CLASSICAL DRY ASHING OF BIOLOGICAL AND AGRICULTURAL MATERIALS .1. FOLLOWING THE COURSE OF REMOVAL OF ORGANIC MATRIX

The course of thermal decomposition of several selected biological and agricultural materials during classical dry ashing (dry ashing perfor med on air, in open vessels, and at atmospheric pressure) was studied by chemical analysis of solids, gaseous intermediates and products, as well as with the help of thermogravimetry, DTG and DTA. The decomposi tions were complex processes that consisted of dehydration and of a pr onounced exothermic degradation of organic components that proceeded i n at least two overlapping stages. Water as a gaseous product is the m ajor product of the first stage, while carbon dioxide and nitrogen are released mainly during the latter stages. The course of decomposition can be affected considerably by the experimental parameters. In the a bsence oi ashing aid, a temperature of about 500 degrees C is necessar y for complete decomposition of plant tissues, while the more resistan t animal tissues need much higher temperatures.