ISO 7625:2006 specifies methods for preparing a sample from one or more sintered parts of materials to be analysed for free or total carbon content. Combined carbon is determined as the difference between total and free carbon. This standard covers the preparation of samples for the determination of carbon by a chemical method, i.e. combustion in oxygen and measurement of the carbon dioxide produced, in accordance with ISO 437. It does not cover the preparation of samples for carbon determination by physical methods, such as metallography or spectroscopy.