1422
A. C. NIXONAND R. E. SMITH
VOl. GO
PHASE RELATIONS IN THE SYSTEM CALCIUM BROMIDE, CALCIUM OXIDE AND WATER BY A. C. NIXON AND R. E. SMITH Shell Development Company, Enieryvdle, California Received M a y 18, 1966
Isotherms for the system calcium bromide-calcium oxide-water were determined a t 40 50 and 60". Existence of the complex salts. CaBr2.3Ca0.16H20(Dl.a.16) and 3CaBr2.4Ca0.16H20. (Ds.4.16) was confirmed. The decomposition temperaappears to be stable below lOO", at which temperature water is lost. The heat of formation of ture of D1.3.16 IS 52.5". Da.4.16 DI.~.IF, is approximately 1100 kcal. hase separating cell containing a sintered glass filter plate Introduction gut separated by a puncturable rubber diaphragm. After This paper describes the results of an investiga- charging the equilibrium cell the mounted assembly was imtion of the ternary system calcium bromide-cal- mersed in a constant temperature water-bath and vented cium oxide-water at 40, 50 and 60". A previous after reaching the bath temperature. The cell was rotated end-over-end a t approximately 30 revolutions per minute for investigation by Milikanl established the existence 24 hours. The liquid phase was sampled by (1) slightly of two complex salts, CaBrz.3Ca0.16Hz0 (D1.3.16)elevating the unit to allow connection of a vent line to the and 3CaBrz.4Ca0.16H20 (D3.4.16), and defined liquid sample bottle, (2) rotating the assembly and puncthe phase diagram at 25". He reported a de- turing the rubber diaphragm with a stainless steel wlre, and attaching an air line to permit pressure filtration of the composition temperature of 49.2" for D1.3.16.'(3) slurry. A Dow-Corning medium porosity (fine series) sinOur data indicate that this value is low. tered glass filter was employed. Only a t the time of actual The current work employed the "wet residue" manipulation were the,connections above the surface of the method of Schreinemakers.2 In connection with bath. Atter the filtration was completed the assembly was from the bath, dismantled and a sample of the the application of this method a useful experi- removed solid filter cake was taken. mental technique was developed during this study. This experimental device prevents the vapor loss norThe decomposition temperatures of D1.3.16and mally found with all packing gland-type stirrers. As a result, it provides a check on the accuracy of each experiD3.4.16 were investigated by thermal analyses. ment since the composition of the charge lies on a straight line connecting the compositions of the two phases, when Experimental plotted on a three component diagram.
Chemicals .-Calcium oxide was prepared by two methods. I n the first method a selected sample of Mallinckrodt Chemical Works reagent grade calcium acetate was calcined at 1050 to 1100" for approximately 20 hours. In the second method a selected sample of Allied Chemical and Dye Corporation Baker and Adamson reagent grade CaO was recalcined and used without further purification. The impurity level for both samples, as determined by emission spectrometric analysis, varied from 0.4 to 0.8%; the chief im urity was strontium. 8alcium bromide was prepared initially by the reaction between hydrobromic acid and calcium oxide followed by concentration and repeated crystallizations. Later in the work a selected sample of J. T. Baker Chemical Co. reagent grade calcium bromide was used without further treatment. The maximum impurity level for both samples was 0.1 to 0.2%. Distilled water was employed in all experiments. Analytical Methods.-Bromide was determined by the Volhard methods for total halides. Calcium oxide was determined by titration with 0.1 N "08, using phenolphthalein as an indicator. Total calcium was determined either by the volumetric oxalate method4 or by the Versenate method6 for total cations. The Versenate method gave calcium values which checked to within 1yoof the oxalate method for a few test samples. The total calcium value, used as a cation check, gave closures which showed an average deviation of 1%for all experiments. Water was determined by difference. Equipment.-The bulk of the experimental work was performed in a stoppered test-tube type cell equipped with a sintered glass liquid phase sampler and a stainless steel stirrer. This assembly was contained in a constant temperature water bath controlled to f 0 . 2 " . Equilibrium periods of 24 to 48 hours were allowed. A portion of the work employed a useful equipment variation in which the equilibrium cell was attached to a
(1) J. Milikan, Z . physik. Chem., 92, 59 (1918). (2) F. A. H. Schreinemakers, ibid., 11, 81 (1893). (3) "Scott'B Standard Methods of Chemical Analysis," 5th ed., Vol. 1, D. Van Nostrand Co., Inc., New York, N. Y., 1939, p. 192. (4) Ref. 3, p. 211. ( 5 ) G. Schwarzenbach, and W. Biedermann, H e b . Chim. Acta, 81, fi78 (1918).
