Characterization of Nonortho P3'in Neutron-Irradiated Potassium en Phos J. W. BORLAKD1, A. J. NIACKENZIE~,AND W. L. HILL Bureau of Plant I n d u s t r y , Soils, a n d Agricultural Engineering, U . S . D e p a r t m e n t of Agriculture, Beltsuille, Md.
F
OR several years radioactive phosphorus has been used extensively as a tracer t o follow the behavior of phosphorus. The source of P32customarily used is irradiated potassium dihydrogen phosphate, which may contain more or less P32 in forms other than orthophosphate. These carrier-free, contaminating forms, if allowed to persist in the labeled material, cause uncertainties that can well render the experimental results worthless. Dependable methods for measuring the total amount of contaminants are necessary. Also, methods for their identification are desirable, in order to predict the possible effect of the labeling process on their destruction. The efficacy of precipitation as phosphomolybdate, magnesium ammonium phosphate, and manganous phosphate for the separation of ortho-, pyro-, and metaphosphate and phosphite from one another was investigated in some detail. The results were used to identify the nonorthophosphate in irradiated potassium dihydrogen phosphate as dehydrated forms of phosphate-pyro- and/or metaphosphate. Methods are given for converting the nonorthophosphate into orthophosphate. That a part of the radioactive phosphorus in neutron-irradiated sodium orthophosphates is not in the orthophosphate form was noted by Libby in 1940 ( 5 ) and more recently by Thomas and Nicholas (8). Similar observations have been made on irradiated potassium dihydrogen phosphate ( 4 )and calcium phosphate (g, 6). The nonorthophosphate in alkali phosphate was considered to be phosphite ( 4 , 6 , 8 )and that in calcium phosphate to be hypophosphate (2). Phosphite is not readily oxidized t o orthophosphate in aqueous solution (9); thus, if the spurious form of radioactive phosphorus in potassium dihydrogen phosphate were indeed phosphite, it would not be readily destroyed by boiling the sample in dilute acid solution without the benefit of strong oxidizing agent. Nevertheless, the nonorthophosphate occurring in potassium dihydrogen phosphate irradiated by the Oak Ridge National Laboratory is converted to the ortho form in hot dilute acid solutions, as would be expected in the case of molecularly dehydrated phosphates, but not in the case of phosphites. The possibility of the presence of molecularly dehydrated phosphates was mentioned by Libby ( 5 ) . This discrepancy between the behavior of the nonorthophosphate constituent of irradiated potassium dihydrogen phosphate and its characterization as phosphite points to a need for an examination of the methods used for characterizing the several types of phosphorus compounds when they are present in tracer concentrations in orthophosphate samples. The work reported in this article was concerned primarily with the efficiency with which ortho- and pyrophosphates can be separated from each other and from the other types of phosphorus compounds by precipitation with molybdate, magnesium, and manganous ions. Also reported is the effectiveness of elevated temperatures as a means for converting the nonorthophosphate to the ortho form. 1 Present address, General Chemical Division, Allied Chemical & Dye Corp., Laurel Hill Research Laboratory, Long Island City, N. Y. * Present address, Southwestern Irrigation Field Station, P.O. Box 1339, Brawley, Calif.
1414TERIALS
KH2P3204. The irradiated units containing nonorthophoaphate were routine shipments received from the Oak Ridge Xational Laboratory. Half-life determinations showed the contaminant to be P 3 2 , Selected units which were found to contain no contaminant, as all the P32 was precipitated with ammonium molybdate, were also used. POTASSIUM METAPHOSPHATE. Prepared by heating nonrontaminated units of KH2P320a at 350' C. until the theoretical weight loss (13.24%) was obtained. POTASSIUM PYROPHOSPHATE. A weighed amount of noncontaminated KH2P3204 was dissolved in water, and the required amount of standard potassium hydroxide was added to form K2HP3*04. The solution was evaporated to drynem, weighed, and the residue heated a t 300' C. until theoretical weight loss (5.17%) occurred. PHOSPHOROES ACID. Prepared from phosphorus anhydride Tvhich was sealed in ampoules and irradiated a t the Oak Ridge Kational Laboratory. The contents of the capsule were highly colored with red phosphorus, much of whichwas formed by thermal decomposition when the ampoule was sealed. The capsule was carefully- broken, water was added to the material, and the mixture allowed to equilibrate for 68 hours. The mixture was filtered and the solution phase used in subsequent investigations. SEPARATION OF PHOSPHORUS COMPOUNDS BY PRECIPITATION
PHoSPHonfoLYBD.kTE PRECIPITATIOKS. The method used is described fully by RlacKenzie and Borlaiid (6). All radio assays were made by means of a solution counter. Carriers were added in all cases immediately preceding precipitation. Metaphosphate and pyrophosphate were found to be left completely in solution. Phosphite appeared in the phosphomolybdate precipitate in varying amounts (Table I). The precipitating solution, 1.25 S m-ith respect to nitric acid, apparently oxidized some phosphite to orthophosphate, a-hich subsequently precipitated. If the contaminant in neutron-irradiated potassium dihydrogen phosphate were phosphite, this method would not be applicable for determining the amount of the contaminant present.
