GB1025942A - Analytical method and apparatus - Google Patents

Abstract

A method of determining the amount in a solid test sample, of an element capable of forming a volatile oxide, e.g. C or S in a steel sample, comprises reacting particles of the test sample in a heated reaction zone (10) with oxygen, completely withdrawing a stream of oxygen and the volatile oxide and monitoring changes in thermal conductivity of said stream (measured by thermistor 20) at constant flow rate. The above numerals refer to the Figure (not shown) in which an oxygen inlet conduit 11 is connected to the furnace 10, having a pressure regulating valve 12 giving constant oxygen pressure in the furnace, regardless of furnace oxygen requirements. The volatile oxides formed may be passed through a filter 16, and thence to purifying towers in which one or more of the volatile impurities is removed. A three-way valve 14 enables the gas to be passed to atmosphere, or, via capillary tube 15 reducing the pressure to atmospheric, to an oxidizing tower 18, containing, e.g. heated catalytic cupric oxide, to oxidise the volatile oxide to its highest form. A heat exchanger 19 brings the gas stream to the temperature at which thermistor 20 has been previously calibrated with oxygen alone, and the signal from the thermistor is passed to an integrating recorder 21, which enables the signals to be read as a direct percentage of the element in the gas stream and as the total element of interest in the sample. The C and S contents of a steel may be determined together by first monitoring a stream containing both oxides, then passing the stream through an SO2 absorber and a second monitoring stage. The first monitor gives total C + S and the second gives C content.