buffered papers. Many other controlled separations can be carried out (Tables I and 11). ACKNOWLEDGMENT
The authors are indebted to Carmine Auricchio for the photographic work. LITERATURE CITED
(1) Block, R. J., Durrum, E. L., Zweig,
G., "Manual of Paper Chromatography and Paper Electrophoresis," Academic Press, New York, 1955.
The System
2 Clark, W. M., Lubs, H. A., J . Bacteriol2, 1, 109, 191 (1917). ( 3 ) Hais, I., Macek, K., "Chromatografia papirova," Xakladatelstvi Ceskoslovensk6 Akademie, Prague, 1954. (4) Lederer, E., Lederer, M., "Chromatography," Elsevier, Houston, Tex., 1953. ( 5 ) MacIlvaine, T. S., J . Biol. Chem. 49, 183 (1921). (6) Schmall, Morton, Pifer, C. W., Wollish, E. G., ANAL. CHEX 25, 1486 (1953). ( 7 ) Schmall, Morton, Wollish, E. G., Shafer, E. G. E., Zbid., 28, 1373 (1956).
(8) Soerensen, S. P. L., Compt. rend. trav. lab. Carlsberg 8,41 (1909). (9) Strain, H., Sato, T. R., ANAL. CHEM.28, 687 (1956). (10) Turba, F., "Chromatographische Methoden in der Protein-Chemie, einschliesslich verwandter Methoden wie Gegenstromverteilung, Papier-Ionophorese," Springer, Berlin, Gottingen, Heidelberg, 1954.
RECEIVED for review October 20, 1956. Accepted December 13, 1956. Division of Analytical Chemistry, 130th Meeting, ilCS, Atlantic City, N. J., September 1956.
Na pht haIene-T hia na pht hene
S. V. R. MASTRANGELO and R. W. DORNTE Barreff Division, Allied Chemical & Dye Corp., Glenolden, Pa.
A solid solutions treatment for calorimetric melting point data was verified for the system naphthalenethianaphthene. The solid solutions phase diagram, including liquidus and solidus lines, was also determined. Theoretical analysis permitted an accurate prediction of the solid-liquid equilibrium. The heat of fusion was determined as a function of composition. The use of these data for the evaluation of purity of naphthalene i s presented.
T
of freezing point a s a specification for the evaluation of purity depends upon knowledge of the character of the impurities present and their behavior in solution with the major component. The formationof solid solutions is 3 serious deviation of a system from the results predictable by the ordinary form of the melting point equation : HE USE
Log,,Nl = 2,00000
'
- 2.30209 A% 1 1 + BAL( (1)
where iYl = mole per cent purity to
At
A
3
- ti
c.
=
freezing point depression,
AH A degrees-'
RTO2
where AH, = heat of fusion of the major component, calories per mole To= freezing or melting point of 100.0 mole % major component, O K.
794
ANALYTICAL CHEMISTRY
( L W ~ )=~difference in molar heat capacity between liquid and solid at To The system naphthalene-thianaphthene was described in the liquidus region ( 2 ) , and the only reference to solid solution formation (8) gave no specific information in the solidus equilibrium region. The present investigation used both the calorimetric ( 1 ) and the freezing curve met'- ods to determine the equilibrium regions bounded by the liquidus and solidus curves. Application of the analytical treatment (6) of calorimetric-melting point data for a dilute impurity forming solid solutions n a s verified for this system. EXPERIMENTAL
Apparatus and Procedure. An adiabatic calorimeter was used ( 5 ) . The method of Aston, Cinnes, and Fink ( I ) for plotting energy input vs. equilibrium melting temperatures was used t o determine the liquidus and solidus temperature. Cooling curves were plotted a t two concentrations so t h a t t h e equilibrium points were approached from both sides. The cooling curve method employed an air-jacketed test tube and stirrer, and an KBS-calibrated, short-range thermometer to define the liquidus line over short composition intervals. Materials. Refined, liquid naphthalene (Barrett Division. Allied Chemical & Dye Corp.) was further purified by slow freezing in a n insulated Dewar flask, discarding the central core. This procedure was repeated four times in successively smaller Dewar flasks. The thianaphthene (Jefferson Chemical Co., Inc.) was purified by frac-
tional distillation. I t s freezing Doint v a s 31.40" C. Molecular Sieve, 4ii powder (Linde Air Products Co.) was used to drv samples; 2 grams were required f i r every 50 grams of sample. "
1
SOLID SOLUTIONS TREATMENT T O NAPHTHALENE
A calorimetric purity determination was carried out (5) on a 36-gram sample of the purified naphthalene. Equilibrium temperature was plotted against the reciprocal fraction melted (Figure 1). The melting point obtained by extrapolating the best straight line through these points was 80.081' C., while the derived melting point of 100.00 mole % naphthalene was only 80.193" C. Other reported naphthalene freezing points are 80.290" C. ( 7 ) and 80.287' C. (4. Figure 1 indicates the presence of solid solutions. The treatment of Rlastrangelo and Dornte (6) was applied
RECIPROCAL fRACTION MELTED,+
Figure 1 . Equilibrium melting curve for naphthalene sample
equilibrium temperatures us. the funcTable I.