Results and Discussion Equilibrium data for the system calcium oxidecalcium bromide-water a t 40, 50 and 60" are presented in Tables I, I1 and 111, respectively. The solubility data for calcium oxide in water and for calcium bromide in water were taken from the literature.6 The corresponding equilibrium phase diagrams are shown in Figs. 1, 2, and 3. I n these diagrams the composition of the liquid phase has been intentionally shifted away from the calcium bromide-water axis to clarify the diagram. The
ao Fig. 1.-System
60
40
20
CaQ
CaO-CaBrz-HzO a t 40°, weight percentages.
(6) N. A. Lanpe, "Handbook of Chemistry," 3rd ed., Handbook Publishers, Inc., Sandusky, Ohio, 1939, p. 1024.
1423
PHASE RELATIONS IN THE SYSTEM CABR~, CAO AND HzO
Oct., 1956
compositions of the field intersection points a t these temperatures, including the 25" data by Milikan,' are presented in Table IV. TABLE I THE SYSTEMCALCIUMOXIDE-CALCIUM BROMIDE-WATER AT 40°, WEIGHTPERCENTAGES Liquid phase CaBrz 0 12.9 22.5 .13 28.2 .18" 30,4a .21 32.3 .16 36.5 .1G 37.9 ,24 41.G .41 50.0 .55a 52.la 52.5 .70 .45 54.0 55.3 .35 58.5 .26 59.5 .25 .20 61.7 68.0
CaO 0.11 .045 .13
a
Hz0 99.9 87.1 77.4 71.7 G9.da 67.5 63.4 61.9 58.2 49.6 47.4a 40.8 45.G 44.4 41.2 40.3 38.1 32.0
Wet residue phase CaO CaBrz HzO
...
...
...
31.3 33.2 40.5 15.13~ 25.5 14.8 11.6 16.2 10.8 12.1a 13.1 11.0 11.0 9.45 8.33 5.45
7.66 12.2 12.8 28.ga 25.8 33.6 34.5 35.7 42.G 42.8" 43.7 53.G 54.5 56.7 58.2 G2.7
Gl.0 54.G 46.7 55.5" 48.7 51.6 53.9 48.1 46.6 45.1' 43.2 35.4 34.5 33.8 33.5 31.8
...
...
at 50°, weight percentages.
Fig. 2.-CaO-CaBr2-Hz0
...
Modified apparatus.
TABLE I1 THESYSTEMCALCIUMOXIDE-CALCIUM BROMIDE-WATER AT 50°, WEIGHTPERCENTAGES CaO 0.097 ,045 .15 ,092 * 12 .I1 .14 .10 .21 .30 .30a .I4 .68 .74 .89 1.07 0.68 .46 .38 .30 0 a
Liquid phase CaBra 0 9.24 14.0 15.1 18.8 22.8 34.6 35.4 37.2 40.3 40.6" 41.9 47.7 49.1 51.4 51.5 52.6 55.3 59.1 59.7 72.0
HzO 99.9 90.7 85.8 84.8 81.1 77.1 65.3 64.5 62.6 59.4 59.1" 58.0 51.6 50.2 47.7 47.4 46.7 44.2 40.5 40.0 28.0
Wet residue phase CeO CaBrz HzO
...
...
...
36.2 30.5 30.5 29.3 31.4 32.9 46.5 40.9 12.6 28.5" 13.1 12.2 9.91 14.7 9.11 11.5 10.3 6.79 11.2
5.5 7.89 9.58 13.8 13.6 19.8 13.8 17.3 35.6 25.4" 36.6 40.6 42.9 42.1 49.1 53.3 54.6 61.5 57.0
58.3 61.6 59.9 56.9 55.0 47.3 39.7 41.8 51.8 46.1' 50.3 47.2 47.2 43.2 41.8 35.3 35.1 31.7 31.8
i
..
