X-Ray Powder Diffraction Patterns of Some Cadmium Phosphates R. C. ROPP, R. W. MOONEY, and C. W. W. HOFFMAN Chemical and Mefallurgical Division, Sylvania Elecfric Products Inc., Towanda, Pa.
b The x-ray powder patterns of 10 cadmium ortho- and pyrophosphates are reported for their value in the identification of phosphate materials and in the elucidation of the reactions of the cadmium phosphates. Three condensed phosphates obtained from thermal treatment of monobasic cadmium orthophosphate were also isolated, but their chemical nature remains undefined.
recent paper (8) reviewed published d a t a on the phosphates of cadmium and described the preparation :d properties of several cadmiurn phosphates. The present paper complements the earlier report by presenting the x-ray powder diffraction patterns of the phosphates isolated in the pre\ious study as well as the patterns of two monobasic orthophosphates of cadmium. Chromatographic analyses of the samples are reported where they are corroborated by infrared analysis. The ASTN x-ray ponder data file ( 1 ) has listcid two sets of results for C'd,(P04)2 mith one of them being reniowd from the most recent edition. 130th sets of d a t a are discussed in relation t o the present results. EXPERIMENTAL PROCEDURE
The methods used to obbain the x-ray diffraction patterns were the same as those reported in the recent study of the powder diffraction patterns of strontium phosphates ( 7 ) . The paper chromatographic studies were conducted as follovis. A 3-mg. sample of cadmium phosphate and 1 gram of Illco S R - 1 ion exchange resin were added to 25 ml. of distilled water and swirled until the sample dissolved. The time required for dissolution varied from 10 minutes for the orthophosphates obtained from solution to 2 hours for the condensed phosphates prepared by heating the monobasic dihydrate. The resulting solution was filtered to remove a n y trace of iiwcipitate and a l@pl. aliquot of the filtrate was analyzed by the Inethod given by Bernhart and C'hcss ( 2 ) . X 2.5-hour run a t 20" C. \vas emploj.ed using Solvent B. The L3-5 cam and 650-nip red filters were used ivith the Spinco Analytrol. Infrared absorption spectra of the solid cadmium phosphates were obtilined with a PerkimElmer Model 221
spectrophotometer on K B r pellets. Pellets of 5.0 and 0.20% sample in K B r were employed and the spectra were taken over the iYaC1 (1- to 15-micron) and the KBr (11- to 25-micron) regions.
Orthophosphates from Solution. T h e preparation a n d regions of stability of the compounds, Cd5H2(P04)4(H20)4r (CdHP04)3 3NH3 3H20, and ( C d H P 0 4 ) 34NH3 2H20, were described in the previous paper (8). The monobasic cadmium phosphates were prepared by the method of Tartar and Lorah (IO). Specifically, CdO, C d 0 2 , Cd(OH)2, or CdCO3 was dissolved in phosphoric acid keeping the acid in excess. Evaporation gave the monobasic cadmium orthophosphate dihydrate n hen the concentration was less than 251. ANALTSIS. Calcd. for Cd(H2P04), 2H20: Cd, 32.8%; P, 18 1%; H20, 10.5700. Found: Cd, 33.07,; P, 17.9%: H20, 10.7%. K h e r e concentrations above 2.11 were used, anhydrous monobasic cadmium orthophosphate, Cd(H2P04)2,was obtained from solution. The anh\ drous material IS unstable in air and reverts to the hydrated form within a few hours. Hence, both the chemical analyses and the determination of the x-ray diffraction pattern were carried out inimediately after preparation. ANALYsIs Calcd. for C d ( H 2 P 0 & : Cd, 36.77,; P, 20.27,. Found: Cd, 36.1%; P,20.7%. Chromatographic analyses of Cd&(P04)4(H,0)4, (CdHP04)3 3NH3 3H20, (CdHP04)34 5 H 3 21120, and Cd(H2P04)2 2H20 indicated the pre,qence of the orthophosphate ion only. T h e x-ray diffraction patterns of the five orthophosphates precipitated from solution are listed in Table I . There are no previously published patterns for these compounds. The innermost lines and the three main lines are listed in Table TI for convenience in idtintification of the phases. The u-ray diffraction patterns of the tRo cadmium ammonium phosphate hydrates differ only slightly a i t h the principal differences being the position of the line in the region 8.7 to 8.8 A,, the intensities of the lines a t 4.41 and 4.33 A., and the line a t 2.94 A. in one case and not the othei.
