The thermal decomposition of anhydrous (orthorhombic) copper(II) formate was studied by programmed rising-temperature methods (TG, DTG, DTA and DSC) to about 250degreesC in flowing gas atmospheres of nitrogen (inert), hydrogen (reducing) and air (oxidizing). The degradation reaction, anion breakdown, proceeded to completion in two distinct, but partially overlapping, rate processes and apparent Arrhenius parameters. calculated by the Ozawa nonisothermal kinetic method, agreed satisfactorily with the literature results. It was concluded that the two consecutive processes contributing to the overall reaction, involved stepwise cation reduction: Cu2+ --> Cu+ --> Cu-0 with copper(I) formate as intermediate. This mechanism is similar to that proposed in previous studies of the decompositions of copper(II) oxalate, malonate, maleate, fumarate, mellitate and squarate. For all of these reactants, the Cu+ salt has been identified as an intermediate, exhibiting a (slightly) lower relative reactivity than the corresponding Cu2+ salt. For copper(II) formate the response curves in the three different gaseous atmospheres were generally similar, showing that neither oxidizing nor reducing conditions caused a marked chan e in reactivity. The temperature of reaction initiation in H-2 was slightly diminished and the temperature of the second stage of reaction in O-2 Was raised appreciably. It is believed that electron transfer contributed to the control of reactivity and that the gases present appreciably influence the rates of the contributory reactions occurring. (C) 2003 Elsevier B.V. All riahts reserved.