...
...
Modified apparatus.
HzO
a
Liquid phase CaBri 0 24.5 34.4 42.3 51.6 52.4 56.5 59.8 01.1 73.5
Ha0 99.9 75.2 65.3 57.3 47.1 46.4 43.1 39.8 38.6 26.5
Wet residue phase CaO CaBrz Hz0
...
...
...
37.9 32.9 45.9 5.98 8.15 9.75 8.41 5.99
13.4 19.5 16.7 49.1 52.3 55.4 64.1 60.0
48.7 47.6 37.4 44.9 39.5 34.9 27.5 34.0
...
...
...
All except first four in modified apparatus.
Milikan' reported a decomposition temperature of 49.2' for Dl+~a; however, the 50" isotherm shows that Dl+~ais stable a t this temperature. This salt was prepared by precipitation from a supersaturated solution and was separated from
40
CaO
20
at 60",weight percentages.
TABLE IV EQUILIBRIUM FIELD INTERSECTION COMPOSJTIONS IN WEIQHTPERCENTAGES
TABLE I11 THE SYSTEM CALCIUMOXIDE-CALCIUM BROMIDE-WATER Temp., AT 60°, WEIGHTPERCENTAGES' OC. CaO 0,088 .33 .28 .40 1.26 1.20 0.38 .37 .27 0
60
80
Fig. 3.-CaO-CaBrz-H,O
25 40 50 60
Ca(OH)z-Di.a.ls CaBrr 20.8 31' 40.4 52.0'
CaO 0.38 0.70 1.07 1.25'
Di.a.ieDa.c.:a CaBrz 54.3 52.5 51.5
...
Obtained two values: Da+le field.
CaO 0.11 0.22 0.30
...
Da.r.rCaBrz. zHzO CaBrz CaO 60.0 0.20 59.5 .25 59.5 .32 59.8 .35
32.3 and 30.4.
2
6 4 4 4
Ca(0H)Z-
the mother liquor by centrifuging. The white crystals, after drying between filter papers, appeared to be stable and non-hygroscopic. Freezing point determinations on this sample indicate that the formation temperature of D l . 3 . ~is 52.5". Warming curves attempted in a modified Rossinitype apparatus gave high results (54.8'), but this is believed due to poor heat transfer between the crystals and the benzene suspending agent. Based on the heat input to the benzerie-crystal slurry and
.
1424
W. FORSTAND C. A. WTNKLER
the warming curve, the heat of formation of D1.8.16 is approximately 1100 kcal. The complex D3.4.16 was prepared in a similar manner. A simple warming experiment showed no evidence of decomposition below approximately looo, a t which temperature some water loss
Vol. 60
occurred. The authors wish to express their appreciation to Shell Development Company for permission to publish this work, and to R. C. Hurlbert for assistance in evaluation of the heat of formation of D1+*e. I
REACTION OF ACTIVE NITROGEN WITH METHYL CYANIDE' BY W. FOR ST^ AND C.A. WINKLER Contributionfrom the Physical Chemistry Laboratory, McGill University,Montreal, Canada Received May 81, 1966
The reaction of active nitrogen with methyl cyanide was studied at five temperatures in the range 90 to 460'. The main products were hydrogen cyanide and hydrogen. Smaller amounts of cyanogen, methane, ethane, ethylene, acetylene and (probably) methylisonitrile were also recovered. The yields of primary products, in relation to the methyl cyanide flow rete, indicate complete consumption of active nitrogen at each temperature, but the maximum yield increased markedly with increase of temperature.
