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The initial chemical changes in the pyrolysis of the five alkali metal (M) chlorates under a slowly rising temperature program involve the reactions: (a) MC1O3 -. t MC1 + 1.502, and (b) hfC103 -0.75hIC104 + 0.25MCl; subsequent phenomena are associated with the decompositions of the more thermally stable perchlorates, (c) MC1o4 + SIC1 + 20a.The extent of conversion of ;\tClOa per reaction b increases in the order Li (40%) < Na (6770) < E(, Rb, Cs (87%) a t the expense of reaction a. The increasing order of thermal stabilities of these metal chlorates follows the decreasing polarizing powers of X f though the stability differences among I(c103, RbC103, and CsC103 are rather small. Each of the MClO3 compounds appears to possess a congruent melting point in contrast to the corresponding Mc10.1 salts which, except for LiC104, undergo simultaneous fusion and rapid decomposition. The catalytic effects of MnO2 additions to MC103 salts result primarily in the acceleration of reaction a. The general trends in thermal stability among compounds of the type MC10, (x = 1, 2, 3, 4) as a function of M and ~t: are discussed briefly.

The thermal stabilities of the pure alkali metal perchlorates (MCIOI) and of admixtures with 10 mole % RhOz catalyst follow the order Li < Na < K, Rb, Cs. For both pure and catalyst-containing materials, rapid decomposition is preceded by liquid phase formstion. Analyses of molten perchlorates near their fusion temperatures show that fusion is coincident with decomposition except for LiClO, which has a congruent melting point; the simultaneous occurrence of fusion and decomposition is in contrast to the behavior manifested by RIC103 salts, each of which possesses a congruent melting point and a significant range of liquid phase stability. Catalysis of Mc101 pyrolysis by basic substances yielding 02ion, in conjunction with other evidence, suggests the presence of 0 atoms in decomposing perchlorates. A proposed mechanism for Clz evolution from lIC104 melts (order of extent of Clz release: Li >> Xa > K > Rb, Cs = 0) stipulates an autoionization equilibrium of the type C104-4 c103+ + 02-, so that Clz release occurs through the reaction Clod-+ ClO3+ -+ [C1207] -+ Clz + 7/z02. Such a scheme removes acidic oxides (e.g., P206, B203, W03, Moo3, etc.) from consideration as true catalysts inasmuch as they function by removal of oxide ions and hence undergo specific, irreversible reactions with RIC104 salts. In this regard, MnOZ is primarily a true catalytic agent for MC104 decomposition, but it also does appear to undergo a small amount of chemical reaction with LiClO,, in particular, to foster Clz evolution, viz., LiC104 + MnOz 4 Li?tfnOz + l/zClz + 2OZ.(1) "Gmelins Handbuch der anorganischen Chemie," 8 Auflage, System No. 6, "Chlor," Verlag Chemie, G.m.b.h., Berlin, 1926, pp.