NOTES
J. Phys. Chem. 1960.64:187-188. Downloaded from pubs.acs.org by UNIV OF SOUTH DAKOTA on 09/13/15. For personal use only.
Jan., 1960 citrate-0.1 N sodium hydroxide buffer of KolthoffVleeschhouwer and (c) 0.1 M potassium biphthalate -0.1 N sodium hydroxide buffer of Clark-Lubs. According to our results, SCMC can form a soluble complex with albumin only in the acetate buffer, while DS can form the complex in all buffer systems except in potassium biphthalate-sodium hydroxide buffer, the ionic strength of which is 0.18. The mobilities of albumin, DS, and the complex of them measured in solutions mixed a t various concentrations are given in Table 111. When the concentration of DS is between 0.125 and 0.25%, we could observe only one pattern in all buffer systems; the mobility of this single peak was intermediate between those characteristic of albumin and DS, corresponding to that of the soluble complex. As seen in the table, the mobility of the soluble complex in solutions containing free albumin and no free DS differs considerably from the mobility in solutions containing free DS and no free albumin. This result may arise from the differences in the viscosity of solutions and in the proportion of albumin and DS in the complex. TABLE I11 COMPLEX OF SERUM ALBUMINA N D DS-2 Ionic Buffer str. Acetic acid0 10 sodium acetate Succinic acid23 sodium borate Monopotassium 24 citrate-NaOH
Albumin concn.
(%)
0 83 83 83 83 83 83
AT
pH 5.6 A N D 0"
ComDS-2 Albumin plex 09-2 ooncn. (%) u X 105 u X 105 u x 106 0 40 -10 4 -16 8 0625 -2 8 4 2 375 9 9 -15 6 0625 -3 8 5 1 40 - 9 4 -151 0625 -4 3 5 9
-
At present, we cannot separate the specific effect of buffer anions due to binding on albumin from their non-specific effect due to screening. At least apparently, howel-er, we can arrange various anions in the order of the affinity to albumin: acetic ion, SChlC, succinic ion and citrate ion, DS, biphthalate ion. Discussion Thus, we found that the composition of buffer has a considerable influence on the formation of soluble complex between polyanions and albumin, particularly through the specific interaction between small anions and albumin. The order of affinity of various small anions and polyanions is determined. Special attention must be paid to the difference between DS and SCMC. This means that the -SO, groups on polyanions have a stronger affinity to albumin than -COO- groups. A similar phenomenon was found in the interaction between fibrinogen and these polyanions as reported in the previous paper.2 There we assumed that -SOS- groups have a stronger tendency to make hydrogen bonds with amino groups on protein than -COO- groups. A similar situation is expected in the present case. Acknowledgments.-I am very deeply indebted to Prof. Inoue for measuring the molecular weights of polyelectrolytes by the osmotic pressure method. It is a great pleasure to acknowledge the advice and discussion of Prof. Oosawa and Dr. Imai of Nagoya University.
187
THE ENRICHMENT OF LITHIUM ISOTOPES BY ION-EXCHANGE CHROMATOGRAPHY.' 11. THE INFLbTENCE OF TEMPERATURE ON THE SEPARATION FACTOR BY D. 8.LEE Chemzstry Dzvzsion, Oak Radoe Natzonal Laboratoru, Oak Rzdge, Tennessee Received September 16, 1959
Equilibrium constants for isotopic exchange reactions generally decrease with increasing temperature.2 The manner in which the equilibrium constant of a reaction depends on temperature is readily deducible from thermodynamics. The van? Hoff reaction isochor defines the temperature coefficient of In K, Assuming that AHo is independent of the temperature or that it varies only very slowly with the temperature, the equation may be integrated between two temperatures. This integration is valid if the temperature range is not large. AHo therefore can be determined from the slope of the line obtained by plotting log Kc against 1/T. The heat of isotopic exchange is naturally quite small. Glueckauf13using the data of Betts, Harris and Stevenson4for YaZ4and NaZ2separation by ion exchange, has calculated the heat of isotopic exchange to be 0.4 cal./mole. The effect of temperature on the equilibrium constant (a)for the reaction 6Ti(H20):
+ ?Li(H*O):R-
7Ii
+
(H*O),+ 6Li(H20): R-
where x > y, and R- are the exchange sites on the resin, was measured in a series of isotopic separation experiments performed a t several temperatures between 3 and 59". The method used in these experiments was described in the previous paper.5 SlJllMARY O F
Tzmp..
C.
3 20
TABLE I EXPERIMENTS T O DETERMINE T H E EFFECT OF TEMPERATITRE ON (Y Flow rate 10-3,cm./sec.
1.13 1 42 1.92
Plates
1400 2000
(Lis/Li')res. (Lio/Li')aq. (a)
1.0033 1.0031
1900 1,0028 1700 1 ,0026 2.02 59 Experimental One column was used in these experiments. Constant temperature water ( f0.3') was circulated in a jacket around the resin column. The resin was analytical grade sulfonated polystyrene-divinglbenzene Dowex X-16 ground to 200-400 mesh. The resin column dimensions were 19 mm. i.d. and 1080 mm. long. The resin was washed thoroughly with 0.25 N HC1 before adding 1 ml. of 8.75 N LiCl as the lithium band to the top of the column. The eluent in each experiment was 0.25 N HCl. The temperatures a t which the experiments were made were 3, 20, 40.5 and 59". The analyses were made a8 described previously P 40 5
(1) This paper is based on work performed for the U. S. Btomic Enprgy Commission by Union Carbide Corporation. (2) H. C. Urey, J . Chem. Soc., 562 (1947). (3) E. Glueckauf, Trans. Faradag SOC.,6 4 , 1203 (1958). (4) R. H.Betts, W. E. Harris and M. D. Stevenson, Can. J . Chem, 34, 65 (1956). (5) D. A. Lee and G. M. Begun, J . A m . Chem. Soc.. 81,2332 (1459).
