Strontium oxalate, decomposition

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... 

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. 

It may be seen that a change in atmosphere often causes a change in shape of decomposition curve. Calcium, strontium and barium oxalates, however, behave somewhat differently. Their carbonates are all more stable than their oxalates. For this reason their oxalates decompose to carbonate first and to oxide at a higher temperature. This is shown for calcium oxalate in Figure 6 and discussed above. 

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