tion of the dextrose, levulose, and sucrose was then observed under ultraviolet light. Using the location of dextrose on the outer strips as a guide, the position of the dextrose on the center portion of the chromatogram was determined. The portions of paper containing dextrose were clipped off and the dextrose on each was transferred to glass fiber paper and analyzed as described above. The results are given in Table 11. The floral origin of the honey samples is not known; however, the dextrose found is of the same order as that reported by J$71~ite and Maher (3). I n products such as honey n here large quantities are available, micromethods of analysis are not generally used because of their lower precision. However, when a n individual sugar is quantitatively separated prior to its determination, the accuracy of the results depends solely upon the method of analysis. Paper chromatography piovides such a separation of microquantities. TVhen using the conventional selective methods, one must consider the
Table II. Determination of Dextrose in Sugar Mixture and in Honey
%
Dextrose, Mg. Dextrose Presin Dextrose-suerose-levulose mixture Honey I Honey I1
ent
Found
1
1.00 1.04 0.98 0.938 0.930 1.28 1.31
30 (approx,) 23.45 23.25 32.0 32.75
effect of all of the constituents on the results. White, Ricciuti, and Maher (4) made an extensive investigaton of the dextrose and levulose content of 15 honey samples from different floral sources. I n this study they compared the results obtained by five different macroselective methods. By statistical nieans they were able to determine the method that gave the greatest precision. However, because nondextrose constitu-
ents have a different effect ou the individual methods, the authors were unable to tell which one gave results closest to the actual composition of the honey. White and hlaher (3) later partially resolved this problem by separating honeys into their monosaccharide, disaccharide, and polysaccharide constituents by means of carbon-Celite columns. The procedure for transferring a sugar onto glass fiber and subsequently adding the sample and glass fiber to the react8ion mixture is applicable to other sugars of this mixture as well as to any sugar mixture that can be separated on a paper chromatogram. LITERATURE CITED
(I) Sattler, L., Zerban, F. K . , Ax.4~. CHEJI.24, 1862 (1952). (2) Soniogyi, If., J. Biol. Chem. 160, 61 (1945). (3) White, J. IT.,Jr., Maher, J., J . Assoc. Ojic. Agr. Chemists 37, 498 (1954). (4) Khite, J. W., Jr., Riceiuti, C., Maher, J., Ibid., 35,859 (1952). RECEIVEDfor review May 9, 1956. rlccepted October 12, 1956.
Coprecipitation of Radium with Barium Sulfate LOUIS GORDON Syracuse Universify, Syracuse, N . Y KEITH ROWLEY Brookhaven National Laborafory, Upfon, L. I . , N. Y.
b The technique of precipitation from homogeneous solution was used to determine the nature of coprecipitation of radium with barium sulfate. The distribution of radium between the aqueous and solid phases follows the law of Doerner and Hoskins. The value of A, the distribution coefficient in the Doerner-Hoskins equation, was found to b e constant within experimental error over the range in which the fraction, f, of the barium precipitated was 0.03 to 0.96. Its value is 1.21 f 0.009f under the experimental conditions a t 90" C.; its value a t other temperatures obeys the relationship, loglo X = 2 2 0 / ( 2 7 3 t ) - 0.520, for values of t between 50" and
+
90" C.
