Metal oxalates, table

Results and Discussion The values of the above-mentioned parameters and the compositions of the primary products, found from their comparison, are listed in Table 16.64. The discrepancies between the calculated and experimental values of AyH do not exceed 5% for Ag, Ni, and Mn oxalates and 10% for Hg and Pb oxalates. For the latter two reactants, the discrepancies are most likely due to underestimation of the initial parameter E. This is confirmed by the overestimated experimental values of the Tm/E ratio for these oxalates (Table 16.63). When determining the optimal composition of the primary gaseous products, the similarity of the decomposition schemes for the reactions yielding similar solid products (metals or oxides) was taken into account. The most unexpected result was that the primary gaseous products contained, instead of equilibrium CO2 molecules, a mixture of CO and 02 molecules for Ag, Ni, Mn, and Pb oxalates and a mixture of CO and O for Hg oxalate. The corresponding differences in the enthalpies are 283 and 532 kJ moP, respectively, exceeding by an order of magnitude the possible measurement and calculation errors. 

Table 4.9 Stability constants of various metal-oxalate complexes.

Freshly prepared metal oxalate hydrates are treated with stoichiometric quantities of hydrazine hydrate. As the mixture is thoroughly stirred the reaction takes place instantaneously with the evolution of heat. In some cases, a change of color in the original salt is observed due to complex formation (Table 3.10). 

Thermal analysis data of metal hydrazine carboxylates, given in Table 4.2, reveal that the compounds decompose exothermically. The two exotherms observed in all cases are due to the decomposition of hydrazine carboxylate complex. These complexes decompose to the corresponding metal oxalate first, and later to form the carbonate salt. Formation of the oxalate intermediate is confirmed by interrupting the DTA... 

Table 4.7 gives thermal decomposition data of N2H5M(N2H3COO)3-H2O. The iron complex shows a single step in TG-DTG and two exotherms in DTA, while both cobalt and nickel complexes show two-step decomposition in TG-DTG and two exotherms in DTA. The observed weight loss after the first step corresponds to the formation of metal oxalate hydrazine... 

All these complexes have been investigated by infrared, electronic, and ESR spectroscopy. Magnetic studies were carried out using a Gouy balance at room temperature. Tables 5.7 and 5.8 list, respectively, the IR absorption frequencies and the electronic spectral details and magnetic data of hydrazinium metal oxalates. 

Mixed metal oxalate hydrates do not yield ferrites at such low temperatures. However, complex formation with hydrazine makes it possible to obtain ferrites from the oxalates precursors at low temperatures of —150 °C. This shows that the exothermic decomposition of hydrazine plays a vital role in the formation of these spinels at such temperatures. Properties of the ferrites formed are summarized in Table 6.7. 

Table XIX contains stability constants for complexes of Ca2+ and of several other M2+ ions with a selection of phosphonate and nucleotide ligands (681,687-695). There is considerably more published information, especially on ATP (and, to a lesser extent, ADP and AMP) complexes at various pHs, ionic strengths, and temperatures (229,696,697), and on phosphonates (688) and bisphosphonates (688,698). The metal-ion binding properties of cytidine have been considered in detail in relation to stability constant determinations for its Ca2+ complex and complexes of seven other M2+ cations (232), and for ternary M21 -cytidine-amino acid and -oxalate complexes (699). Stability constant data for Ca2+ complexes of the nucleosides cytidine and uridine, the nucleoside bases adenine, cytosine, uracil, and thymine, and the 5 -monophosphates of adenosine, cytidine, thymidine, and uridine, have been listed along with values for analogous complexes of a wide range of other metal ions (700). Unfortunately comparisons are sometimes precluded by significant differences in experimental conditions.

Inactive metals in the wastes, such as Fe(III), Mo(VI), and Zr(IV), are retained in the aqueous feed by addition of suitable quantities of oxalic acid. As with CMPO, some Ru is extracted. Currently, the extraction of Pd, Tc, Np and their poor stripping remain a problem for which process modifications are necessary. The flow sheet in Fig. 12.13 and Table 12.11 has... 

The physical and chemical properties of elemental thorium and a few representative water soluble and insoluble thorium compounds are presented in Table 3-2. Water soluble thorium compounds include the chloride, fluoride, nitrate, and sulfate salts (Weast 1983). These compounds dissolve fairly readily in water. Soluble thorium compounds, as a class, have greater bioavailability than the insoluble thorium compounds. Water insoluble thorium compounds include the dioxide, carbonate, hydroxide, oxalate, and phosphate salts. Thorium carbonate is soluble in concentrated sodium carbonate (Weast 1983). Thorium metal and several of its compounds are commercially available. No general specifications for commercially prepared thorium metal or compounds have been established. Manufacturers prepare thorium products according to contractual specifications (Hedrick 1985). 

Silver is a white, ductile metal occurring naturally in its pure form and in ores (USEPA 1980). Silver has the highest electrical and thermal conductivity of all metals. Some silver compounds are extremely photosensitive and are stable in air and water, except for tarnishing readily when exposed to sulfur compounds (Heyl et al. 1973). Metallic silver is insoluble in water, but many silver salts, such as silver nitrate, are soluble in water to more than 1220 g/L (Table 7.3). In natural environments, silver occurs primarily in the form of the sulfide or is intimately associated with other metal sulfides, especially fhose of lead, copper, iron, and gold, which are all essentially insoluble (USEPA 1980 USPHS 1990). Silver readily forms compounds with antimony, arsenic, selenium, and tellurium (Smith and Carson 1977). Silver has two stable isotopes ( ° Ag and ° Ag) and 20 radioisotopes none of the radioisotopes of silver occurs naturally, and the radioisotope with the longest physical half-life (253 days) is "° Ag. Several compounds of silver are potential explosion hazards silver oxalate decomposes explosively when heated silver acetylide (Ag2C2) is sensitive to detonation on contact and silver azide (AgN3) detonates spontaneously under certain conditions (Smith and Carson 1977). 

Many formation constants involve polycarboxylates Table 28 summarizes the data. Nagyp l and Fabian s report on the oxalic and malonic systems seems the most complete as hydrolysis of both metal ion and complexes has been included.584 A concentration distribution of the complexes in the malonic system is shown in Figure 25. The order of basicities is succinic > citraconic > itaconic > maleic > malonic acid and log /3U0 should follow the same order. However, from Table 28, the order of stabilities is citraconic > malonic > maleic > itaconic > succinic acid.608... 

Several groups have been successful at the catalytic conversion of carbon dioxide, hydrogen, and alcohols into alkyl formate esters using neutral metal - phosphine complexes in conjunction with a Lewis acid or base (109). Denise and Sneeden (110) have recently investigated various copper and palladium systems for the product of ethyl formate and ethyl formamide. Their results are summarized in Table II. Of the mononuclear palladium complexes, the most active system for ethyl formate production was found to be the Pd(0) complex, Pd(dpm)2, which generated 10/imol HCOOEt per /rniol metal complex per day. It was anticipated that complexes containing more than one metal center might aid in the formation of C2 products however, none of the multinuclear complexes produced substantial quantities of diethyl oxalate. 

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