Non-isothermal decomposition of silver maleate dihydrate and anhydrous silver fumarate

Article abstract of DOI:10.1007/BF02549323

The non-isothermal decompositions of silver maleate dihydrate (C₄ H₂O₄Ag₂.2H₂O) and an hydrous silver fumarate (C₄H₂O₄Ag₂) were studied up to 500°C, in a dynamic atmosphere of air, by means of TG and DTA measurements. Both compounds showed some sublimation (at 120°C for silver maleate and at 280°C for silver fumarate) prior to the onset of decomposition (at 170°C for silver maleate and at 280°C for silver fumarate). The gaseous decomposition products of both compounds were found, using IR spectroscopy, to be dominated by maleic anhydride and CO₂. Minor proportions of ethylene, ethyl alcohol, acetone, methane and isobutene were also identified. Metallic silver was the final solid product, as identified by X-ray diffractometry. NMR analysis was used to monitor the isomerization of the maleate radical into the more stable fumarate above 230°C. Kinetic parameters (E_a and In A) were calculated from the effect of heating rate (2,5,10, and 20 deg.min^-1) on the DTA measurements. A mechanism is suggested for the decomposition pathways of these compounds, on basis of the results obtained and, also, on similarities with analogous systems.