T
HE coprecipitation of radium with barium sulfate during the slow precipitation of the latter has been previously studied. Doerner and Hoskins ( 2 ) have deduced that the distribution of radium between the solid and liquid phases should obey the relationship:
34
ANALYTICAL CHEMISTRY
where X is the logarithmic distribution coefficient and i and f represent initial and final solution concentrations. Another mode of distribution (10) is given by /Ra++\
D =
\Ba++)orystnl
(E+)
(2)
Ba++
where D is the homogeneous distribution coefficient. The two modes of distribution result from different mechanisms of attainment of equilibrium between solid phase and solution. There are two conditions under which the Doerner-Hoskins distribution equation is obeyed: The surface of the growing crystal is in equilibrium with the hody of the solution-i.e.,
(3)
and the rate of diffusion of ions n-ithin the crystalline lattice is negligible compared to the rate of precipitation. It is also usually assumed t h a t activity coefficients remain constant. Doerner and Hoskins utilized evaporation and cooling of saturated barium sulfate solutions in some experiments t o attain equilibrium between the crystal surfaces and solution. The data they obtained were not sufficient to prove the constancy of the logarithmic distribution coefficient over a n-ide range of "fraction of barium precipitated." Narques (6) also subsequently precipitated barium sulfate by an evaporation process; her data are shown in Figure 1,a. The values of the logarithmic distribution coefficients found by Marques for the evaporation process a t 20" C. were slightly higher than those found by Doerner and Hoskins; the latter investigators did not state the temperature at which their esperiments were conducted. Both Marques [cf. (6, Figure l,a)] and Doerner and Hoskins found smaller logarithmic distribution coefficients by precipitation
1
I
1
MARQUES' METHODS =PRECIPITATION METHOD, K :EVAPORATION
+
G2
t
K I
-
0
0
Y
1.5 -
0
o
5
m
"t
0
-
( k = 164-0026XFRACTIONl
LL
0
i i.
0
l9 17-
METHOD1
r
(b)
, 1
S U L F A M I C ACID M E T H O D HOMOGENEOUS DISTRIBUTION COEFFICIENT o = LOGARITHMIC DISTRIBUTION COEFFICIENT
1.8 -
x=
,,'
-
1
0
I
1.0 I
1
0.1
03
( X = I21 + O . O 0 9 x FRACTION) I
05 07 FRACTION OF BARIUM PRECIPITATED
Figure 1.
I
09
Distribution coefficients
Hypothetical curve for D obtained as described in texi from Equation 5
processes in which there was external addition of a reagent. Such processes favor "no enrichment," since the addition of each drop of precipitant can deplete the immediate area where it enters the solution of virtually all barium and radium ions. The technique of precipitation from homogeneous solution (3, 11) affords a means for attainment of equilibrium between crystal surface and solution. I n this study of the coprecipitation of radium with barium sulfate. the latter was precipitated from homogeneous solution by the hydrolysis of sulfamic
Table I.
acid (9). A specially devised cell was used t o effect complete separation of solid and liquid phases by centrifugation. The use of this cell permitted reliable independent measurements t o be made of the distribution of the radioactive tracer in the two phases and thus allowed a material balance. EXPERIMENTAL
Reagents. BARIUMSOLUTION. Barium chloride dihydrate, c.P., was purified by a single recrystallization. A standard solution was prepared which was found to contain 24.7 mg. of barium
Coprecipitation Data at 90" C. with Constant Amount of Sulfamic Acid Present.
Barium Precipitated,
7%
28 2 29.6
Reaction Time, Hours
3 5 3 5
x Filtrate data
Precipitate data
Ah
1 23 1 24
1 16 1 17
1 20 1 21
1 24 1 26
81 6 12 0 1 22 1 20 1 21 1 j3 81 SC i 5 1 36 1 32 1 3-1 1 92 93 5 12 1 1.18 1 18d 1 95 9 13 1 1 19 1 09 1 19 1 84 a 43.i mg. of sulfamic acid-i.e., 2.5 times the stoichiometric quantity required for complete precipitation of barium-used in each experiment. Unless otherwise specified, values for A and D represent averages of distribution coefficients calculated from both filtrate and precipitate data for a particular run. For "barium precipitated" less than loyo,counting data for precipitate only were used. For values greater than 90%, counting data for filtrate only were used.
KO KH&l added. Derived on basis of filtrate counting data only, because parts of precipitate nere lost.
