WILLIAM J. LIGHTFOOT AND CARLF. PRUTTON
2098 [CONTRIBUTION FROM
THE
Vol. 69
DEPARTMENT O F CHEhIISTRY AND CHEMICAL ESGINEERING O F CASE SCHOOL SCIENCE]
OF
APPLIED
Equilibria in Saturated Salt Solutions. 11. The Ternary Systems CaCl,-MgCl,H,O, CaC1,-KCl-H20 and MgC1,-KC1-H,O at 75 ' BY WILLIAMJ. LIGHTFOOT AND CARLF. PRUTTON I n a previous paper,' the three isotherms for the systems, CaC12-MgC12-HZ0, CaC12-KC1-H20 and MgC12-KCl-H20 a t 35' were reported. Experimental Method The methods were similar to those used a t the lower temperature where solutions were brought to equilibrium a t 75 *0.02' with the exception that the saturated solution was filtered through cotton in a preheated capillary tube directly into a weighing bottle. Six to eight hours were found to be sufficient for equilibrium. However, the samples were agitated for several days before sampling. H?O
A / \
The Ternary System C ~ C ~ Z - M ~ C ~ Z - H ~ O Table I, Fig. 1.-In the temperature interval from 35 to 75' the isotherm for this system has gone through some marked changes. WhiIe there TABLEI THETERNARY SYSTEM CaClz-MgCln-H20 AT 75" Saturated solution Wet residue --Weight per cent.--CaClz MgClz CaC13 MgCh
58.58 55.76 52.59 52.57 45.01 34.97 29.15 19.28 13.83 12.52 10.15 9.97 8.32 8.31 8.04 3.84 0
0 2.53 5.27 5.28 8.74 14.70 18.63 25.55 29.65 30.59 32.39 32.59 33.90 33.91 34.07 36.62 39.12
...
...
62.72 51.38
1.65 7.99
.._
...
34.12 21.42
... ... ... ... ... ...
... ... ...
... .. . . ..
14.09 34.06
...
.. .
11.06 36.22 6.00 37.27
...
. ..
... ...
Solid phase
CaCl2.2HZ0 CaC12.2Hz0 CaC12.2H20 Tachydrite CaC12.2H204- Tachydrite Tachydrite Tachydrite Tachydrite Tachydrite Tachydrite Tachydrite Tachydrite Tachydrite Tach. MgC12-6Hz0 MgCl2.6Hz0 Tach. MgCln.6HzO MgClr.6HpO MgCla.6HzO
+
+ +
has been only a small change in the extent of the satukation curve for calcium chloride in the ternary system, the range of existence of tachydrite has opened so much that it occupies a major portion of the entire diagram. Where a t 35' tachydrite incongruently saturated the solution, a t 75' it shows congruent solubility. The field of existence of MgC12.6H20now only covers a fracCaCll MgCl tion of what it had covered a t the lower temperaFig. 1.-The ternary system: CaClz-MgClrHzO at 75'. ture. The Ternary System CaC12-KC1-H20 All wet residues were examined microscopically Table 11, Fig. 2.-The diagram again shows and the solid phases identified by Schreinemakers' method. In examining a sample, saturated solu- the retrograde solubility of potassium chloride tion together with some of the crystalline solid which was present a t 35'. A new ternary comphase were removed with a stirring rod and placed pound 2KC1CaC12.2Hz0 has appeared which is on a microscope cover glass. When samples of incongruently soluble at 75'. In order to estabthe mixtures from the studies a t 35' were placed lish more completely the identity of this salt, a on the slide, very little subsequent crystallization series of tests were run at 95" to see if its area of took place except when dealing with the meta- existence could be opened. The data are given in stable forms of CaCl2.4H20. To prevent crystal- Table 111. Since little could be gained by going lization of the samples taken a t 7 5 O , a small to 95' as the compound still showed incongruent electrically heated microscope stage as described solubility, no further work was done at this temperature. by Chamot and Mason2 was used. No information was available on the crystal (1) Lightfoot and Prutton,THISJOURNAL, 68, 1001 (1946). structure and optical properties of CaC12.2H20 and (2) Chamot and Mason, "Handbook of Chemical Microscopy," 2nd ed., John Wiley and Sons, Inc.,New York, N. Y., 1938. 2KC1CaC12.2Hz0. It was found that CaC12.