Orthophosphates and Pyrophosphates by Solid-state Reactions. T h e preparation of Cds(P04)z Cd2P20, by heating Cd6H2(P04)4(H20)4 t o constant weight at 700" C. and the preparation of Cd2P207 by heating either of the cadmium ammonium phosphate hydrates at 980" C. were described previously (8). In the latter instance, a n intermediate having the suggested composition (CdHP04)$ KH3 was also isolated. I n the same study, the tribasic orthophosphate, Cd3(P04)2 mas prepared by solid-state reaction. Chromatographic analyses of these four compounds gave results listed in Table 111. The chromatographic analyses corroborate the formulas suggested. Thus, the phosphorus in Cd3(P04)2Cd2P207 is about equally divided between ortho and pyro groups Infrared absorption spectra show the presence of orthophosphate (PO4+ bands a t 9 t o 11 microns, 16.8 and 17 8 microns) as well as pyrophosphate (P207-4hands at 8.5 to 11 microns, 13.8 and 16 5 to 21 microns). I n the case of the intermediate. ( C C ~ H P ONH, ~ ) ~ infrared spectra show only the presence of orthophosphate groups, bands due to iYH3 (3.3 and 6.9 microns) and the absence of more than a few per cent of pjrophosphate. It is probable that the chromatographic results are inaccurate, perhaps due to rearrangement during dissolution. An infrared spectrum of (CdHP04)3ISH3 intentionally contaminated by 5% of Cd2P207indicated that this much Cd2P,07 is detectable by infrared absorption. Tribasic cadmium orthophosphate showed only orthophosphate groups by both infrared and chromatographic analysis. Of these four cadmium phosphates. the only one on which x-ray diffraction data are available for cornparicon is the tribasic orthophosphate. Cd3(P04)2.For this compound. the rcsults reported herein agree substantially 111th the diffraction pattern reported by Smith and Pone1 (9) and listed in the latest revision of the ,ISTLl u-ray ponder data file (card S o . 8-260). Neither the pattern listed in this paper nor that given by Smith and Power agree with the pattern listed by Hanawalt, Rinn, and Frevel (3) (ASTM card No. VOL 33, NO. 12, NOVEMBER 1961
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Table 1.
Paiwder
X-Ray
Diffraction Data
Cd(HzPO4)n. 2H2O d 8.9
8.3
6.5 6.1 4.8 4.7 4.6 4.45 4.23 4.16 3.47 3.36 3.32 3.24 3.15 3.10 3.07 2.97 2.95 2.80 2.78 2.70 2.66 2.62 2.58 2.48 2.37 2.32 2.25 2.22 2.20 1.79 1.74 1.68 1.67 1.62 1.55 1.49
d
1/11
d
1/11
100 80 10 10 25 25 35 10 25 25 10 10 25 45 10 30 40 55 20
6.0 4.8 4.5 4.22 4.12 3.90 3.75 3.67 3.45 3.27 3.14 3.00 2.92 2.83 2.51 2.45 2.39 2.38 2.28 2.25 2.2i 2.09 2.07 2.06 2.01 2.00 1.84 1.75 1.73 1.72 1.70 1.68
100 35 85 5 10
2.45 2.33 2.30 2.17 2.12 2.08 2.03 2.00 1.99 1.94 1.92 1.85 1.79 1.77 1.71 1.67 1.64 1.60 1.56 1.52 1.40
30 20 20 20 20 15
15
20 50 15 20 10 20 15 15 10
20 15 15 10 10 10 20 10 10