per 10.00 mi. by evaporation of an aliquot of the solution to constant weight after addition of a slight excess of sulfuric acid. SULFAMICACID. The C.P. product was purified according to the method of Butler and coworkers (1). No visible opalescence was produced-except after many hours-upon addition of barium ions to a freshly prepared solution of the purified acid. The purity was also checked by titration with standard base. Ra~1u~1-223.Five millicuries of the radioisotope were obtained (Mound Laboratory, Monsanto Chemical Co., Dayton. Ohio) as a solution of the nitrate containing 10 mg. of barium nitrate. Dilute solutions of the radiumbarium mixture were prepared as required from a stock solution. The amount of barium introduced with rndium was negligible compared to the barium added in the distribution experiments. The half life of the radium was found to be 11.5 days which compares favorably t o the value of 11.685 found by Hagee and coworkers (4). OTHERREAGEKTS. All other chemicals were of either reagent grade or C.P. quality. Reaction Vessel. Figure 2 shows the combination reaction and centrifugation ve3sel used (I. Neyer, Box 318, %,ding River, L. I., N. Y.). The necessary reagents were placed in component A (reaction vessel), which !vas then fitted rrith a glass stopper. The neck of the vessel was then covered with a rubber bulb securely wired on so that the glass stopper was rigidly positioned. The yessel was placed in a brass cup which could be tightly sealed, placed on an agitator wheel (Walsh-RlcCafferty Machine Co., 160 Jayne Ave., Patchogue I,. I., N, Y.) in a thermostated bath ('t 0.1" C.), and the reaction vias allon ed to proceed for a given number of hours. After this, the vessel was removed from the bath, the stopper was removed, and the vessel was coupled with components B and C. Component B was fabricated with a fine frit, but :I filter paper circle prepared from K h a t man No. 42 paper was aliyays used to retain any fine particles. The three components were coupled using Teflon washers as spacers, taped togethei , placed in a 100-ml. Cornell-type centrifuge tube, and the liquid and solid phases were separated first by slon centrifugation and then finally a t 2000 r.p.m. for several minutes. Analyses of the two phases ITere made as s u l w quently described. Methods of Analysis. Barium in the aqueous phase mas determined by titration with (ethylenedinitri1o)tetraacetic acid (EDTA) according t o the method of Ronley and coworkers (7). Radium m-as determined by gamma counting using conventional scintillation techniques with liquid samples. Approximately 0.5 pc. of radium n as used in each run. Precipitation Rate Studies. Preliminary studies indicated that a favorable precipitation rate could be obtained n t BO" C with mixtures of barium VOL. 29, NO. 1, JANUARY 1957
35
chloride and sulfamic acid. These studies also indicated that the presence of ammonium chloride Tvould result in the production of large, readily filtered crystals. If ammonium chloride was absent, finely divided particles of barium sulfate were obtained which passed through the sintered-glass frit (fine) of the centrifugation vessel.
Figure 2. Reaction and centrifugation cell
I n a 27-ml. volume containing 25 mg. of barium, 0.5 gram of ammonium chloride, and a quantity of sulfaniic acid equivalent to 2.5 times that stoichiometrically required for complete precipitation, a rate was obtained such that approximately 50% of the barium was precipitated in about 4 hours. Somewhat over 12 hours' were required to precipitate 95% of the barium. Tables I to I11 show the times required under various conditions to precipitate the barium.
Procedure. Ten milliliters of solution containing 24.7 mg. of barium were introduced through a funnel into the reaction vessel. Kext, approximately 0.5 pc. of radium was introduced b y a 500-pl. pipet which was subsequently rinsed with 1500-pl. of water. The quantity of radium added corresponded, upon final dilution in the cell, to from 2 to 7 x lO-'3M. Sulfamic acid (solid) and 0.5 gram of ammonium chloride were then placed in the funnel and washed into the vessel with 15 ml. of water delivered from a pipet. Any water clinging t o the tip of the funnel was blown off with an air blast. The vessel was then stQppered and placed on the agitator wheel, as previously described. After a suitable interval of time the vessel was removed, and the solid and liquid phases were separated b y centrifugation. The liquid phase was immediately diluted to volume, and aliquots were taken for duplicate determinations of 36
ANALYTICAL CHEMISTRY
