Steel or Iron clips of samples under test are heated in a stream of oxygen gas to about 1200⁰C - 1350⁰C converting carbon and Sulphur contents to carbon dioxide and sulphur dioxide gases respectively. These gases are passed through a solution of hydrogen peroxide. The sulphur dioxide gas dissolves in hydrogen peroxide forming sulphuric acid which is titrated against caustic soda solution to know strength to determine the percentage of sulphur in the sample under test.

The gaseous mixture from which sulphur dioxide has been removed (absorbed) is now taken into a calibrated burette. Then the gases are taken into a absorption vessel containing potassium hydroxide solution to absorb carbon dioxide gas. The reduction in volume of the total gas equals the volume of carbon dioxide gas knowledge of which then gives the amount of carbon. The scale reading directly gives the percentage of carbon in 1(one) gm sample.

In carbon determination apparatus the parts required for determination of carbon are not supplied determination of sulphur is done as in the carbon & sulphur determination apparatus.