8.8 100 4.86 5 4.41 30 4.33 20 3.81 5 3.49 20 2.91 15 2.88 50 2.77 5 2.54 10 5 2.51 2.42 5 2.33 15 2.21 10 2.19 10 2.07 10 1.91 15 1.68 5 (CdHP04)a.4NHa.2HzO 8.7 100 5 4.86 4.41 20 4.33 30 3.83 5 3.51 10 2.94 25 2.91 10 2.88 40 2.78 5 2.54 5 2.51 10 2.43 5 2.32 10 2.19 5 2.OA 5 2.04 5 1.91 10 1.68 5
1688
(CdHPO4)a.NHs
1/11
5
5
5
15 30 15 45 5 5
10 __ 5
5
5
10 35 ~lo
10 5 5 5
5 5 5 20 5 5 10
Cd(HzP0dz 8.2 100 5.8 15 5.4 30 4.5 10 4.08 10 3.75 30 3.50 25 3.28 25 3.13 15 2.88 10 2.72 100 2.60 10 2.45 25 2.36 25 2.14 2o 2.07 25 1.90 10 ~. 1.77 lo 1.59 10 1.49 20 1.31 10 1.14 15 ~~~
4.6 4.37 4.20 4.16 4.02 3.73 3.54
3.35
3.27 3.19
3.i5
3.09 3.03 2.99 2.94 2.89 2.84 2.79 2.67 2.62 2.57 2.50
ANALYTICAL CHEMISTRY
20 15 30 20
40 20 50 25 30 25 30 65 40 50 100 25 50 50 10 10 15 15
5.9 4.6 4.55 4.36 4.19 3.98 3.35 3.26 3.18 3.12 3.09 3.06 2.96 2.94 2.83 2.61 2.48 2.45 2.32 2.30 2.21 2.17 2.14 2.11 1.95 1.92 1.85 1.77 i .67 1.64 1.60 1.55 12.5 7.4
5.1
4.6 4.32 4.i8 3.58 3.50 3.30 3.13 3.09 2.97 2.92 2.76 2.71 2.66 2.51 2.47 2.17 2.12 1.91 1.87 1.82
15
25 25 20 20 20 20 20 20 10
10
15 15 10 10
10 10 20 10 40 10
20 80 20
10
100 80 30 60 70 15
10 ~.
30 10 10
10 26 10 25 10
15 10
in ~-
10 10 15 10 100
5 15 10 20 20 10 10 15 50 20 40 30 55 30
30 10 10 10
10
15 20
10
d 1/11 1.76 10 1.73 10 1.66 10 Cdr(POd)2 4.31 30 4.25 15 4.18 5 3.96 15 3.83 20 3.80 15 3.55 25 3.41 70 3.35 85 3.29 100 3.22 20 3.14 60 3.09 15 2.99 35 2.95 60 .. 2.92 15 2.89 40 2.84 20 2.65 50 2.64 55 2.62 25 2.58 50 2.54 10 2.50 25 2.44 25 2.42 25 2.14 20 2.10 15 2.09 20 2.03 20 1.99 15 1.98 20 1.97 30 1.93 20 1.92 20 1.90 30 ~. 1.88 20 1.86 15 1.84 15 1.77 10 1.71 20 1.64 20 1.60 10 1.58 10 1.44 20 1.24 10 1.14 10 Cd,(OH)(PO,)r 4.65 10 4.03 60 3.81 25 10 3.32 3.07 35 3.05 65 2.77 100 2.71 75 2.69 85 2.24 10 2.02 10 2.00 10 1.91 30 1.86 20 1.85 15 1.79 20 1.78 20 1.76 25 1.73 25 1.66 10 1.53
1.51 1.46 1.45 1.42 1.27 1.23 1.21
10 10
10 15 25
10
10
10
1-04001, and later ascribed to the compound Cda(PO4)n.4H20 (9). However, the precipitation of a crystalline tribasic cadmium orthophosphate from solution was not achieved in this work. A comparison of the pattern listed for Cda(P04)2 by Hanawalt et a2. (3) to the pattern listed herein for Cd&2(P04)4(HzO), reveals some marked similarities especially in the low d-values. Since i t has been shown that Cd&(P04)4(HzO), is the stable cadmium phosphate obtained from solution over a wide range of concentration, temperature, and p H (8), i t seems likely t h a t the compounds reputed (5, 6, 9) to be hydrates of Cd3(P04)2 were, in fact, the compound, C ~ ~ H ~ ( P O ~ ) J H Z O ) ~ . The characteristic x-ray diffraction pattern for (CdHP04)3."Ha, especially the very strong line a t 12.5A., which is not present in either the starting cadmium ammonium phosphate hydrates or CdzP207,lends credence to the existence of (CdHPOJa.NH3 as a distinct specie formed during the pyrolysis of the cadmium ammonium phosphate hydrates to CdZP207. Hydroxyapatite via Hydrolysis. Cadmium