文摘
Microcalorimetry was used to characterise bicarbonate after treatment at high temperatures. By measuring the heat flow from a sample of bicarbonate at 100 % relative humidity, the net exothermic contribution could be used to estimate the fraction of pyrolytically formed Na<sub>2sub>CO<sub>3sub>. The enthalpy value corresponding to the heat of solution of Na<sub>2sub>CO<sub>3sub> was also applicable to a physical mixture of NaHCO<sub>3sub>/Na<sub>2sub>CO<sub>3sub>. However, from the characteristic peaks of the heat flow versus time curve, pyrolytically formed Na<sub>2sub>CO<sub>3sub> could be distinguished from that present in the physical mixture. The different bicarbonate batches of varying degree of pyrolytic decarboxylation were also observed at an elevated relative humidity of 54 % . From these measurements it could be inferred that a decarboxylation of up to 4.5 % could be allowed without any significant effect on the stability of bicarbonate at 54 % .