Sept., 1947
A!lQUEOUS TERNARY SYSTEMS O F
CAILCIUM,MAGNESIUM AND POTASSIUM CHLORIDES 2099
TABLE I1 THET E R N A R Y SYSTEM CaC12-KCl-H20 AT 75"
--
Saturated solution Wet residue Weight per cent.-CaCh KC1 CaCh KC1
...
Saturated solution weight per cent. CaClz KCl
Solid phase
49.47 49.40 52.47 58.26
... .. . ... ... ...
12.42 12.44 7.25 3.93
+
AT
95"
Solid phase
KC1 2KC1.CaCl2~2H20 KC1 f 2KC1 CaC12.2H20 2KCl.CaC12.2H20 2KC1 CaC12.2H20 CaC12-2H20
KCl KCl KC1 ... KCl .,, KCl coid, the edges forming a rhomboid. It shows ... ... KC1 symmetrical extinction with low birefringence. 37.52 27.17 KCl 39.68 35.30 KCl 2KC1.CaC124?H20 2KC1.CaC12.2Hz0 is probably orthorhombic, bi41.80 30.92 KC1 2KCI.CaCl2~2H2O axial negative with an index of refraction greater .. ... KC1 f 2KC1~CaCl2~2Hz0than 1.49. I t crystallizes out in large rectangular 4 4 . 1 8 30.07 KC1 2KC1~CaC12.2Hz0 plates or in small, well-defined cubes having a face across opposite corners, the usual form being in 45.68 25.97 2KCl.CaC12.2H20 plates with the optic axis steeply inclined to the 58.56 16.92 2KCl.CaC12.2H20 plate, about 20' from vertical. Depending on the 50 14 18.25 2KCl.CaC12.2H20 development of the crystal, it will show either 45 58 30.75 2KCl.CaC122HzO 51 21 14.67 2KClCaC122H20 TABLE IV 51 40 14.40 2,KCl.CaClg2H20 THE TERSARY SYSTEM. MgC12-KC1-H20 AT 75' 54.85 7.92 2KCl.CaCly2HzO Saturated solution Wet residue 62 72 13.22 2KClCaC12GH20 Weight per cent.45,58 30.41 2KClCaC122HzO MgCh KC1 MgClz KC1 Solid phase 47,99 24.15 2KCl.CaC12.2H20 0 33.16 ... KCI 2KCl.CaC12.2H20 47,67 26.22 7.51 23.98 ... . . . KCl 44.64 34.09 2KClCaC122H20 f 12.65 18.36 . . . . . . KCl CaC12.2H20 . . . KC1 20.95 10.73 ... 57.64 3.58 52,79 20.47 2KCl.CaC12.2HzO 28.43 5.88 18.85 37.23 KC1 CaC12.2H20 29.26 5.57 . . . . . . KC1 f Carnallite 57.69 3.58 57,93 5.59 Z K C ~ . C ~ C ~ Z , ~ H Z O 29.25 5 . 5 7 2.5.54 28.73 KCl f Carnallite CaC12.2H20 30.08 4.54 32.49 16.46 Carnallite 57.68 3.60 54,80 11.95 2KCI.CaC12G2HzO 431.75 3.00 ... . . . Carnallite CaC12.2Hz0 1 . 7 3 33.83 15.16 Carnallite 33.57 57.77 2.56 t%80 1.57 CaC12.2H20 ... 35.84 0.81 . . . Carnallite 58.58 0 ... . . . CaCly2H20 37.04 0.58 35.62 13.20 Carnallite 38.85 0.32 39.33 4.29 Carn. MgClr62HO 2H20 is probably orthorhombic, biaxial. I t ... 38.86 0.32 . . . Cam. MgC124HaO crystallized out on the largest face, a basal pinaMgCl?.GH?O 39.12 0 ... ... Hz0 0 11.73 18.27 28.47 37.65 42.84 47.64 50.19 50.18 50.21 50.22 50,311 50.92 53.85 54.03 54.52 54.79 56.33 56.28 56.57 56.79 57.00 57.62
33.16 21.62 16.00 9.62 6.77 6.97 8.43 10.32 10.31 10.36 10.32 10.36 9.36 6.21 6.08 5.15 5.55 4.51 4.33 4.20 4.00 3.92 3 . BO
TABLE I11 THETERNARY SYSTEM CaC12-KCl-H20
... ~, .
.
+
+ + +
--
+ +
+
+
KCl Fig. 2.-The
CaC12 ternary system: CaClrKCI-H20 a t 75 '.