hydroxyapatite was easily prepared by the hydrolysis of (CdHP04)3,3NH3.3H20 by refluxing in water. The diffraction pattern of the hydroxyapatite is listed in Table I, and is in general agreement with the d a t a of Klement and Zureda ( 6 ) and with the more recent d a t a of Hayek and Petter (4). Condensed Phosphates from Monobasic Salts. Differential thermal a n d thermogravimetric analyses revealed that the compound Cd(HzP04)z. 2H20dehydrates endothermically starting at 100" C. and is converted to the anhydrous monobasic salt by 160" C. Above 160" C., Cd(H2P04)2 is converted successively into three distinct condensed phosphates. The first condensed phosphate is formed at 210" C. However, the material is unstable and deliquescent, dissolving in its own n-ater of hydroscopicity to form a viscous melt-like solution. It may be prepared with difficulty by carefully controlling the time and temperature of heating of the monobasic orthophosphate, and under ideal conditions i t corresponds to the formula, CdH2P207. However, chromatographic analyses showed mainly orthophosphate ions present and, therefore, in view of the unstable nature of the compound and the questionable analyses, no x-ray diffraction data are listed. Further heating resulted in the formation of two additional condensed phosphates-each of which exhibited a characteristic diffraction pattern. The first was formed at 410" C. and the second a t 550" C. However, neither could be uniquely defined. Thilo and Grunae (11) claim the isolation of a
~
Table II.
Table 111. Paper Chromatographic Analyses of Orthophosphates and Pyrophosphates
Three Strongest and Innermost Lines of Cadmium Phosphates
Compound
Innermost 8 . 9 (100) 8 . 8 (100) 8 . 7 (100) 6 . 0 (100) 8 . 2 (100) 4 . 6 (20) 6 . 1 (10) 1 2 . 5 (100) 4.31 (30) 4.65 (10)
cadmium tetrametaphosphate which converts above 700" C. to a high molecular weight polyphosphate. The d-spacings which they list for their compounds did not agree with the diffraction patterns found in this study. Furthermore, chromatographic analyses gave variable results with t h e presence of ortho, pyro, tripoly, tetrapoly, tetrameta, and high polymeric groups all being indicated. On the basis of these results, one could reasonably conclude t h a t the highly condensed phosphates react during dissolution resulting in hydrolysis and questionable chromatographic data. Since the combined information did not permit the
1st
8 . 9 (100) 8.8 (100) 8 . 7 (100) 6 . 0 (100) 8 . 2 (100) 2.94 (100) 3.09 (100) 12.5 (100) 3.29 (100) 2.77 (100)
2nd 8 . 3 (80) 2.88 (50) 2.88 (40) 4 . 5 (85) 2 , 7 2 (100) 3.09 (65) 3.26 (80) 2.76 (55) 3 . 3 5 185) 2.69 i85j
3rd 2.97 (55) 4.41 (30) 4.33 (3oj 3 .OO (45) 3.75 (30) 3.54 (50) 3.06 (80) 3.13 (50) 3.41 (70) 2.71 (75j
yo of Total Phosphorus as High polyPhosphate Ortho Pyro meric Cda(PO~)~.CdzP~O,54 45 1 CdJ'Lh 6 94 ... (CdHPOd)s.KHs 88 12 .. . Cda(PO& 100 . . . ,..
