-soluble PnOs content of the mixtures that contained the largest proportion of superphosphate. Mean of ultimate decreases in water-soluble P205was 17.5 per cent for the nine mixtures aged in relative humidity of 79.2 per cent, against a corresponding mean of 25.2 per cent for the nine mixtures aged in relative humidity of 90.5 per cent. I n general, however, the higher humidlty did not show a consistently substantial effect upon decrease in water-soluble P20Z in mixtures aged a t 30" C. Observations as to limited formation of basic phosphates and absence of fluoride-induced reversion in the mixtures of Table I1 apply also to the mixtures of Table 111. Initial values and those found after 28, 56, and 84 days indicate that inclusionof ammoniumsulfate occasioned no increase in citrateinsoluble P20j,except in those mixtures that contained fused rock and the ordinary superphosphate in the 2:l and 1:1 ratios.
"
Effects of Added Fertilizer Salts during -Aging at High Humidity and Elevated Temperature Effect of included soluble fertilizer salts upon P20jtransitions was considered in the comparisons of Table J7. Mean of
O F A CONSTANT O F FUSED ROCKPHOSPH.ITE WITH vARIhRLE PRnl'ORTIOXS O F THREE TABLE 11. P&j TRASSITIONS IN MIXTURES TYPESOF MOISTEKED SUPERPHOSPHATES DURING AK 84-DAYCURING PERIOD .IT Two TEMPERATURES 7
Type of Phosphate
MixturesQ Coinporientsb
-
Proportions
7
TemCode peraNo. ture
'
Grams
Standard superphosphate
Triple superphosphate
Fluoride-free triple superphosphate
Fused rock Superphosphate Fused rock Superphosphate Fused rock Superphosphate Fused rock T. S. P. Quartz Fused rock T. 6 . P. Quartz Fused rock T. S. P. Quartz Fused rock T. S. P. Quartz Fused rock T. S. P. Quartz Fused rook T . 9. P. Quartz
1201 24 1201 60 1201 120,'
120'1
60
6oJ
iz;]
14.4) 120
c
Total
.
%
7
0
%
%
%
l?.!?
!1.!22
8.30 8.30
4.00 4.00 6.20 3.60
5.80
10.75 10.20 10.80 l o . ? ? 10.75 10.7U 11.80 1 U . 8 U 7.80 8.90 8 . 7 5 8.62 8.62 9.20 10.10 10.10 6.00 6.70 7.23 6.25 7 00 6.25 7.70 7.50
28.2 28.2
2.70 2.70
2.70 2.30
1.90 2.20
3.30 1.80
10.38 11.00 1 0 . 3 8 11.00
17.82 17.70 17.82 17.70
30 45
27.0 27.0
5.20 3.20
3.80
4.20
3.40 3.50
3.40 3 70
8.75 8.73
8.70 9.00
8.00 9.00
8.40 9.00
1 8 . 2 5 18.60 18.25 18.00
30 45
23.G 25.6
7.8:
7.85
4.40
li.10
6.00 0.00
(i 20
7.(52 7.ti2
7.10
5.SO
z.00 1 .90
8.10 7.30
17.98 17.98
17.50 18.30
30 45
29.0 29.0
3.70 3.70
3.10 3.30
3.20
3.30
2.30
10.50 10.50
9.90 10.10
10.70 10.50
10,50 10.80
18.50 18.50
18.50 18.20
30
26.2 26.2
7.10 7.10
6.20 6.10
6.40 6.20
7.60 7.00
8.25 8.25
8.40 S.40
8.50 8.50
8.30 8.10
17.95 17.95
17.90 18.10
30 45
25.4 25.4
10.80 10.80
8.30
10.50
G.25 6.25
6.60 6.35
6.20
6.30
19.1.;
9.30
7.80 9.70
6.00
8.90
6.60
lI),lS
19.10 18.80
1-A 2 2-A 3 3-A 4-A
30 45
5-Ai ti
;-Ai
%
2.20 1.70 4.30 4.00 6.20
28.0 28.0 26.2 26.2 24.6 24.6
6-A
%
2.00 1.50 4.00 3.40 6.10 6.00
30 45 30 45 30 45
1
--
P20~ValuesC --Citrate-Insoluble-%%day %-day 84-day 28-day 56-day 84-day ---AvailableInitial period period period Initial period period period Initial Final
----Tt-ater-Soluble---
2.80 2.80 25 s.25
2.70 2.30
2.50
%
%
9.40
%
%
11.20 10.JO 11.10 10.50
l7.ZJ 17.58
li.2U
17.45 16.10 17.35 17.35 17.35 17.10 17.58
a Each sample was reconditioned by light grinding immediately before analysis of 1-gram chai g e . b Anal tical charges of mixtures 1 and 1-A, 4 Fnd 4-A, 7 and 7-A carried 0.8 grain of fused rock; 2 and .'-.1.3 and >-.\, 8 a d 8-A carlied 0.67 gram of fused roc%. 3 and 3-A, 6 and 6-A, 9 and.9-A carried 0 3 gram of fused rock. C All vaiues corrected for change in weight after curing.