both barium (7') and radium. Sulfuric acid was added to the samples t o be analyzed for radium, and the solutions !?-ere evaporated until fumes appeared. The solutions were cooled and finally introduced into counting cells. The latter were cylindrical in shape, about 5 cm. in diameter and 2.5 em. in height, and fitted with a side opening having a standard taper stopper. After the radium solutions were placed in the cell, concentrated sulfuric acid was added to a mark on the side opening, and the contents were mixed and allowed to stand for 6 hours to reach radiochemical equilibrium. The cell was then placed in a holder designed t o obtain reproducible geometry, and the radium was determined with a scintillation counter. The solid phase-Le., the barium sulfate-was usually distributed between components A and B (Figure 2). About 3 t o 5 ml. of warm concentrated sulfuric acid was added to component A and distributed over the inner glass surfaces to dissolve the solid. Then the three components were coupled as before, and the sulfuric acid was centrifuged through the frit into component C. The addition of sulfuric acid and the centrifugation operation were repeated three more times. Finally, hot nitric acid was added to the reaction vessel and centrifuged. The latter acid dissolved any carbonaceous material, from the filter paper, not affected b y sulfuric acid. Finally, the acid mixture containing the radium was evaporated until fumes appeared and subsequently introduced as previously described into the counting cells. A counting standard containing radium in concentrated sulfuric acid was prepared in a similar manner for each independent series of measurements. RESULTS A N D DISCUSSION
The results obtained a t 90" C. are shown in Tables I and 11. Table I shows the data from 15 experiments in which, with the exception of two runs, the initial conditions rvere identical. In these two runs, the prior addition of ammonium chloride was omitted. The values of X and D from Table I are shown graphically in Figure 1,b.
Table II.
Barium Precipitated, c ,c
22.5 23.2 27.9 42 4 i i l
i
60 4 65 3
Coprecipitation Data a t
Reaction Time, Hours 16 3 16.3 21 . 0 6.5 1
0
96 8 5 8 5
Barium
1.0 B 1.0 B 4 36B i n R
i0
B
1 0 B 1 0 B
For fractions of barium precipitated less than lo%, and for those greater than 90%, only those distribution coefficients calculated. respectively, from precipitate and from filtrate data, were plotted. The values of X and D omitted in the preparation of Figure l,b, involve uncertainties because the calculations were based on the difference between two similar numbers. Within the range of 10 to 90% of barium precipitated, good agreement was obtained for the values of X based on either the precipitate or filtrate data. The equation for the least squares straight line through the X values in Figure l,b, is
x = 1.211 + 0.009,f
(4)
where f is the fraction of barium precipitated. Thus, X is constant within experimental error over the range 3 to 96% barium precipitated. The curve in Figure l,b, for D was determined from the equation
in which X was taken as 1.21. Equation 5 was obtained from Equations 1 and 2. Table I and Figure l,b, show that the coprecipitation of radium sulfate with barium sulfate, under the investigated experimental conditions, follows the Doerner-Hoskins distribution equation. The present data confirm the conclusion of Marques (6) in this respect. Contrary t o the behavior of the system, barium chromate-radium chromate, as observed by Salutsky and coworkers ( 8 ) , X for the barium sulfateradium sulfate system is independent of the fraction of barium precipitated. The value of remained reasonably constant when certain experimental conditions were altered. The effect of the absence of initially added ammonium chloride on the distribution coefficient is shown in Table I. Table
90" C.
with Varying Conditions
Reagent,s Added5 Sulfamic acid 1.0 s 1.0 0.57 S
s
0.8
0 6 2 5 2 5
s
s s s
Radium 1.OR 1.OR 1 . 0R 1.OR 1 0 R 0 1R 10 OR
x 1.19 1.18 1.31 1.22b 130 1 22b 1.20b
D 1.22 1.20 1.38 1.28 142 1 38 137
a Quantity of barium added corresponds to a multiple of B where B equals 24.7 mg. In the case of radium, R amounted to about 0.5 pc. of radium. S represents stoichiometric quantity of sulfamic acid required to precipitate added barium quantitatively. b Only filtrate data r e r e used in computing distribution coefficients because of partial
loss of precipitate.
I1 shox s the results of experiments in which the concentrations of barium, radium, and sulfamic acid were varied. The variation of A with temperature via9 also investigated. The results at 70" and 50" C. are shown in Table 111. Figure 3 s h o m the temperature dependence of A in the range 50" to 90" C. Because A is the equilibrium constant for the reaction Ra'-(aq.) Ba++(aq.)