assignment of specific character to the three condensed cadmium phosphates, no x-ray diffraction d a t a are given. ACKNOWLEDGMENT
The authors are indebted to I. L. Ericson for the chromatographic analyses, and to J. E. Mathers and G. J . Meisenhelter for their chemical analyses. LITERATURE CITED
(1) American Society for Testing Ma-
terials, Philadelphia, X-ray Powder Data File, 1960. 12) Bernhart. D. K.. Chess. W. B.. ' ANAL.CHI&. 31, 1026 (19591. (3) Hanawalt, J. D., Rinn, H. W.,
Frevel, L. K., IND.ENQ.CHEX.,ANAL. ED. 10, 457 (1938). (4) Hayek, E., Petter, H., Monatsh. Chem. 90, 467 (1959). (5) ~, Klement. R.. Zureda. F.. 2. anora. u. allgem. Chem. 245, 229 (1940). (6) Rathje, W., Ber. 74B,357 (1941). (7) Ropp, R. C., Aia, M. A,, Hoffman, C. W. W.,Velcker. T. J., Moonev. R. m., ANAL.CHEM.'31, 1163 (1959).' (8) Ropp, R. C., Mooney, R. W., J . Am. Chem. Soc. 82, 4848 (1960). (9) Smith, A. L., Power, A. D., J . Electrochem. Soc. 101, 244 (1954). (10) Tartar, H. V., Lorah, J. R., J . Am. Chem. Soc. 51, 1091 (1929). (11) Thilo, E., Grunze, I., 2. anorg u. allgem. Chem. 290, 209 (1957). RECEIVEDfor revierr June 8, 1961. Accepted July 5, 1961.
Improvements in the X-Ray Emission Analysis of Cement Raw M i x GEORGE ANDERMANN' Applied Research laboratories, Inc., Glendale, Calif.
b The x-ray emission analysis of the so-called light elements in cement raw mix and other nonmetallics has been carried out to date primarily b y briquetting the powdered sample. With this approach, frequently, accuracy has been considerably worse than instrumental precision. The lack of agreement between precision and accuracy may b e ascribed to mineralogical differences and to inA new fusion homogeneity effects. method based on a favorable sampleto-flux ratio materially reduces the g a p between precision and accuracy and eliminates the need for type standardization. The fusion method also permits the use of synthetic standards.
T
first report on cement raw mix by Andermann, Jones, and Davidson (4) was on a select group of raw samples for the purpose of evaluating the Applied Research Laboratories production control x-ray Quantometer HE
(PXQ). Accuracy based on briquetted samples was within instrumental precision levels for MgO and A120,, b u t not for SiOp, CaO, and Fez03. Curley's report of a later d a t e (9) was definitive in illustrating the possibility of getting completely meaningless x-ray values from briquetted b u t unfused samples. Kester's (13) experiences indicated t h e necessity of using a very large library of standards, and experienced cement chemists to pick the correct type standards. Results b y Croke and Kiley (8) also demonstrated the need for closing the gap between precision and accuracj. for raw mix analysis. The problem of inaccuracy for soft region elements is not limited to cement raw mix (1, 8). I n every case cited the powdered sample was merely briquetted. Whereas claims have been made t o the effect t h a t type standardization is sufficient with briquetted samples, in view of the information presented below, type standardization can be regarded only as a useful s t o p g a p measure.
I n the author's laboratory attempts have been made to go one step beyond the simple briquetting of powdered cement raw mix samples. A number of samples were ground with a Spex mixer mill for different intervals. An increase in silicon intensity and a decrease in calcium intensity were noted. Grinding of t h e sample, however, did not improve t h e over-all accuracy. Whether or not matrix effects existed could not be determined. If interelement effects were present they were masked by other effects. THEORY
Analysis of Soft Region Elements in Powdered Samples. I n trying t o evaluate t h e problem of t h e analysis of powdered samples in general and of soft region elements in particular, i t is
Present address, Austin and Robinson Laboratory, San Gabriel, Calif. VOL. 33, NO. 12, NOVEMBER 1961
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