APRIL, 1940
-
INDUSTRIAL AND ENGINEERING CHEMISTRY
571
TDLB111. P,Os TRANSITIONS rn MIXTWRES OF A CONSTANTOF FUSED ROCKPHOSPHATE WITH V ~ R ~ APROPORTTONS R~~E OF T H R E ~ TYPES OP MOISTENED SUPERPHOSPHATES AND AMMONIUM SWLFATE DWRMQ An &DAY CURWG PERIOD AT T W O HmamrTlEs m CONBT~ TEMPERATURE T OF 30' C. ,
-Mixtures
Type of P h w p h s t e
Components
F
d roak
:;g;$gphate
}
5.0
1.0 4.0
Fused rook Su arphosphate
(N&hSOi Fused roak 8u erphosphate (NkM30, Tri le s u p e r p h a r Pi.,
8i?ESO' Fused rook T. 9. P.
8"' tZ H&SO< (
Fused rook T. S. P.
8GS0, Fused rook T. 8. P. Q"*rtS
(NHdaSO. Fused rock T. 8. P.
8%:so. Fused rock T. 8. P. Q$wrts (
H+)rSO.
5.00 4.00
.
-Citmte-Ina&ble~
56-day period
84 day period
%
%
%
%
Total
%
2% '
%
%
%
A
18.00 18.00
1.60 1.60
1.so
0.90
B
79.2 90.5
1.50
1.20 1.20
6.30 6.30
6.40 6.50
8.80 6.00
6.23 6.15
C
D
79.2 00.5
17.40 17.40
3.72 3.72
3.21 2.74
a.04 2.17
2.87 2.43
5.50 5.50
6.60 6.87
6.77 0.34
7.43 0.52
E
79.2 90.5
17.90 17.90
6.42 6.42
5.35 4.64
5.07 3.85
5.00 4.21
4.34 4.54
5.07 4.93
5.28 4.85
5.71 5.21
E
G
79.2 90.5
17.40 17.40
1.67 1.57
1.80
1.20
1.20 1.50
1.60
1.50
6.55 6.55
6.50 5.SO
6.70 6.50
6.70 6.80
I J
79.2 90.5
17.60 17.60
3.48 3.48
2.60 2.52
2.87 2.87
3.04 3.M
5.82 5.82
6.00 5.91
5.65 5.65
5.91 5.74
K L
79.2 90.5
17.80 17.80
5.43 5.43
4.28 4.50
4.21 4.07
4.36 3.86
5.00
5.00
5.00 5.14
5.14 4.92
5.00 4.78
M N
79.2 90.5
17.80 17.80
2.25 2.25
1.70 1.70
1.40 1.70
1.70 2.40
6.40 6.40
6.40 6.30
6.00 6.20
6.50 6.00
0 P
79.2 90.5
18.20 18.20
3.95 3.95
3.91 3.74
3.65 3.21
3.56 3.47
5.69 5.69
5.47 5.21
5.20 5.19
5.47 5.39
Q R
79.2 90.5
22.00 22.00
11.1s
11.18
10.21 9.07
9.71 9.14
9.43 7.36
4.17 4.17
4.50 4.80
4.21 4.43
4.28 4.64
F
F w e d rock T. S. P.
P,O,Valuea Water-Solubla----------.
2Msy period
%
Relative Humidity
Q,a?lIn.
Standard IUPU?phwphata
--___
Initial datd.
