CONTINUOUS AND SELECTIVE DETERMINATION OF WATER-VAPOR EVOLVED DURING THERMAL-DECOMPOSITION REACTIONS

A method suitable for the continuous and selective determination of water vapor evolved during thermal decomposition processes is described. The water detector can be connected to thermoanalytical equipment of controlled gas atmosphere without any difficulty. Water vapor, together with other gaseous decomposition products, is collected by the carrier gas and transported through a glass reaction vessel containing the measuring and reference cells. The change in cell temperature is sensed by a resistance thermometer coil connected to a bridge circuit. The relationship between the area under the recorded curve and the amount of water released is linear. Hydrocarbons, organic crack products, CO, CO2, SO2, SO3 and NH3 do not interfere. The detection limit is about 0.1 mg water, the reproducibility of the recorded curves is better than 10 per cent. In addition to the semi-quantitative determination of water, the detector trace can be recorded simultaneously along with the TG, DTG and DTA curves and used to identify the decomposition step(s) in which water was formed.