NOTES
May, 1957
OBSERVED
3.48 3.19 2.24 1.80 1.50 1.35 0.910
697
TABLE I MOLAREXTINCTION COEFFICIENTS, SULFURIC ACIDCONCENTRATIONS, ACTIVITYCOEFFICIENTS DERIVED QUANTITIES FOR 1.65 X 10-8 M Sn(1V) I N SULFURIC ACID 1.13 1.03 0.703 .554 .450 .400 ,248
6.70 6.02 3.98 3.12 2.56 2.26 1.45
0.0364 .0368 .0434 .0488 .0543 .0590 .0759
0.174 ,157 .130 .124 .124. .123 $130
0.067 .069 ,078 .085 .091 ,093 .lo5
0.102 .096 .089 .090 .093 .096 .lo7
AND VARIOUS
0.119 .llO .097 .097 ,099 ,101 .llO
0.648 0.743 1.02 1.33 1.41 1.51 1.56
In the course of studies of the mutual solubility of partially miscible solids it became necessary to measure the variation of lattice constant with composition for solid solutions of potassium bromide in potassium iodide. The only previous values of lattice constants in this system are those of Havighurst, Mack and Blake,2 but the range of compositions studied was very limited and the data inconsistent and meager. These two salts form an incomplete series of solid solutions at room temperaturea but their mutual solubility increases to complete miscibility at temperatures well below the melting point.4 By quenching molten mixtures of the two salts it is easy to obtain solid solutions over the entire range of composition at room temperature 0 2 4 6 8 10 12 14 16 even though the solids in the large central portion of (S04-)y,' x 108. this range are then metastable. Fig. - 1.-The deDendence of the observed molar extinction Reagent grade otassium bromide and potassium iodide coeifficient on sulfate ion activity.
of tin(1V) in perchloric acid, but in view of our later findings that SnS04++ is the predominant species in dilute sulfuric acid, we can hardly expect the limiting molar extinction coefficient, €1, in sulfuric acid to be the same as is observed in perchloric acid. In view of the values of the activity coefficients for 2-2 electrolytes and the fact that there is necessarily some uncertainty in the correction of them, we should probably accept €1 and Ki as representing orders of magnitude only. However, we have found that the treatment is not particularly sensitive to the magnitude of y+ and thus the scatter (Fig. 1) is probably experimental. Thus it seems safe to conclude that the &st spectral change does correspond to the formation of Sn(SOS2 from SnS04++and that the equilibrium constant is about lo2. The second spectral change should correspond to equation 2 and the interpretation which was offered in the previous work will still apply. This work was supported by the U. S. Atomic Energy Commission.
LATTICE CONSTANTS O F POTASSIUM BROMIDE-POTASSIUM IODIDE SOLID SOLUTIONS' BYEUQENEI T. TEATUM A N D NORMAN 0. SMITH Deparfmenf 01Chsmisfry, Fordhom University, New York,N. Y. Received December $0, 1866 (1) Presented before the Division of Physical and Inorganic Chemiatry of thc American Chemical Society at Atlantic City, September, 1966.
were recrystallizecPfrom water and dried. Various mixtures, weighing about one gram, were placed in Pyrex tubes (7 mm. 0.d.) sealed at one end, and melted together under vacuum. (This was necessary to revent decom osition and dimcoloration.) They ' were tgen sealed of! while evacuated, and quenched in mercury. Compositions which fell within the miscibility ga maintained their metastability for a period more than Lng enough to permit taking X-ray powder photographs. This was done using a G.E. XRD-3 unit with Cu Ka radiation, the wedge technique being ado ted in all cases. The films were measured wlth a G. E. Auorline Illuminator and the various lattice constants calculated. Simultaneously each sample was analyzed by potentiometric titration with standard silver nitrate, using silver and saturated calomel electrodes with an ammonium nitrate salt bridge. Both the bromine and iodide end-p0int.s were observed. Such analysis was necessary because the composition of the original mixture could not be relied upon after the heating under vacuum.
TABLP~ I LATTICE CONSTANTS OF KBr-KI SOLID SOLUTIONS
--_-
Cnm.
cnm.
position, mole fraction of KI
0.0000 .0707 ,0977 .2128 .2685 ,3352 .448 ,495
Lattice constant,
Dev. from additivity
A. A. x 108 6.599 ... 6.624 -8 6.641 -3 8 6.705 6.734 +ll 7 6.760 6.820 +15 6.848 +21
+ +
pc&on,
mole
fraction
of KI
0.568 .658 .740 .766 .878 .902 .918 1.000
Lattice constant,
A. 6.881 6.925 6.947 6.949 7.001 7.030 7.060 7.059
Dev. from sdditivity
Ax
10'
t2l +23
+- 122 -2
+16
+39
...
(2) R. J. Havighurst. E. Mack, Jr., and F. C . Blake, J . A m . Chsm. SOC.,47, 29 (3925). (3) M. Amadoti and G.Pampanini, Atti. accad. Lineei, 40, [I11 475 (1911). (4) J.