Propor- Code tions No.
decresses in water-soluble P,06 in the ten mixtures during the first period wss 24 per cent of the mean of initial values, ammonium chloride apparently being the most active of the five salts. Material decreases in water-soluhle P206 content O C C U I T ~during ~ the second period in the mixtures that contained either ammonium chloride or potassium sulfate. Every salt, other than the magnesium sulfate heptahydrate, tended to induce some incresse in citrate-insoluble P30scontent, although there was no appreciahle increase in seven of the ten mixtures. The most noticeshle increase after 28 days waa registered by the mixture that contained the fused rock and triple superphosphate in the 2:l ratio and additions of calcined sulfate. Identical citrate-insoluble values obtained by citrate
Components Of Mirtunr Fused rwk T. S. P. Quarts
Proportions
10.0 2.5) 2.5
1.80
Impased Conditions
e!-
midity Temp.
Initisil detd.
28.da
oeriol
56-da
84-ds ~sriodl p e d
P*Os valuas
-Water-Sd.---CitratbInsol.-. Immediate After Immed/ate Aftsr Total analyeis 28 days a n a l y m 28 drya
%
'C.
%
%
%
%
79.2 90.5 79.2
30 30 45 45
26.8 26.8 26.8 26.8
5.10 5.10
5.50
4.40 3.00
3.90
5.50
2.20
9.50 9.50 9.30 9.40
9.80 9.85 10.25 10.88
26.0 26.0 26.0 28.0
6.00 6.00 5.60 5.70
4.20 4.40 2.80
1.80 1.80 2.30 2.30
2.40 2.86 3.38 4.50 8.50 7.70 8.30 8.20
80.5 79.2
%
5.00
F-free fused rock T. 8. P. Uuerts
'$I:}
!90.5 :2"
30 30 45 45
Fused rock
10.0
79.2 90.5 79.2 90.5
30 30 45 45
29.06 29.06 29-06 29.06
9.15 9.16 9.16 9.16
7.50 2.40 7.90
8.50 8.50
79.2
30
29.05 20.06 29.06 29.06
9.25 9.25 9.25 9.25
8.40 2.40 8.30 4.10
1.18
SpeaislT.9.P.
2.5
2.51 2.6
Quarts
F-freefusedrook Special T.8. P. Qusits
10.0 2.S} 2.5
90.5
79.2 90.5
30
45 45
3.80
8.50
8.50
1.18 1.18
1.1s
1.20 1.00 1.15 1.00
( X 235)
digestions of residues from 25o-ml. and 500-ml. aqueous washings indicated that this result waa not due to common ion effect. Moreover, the initial citrate-insoluble value for mixture L4 was the lowest found for the ten systems. The mean of 28day citrate-insoluble P20, values represented an increase of 7 per cent of the mean of initial values. Increases during the second 28day period of elevated temperature and high humidity were mainly in those mixtures that contained either calcium or ammonium sulfate.
Untreated. Coatine of bssip phosphate8 on partidea in aged mixture of 50 parts of Iused rook and 20 parte of special, fluoride-free concentrated superphosphate; ~queouu~ wa8hing had lsiled to rBmDVB ooet,ng. C. Same m B except t h a t coating bed been removed by waahing with diluted nmmonium citrate nt 50" C.
In the laboratory-scale mixtures, oompacted to simulate the condition of large piles, the fused rock phosphate exerted
A
B
FIQWKE 2. MICROPHOTOGRAPHS OF FUSEDROCKPUOSPEATE A B
C PARTICLES
Physical Effects
INDUSTRIAL AND ENGINEERING CHEMISTRY
578
TABLEV. EFFECTOF SALTADDITIONS ON THE PIOs CONVERSION IN MIXTURES OF FUSEDPHOSPHATE AND TRIPLE SUPERPHOSPHATE DURINQ CURING .4T 30" c. AND 90.5 P E R CENT RELATIVE HUMIDITY
-
No.
Components of Mixture
L- 1
Fused rock T. 8. P.
L-2 L-3 L-4
L-5
PnOs Values" -Water-Soluble---Citrate-InsolublPropor- Immediate After After Immediate After After tions analysisb 28 days 56 dayse analysisd 28 days 56 daysc
% E; s0 4 Fused rock
T. S. P. Quartz NHiCl Fused rook T. S. P. Quartz
%
%
%
%
%
%
5.78
4.43
3.92
5.20
5.46
5.90
5.93
1.71
0.50
5.20
5.32
5.17
5.71
5.03
3.57
5,30
5.93
6.71
6.00
5.23
5.00
4.976
6.18
6.71
6.07
5.71
..
5.07
5.21
*.
&SO4
Fused rock T. S. P. Quartz CaSOi Fused rock T.S. P. Quartz MgSO4.7HnO
1.25
1.25 2.00 2.50' 1.25 1.26 2.00.
