Thermoparticulate analysis

The technique of thermoparticulate analysis (TPA) consists of the detection of evolved particulate material in the evolved gases as a function of temperature. In the presence of supersaturated water vapor, these particles provide condensation sites for water, and hence can be detected by light-scattering techniques. Water droplets grow very rapidly on the particulate matter (condensation nuclei) until they are of a sufficient size to scatter light. The scattered light, as detected by a phototube in a dark-field optical system, is proportional to the number of condensation nuclei initially present. It is an extremely sensitive measurement, with the capability of detecting one part of material in 1015 parts of air. The technique was first employed by Doyle (90) and has been reviewed by Murphy (91. 92). 

Murphy (91) has also described a converter that will generate condensation nuclei from a reactant that would normally not be detected by TPA. For example, ammonia can be detected by passing it through a flask containing a small amount of hydrochloric acid. The gaseous HCl above the solution reacts with the ammonia to form condensation nuclei of ammonium chloride. Other gases and the conversion processes employed are shown in Table 

Compound Conversion Process Easily Detected Cone, (ppm) 

The TPA method is continuous, capable of gas analysis through conversion techniques, and able to detect condensation nuclei. It is the only thermal technique with the last named capability. 

---

Methods of EGA using selective sorption, condensation of effluent gases, infrared absorption and thermoparticulate analysis have been reviewed by Lodding [144]. The use of simple gas burette systems should not be forgotten and an Orsat gas analysis apparatus can provide useful measurements in studies of the decomposition of formates [169]. Problems have been encountered in the determination of water released Kiss et al. [170—172] have measured the formation of this compound from infrared analyses of the acetylene evolved following reaction of water with calcium carbide. Kinetic data may be obtained by wet methods ammonia, determined by titration after absorption in an aqueous solution, has been used to measure a—time values for the decomposition of ammonium salts in a fluidized bed [173],... 

The physical property measured and the corresponding thermal analysis technique are tabulated in Table 1.1 (3) and further elaborated on in Chapter 13. Notice that under the physical property of mass, thermogravimetry (TG), evolved gas detection (EGD), evolved gas analysis (EGA), emanation thermal analysis (ETA), thermoparticulate analysis, and others are included. Similar considerations can be included in the physical proparties of optical characteristics, electrical characteristics, magnetic characteristics, and so on. The definitions of each individual technique are given in the chapter in which they are discussed. A select number of the thermal analysis techniques are summarized in Table 1.2. Each technique is tabulated in terms of the parameter measured, a typical recorded data curve, the instrumentation needed, and the chapter in which it is described. 

Evolved gas analysis Emanation thermal analysis Thermoparticulate analysis EGA... 

Optical properties Thermooptometry (spectroscopy) Thermoluminescence (emission) Thermomicroscopy (structure) Thermoparticulate analysis TPA... 

Thermoparticulate analysis (TPA) Technique in which the evolved particulate material in the evolved gases is measured as a function of temperature. 

---