Strontium carbonate, decomposition

Both carbonates decompose to their oxides with the evolution of carbon dioxide. The decomposition temperature for calcium carbonate is in the temperature range 650-850 °C, whilst strontium carbonate decomposes between 950 and 1150°C. Hence the amount of calcium and strontium present in a mixture may be calculated from the weight losses due to the evolution of carbon dioxide at the lower and higher temperature ranges respectively. This method could be extended to the analysis of a three-component mixture, as barium carbonate is reported to decompose at an even higher temperature ( 1300 °C) than strontium carbonate. 

Strontium oxide is prepared by thermal decomposition of strontium carbonate, hydroxide, or nitrate ... 

Strontium carbonate is somewhat less soluble than barium carbonate otherwise its characteristics (slight solubility in ammonium salts, decomposition with acids) are similar to those of the latter. 

Strontium carbonate is almost insoluble in water 0.001 gram per 100 grams of water at 24 C. The solution is alkaline and the pH value was 8.9 at 35 C. If a composition consists mainly of aluminium and nitrates including strontium carbonate, such an alkaline mixture has a risk of spontaneous decomposition in wet state. Strontium carbonate dissolves in water as the bicarbonate, if the water contains COa.. 

Judd and Pope [36] conclude that because the activation energies for decompositions of CaCOj, SrCO, and BaCOj are all close to the corresponding enthalpies of dissociation (apparent values of , are 180,222 and 283 kJ mol and A//, 178, 235 and 269 kJ mol, respectively) the mechanisms of decomposition in all three substances are the same as that proposed by Hills [18] for calcite. Strontium carbonate [37] generally resembles the calcium salt in that an increase in sample size results in a decrease in reaction rate. Differences in behaviour were ascribed [37] to the occurrence of a crystallographic transformation and to fusion. 

After the loss of the water of hydration, the curve exhibited a horizontal mass level from 250-360°C, which corresponded to the composition for anhydrous metal oxalates. Decomposition of the three oxalates then took place simultaneously, the process being completed al about 500°G The anhydrous metal carbonates were then stable from about SOO-eKTG followed by strontium carbonate, which also began to decompose in this range and was completely decomposed at 1100°C, at which temperature barium carbonate began to decompose. 

From the mass-loss curve, then, the following data are obtained D, mass of dry precipitate at 100°C , mass of water of hydration F, mass of carbon monoxide formed by the decomposition of the anhydrous metal oxalates G, mass of carbon dioxide formed by the decomposition of calcium carbonate and L, the mass of carbon dioxide formed by the decomposition of strontium carbonate. From these data, the amounts of calcium, C, strontium, S, and barium, By can be calculated from... 

X-ray patterns of the products formed by the reaction between strontium carbonate and anatase, rutile, and nonstoichiometric rutile each showed SrTiOj to be the only phase present. X-ray patterns of partially reacted compacts revealed the presence of strontium titanate, strontium carbonate, and titania. The absence of strontium oxide indicates that the carbon dioxide evolution was associated with the reaction between SrCOj and Ti02 to form a product phase and not with the decomposition of SrCOj to SrO. The data of Wanmaker and Radielovic for the rate of dissociation of strontium carbonate indicates that interference from dissociation in measuring the kinetics of interaction between SrCOj and Ti02 is negligible below 900°C. Above this temperature a correction may be necessary for the dissociation of SrCOj. However the fact that the same kinetic model can be used to represent the data above and below this temperature suggests that the correction term is small. 

P. G. Morgan Franklin Institute) There seemed to be a temperature rise where your strontium carbonate itself decomposes. In other words, you superimposed some of the complexities of decomposition of strontium carbonate onto further reaction with titanium dioxide, and your supply of strontium ions and oxygen ions is continuously changing as decomposition proceeds. I think you could do one of two things to simplify this. You could either carry out the reaction between the carbonate and oxide in a temperature regime where the carbonate itself would not otherwise decompose, or you could just start with strontium oxide and titanium oxide to simplify things. 

Figure 5B shows the DTA profiles for the as-synthesized powders. The curves presented two well-defined endothermie peaks, the first one, more intense, at 345°C, corresponding to the decomposition of strontium carbonate and the seeond peak, at 545°C, associated with the decomposition of intermediate carbonates. 

The removal of inorganic salts from reaction mixtures afforded by polymeric materials may be simply and effectively accomplished by dialysis,166 178 after decomposition of remaining periodate with ethylene glycol130 131 or butylene glycol. 161 170 Alternatively, the iodate and periodate ions may be removed as such, or after reduction to free iodine. The iodate and periodate ions have been effectively precipitated by means of sodium carbonate plus manganous sulfate,6 or by lead dithionate,191 barium chloride,24 192 193 strontium hydroxide194 202 or barium hydroxide,203 204 lead... 

Thermal decompositions of barium and strontium azides, preirradiated with 1 MeV gamma rays, were conducted by Prout and Moore [78,79]. With dehydrated barium azide a total gamma dose of 20 Mrad (2.24 X 10 R) eliminated the induction period and increased the acceleration of the decomposition. A somewhat greater effect was evidenced with strontium azide. Avrami et al. [80] subjected barium azide to Co gamma radiation to exposure levels up to 1 XIO R (Table XIII). Differential thermal analyses (Figure 16) showed a steady decomposition of the sample, and after 1 X 10 R exposure (W hr at room temperature), infrared analysis indicated that the residue was in the form of barium carbonate. 

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. 

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