2.50' 0.25 1.85 1.80 .. 6.40 6.65 7.25 0.25' 2.00 2.50' H-2 0.25, 0.90 1.75 0.70 6.10 7.00 6.25 0.25 2.00< 2.50 H-3 0.25, 1.65 1.10 0.85 6.30 6.55 6.75 0.25 2.00, KzSOi 2.50 Fused rock H-4 0.25, T. S. P. 1.50 1.05 0.90 6.50' 6.70 7.50 0.25 Quartz 2.00 Cas04 2.50' Fused rock H-5 0.25, T. S. P. 1.85 1.80 6.40 6.35 0.25 Quarti 2.OOJ MgS04.7Hz0 0 Each analytical oharge contained 0.50 gram of fused rock phosphate of 0.67 per cent fluorine content. b Computed initial value of 6.14 per cent water-soluble P2Oa for mixtures L; 1.72 per cent for mixtures H. c Cured at 4 5 O C. during the second 28-day period. d Computed initial value of 5.15 per cent citrate-insoluble PzOs for mixtures L: 6.52 per cent for mjxturee H. Identical citrate-insoluble results were obtained when duplicate charges were washed with 250 and 500 ml. of cold water. H-1
Fused rock T. S. P. Quart5 ("4)rSO4 Fused rock T. 9. P. Quartz NHiCl Fused rock T. S. P. Quartz
..
..
VOL. 32, NO. 4
phosphate toward the fused rocks. The fluoridefree fused rock was more reactive than the ordinary fused rock, and its reactivity toward the special triple superphosphate was almost as great as the reactivity of the calcine. Marked decrease in water-soluble P& occurred in each 20-ml. suspension of calcine and concentrated superphosphate. The avidity of ordinary superphosphate toward the calcine in the suspensions of smaller volume was in marked contrast t o its inertia in the 100-ml. suspensions. Differences in behavior of the suspensions is elucidated by pH values and titrations of filtrates from 20-ml. and 100-ml. control suspensions of 1-gram charges of the superphosphates. The filtrates from the six suspensions had a common pH of 4.2. In terms of 0.1 normality, the total titration values of solutes in the 100-ml. and 20ml. volumes were 36 and 26 for the standard superphosphate, 48 and 42 for the triple superphosphate, and 68.8 and 64.0 for the special triple superphosphate. The PO4 concentrations of the smaller volume, therefore, were 3.6, 4.37, and 4.66 times those of the larger volume for the ordinary superphosphate, triple superphosphate, and special triple superphosphate, respectively. The Cas04 effect and the influence of theiron content of the triple superphosphate are reflected by the respective concentrations of PO1 in the filtrates from the agitated suspensions of the three types of superphosphate. Attrition Effect upon Reactivities of Superphosphates toward Processed Rock Phosphates in Aqueous Suspensions
It was assumed that the addition of quartz to the suspensions of Table VI1 would prevent accumulation of coatings of basic phosphates on surfaces of fused rock particles and thereby accentuate the attack of the acidic phosphates. The abrasive effect of the quartz was reflected by decreases in water-soluble PzOr content in each system that contained the ordinary superphosphate and one of the three processed rock phosphates, but not in the corresponding concentrated superphosphate suspensions. Grinding action apparently induced some increase in citrate insolubility in those systems that contained the fused rock and a fluoride-bearing superphosphate, but differences between computed and determined citrate-insoluble Pz06values in the systems that contained the special fluoride-free superphosphate were not sufficient to establish definite increases attributable to abrasion by the quartz. No effect upon development of citrate-insoluble PnOswas induced by attrition in two of the three suspensions of the finely divided reactive calcine. ~~