MgCL Fig. 3.-The
KCl ternary system: MgC12-KCl-HzO a t 75".
J. M. BLOCHER, JR.,
2100
AND
parallel or symmetrical extinction. There is a tendency to form twins. I t has low birefringence, less than 0.01 and a positive sign of elongation. The Ternary System MgCl*-KCl-H20 Table IV, Fig. 3.-Even with increased temperature the area of existence of MgC12.6H20 has not increased appreciably. I t still represents a very small portion of the entire diagram. Since potassium chloride was determined directly on a sample of saturated solution, the values obtained for the isothermally invariant composition of solutions in equilibrium with carnallite and MgC12.
IVOR E. CAMPBELL
Vol. 69
GH2O are slightly lower than those reported a t nearby temperatures. Acknowledgment.-The authors wish to thank Dr. R. L. Barrett for his assistance in the identification of the crystalline and optical properties of the substances encountered in the experimental portion of the study. Summary 1. The isotherms for the ternary systems a t 75' are given. 2 . The ternary compound 2KC1.CaClz.2Hz0 has been found to exist a t 73". RECEIVED MARCH21, 1947
CLEVELAND, OHIO
[CONTRIBUTION FROM BATTELLE MEMORIAL INSTITUTE]
The Vapor Pressure of Liquid Titanium Tetraiodide BY JOHN M. BLOCHER, JR., The literature is fairly complete with respect to the vapor pressures of zirconium,' thorium,2 and tin3 tetraiodides. However, no data are available for titanium tetraiodide. All references to its volatility and boiling point stem from the original work of Ha~tefeuille,~ who simply states that it has a sensible vapor pressure a t room temperature, melts a t 150' and boils a t a little above 360°, distilling without decomposition. The present work represents the first determination of its vapor pressure. Titanium tetraiodide is extremely hygroscopic as well as being easily oxidized in air. Hence a suitable technique was developed for its preparation, purification, and transfer in zlacuo.
AND
IVOR E. CAMPBELL
After three passes, the conversion was apparently complete. With bulb c cooled in Dry Ice, about one-half of the titanium tetraiodide in h was distilled into c which was then sealed off a t d. One-third of the remaining material was distilled in a like manner into e, a seal made a t g and bulb h pulled off. This left about 30 g. of iodinefree titanium tetraiodide in bulb h. To provide for the breaking of this ampoule, the flame of an oxygen torch was touched to the glass wall, whereupon a concave thin glass "bubble" was formed. This operation required some care and practice. The ampoule containing the titanium tetraiodide was sealed into the vapor-pressure apparatus as indicated in Fig. 2.
Materials and Procedure Titanium tetraiodide was prepared by the direct iodination of crude titanium (98%) containing 1.6% iron and some calcium as the principal impurities. Twenty grams of titanium ( 1 0 0 ~ excess), o having been previously washed with dilute hydrofluoric acid, distilled water, and absolute alcohol and dried, was placed in the middle bulb e of the glass apparatus in Fig. 1 which w-as sealed a t f , stoppered a t a , evacuated with flaming to loF3 mm., and then let down to dry air. One hundred grams of dry resublimed iodine was liquefied in the funnel a t a and allowed t o run into the end bulb a t c. A seal was made a t b and the funnel was pulled off a t that point. With bulb c cooled in Dry Ice, the system was again evacuated and sealed off a t i. The middle bulb was maintained a t 525' while the end bulbs were alternately heated and cooled in air in such a way as to drive the iodine slowly back and forth across the hot tiianium. Fig. 2. 4-
cjVAC
-
Fig. 1.
(1) Rahlfs and Fischer, 2. anorg. allgem. Chem., a l l , 349 (1933). (2) Fischer, Gewehr and Wingschen, ibid., 242, 161 (1989). (3) Negishi, THISJ O U R N A L , 68, 2293 (1936). (41 Hautefeuille, Bull. SOC.Chim., [ 2 ] 1, 202 (1867).
The differences in. the boiling points of iodine (b. p. 184"), titanium tetraiodide (b. p. 3 7 7 " ) , and calcium iodide (b. p. 718") are such as to permit separation by distillation. A qualitative thiocyanate test for iron in the sample used was negative. The vapor-pressure measurements were carried out in an all-glass manometer of the type described by Daniels6 ( 5 ) F. Daniels, THISJOURNAL, 60, 1115 (1928).
