110
JOHN
W. NORMAN AND A. B. GARRETT
conversion to the vitreous form could be realized by more rapid quenching. Table I1 shows the data obtained from a similar study of the devitrified glasses. TABLE I1 EFFECTOF DEWITRIFIEDPOLYPHOSPHATES ON BARIUM CHLORIDE SOLUTIONS Amount of Phosphate Added 2.00 milliequivs. per liter Concentrations of B a + + in milliequivs. per liter. NazO/PzOa
1.2*i
1'50
Initial concn. BaCli
Final concn.
5.00 3.00 5.00 3.00 5.00 3.00 5.00 3.00
3.96 1.84 3.34 1.42 2.96 1.06 3.22 1.22
Ba++
Average Millie uivs. moles Ba Bay+ per mole removed phos.
+
1.04 1.16 1.66 1.58
2,7
2'04 1.94
2.5
1.78 1.78
6.2
'
2.4
According to the thermal studies of Partridge, Hicks and Smith13the crystalline products are mixtures of sodium triphosphate and crystalline metaphosphate or pyrophosphate, depending on whether the NazO/Pz06 ratio is less than or greater than 5/:3. Table I11 gives a comparison between the results expected from this theory and those actually found. The agreement is such as to inspire additional
VOl. 69
TABLE 111 COMPARISON OF THEORETICAL A N D OBSERVED VALUESOF MOLES B a + + PER MOLE PHOSPHATE FOR DEVITRIFIED POLYPHOSPHATE GLASSES Composition of NatO/ PzOr
1.25 1.50 1.67 1.75
Moles NaPOi (cryst.)
1 mole of phosphate Moles
Moles NasPlO10
Nad':O1
1
..
..
1 1
..
..
2
1
5 1
..
per Moles moleBa phos. +
+
Calcd.
Obs.
2.5 2.5 2.5 7.0
2.7 2.4 2.5 6.2
confidence in the Partridge, Hicks and Smith formulation of the system NaP03-NadP207. Acknowledgment.-The writer wishes t o thank his wife, Eunice S. Campbell, for help with much of the experimental work here described. Summary From a polarographic comparison of barium removal by both glasses and the devitrified products of the system NaP03-NadP20s, ,it is concluded that : 1. Sodium phosphate glasses of NaaOIPz06 ratios between 1 and 2 would, if pure, have all sodiums replacable by barium, and thus behave as though they form a continuous series. 2 . Additional support has been given to the phase studies of Partridge, Hicks and Smith on the NaPOs-Na4P20, system. Moscow, IDAHO
[CONTRIBUTION FROM THE DEPARTMENT OF CHEMISTRY, THEOHIO
RECEIVED MARCH4, 1946
STATE
UNIVERSITY]
The Conductances of Lead Chloride in Ethylene Glycol-Water Mixtures BY JOHN W. NORMAN AND A. B. GARRETT The purpose of this investigation is t o present data for the conductances of lead chloride a t various low concentrations in pure water, pure ethylene glycol and in four mixtures of ethylene glycol and water consisting of 20, 40, 60, SO% of glycol, and t o compare these values with the Onsager equation. Previously measured activity coefficients of lead chloride in these six solvents will be compared with the Debye-Huckel limiting law. We shall be able to show qualitatively some of the reason:; for the failure of these theories. The general conclusions which will be reached are that the principal cause of discrepancy between theory and experiment is that the effective dielectric! constant in the Debye-Huckel equation is less than the measured macroscoDic dielectric constant, and that the effective d&lectric constant in the onsagerequation, which applies when an external field is present, is considerably less than the ieffective dielectric constant in the Debye-Huckel equation. Experimental Lead Chloride.-Triple distilled water at 100" was saturated with Mallirickrodt Analytical Reagent lead chloride.
After iiltration precipitation was brought about by cooling and by the addition of a small percentage of rcagctit quality concentrated hydrochloric acid. The product was dried at 110' for twenty-four hours and was stored in a desiccator until used. Ethylene Glycol.-Eastman Kodak best grade ethylene glycol (E. K . Co. 133) was dried over anhydrous sodium sulfate and decanted. The dried glycol was distilled twice at reduced pressure. The middle third was kept each time. Solutions.-The solveiits and solutions wcre prepared gravimetrically and the weights were converted to vacuum weights. All the solvents and solutions wcrc in equilibrium with air. The accuracy desired was O.l%, and all the weight concentrations were determitied to well within this accuracy. Apparatus.-The apparatus has been described by Garrett and Ve1lenga.l T h e frequency of the oscillator was 2000 cycles/second. The detector was an oscilloscope arranged as sunrrested bv Lanison.2 The ccll was clcdned by t h i method-of Morgan and Larn~nert,~ atid was kept filled with hot triple distilled water for several days to remove adsorbed ions from the cell and electrode surfaces.