about the same effect as sand in the mixtures aged at 45" C. in ordinary humidity. Caking occurred only in those systems where acceleration in chemical activity was induced by humidity far beyond that of practical conditions. Caking induced by excessive humidity was increased by concomitant elevation in temperature. Reactivities of Superphosphates toward Processed Rock Phosphates in Aqueous Suspensions Since reactions between the acidic phosphates and the fused rock were either substantially retarded or practically terminated by deposits of basic phosphates upon surfaces of glassy particles in mixtures, the ordinary fused rock was brought into reactivity with the three types of superphosphate in aqueous suspensions, Parallel suspensions included the completely defluorinated fused rock and also the vigorously reactive calcine, previously shown to be incompatible with superphosphates ( 2 , 6). Neither of the three processed rock phosphates was attacked appreciably by the ordinary superphosphate, in either of the three proportions, in the 100-ml. systems of Table VI. The same was true of both the regular and the fluoride-free fused rock in suspensions carrying either of the concentrated superphosphates. The calcine was attacked in each of the corresponding concentrated superphosphate suspensions but not by the ordinary superphosphate. I n corresponding 20-ml. systems the two concentrated superphosphates were more reactive than the ordinary super-
Discussion of Results The partially defluorinated rock phosphate was devoid of reactant fluorides. Microscopic and x-ray examinations showed that its fluoride content was a constituent of the apatite of the initial rock. Formation of fluorphosphate in the mixtures of the fused rock with conventional superphosphates was restricted, therefore, to reaction between the component fluorides of the superphosphates and tricalcium phosphate, which occurred in two forms-the known alpha occurrence that accounted for two thirds of the Pd& of the
INDUSTRIAL AND ENGINEERING CHEMIS‘TRY
APRIL, 1940
TABLE VI. REACTIVITIES O F FUSED ROCKPHOSPHATE, FLUORIDE-FREE FUSED ROCK PHOSPHATE, AND CALCINED ROCKPHOSPHATE TOW.4RD THREETYPESO F SUPERPHOSPHATES IN AGITATED AQUEOUSOXE-HOUR SUSPENSIONS, AS MEASURED BY CHANGES IN WATER-SOLUBLE PZOs -Superphosphate hlixt.
in-
--Water-Sol.
PzOs Content of Aqueous SuspensionsaFused rock F-free fused rock Calcined rook phosphate after phosphate after phosphate after agitation agitation agitation 100 ml. 20 ml. 100ml. 20 ml. 100ml. 20 ml.
Ratio t o processed rock
Initial computed
%
%
%
%
%
%
%
Standardb
1:4 1:2 1:l
3.83 6.54 9.82
4.00 6.40 9.70
3.75 6.00 9.10
4.03 6.50 9.40
3.95 6.25 9.65
4.00 6.50 9.80
2.00 4.30
Triple
1:4 1:2 1:l
3.44 5.71. 8.60
3.50 5.60 8.60
3.40 5.65 8.40
3.50 5.80 8.60
2.00 3.10 8.35
2.40 2.70 4.00
1.30 1.70 3.10
Type
1.%0
579
(b) tricalcium phosphate, and ( c ) calcium fluoride. Continued contact between dicalcium phosphate and any calcium silicate not decomposed by the acidic phosphates tends to bring about further formation oi’ tricalcium phosphate. Adjacent particles of the tertiary phosphate and calcium fluoride react to form fluorphosphate, as indicated by the equation: 3[Car(PO&]
+ CaFz = Calo (P04)a.F~
This formation is accelerated by alkalinity induced by any residues of calSpecial triplec 1:4 4.41 4.50 3.30 4.50 1.65 2.20 1.40 1:2 6.63 6.55 5.00 6.60 2.25 2.50 1.70 cium silicate, by humidity, and by 1:l 11.05 10.80 10.90 10.86 5.90 5.00 5.20 elevation of temperature. I n contraa One hour a t room temperatuse. distinction, no development of citb Water-soluble PtOs content, L9.65 per cent (product of Table I , after aging). c Water-soluble PzOa content, s5.25 per cent (product of Table I , after aglng). rate-insoluble PZOSoccurs when either defluorinated calcined rock or defluorinated fused rock is mixed with superphosphates devoid of fluorides, and the mixtures are aged fused rock, and the limited occurrence resultant from reaction under ordinary conditions. between engendered dicalcium phosphate and the calcium silicate of the fused rock. Conclusions The nature of the fused rock was such that limited opportunity was afforded for the fluorides of the superphosphate to Because of its glassy nature, fused rock phosphate reacts react with the alpha form and convert it into fluorphosphate. slowly with superphosphates and the extent of reaction is reRelatively small decreases in water-soluble PZOs content in stricted by the