The influences of gaseous and solid reactants on the yields of oxalates and carbonates in the thermal decompositions of alkali metal formates have been studied. A mechanism of formation of these products is proposed, which explains the influences of basic and acidic species formed in the medium on the thermal decompositions of the alkali metal formates.Extensive studies concerning the mode of thermal decomposition of alkali metal formates indicate a considerable effect of the process conditions on the yields of the main solid products, i.e. oxalates and carbonates formed according to the equations 9 '~ H2 + C2 O2-(1) 2 HCO 2 H2 4-CO + CO23-

The effects of active (carbon dioxide and carbon monox{de) and neutral (helium, argon and nitrogen) atmospheres on the course of thermal decomposition of oxalates have been studied and compared. A mechanism of thermal decomposition has been proposed on the basis of the results obtained, the first stage of which consists in a heterolytic dissociation of the C~ bond, with the formation of carbon dioxide and the CO~-anion.In our earlier studies on the systematics of thermal decomposition mechanisms, it was shown that heterolytic cleavage is the first stage in the thermal decomposition of salts with bicentric anions containing a direct electron bond between the central atoms and a full coordination by oxide ligands (e.g. hyposulphates, $2062-, and hypophosphates, P20~-) [1, 2]: S2062-~SO3 + SO~-P20~ ~PO; +P033-Since carbon is an element of the previous period, oxalates are analogues of hyposulphates and hypophosphates and in the first stage they should decompose analogously:

The gaseous products of the thermal decomposition of formates have been investigated and compared with the products of formaldehyde and synthesis gas transformation under analogous conditions in the presence of the solids formed in the thermal decomposition of particular formates. It was found that formaldehyde transformation leads to organic compounds identical to those obtained in the thermal decomposition of the respective formates, while synthesis gas does not react under such conditions. This fact substantiates the hypothesis that formaldehyde is a precursor of the organic compounds identified in the thermal decomposition of formates. The nature of the organic componds obtained in the thermal decomposition of formates indicates that the formaldehyde formed in the initial stages is then transformed in the Cannizzaro or Tishchenko reactions. , and only inorganic compounds were found in some studies of the thermal decompositions of alkali metal formates [11] and transition metal formates [7,12,13].The reported mechanisms of formation of organic products can be divided into two groups. In the first group of mechanisms it is accepted that synthesis gas (H 2 + CO) i ; the precursor of the organic products [1,4,5,11], whereas in the second group the precursor is formaldehyde [2,3,7]. It is assumed in both mechanisms that these precursors of the organic products are formed in the initial stages of thermal decomposition of the formates, and are then transformed in secondary reactions catalyzed by solid phases produced in the thermal decomposition of the formates.In order to verify the above hypotheses, the gaseous products of thermal decomposition of formate have been studied in this work and compared with the

Three stages have been distinguished in the thermal decomposition of formates: It was found that in the first stage carbon dioxide is evolved, leaving structural elements of the respective cation hydride in the reaction system:The second stage depends on the character of the bond in the intermediately formed hydride: Among the ionic mechanisms, the concept of H--C bond cleavage has been considered [7]. A separate group of ionic mechanisms is based on the assumption of the formation of a two-molecule active complex, which then decomposes to John Wiley & Sons, Limited, Chichester Akad~miai Kiad6, Budapest