Data The data are given in Table I and are shown (1) Garrett a n d Vellenga, THISJ O U R N A L , 61, 225 (1945). (2) Lamson, RCV.Sci. Instruments, 9, 273 (1938). (3) Morgan and Lammert, TEISJOURNAL, 46, 1692 (1923)
Jan., 1947
CONDUCTANCES OF LEADCHLORIDE I N ETHYLEWGLYCOL-WATER MIXTURES
111
TABLE I MOLARCONDUCTANCES OF LEADCHLORIDE IN ETHYLENE GLYCOL-WATER MIXTURES % Glycol 0
20
40
60
80
100
Gdarity 0.07316 .05258 .01178 .02194 ,07049 .02630 ,009935 ,02128 .0 15246 .02,4463 ,084542 .049009 ,02318 ,01390 ,02495 .02968 .03783 .05453 .08553 ,01244 .02203 ,02731 .03876 ,05504 ,08553 ,01285 ,02136 ,02852 .04079 .06015 .09185
,011684 .02374 .02811i ,03770 ,05197 .OR322 ,01406 .01‘J52 ,02418 ,03215 .04,i63
.of5145
l/R(corrected)
0.04363 .02417 .001378 .004636 .04076 .006577 .009895 .004373 ,0022795 ,0057115 ,011034 .021192 .0031989 ,0011859 ,0036817 .0051400 .0080860 .015759 .034821 .00056073 00 17069 .0025670 .0049623 ,0093506 .016630 .00034776 .00092576 .0015992 .0030917 .0061638 .012647 ,00030181 .00057779 .00084352 ,0013415 ,0023507 .0051798 .000095426 .00017512 .00025607 .00041740 ,00075493 .0012309
.
Am
232.6 249.5 283.6 274.9 234.1 271.5 285.4 275.3 279.9 272.6 264.0 250.6 169.9 175.1 168.8 166.5 161.3 151.3 134.8 103.5 100.4 98.39 94.29 88.09 81.05 60.12 57.92 56.11 53.02 48.63 42.78 30.38 29.27 28.32 26.95 24.84 21.34 13.78 13.12 12.50 11.53 10.35 9.296
graphically in Fig. 1 as Am, the molar conductance, z’s. 6, where m is the molarity of the lead chloride. The densities which are used to convert from weight concentrations to volume concentrations are the densities of the pure solv e n t ~ . ~The value of the corrected specific conductance is L (corrected) = l/R (corrected) = 1/R (measured) - l / R (solvent). The constant of the conductivity cell used is 0.02854. The slopes and intercepts of these curves, in units consistent with Onsager’s equation written in terms of equivalent conductivity and equivalents/ liter concentratron, are given in Table 11. The ’4) Black, Ph D. Thesis, The
Ohio State University. 1942.
100
---
-I
0 0.04 0.06 0.08 0.10 Molarity. Fig. 1.-Molar conductances of solutions of lead chloride as a function of dmolarity in A, water; B, 20% glycol80% water; C, 40% glycol-600/0 water; D, 60% glycol40% water; E, 80% glycol-ZO% water; F, 100% gIycol.
0.02
terms which we shall use are defined by MacThe theoretical slopes, assuming as a first approximation that the transport numbers of the ions do not change with a change in solvent, are also given in Table 11. The viscosities of TABLE I1 EXPERIMENTAL SLOPES AND THEORETXCAL SLOPES OF THE DEBYE-H~CKEL AND ONSACER CURVES, AND LIMITING EQUIVALENT CONDUCTANCES FOR LEAD CHLORIDEIN ETHYLENE GLYCOL-WATER MIXTURES ToGlycol
0 20 40 60 80 100
Experimental slopes DebyeHiickel Onsager
1.230 1.339 1.536 1.970 2.523 3.22
310 210 129 88.2 60.5 43.3
Theoretical slopes DebyeHiickel Onsager
1.012 1.134 1.294 1.543 2.026 3.044
184 120 78.0 50.0 30.8 19.8
liQ
147.0 91.8 54.2 31.6 16.6 7.73
these solvents were taken from Dunstad and the dielectric constants from Akerlof The value of w in water is obtained as follows: IOJ/,Pb++ = AO - loa- = 147.0 - 76.348 = 70.7, n l / , p b + + = 70.7/147.0 = 0.481, q = 2(147.0)/3[70.7 2 (76.84)] = 0.439, w = 4(0.439)/(1 0.439) = 1.06. In Table I1 are also listed the theoretical Debye-Huckel slopes and the actual slopes of the log y vs.