formation of films of basic phosphates upon the mixtures of Tables 11,111,and IV demonstrated that only the glassy particles. The formation of basic phosphates and small quantities of dicalcium phosphate were formed. The fluorphosphate does not proceed to the extent of causing small amounts of dicalcium phosphate formed upon particle penalizable increases in citrate insolubility under ordinary consurfaces reacted slowly with the calcium silicate content of ditions. Fused rock phosphate can be used to condition superthe fused rock, and amounts of tricalcium phosphate so formed phosphates and t o effect their concentration or dilution were small. The amounts of tricalcium phosphate thus without the marked detrimental effect that has been shown to formed, and also the subsequent formation of fluorphosphate result from similar admixtures of the unfused rock phosphate were so small and dispersed as to be dissolved by the convencalcine (2, 6). tional citrate digestion. In some mixtures the joint effect of elevation of temperature and high humidity induced the forLiterature Cited mation of fluorphosphate in amounts sufficient t o show in(1) A. 0. A. C., Methods of Analysis, p. 19 (1935). creases in citrate insolubility. This result did not occur, (2) Beeson, K. C., and Jacob, K. D., IND.ESG. CHERI.,30, 304-8 however, in the mixtures devoid of uncombined fluorides. (1938). (3) Curtjs, H. A., Copson, R. L., Brown, E. H., and Pole, G. R., Reactivity of admixed fused rock toward superphosphates Ibtd., 29, 766-70 (1937). is governed more by its physical nature than by the extent of (4) MacIntire, W. H., and Hammond, J. W., J. Assoc. Oficial Agr. defluorination and resultant content of tricalcium phosphate. Chem., 22, 231 (1939). Meager reactivity of either partly or completely defluorinated ( 5 ) MacIntire, W. H., and Hardin, L. J., ISD.ENO.CHEM..29, 768 (1937). fused rock is in marked contrast t o the decided avidity of the (6) Ibid., 32, 88 (1940). powdery calcine (2, 6). About 20 per cent of the calcium (7) MacIntire, W. H., Hardin, L. J., and Oldham, F. D., Ibid., 28, 48, content of the calcine is in the form of finely divided silicate. 711 (1936). This and also the tricalcium phosphate of similar fineness re(8) Willard, H. H., and Winter, 0. B., IND. ENO.CHEM.,Anal. Ed., 5, 7 (1933). acts quickly with the free acid and with most of the monocalcium phosphate of the superphosphates. The resultant sysPR~SENTBD before the Division of Fertilizer Chemistry a t the 98th Meeting of the American Chemical Society, Boston, Mass. tems are substantially mixtures of (a) dicalcium phosphate,
EFFECTOF LARGE QUARTZ ADDITIONS ON THE REACTIVITIES OF FUSED ROCKPBOSPHATE, FLUORIDE-FREE TABLEVII. ATTRITION FUSED ROCKPHOSPHATE, AND CALCINED ROCKPHOSPHATE TOWARD THREETYPESOF SUPERPHOSPHATE IN AGITATEDAQUEOUS SUSPENSIONS, AS MEASURED BY CHANGES IN WATER-SOLUBLE AND CITRATE-INSOLUBLE PzOs Superphosphate in Mixt. Ratio t o processed Type rock
-Fused Quartz Addition
Rock.Phpsphate afterAgitation Water-soluble Citrate-insoluble Computed Found Computed Found
PtOb Content of Aqueous Suapensionea -F-Free
Fused Rpck.Phoaphateafter Agitation Water-soluble Citrate-insoluble Computed Found Computed Found
YCalained Rock Phosphate afterAgitation Water-soluble Citrate-insoluble Computed Found Computed Found
Grams
%
%
%
%
%
%
%
%
%
%
%
%
Standardb
1:l 1:l
None 10
9.82 9.82
9.00 6.70
6.45 6.45
6.50 6.50
9.82 9.82
9.30 6.40
1.35 1.35
1.20
..
9.82 9.82
2.50 1.80
2.60 2.60
2.70 2.80
Triple
1:1 1:l
None
8.60
7.23 7.23
6.90 7.90
8.60 8.60
3.50 5.80
2.13 2.13
2.20 2.50
8.60
8.60
6.10 5.90
S.60
1.75 1.75
3.38 3.38
3.60 3.80
Special triplec
1 :1 1:l
None 10
11.00 11.00
7.50 8.35
6.35 6.35
6.40 6.70
11.00 11.00
6.25 6.90
1.25 1.25
0.90 1.20
11.00 11.00
3.20 3.80
2.50 2.50
2.50 3.10
0
b c
10
Three hours a t room temperature with 20 ml. of water. Water-soluble PiOa content of 19.65 per cent (product of Table I after aging). Water-soluble PzOa content of 55.25 per cent (product of Table 1,’after aging).