TABLEI. BEHAVIOR O F RADI04CTIT7E PHOSPHOROCS ACID IN PHOSPHOMOLYBDATE PRECIPITATION (H8POa equivalent to 20 mg. P) SaHzP04 Present, Mg. P 5.5
11 22 44
Activity in Precipitate, % ' of Total S o carrier Carrier 30.1 28.5 41.3 39.7 43 7 40.5
-~
46 0
75 4
~IAGNESIUM A ~ i u o ~ ~ r PHOSPHATE mr PRECIPITATIOK. Solutions were made acid with hydrochloric acid, and magnesia mixture was added. The solutions were heated. neutralized to the end point of phenolphthalein (pH 9 to 10) with ammonium hydroxide, and allowed to stand overnight. The precipitates were separated by filtration and aashed with normal ammonium hydroxide. Filtrates and washings were combined and diluted to a definite volume for assay of radioactivity by solution counting. Results shown in Table I1 indicate fair separation of the phosphite ion, which remained in solution when about equal a.moupts of phosphate and carrier phosphite were added. The radioactwe
2726
November 1952
INDUSTRIAL AND ENGINEERING CHEMISTRY
TABLE 11. BEHAVIOR OF DIFFERENT RADIOACTIVE SOURCES IN MAGNESIUM AMMONIUM PHOSPHATE PRECIPITATION
KaPa01 (KP0a)a HsPOa a
I
None Na4PaOia None (KPOa)aa None HaPOsa
71.1 79.6 79.1 10.7 23.0 20.0
94.8 93.2 94.4 57.4 25.8 21.6
94.0 86 0 100 82.4 26.9 24.0
100 94.2 100 89.5 37.0 28.1
2727
phosphate and phosphite appeared in the solution phase. Metaphosphate (Table IV) was apparently hydrated and precipitated as the yrophosphate. A study made to determine whether or not a preci itation period could be used to follow this hydration indicatezthat an overnight period was necessary for com lete precipitation of manganous pyrophosphate. Tfese results indicate that any phosphorus which precipitated with the manganous pyrophosphate under these conditions was a dehydrated form of phosphate.
starter
IDENTlFICATION OF NONORTHOPHOSPHATE IN 1RRADlATED POTASSIUM DIHYDROGEN PHOSPHATE
Equivalent to 20 mg. P.
Samples of several units of contaminated potassium dihydrogen phosphate were dissolved in water and boiled for varying periods of time as indicated in Table V. The amount of contaminant reTABLE 111. EFFECTO F PERIOD O F STIRRING ON PRECIPITATION maining was determined by the phosphomolybdate method and OF PYROPHOSPHATE AND METAPHOSPHATE WITH MgNH4P04.6H20 found to have decreased by being converted into orthophosPyrophosphate Metaphosphate, phate. Period of Stirring, P32 in ppt., Ppt. weight, P*z in Ppt., % mg.a % Hours An examination of the effect of heat, acidity, and oxidation was 87.4 29.7 0.5 85.4 made on several types of phosphorus compounds. Materials, 92.1 31.6 1.0 90.0 treatments, and results are shown in Table VI. The orthophos92.0 31.8 132.0 2.0 90.5 33.4 123.9 4.0 phate was determined by the colorimetric metavanadate method 37.9 90.4 95.4 8.0 89.4 38.2 89.0 16.0 ( 1 , 7 ) , and no radioactive tracers were used. The dehydrated a Total weight less weight of MgNHaPOa from orthophosphate added orthophosphate compounds in every case were being converted to orthophosphate. The phosphite and hypophosphite required the presence of an oxidant for conversion into orthophosphate. This TABLEIV. BEHAVIOROF DIFFERENTRADIOACTIVE SOURCES observation indicated that the contaminant in the irradiated IN MANGANOUS PYROPHOSPHATE PRECIPITATION potassium dihydrogen phosphate was a dehydrated form of phosActivity in Precipitate, % of Total phate. Activity Obtained in Presence of Analytical Solution - NapPlOi.iOH~0Equivalent to, Mg. -P The amount of the contaminant in three units of irradiated P82source Carrier 5.5 11 22 44 potassium dihydrogen phosphate was determined by the phosKH2POa None 0.0 0.0 0.0 0.0 phomolybdate method. Other aliquots of the units were also NaHaP04a 0.0 0.0 0.0 0.0 tested by the manganous pyrophosphate precipitation. Results 100 100 100 100 (KP0a)a None 100 100 98.5 (KPOa)aa 74.3 shown in Table VI1 indicate that the contaminant is a dehyHaPOa h*one 0.0 0.0 0.0 0 0 drated phosphate-pyrophosphate and/or metaphosphate. HsPOaa
0.0
0.0
0 0
0.0
Equivalent to 20 mg. P.