Introduction Previous studies in this Laboratory have shown that, although reactions of active nitrogen with hydrocarbons yield mainly hydrogen cyanide, small amounts of cyanogen may also be formed. The present study was made to determine whether, with the CN group present in methyl cyanide, reaction of this molecule with active nitrogen would reveal another aspect of active nitrogen reactions that might be useful in their interpretation. Experimental
the resence of methylisonitrile in the reaction products. Metgylisonitrile was identified by its hydrolytic products, z.e., methylamine and formic acid, which were detected in the acidified reaction mixture by tests due t o Valtons and Grant,o respectively. No attempt was made to determine the methylisonitrile quantitatively, in view of the small amounts involved (at most 3% of total products a t 235'). The difference (6 - d ) was assumed to represent methylisonitrile, and the carbon and hydrogen balances calculated on this basis were between 99 and 101%. Non-condensable reaction products were withdrawn from the nitrogen stream with a Toepler pump and analyzed on the mass spectrometer. Experiments were made a t 90,160,245,345and 460".
The apparatus was similar t o that described in an earlier paper.* The molecular nitrogen flow rate was 5.98 X 10-5 mole/sec., corresponding to an operating pressure of 1.03 mm. in the system. Methyl cyanide "chemically pure" was purchased from Brickman and Company, Montreal, and was purified as outlined previously.* Condensable products of the reaction were distilled into a low temperature still of the type described by Le Roy.P The CZhydrocarbons were distilled a t - 140" and analyzed on a mass-spectrometer.K The excess of the reactant and the products were condensed on N/2 KOH frozen in liquid nitrogen. Upon melting, the solution was divided into three aliquots. I n one aliquot, total cyanide ( = a ) was determined by titration with silver nitrates; the second ali uot was acidified with dilute sulfuric acid (1 :10) and bqjed '/z hour. The ammonia so formed ( = 6 ) was determined by KjeIdahl distillation. The third aliquot was transferred into a tube, frozen in liquid nitrogen, and an e ual volume of concentrated sulfuric acid slowly added. T%e tube was then evacuated, sealed and digested for 12 hours at 150'. Total ammonia ( = c ) was then determined in another Kjeldahl distillation. Cyanogen ( = d ) was determined in a separate experiment by the method of Rhodes.' Net hydrogen cyanide was given by the difference ( a - d ) , and unreacted methyl cyanide by ( c - a - 6 ) . In the absence of any reaction products easily hydrolyzable by dilute acids, the determination of cyanogen as ammonia ( b ) , or by the direct method ( d ) should have yielded identical results. However, the result ( 6 ) was consistently higher than the result (d), and the discrepancy was attributed to
Results The results for all the products exclusive of methane are summarized in Figs. 1, 2 and 3. No methane was found at 90"; the results of analyses at 460' were:
(1) With financial assistance from the National Research Council of Canada. (2) Holder of National Research Council Bursary and Studentships, 1952-1955. (3) W. Forst and C. A. Winkler, Can. J . Chem., SS, 1814 (1955). (4) D. J. Le Roy, Can. J . Res., BEE, 492 (1950). (5) The authors are indebted to Dr. H. I. Schiff for permission to use the mas8 spectrometer, and to Dr. D. Armstrong for the analyses. (6) I. M. Kolthoff and V. A. Stenger. "Volumetric Analysis." Vol. 11, John Wiley and Sons,New York, N. Y., 2nd Ed., 1947. (7) F. H. Rhodes, J . Ind. Eng. Chem., 4 , 652 (1912).
MeCN flow rate mole/sec. x IO;
3.5 8.1
15.5
Methane yield, mole/seo. X 10'
0.00 .00 .184
The data for methylisonitrile are uncertain, Le., the amounts calculated might represent methylisonitrile plus other unidentified components. At lower temperatures these results were fairly reproducible, but at 345 and 460" the reproducibiIity became very poor and no consistent data could be obtained. Discussion In discussing the results, the assumption will be made that the reactive species in active nitrogen is atomic nitrogen in the ground state, for reasons indicated elsewhere.l o Since the main products of the reaction were hydrogen and compounds containing a carbonnitrogen bond, it would appear that the initial attack of the nitrogen atom was at a carbon atom in the methyl cyanide molecule. Seven possible (8) P.A. Valton, J . Chem. Soo., la7, 40 (1925). (9) W. M. Grant, Anal. Chem., 20, 267 (1948). (10) (a) H. G. V. Evans and C. A. Winkler, Can. J . Chem., in press; (b) H. G. V. Evans, G. R. Freeman and C. A. Winkler, ibid., in press.
