.July, 1961
FVSION P O I N T . ~ N DTEIERJrAL DECOMPOSITIOY OF KC104
of water was formed a t 703°K. from 1.11 X mole of 2-butanol in every second. The calculated residence time in the catalyst bed of an average reactant molecule then becomes about one second. Thus for every se'cond, 3.73 X 1 0 1 9 molecules of 2butanol are dehydrated by 3.61 X loz1sites, and accordingly one in 100 sites is actually in use a t any instant. Because of the excess of available active sites, the clomplexed molecules do not inter-
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fere appreciably with the approach of entering molecules. Acknowledgment.-This investigation was supported in part by a research grant PHS E-l354(C5) from the Department of Health, Education, and Welfare of the Public Health Service, and in part by a Frederick Gardner Cottrell Grant from the Research Corporation. The authors wish to thank both of these sponsors.
THE FUSION POINT AND THE THERhIAL DECOMPOSITION OF POTASSIUM PERCHLORATE BY A. E. SIMCHEN Scientific Department, Ministry of Defense, P.O.B. 7063, Tel Aviv (Israel) Recezved September 18, 1960
When heated isothermally above 570", pure KC104 undergoes first a partial decomposition in the solid state, then the resulting solid mixture melts while continuing to lose oxygen and solidifies again when the KC103 intermediately formed has disappeared, and the KC1 content approaches about 60 mole yo; the still remaining KC104 continues to decompose until pure KCl remains. The detailed kinetics of the decomposition is complicated because of consecutive, simultaneous and reverse chemical reactions: (1) KC104 + KClOs + KC1; (2) simultaneously with the simple decomposition, there are the reactions betxeen K(>1O4and KC1; between KC104 and KC103; (3) 4KC!03 + 3KC1O4 KCI. The initiation of the decomposition is considered to be a monomolecular process a t germs distributed throughout the volume of the substance, and then propagated by a branching chain of oxygen atoms migrating through the crystal lattice or through the melts.
+
1. General Description of Phenomena Obtained on Heating KC104.-For the fusion point of KC104 several different \-allies are quoted: 525530°,6,58811,12 and 610 i l O O . 4 On the other hand, partial decomposition on heating, giving KC1 and KClOs, has been known for more than a century.l4>l5 In view of the practical importance of the thermal decomposition of KC104 as a source of oxygen in solid rocket, propellent formulations, it seemed of interest t o have a clearer picture of the phenomena in question. The vacuum decomposition apparatJusin which the data reported below were obtained, has been described in a previous paper.' The essent'ial fact emerging from this study is that KC104 has no congruent fusion point. The substance remaining aft'er the resolidificat'ion of the fused mass is riot KC10,. When heating KC104 at a constant and sufficiently high temperature, and waiting for a sufficient time, it undergoes first n partial decomposition in the solid state2 (1) Benrath and Braun, 2. anorg. Chem., 244, 348 (1940). (2) Bircumshaw and Phillips, J. Chem. Soc., 703 (1953). ( 3 ) Caban4 and BBna-d. C.R.Sc.Sc., 260, 128, 331 (1960). (4) Carnelley and Carleton-Williams, J. Chem. SOC.,37, 125 (1880). (5) Duerre, Dissertation, Giessen, 1907. (6) Frankland and Dingwall, J . Chem. Soc., 61, 2747 (1887). (7) Glasner and Simchen, Bull. soc. chim. France, 18, 233 (1951). (8) "Gmelins Handbrich der anorganischen Chemie," 8th edn., "Chlor," and fol., Verlag Chemie, 1927, p. 398. (9) Harvey, Edmison, Jones, Seybert and Catto, J . A m . Chem. Soe., 76, 3270 (1954). (10) Hodgman, "I!andbook of Chemistry and Physics," 41st edn.. Chemical Rubber Publishing Co., Cleveland, Ohio. 1959, p. 627. (11) Markowits, J . Phgs. Chem., 61, 505 (1957). 112) hIarkoaitz, ihid., 62, 827 (1958). (13) Marignac, Bibl. Univ., 46, 353 (1843). (14) Millon, Ann. p h y s . , [3] 7, 334 (1843). (15) Millon, Lieh. A n 7 ~46, , 281 (1843). 116) Otto and F r y , J . A m . Chem. Soc.. 46, 1138 (1923). (17) Rodgers and Wassink, Univ. of Arkansas, Final Summary R e port, 1 Sept. 54-31 Jan. 58. Contract No. DA-23-072-ORD-1049. (18) J. C. Schumacher, "Perchlorates," Am. Chem. SOC.Monograph, Reinhold Publ. Gorp., N,aw York, N. Y..1960, pp. 37-38.
the solid salt mixture thus obtained undergoes further chemical reactions accompanied by the complete fusion of the sample. The fused mass, too, decomposes, its rhemical composition continues t o change and in the long run a re-solidification of the mass sets in at a (more or less) constant temperature (the exothermal effects of the chemical reactions" and of crystallization being balanced by the temperature-regulating mechanism of the apparatus and by the heat transfer to the surroundings). The chemical reactions preceding3s20 and accompanying fusion are dependent on time and temperature, and so is the heating up of the sample and of the glass support. This leads to a timetemperature dependency of the fusion which is given in Table I. TABLE I TIMESOF BEGINNING FUSIONAT DIFFERENTTEMPERATURES, OF 100-hfG. SAMPLES O F PURIFIED ANALYTICAL KCIOI (INCLUDING HEAT-UP TIMES) Temp., OC.
Time, min.
570
120
580 590 600
33 24 20 16 15
610
620
Mole
7' XCl in residue after isothermal resolidification
23 3 mole yo in 1 residue; 2.2 mole % in a 2nd sample that had not melted
. . . . . .. . . . .
52.5; 52.9; 53 8
. .. . . . . . . . .
56 7 57.1
The re-solidified, partially decomposed residue still contains appreciable quantities of KC104, but almost no KC103 if one waits until the evolution of gaseous O2has died down. The composition of the residue is not exactly reproducible, perhaps due t o a different extent of the decomposition in samples (19) Scobai, Z. phymk. Chem., 44, 328 (1903). (20) Simchen and Glasner, BulL SOC. chzm. France, 20, 127 (1953).
A. E. SIMCHEN
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Vol. 65
TABLE I1 COMPOSITION OF ISOTHERMALLY RE-SOLIDIFIED RESIDUES, IN MOLE% KCl Description of the KC104
540
550
560
570
580
590
b10
til0
620°
33.3
43 3
52.7 52 8
60 0
.
..
..
31 0 4 4
2 2
53 9
.. ..
4 Recrystallized from Baker Analyzed ( N o 3)
..
..
..
55 0 50.2 50.8 52 5