Solid Solutions Treatment for Dilute Impurity in Naphthalene -+YK ( R K+ Y > -1
1-K 0.55892 0.66546 0.77196 0.88096 0.98927 1.21686
Y 0.34206 0.44860 0.55510 0.66410 0.77241 1.00000
C. 79,8781 79.9443 79.9911 80.0246 80.0538 80 09% 80.287* t,,
1,7893 1.5027 1.2954 1,1351 1.0108 0.82179
O
79.878 79.944 79.991 80.025 80.054
1
tl.00 - t 0 . 5 0 2 tl.00 - f0.50 1) '1 = 3 if0.50 - to.25 - 2 2 (tO.60 - t0.33 = 79.868 (Figure 1) Ll.00 = 80.106, t0.50 = 79.969, 1 (0.137 K = jo,lo3 - 11 = 0.17821
K
=
--
(I
* c
- 0.21686 1-K Extrapolated from solid solutions plot. Calculated bv solid solutions treatment K Read from sensitive plot of t, us.
(n g).
-1
tion
(rK K + y)-l gives a straighter
line, from which better values of t1.00, t0.50, and can be obtained and hence, a better value of K recalculated. Table I1 illustrates the calculation of to, the melting point of 100 mole % naphthalene (nitrogen saturated, 1 atm.), and X " , the total mole fIaction of impurity. By this method to was 80.287' C.; this melting point is in excellent agreement with the other literature values. The total mole fraction of impurity was 0.0042. The impurity mas identified as thianaphthene by mass spectrometry and its concentration was 0.004 mole fraction by infrared spectroscopy, confirming the calorimetry result. PHASE DIAGRAM
Table II. Calculations by Solid Solutions Treatment of Naphthalene
(1) Calculation of to.
+
t. =
tl.00
to =
80.098
(tl.00
- t0.60)
(1 + K ) ~
(1
- K)
+ 0.130a):;;:( __80.098
t o = 80.287' C.
=
+ 0.189
[Literature values. Glasgow, StreifT, and Rossini ( 3 ) = 80.290; Herrington, Densham, and Malden (4)= 80.287 f 0.002" C.]
to these same data with the results shown in Tables I and 11. The terminology used has been described in ( 6 ) . Table I illustrates the calculation of distribution constant K of the impurity between the solid and liquid phases from tl.ao, tO.50, and t0.33, or from t1.00, t0.60,and where t and subscripts refer to equilibrium temperatures a t various fractions melted. A plot of
To confirm the predictions of the solid solutions treatment ( 6 ) and to evaluate the freezing point as a measure of the purity of naphthalene, the phase diagram for the system naphthalenethianaphthene, on the naphthalene side, was determined (Figure 2). The average deviation of experimental points from the smooth curves was h0.5 mole %. The smooth liquidus line incorporates the data of Franck ( 2 ) .
(2) Calculation of Xi,total mole fraction of impurity. AH 1+K = -7(t1.W - tO.60) RT, (1 - K ) * 1.18421 X';= 0.0181 (0.130) 0.66551 X i = 0.0042 mole fraction impurity (confirmed by infrared spectrometry) Purity = 99.58 mole 70.
x':
~
~
a Xew values of tl.0o - t0.50 and K calculated from solid solutions plot.
Table 111. Liquidus Curve b y Test Tube Freezing Point Method
a
Freezing Pojnt, t , C. 79.78 79.31 78,98 77.69 76.50 72.07 67.57 63.90 58.84 55.69 48,37 42.16 36.46 32.83 30.54 30.22 30.39 30.74 By synthesis.
Naphthalene, Mole yoa 99.20 98.18 97.33 94.34 91.60 81.60 72.69 65.52 56.56 51.28 38.58 27.89 18.97 13.53 9.83 7.59 5.92 3.00
3
Figure
2.
Naphthalene-thianaphthene
Table IV.
Composition, Mole 7G Kaphthalene 100.00 99.58 94.44 80.95 59.74 34.70 34.70 37.07 9.2
phase
diagram
Solid-Liquid Phase Diagram
Liquidus @e, C. 80.287 80.098 77 89 72.20 61.26 46.60 46.63 29.88 (eutectic)
Solidus Line, O
c.
80.287 z9.27 12 30 58.00 41.10
...
29'88 (29.88)
Method Calorimetric Calorimetric Calorimetric Calorimetric Freezing curve Calorimetric Freezing curve Calorimetric Freezing curve
VOL. 29, NO. 5, M A Y 1957
795
Table V. t,
c.
-O
I 3
70 65
60 55
50 45
N,(I)a
Y,,(sY
0 878 0 770 0 670 0 578 0 488
0 962 0 923 0 878 0 831 0 782 0.718 0.651 0.573 0.481 0.370
0,401
0.324 0.246 0.169 0,092
40
35 80
Temperature Dependence of Thianaphthene Equilibrium Distribution Constant
.V