At 20" C., the value of X calculated from Equation 6 is 1.69. This value compared favorably with the average value of 1.63 obtained b y lrarques in her precipitation experiments but not with the niean value of 1.92 obtained in her evaporation experiments. Because of the temperature dependance of A, the interpretation of data ohtained b y evaporation and cooling of saturated barium sulfate solutions as descrihed by Doerner and Hoskins (2) is doublful.
+ BaSOr(s) = + RaSOi(in BsS04) Table 111.
Coprecipitation at
Sulfamic Acid Addeda
Temperature,
c.
io
5 5iS
70" and 50" C.
Reaction Time,
Barium Precipitated,
Hours 10.3
28 3
%
h 1 33
D 142
a S represents stoichiometric quantity of sulfamic acid required to precipitate added barium quantitatively.
the experimental conditions of this type of precipitation process is evidence that the requirements of the DoernerHoskins distribution can be met. The real advantage of this technique of precipitation is that it permits close control of the rate of precipitation, thus preventing sudden, large concentration changes characteristic of a conventional precipitation process. Recently, Jucker and Treadwell (6) have also precipitated barium-radium sulfate mixtures using sulfamic acid. They concluded on the basis of radioautographs that radium was uniformly distributed within the barium sulfate crystal. If their experimental evidence is valid, i t means that the rate of diffusion of radium ions within the crystalline lattice is small enough so that the Doerner-Hoskins distribution is obtained but also large enough that the radium becomes uniformly distributed in the crystal. This seems highly improbamble. ACKNOWLEDGMENT
The authors wish to acknowledge the advice and assistance of Murre11 Salutsky, hround Laboratory, ;\Ionsanto Chemical Co., who was instrumental in securing radium-223, and of Garman Harbottle, Brookhaven National Laboratory. One of the authors (L. G.) gratefully acknowledges the support of the U. S. Atomic Energy Commission under Contract AT(30-1)1213. LITERATURE CITED
(1) Butler, i'vl. J., Smith, G. F., Audrieth,
L. F., I N D . ESG. CHEM., A N A L . ED. 10, 690 (1938). (2) Doerner, H., Hoskins, W., J. Am.
26
Figure 3.
28
220 273 f t ~
- 0.520
3.2
c4
Temperature dependence ofX
a plot of log,, h us. 1, T should be linear. The straight line shown in Figure 3 was obtained by a least squares calculation. I n performing this calculation, the value of X a t 90" C. was taken as 1.21 and weighted in accordance with the 15 experiments it represented. The equation for the resultant straight line is logloA =
30
iX 103
This investigation shows that precipitation from homogeneous solution is a useful technique for distribution studies in solid-liquid systems. T o obtain a distribution which follows the DoernerHoskins law, the rate of precipitation must be small enough to permit concentrations near the surface of the crystal to be essentially the same as those in the bulk of the solution, but large enough so that recrystallization is not significant. The fact that A remains constant under
Chem. SOC.47, 662 (1925). (3) Gordon, L., ANAL. CHEM.24, 459 (1952). (4) Hagee, G. R., Curtis, M. L., Grove, G. R., Phys. Rev. 96, 817A (1954). (5) Jucker, H., Treadwell, W. D., Helv. Chim. Acta 37, 113 (1954). (6) Marques, B. E., Compt. rend. 198, 1765 (1934). (7) Rowley, J. K., Stoenner. R. W., Gordon, L., ANAL.CHEM. 28, 136 (1956). (8) Salutsky, M. L., Stites, J. G., Martin, A. W., Ibid., 25, 1677 (1953). (9) Wagner, W. F., Wuellner, J. A., Ibid., 24, 1031 (1952). (IO) Wahl, .4.C., Bonner, N. A., "Radio-
activity Applied to Chemistry," Wiley, Kew York, 1951. (11) Willard, H. H., AXAL. CHEM. 22, 1372 (1950).
RECEIVEDOctober 25, 1955. Accepted October 26, 1956. XVth International Congress of Pure and A plied Chemistry (Analytical Chemistry), ksbon, Portugal, September 1956. VOL. 29, NO. 1, JANUARY 1957
37