TABLE V. phosphorous acid used appeared to contain about 24% phosphoric acid. Pyrophosphate and metaphosphate were gathered in the magnesium ammonium phosphate precipitate to a very marked extent (Table 11), mainly because of hydration to the orthophosphate. Some occlusion of the dehydrated forms is indicated since the amount of activity increased with weight of precipitate. A study of the effect of time on the precipitation of magnesium ammonium phosphate indicated that stirring for 0.5 hour was as effective as overnight standing on the completeness of recipitation. The effect of time on the h. dration of the detydrated forms of phosphate was determined ?Table 111). There was but slight effect of period of stirring on the amount of radioactivity from the pyrophosphate appearing in the precipitate. This would ordinarily be interpreted as evidence that hydration was unimportant in the pyrophosphate removal. However, the wei hts of the precipitates make this conclusion doubtful. The pf ysical appearance of precipitates a t different stirrisg times indicated that yrophosphate was originally precipitated as magnesium pyroptosphate and was then hydrated to magnesium ammonium phosphate. The nature of this reaction and its roduots was not studied. The results indicate that about l o g o f the pyrophosphate and 62 to 70% of the metaphosphate is left in solution. Therefore the magnesium ammonium phosphate precipitation does not separate pyro- and metaphosphate from phosphite. MANGANOUS PYROPHOSPHATE PRECIPITATIONS. Solutions were made acid to methyl orange with hydrochloric acid, 10 ml. of manganous chloride (25 grams per liter) were added, and the solution was neutralized to p H 4.3 with a dilute sodium hydroxide solution. Five milliliters of acetone were added and the precipitation was allowed to proceed overni ht. Precipitates were separated by filtration and washed wit% man anous chloride solution (2.5 grams per liter). The filtrates a n d washings were combined and diluted to a definite volume for assay of radioactivity by solution counting. It was found that all of the ortho-
Time of Boiling, Hours
CONVERSION OF CONTAMINANT BY HEATINGIN
SOLUTION
No. 141
TABLE VI.
CONVERSION OF VARIOUSFORMS OF PHOSPHORCS TO ORTHOPHOSPHATE BY HEATAND OXIDATION
Material"
a b
Contaminant Remaining after Treatment, % No. 164 No. 165 No. 166 No. 167
Orthophosphate Present after Treatment, % Bromine 4Boiling Boiling (pH 1) boilingb 47 63 59 48 39 100 81 78 100 68 21 100 60 26 87 100 0 3.0 100 0 3.0
No treatment
200 micrograms of phosphorus present in each material. All boiling times were 1 hour.
TABLEVII. PRECIPITATION OF CONTAMINANT IN IRRADIATED POTASSIUM DIHYDROGEN PHOSPHATE WITH MANGANOUS PYROPHOSPHATE Sample 1 2 3 a
Contaminanta,
Dehydrated Orthophosphate,
Total Activity 4.62 7.63 21.07
Total%Activity of 4.40 7.93 21.05
% of
Separated by phosphomolybdate method (6).
