Magnesium oxalate, decomposition

The rate equation [eqn. (26)], given above for the reaction of magnesium oxalate, is also obeyed [1012] by the decomposition of zinc oxalate (620—646 K), although here the catalytic (second) term is dominant, so that behaviour approximated to the Prout—Tompkins equation [eqn. (9)]. The value of E (201 8 kJ mole 1) was the same as that found... 

Mikhail et al. (1971) obtained a series of porous products by the thermal decomposition of magnesium oxalate dihydrate in vacuo at temperatures in the range 400-600°C. The BET areas derived from the adsorption isotherms of nitrogen and cyclohexane are given in Table 10.14. The values of ct(N2) and ct(C4H4) have been taken as 0.162 nm2 and 0.39 nm2, respectively. 

Similarities were found between the patterns of behaviour reported for the zinc and magnesium oxalates. The stoichiometry of decomposition of magnesium oxalate (claimed to be accurate to 1%) (623 to 773 K) is [76] ... 

The initial acceleratory stage a < 0.3) was attributed primarily to the growth of nuclei formed during removal of water from the dihydrate, and it was suggested that similar elementary processes operate during the decay period. Kinetic observations [75] for the isothermal decomposition of magnesium oxalate (603 to 633 K) were represented by the two term rate equation ... 

A further possibility of preparing mixed-salt catalysts is provided by decomposition of complex salts of the type A [BXm],181 where A is a non-noble metal cation and B is a noble metal present in a complex anion an example is the oxalate complex Li2[Cu(Ox)2]. In all cases, highly active catalysts result they are usually more efficient than other catalysts containing the metal in question, and maximum activity is found with a molar ratio of, e.g., nickel oxalate magnesium oxalate = 1 1. 

Black, pyrophoric powder. Aside from the metallic Ni produced in the decomposition, contains a nearly im-changed magnesium oxalate carrier [32]. Extremely active hydrogenation catalyst. 

We would lose 73 mg for every 100 mg of pure magnesium oxalate dihydrate we had in the mixture on heating the mixture to 500°C. Note that the decomposition of magnesium oxalate does not follow the same process as the decomposition of calcium oxalate. Calcium oxalate first forms calcium carbonate, which only loses carbon dioxide to form CaO at temperatures above 600°C. Magnesium oxalate appears to decompose directly to MgO in one step at about 500°C. The weight remaining from the magnesium oxalate is equal to ... 

From the reported data, only MgO has been synthesized with high surface areas (usually between 130 and 300m2g 1) whereas for CaO, SrO and BaO only very low surface areas have been achieved ( 60, 10 and 2 m2 g 1, respectively).[37 39] For the preparation of high-surface-area MgO, the thermal decomposition of magnesium salts such as oxalates, hydroxycarbonates, sulfates and preferentially Mg(OH)2 has been frequently selected. The surface area is strongly dependent on the nature of the precursor salt,[40 41] the method and conditions of its prepara-tion[42] as well as the conditions of the thermal decomposition of the precursor salt.[43]... 

By reacting aluminum hydroxide with oxalic acid, basic aluminum oxalate can be produced, which is thermally stable to 330°C, losing 51% of its mass on decomposition at temperatures above 450°C. It is reported to have a flame-retarding and smoke-suppressing action similar to ATH, but because of its increased thermal stability, it can be used in polyamides and thermoplastic polyesters. However, unlike magnesium hydroxide, in these polymers it does not cause hydrolytic degradation.2... 

A classic example of a solid—fluid ceramic powder synthesis reaction is that of calcination and dehydration of natural or synthetic raw materials. Calcination reactions are common for the production of many oxides from carbonates, hydrates, sulfates, nitrates, acetates, oxalates, citrates, and so forth. In general, the reactions produce an oxide and a volatile gaseous reaction product, such as CO2, SOg, or HgO. The most extensively studied reactions of this type are the decompositions of magnesium hydroxide, magnesium carbonate, and calcium carbonate. Depending on the particular conditions of time, temperature, ambient pressure of CO2, relative humidity, particle size, and so on, the process may be controlled by a surface reaction, gas diffusion to the reacting... 

Iron(n) oxalate dihydrate loses water above 420 K to yield the anhydrous salt [53] in an inert atmosphere, but in the presence of oxygen FejOj may be formed [54]. At about 590 K the anhydrous oxalate decomposed slowly to yield magnetite and iron but no wustite was detected [53]. Kadlec and Danes [55] showed that the ar-time curves are sigmoidal and Zr, = 167 kJ mol. During decomposition of the mixed (Fe-Mg) oxalates, magnesium may stabilize the wustite product against either oxidation or reduction [56]. 

Zhabrova etal. [151] identified the reactions of nickel, cobalt and copper oxalates ( , = 150, 159 and 129 kJ mol respectively) as redox processes in which there is an autocatalytic effect by product metal on the electron transfer step. The decomposition rate was determined by the area of the reactant and results were fitted by the Prout-Tompkins equation. In contrast, the reactions of magnesium, manganese and iron oxalates (f, = 200,167 and 184 kJ mol ) are not autocatalytic and the area... 

Erdey and Paulik (100), in a simultaneous DTA-TG study, investigated the thermal decomposition of barium, strontium, manganese(II), calcium, magnesium, and zinc oxalates in air and nitrogen atmospheres. It was found that the evolved carbon dioxide formed in the reaction played an important part in that it may inhibit the progress of the reaction and shift the peak temperatures to higher values. 

Thermal decomposition of nitrates, carbonates, oxalates and so forth (see magnesium oxide, p. 1663 zinc oxide, p. 1664). 

However, Biirker has returned to this conception. According to him, coagulation of the blood is intimately related to the decomposition of the plates. All the conditions which influence thrombin, and consequently coagulation, such as temperature, contact, chemical products, act equally on the transformation of the plates. Sodium metaphosphate, magnesium sulphate, ammonium oxalate, all of which hinder coagulation, also preserve the blood components. This decomposition of the plates would take place under the action of a trypsin contained in the blood. Once these particles are destroyed, coagulation would appear. The quantity of fibrin formed is then in direct proportion to the... 

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