B. Wrcsnewsky, 2.anorg. Chem., 74, 95 (1912).
698
NOTES
Table I gives the resulting data. Each lattice constant is an average of the values calculated for the three or four lines with greatest glancing angle, and the average deviation for any one film was about 0.005 A. The inherent lack of accuracy of the wedge technique, however, is good reason for believing that the uncertainty in the lattice constants is about 0.008 A. The compositions are believed accurate to a mole fraction of 0.0002. The lattice constants for the pure components, viz., 6.599 and 7.059 A. for the bromide and iodide, respectively, may be compared with the most recent figures of the National Bureau of Standards166.6000 and 7.0655 A., at 25". Lack of temperature controlin thepresent work would not account for differences greater than 0.002 A. Except for some irregularity for the highest potassium iodide contents, the cause of which is not certain, the values lie on a smooth curve within experimental error. Shown also' in Table I are the deviations of the experimental values from those predicted by Vegard's rule of additivity. The positive deviations in the central composition range are believed to be real. (5) H. E. Swanaon and E. Tatge, "Standard X-Ray Diffraction Powder Patterns," Vol. 1, National Bureau of Standards, 1963, pp. 66, 68.
Vol. 61
been described.' The other alcohols have been described elsewhere.8
Results The results of measurements on six tertiary alcohols are shown in Table I. The first column after the compound name lists the integrated intensity A', in units of 1 X lo4 mole-' liter cm.-2. The second column lists the half-intensity width, AVII,, in units of cm.-l, and the third lists the frequencies of .band maxima, Y,. From the values of Awl, listed it is possible to apply wing corrections as described by R a m ~ e y .These ~ corrections would be of the same order of magnitude for all the compounds listed, and would not change the relative values of intensity appreciably. The relative in tensity values are probably correct to 0.02 intensity unit, while the values of vm are within 2 cm.-'. TABLEI RESULTS OF THE MEASUREMENT OF THE 0-H B ~ N INTEND SITY FOR SIX TERTIARY ALIPHATIC ALCOHOLB Compound
A'o
0.33 &Butylalcohol .25 Triethylcarbinol Triisopropylcarbinol .22 Diisopropylcyclopropylcarbinol .28 Isopropyldicyclopropylcarbinol .33 Tricyclopropylcarbinol .37 a In units of 1 X lo4 mole-' liter om.-*.
AVio
urn
(cm.-I)
(om.-')
22 19 25 24 25 20
3613 3617 3625 3622 3617 3620
THE INTENSITY OF INFRARED 0-H ABSORPTION FOR SOME TERTIARY Discussion ALIPHATIC ALCOHOLS; THE INDUCTIVE It is noteworthy that although different optics PROPERTIES OF THE CYCLOPROPYL were used, the result obtained here for t-butyl alcoGROUP hol is in excellent agreement with that obtained BY THEODORE L, BROWN,J. M. SANDRIAND H. HART previously. 1 The decrease in intensity ,which accompanies A Joint Contribution from Noyas Chemical Laboratory, University of Illinois, Urbana, I l l . , and Ksdzia Chemical Laboratory, Michigan Slats increased branching of the alkyl groups attached to University, East Lansing, Michigan the carbinol is to be expected, since the intensity is Recaivad Decambar .@I,1966 known to decrease with increasing electron-donatMeasurement of the inkgrated intensity of in- ing power of the attached groups.' The intensity frared absorption for compounds in solution is for the tricyclopropyl compound, however, is much capable of providing information about the elec- larger than that for the triisopropyl compound, and tronic properties of molecules, particularly when is in fact larger than that for the trimethyl. Since the variation in intensity throughout a series of re- the value of intensity for the tricyclopropyl comlated compounds is investigated. Recently it has pound lies between that for t-butyl alcohol and been shown that the intensity of absorption of the methyl alcohol (A' = 0.45),' it is to be concluded 0-H group in aliphatic alcohols is determined al- that the cyclopropyl group exhibits a +I effect most completely by the inductive properties of the relative to hydrogen, but is less electron-donating groups attached to the hydroxyl.' I n the present than the methyl group. This behavior may be compaper these results are used in interpreting the pared with that shown by the vinyl group; the measurements of the 0-H intensity for a series of intensity result for allyl alcohol (A' = 0.48)' shows that the vinyl group exhibits a -I effect relative to tertiary alcohols. hydrogen, The intensity for trivinylcarbinol would Experimental probably be much larger than 0.48, and considerably Method.-The procedure used in determining the intensi- greater than that for the tricyclopropyl compound. ties has been described previously.1 In the present work a I n the picture of the cyclopropyl group given by Perkin-Elmer Model 112 spectrometer with lithium fluoride optics was employed. Use of a mechanical slit width of 0.1 Walsh the bonds to cyclopropyl are made with carmm. resulted in a spectral slit width of about 4.5 cm.-1. bon sp2 hybrid orbitals.6 Since this is the same hyA cell thickness of 1.00 mm. was employed; solution con- bridization as that possessed by the carbons in the centrations were in the range 0.03-0.01 M. Materials.-Fresh bottles of reagent grade carbon tetra- vinyl group it might be expect,edthat; the inductive chloride were used in making up the solutions. t- properties of the two groups would be similar, and Butyl alcohol and 3-ethyl-3-pentanol were Eastman White Walsh has cited some evidence that this is the case.
Label materials, carefully fractionated prior to use. The preparation and properties of tricyclopropylcarbinol have (1) T. L. Brown and hl. T. Rogers, J . Am. Chnm, SOC.,79, 677 (1067).
(2) H. Hart and J. M . Sandri. Chemintry and Industry, 1014 (1856). (3) J. M. Sandri. Ph.D. Thesis, Michigan State Univeraity, 1966. (4) D . A. Ramsey, J . A m . Chem. SOC.,7 4 , 72 (1952). (6) A. D. Walsh, T r a m . Faraday Soc., 45. 170 (1040).
4
4
Y
f
