4F - C,S - Infared

Accelerator material is added to a 0.2 g sample. The inductive elements of the sample and accelerator couple with the high frequency field of the induction furnace. The pure oxygen environment and the heat generated by this coupling cause the sample to combust. During combustion, carbon-bearing elements are reduced, releasing the carbon, which immediately binds with the oxygen to form CO and CO₂, the majority being CO₂. Also, sulphur-bearing elements are reduced, releasing sulphur, which binds with oxygen to form SO₂. Sulphur is measured as sulphur dioxide in the first IR cell. A small amount of carbon monoxide is converted to carbon dioxide in the catalytic heater assembly; SO₂ is converted to SO₃, while sulphur trioxide is removed from the system in the cellulose filter. Carbon is measured as carbon dioxide in the IR cell as gases flow through the IR cells. Carbon dioxide absorbs IR energy at a precise wavelength within the IR spectrum. Energy from the IR source is absorbed as the gas passes through the cell, preventing it from reaching the IR detector. All other IR energy is prevented from reaching the IR detector by a narrow bandpass filter. Because of the filter, the absorption of IR energy can be attributed only to carbon dioxide (CO₂). The concentration of CO₂ is detected as a reduction in the level of energy at the detector. An Eltra CS-2000 is used for the analysis.