Microwave ashing apparatuses and components

Abstract

An apparatus for use in analyzing materials for ash content includes a walled chamber which retains microwave radiation therein, a source of microwave radiation, such as a magnetron, for radiating onto contents of such chamber, and an ashing furnace in the chamber which includes a heat resistant wall of low thermal conductivity, which is transmissive of microwave radiation, and a microwave absorptive material which is capable of being heated by microwave radiation to an ashing temperature. The furnace includes a passageway through it for the entry into the furnace cavity of a gas, such as air, and for venting gas, such as combustion products, from the furnace cavity, and preferably also includes a removable trapezoidally shaped door in a front wall thereof, which, when the chamber door is open, is readily removable from the furnace by hand, without burning the operator's fingers, despite the high internal temperature in the furnace cavity. Air flows through the chamber and around the furnace, helping to cool the exterior, of the furnace walls. It is preferred that the operation of the furnace and the ashing temperature be controlled by a combination of a temperature sensor, preferably a thermocouple, and a control mechanism, which turns the magnetron on and off as the temperature in the furnace cavity falls below or rises above a desired set temperature, respectively.