NOTES
188
sideration to the measurement of acidity in DzO with ordinary electrodes. We have recently learned that this latter problem was considered some time ago by Hart, and by R. B. Fischer and R. A. Potter but the results are available only in special publications.’.*
0.0045
0 0044
Experimental All measurements were made with a Beckman Model G pH meter rt.t 25’. The Beckman No. 39166 (old No..l9166)
d 0.0013
J. Phys. Chem. 1960.64:187-188. Downloaded from pubs.acs.org by UNIV OF SOUTH DAKOTA on 09/13/15. For personal use only.
0.0042
30
3 2
34
36
38
4o3/r. Fig. 1.-The
VOl. 64
log of
Q!
as a function of 1Os/T.
Results and Discussion The results of these experiments are summarized in Table I. The uncertainty in the isotopic equilibrium constants is estimated to be less than one digit in the last decimal place shown. As expected, the data show an inverse dependence upon temperature. By plotting log a vs. 1/T, a straight line was obtained, as shown in Fig. 1. The heat of exchange calculated from the slope of this line was 2.26 cal./ cal./mole degree at mole and -AS was 1.81 X 25”. These results are slightly higher than those given by Glueckauf3 for the Na2z-Na24exchange, and doubtless reflect the greater mass difference ratio ( a M / M )which exists between the isotopes of lithium as compared to NaZ2and NaZ4. USE OF GLASS ELECTRODES TO MEASURE ACIDITIES IN DEUTERIUM OXIDE’,’ BY PAULK. GLASOE~ AND F. A. LONG Department o f Chemistry, Cornell University, Ilhaca, New York Received August 86, 1969
Recent studies have shown that a conventional glass electrode apparatus can be used to give fairly precise values of acidity in aqueous solutions, particularly when only relative values of the acidity are needed.4*6 One situation where it would be helpful to have additional data on relative acidities is for solutions of weak acids and bases in the solvents DzO and H20. We have therefore investigated the applicability of the glass electrode to measurement of acidity in D20 solutions. A general study is already available on some of the properties of glass electrodes in Dz0,6but it does not give much con(1) Supported in part by a grant from the Atomic Energy Commiesion. (2) Preaented a t the 136th meeting of the American Chemical Society, Atlantic City, September, 1959. (3) National Science Foundation Science Faculty Fellow a t Cornell University, 1958-1959. (4) E. Grunwald, J. Am. Chem. Sac., 73, 4934 (1951). ( 5 ) A. L. Bacarella, E. Grunwald, H. F. Marshall and E. L. P u r lee, THIS JOURNAL,62, 856 (1958).
glass electrode and saturated calomel electrode combmatlon was used for all measurements, unless otherwise noted. The pH meter was standardized with conventional buffer mixtures chosen to be close to the range of the pH measurements. Reagent grade chemicals were used without further purification. Formic acid was redistilled and maleic acid, aniline hydrochloride and pyridinium perchlorate were recrystallized. The DzOwas 99.5 atom % ’ deuterium. Solutions of NaOD were made by passing water vapor over sodium. Other solutions in DzO were made by dissolving the anhydrous hydrogen compound (except for hydrochloric acid where a concentrated aqueous solution was diluted). For the low concentrations studied, this did not change the deuterium content by a significant amount. All concentrations are in moles (or equivalents) per liter.
Results and Discussion Glass Electrode Measurements in Solutions of Strong Acids.-Solutions of roughly 0.01 M hydrochloric acid in H20 and in DzOwere prepared by dilution and the exact concentration of acid was determined by titration with standard base. The averages of several pH meter readings with the standard electrode combination are given under (a) of Table I. For solutions of comparable acidity TABLE I GLASSELECTRODES IN SOLUTIONS OF HYDROCHLORIC ACID I N &o AND I N D20 Solutions are 0.00976 M HC! in HnO and 0.00983 M DC1 in D20;pH meter standarized mth pH 4.00 phthalate buffer
-Av.
rdg8.-
HIO soh. DzO eoln.
(a) Standard glass electrodeBeckmann No. 39166; 39168 calomel (b) Beckmann 1190-80 glass electrode; 1170 calomel (c) Beckmann type E glass electrode; 1170 calomel (d) “Synthetic” 1190-80 glass electrode; 1170 calomel
Difference
2.08
1.69
0.40
2.08
1.69
.39
2.02
1.62
.40
2.13
1.73
.40
the pH meter reading in DzO solution is 0.40 pH unit lower than in H 2 0 solution. To determine whether this difference was characteristic only of this particular electrode system, these same solutions were measured using various glass electrodecalomel electrode combinations. The results are given in (b), (c) and (d) of Table I. It is apparent that the difference is constant for the different electrodes, within the error of reading the meter. The “synthetic 1190-80“ electrode in (d), Table I, is an ordinary Beckman 1190-80 electrode from which the internal solution was poured out and replaced with a solution of 0.100 M HC1 in HzO. The (6) D. Hubbard and G. W. Cleek, J. Research Natl. Bur. Standarda. 49, 267 (1952).
(7) R. G . Hart, Nat. Res. Council, Canada, C R E 423, June 1949. (8) R. B. Fiacher and R. A. Potter, A.E.C. document NODC-715, Sept. 12, 1945.