INDUSTRIAL AND ENGINEERING CHEMISTRY
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T A 4 B L E 1'111. EFFECTO F IRR.4DIlTION CONDITIOXR O N THE h O U N T O F COSTAMIXAKT IN P O T A S S I L X DIHYDROGEN
PHOSPHATE
Irradiation Conditions Low neutron flux, l o w temperature High neutron flux, intermediate temperature High neutron flux, high temperature
Contaminant
of % Total Acti&
26.69 18.31 0.57
Vol. 44, No. 11
24 hours (Table IX). Since there was no x-eight loss or change in specific activity in any of the samples after the treatment, no material was lost by gasification. Therefore, the contaminant in irradiated potassium dihydrogen phosphate can be substantially eliminated by oven heating at temperatures low enough to prevent decomposition of the potassium dihydrogen phosphate. The same is not true of irradiated calcium phosphates (5,4 ) . ACKSO W LEDGM E h T
TABLE Ix
EFFECT
O F HEATO U COSTAVINlNT I N S E L T R O A I R R 4 D I 4 T E D POT4SSIUM DIHYDROGEY PHO SPH lTE
Temp , C. Room temp. 40 60
108 125 150 175
Contaminant 70 of Total hcti&ty 21.08 20.26 19.38 6.64 1.50 1.01
The potassium metaphosphate and potassium pyrophosphate used in this stud) were prepared by G. -4.Wieczorek of the bureau. The phosphorus anhydride was kindly supplied by the Research Section, Division of Chemical Engineering, Tennessee Valley Authority, TTilson Dam, Ala. LITERATURE CITED
0.24
COSVERSION OF THE NONORTHOPHOSPHATE COYTAMINANT INTO ORTHOPHOSPHATE
Pile-irradiated units of potassium dihydrogen phosphate prepared by the Oak Ridge National Laboratory under different conditions of neutron flux and temperature showed (Table T'III) nonorthophosphate contents in an order inverse to that of the irradiation temperature. This indication of the beneficial effect of temperature in reducing the amount of nonorthophosphate was confirmed in the laboratory by heating 100-mg. samples of an irradiated potassium dihydrogen phosphate containing 21.07% of nonorthophosphate P32in an oven at different temperatures for
Barton, G. L., Anal. Chem., 20, 1068 (1948). Fiskell, J. G. A , , Science, 113,244 (1951). Fiskell, J. G. A , et al., Can. J . Chem., 30, 9 (1952). Fried, M., and MacKensie, A. J., Science, 111,492 (1950). Libby, W. F., J . A m . Chem. Soc., 62,1930 (1940). MacKenzie, A. J., and Borland, J. W., Anal. Chem., 24, 176 (1952). Mission, G., Chem. Ztg., 32,633 (1908). Thomas, W, D. S.,and Sicholas, D. J. D., Nature, 163, 7 (1949). l o s t , D. RI., and Russell, H., "Systematic Inorganic Chemistry," New York, Prentice-Hall, h e . , 1944. RECEIVED for review December 18, 1931. A C C E P T E D June 9, 1952. Presented before the Division of Fertilizer Chemistry a t the 120th JIeeting of the .kMERICAN CHElriIC.4L 8 0 C I E T Y , New York, N. Y. Investigation supported in part by U. S.Atomic Energy Commission.
f Liquid Ammo gh Pressu L. T. CARMICHAEL AND B. H. SAGE California Znstitute of Technology, Pasadena, Cal;,f.
T
HE determination of the viscosity of ammonia is of iniportance in many industrial operations involving transfer of energy or momentum. Measurements in the liquid phase \%*ere made by Plank and Hunt ( l 7 ) , Stakelbeck ( W ) , Fitzgerald ( 2 ) , Shatenshtein and coworkers ( 2 6 ) , and Pinevich ( 2 6 ) . These data have served to establish the characteristics of ammonia near bubble point for most industrial applications at low temperatures. The viscosity a t elevated pressures has not been investigated in detail except for the work of Stakelbeck ( 2 7 ) and a few measurements upon gaseous ammonia a t lo^ pressures which were reported by Rankine and Smith (18) and Wobser and Muller (28). These last data appear to offer the most satisfactory measurements presently available. Apparently no data exist describing the effect of pressure upon the viscosity of ammonia in the liquid phase a t pressures markedly above that of the critical state. The present investigation involves measurements for ammonia at states a t which the viscosity is greater than 500 micropoises throughout the temperature range from 40" to 220" F. a t pressures up to 5000 pounds per qquare inch. For these measurements the rolling ball viscometer first proposed by Flowers ( 3 ) and developed by Hersey ( 5 , 6 , 12) was employed. Such an instrument was used earlier for the measurement of the viscosity of liquid and gaseous hydrocarbons at
pressures up to 5000 pounds per square inch (21-23, 25). This equipment, vias revised to permit measurements upon substances with electrical conductivity high enough to prevent the use of electrical cont,acts for determining t,he position of the hall. In some respects the instrument, is similar to that of Hopplrr ( 7 ) which is used at, a much greater angle of inclination. Figure 1 depicts the schematic arrangement of the viscometer used for the present studies. I n principle, it consisted of a steel tube inclined at approximately 15' from the horizontal shov-n a t A , viithin which a closely fitting steel ball was permitted to roll. The lower end of the tube was closed by the manually operated valve, B , the stem of, vc-hich extended outside the agitated oil bath, C. The fluid TT-ithin the system was circulated by means of a three-stage centrifugal pump, D, which was driven a t approximately 1200 r.p.m. t,hrough the water-cooled, pressurecompensated, shaft-sleeve unit a t E. The details of the arrangement of the ground joint are illustrated in Figure 2. This pump was used to return t,he ball to the upper end of the tirhe after a measurement of roll time. It was not operated while measurements were being made. Three symmetrically located cooling units like the one shown in this figure were provided for the circulation of water to prevent overheating of the joint. I n order to avoid leakage betvieen the shaft and sleeve, E , of Figure 1,
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