The procedures for the determination of total carbon are therefore structured as combustion techniques, detection techniques and detection methods constituting the laboratory procedure.
5.2 Combustion techniques
5.2.1 General
Two different combustion techniques with different decomposing agents/accelerators can be used.
5.2.2 Resistance furnace in oxygen and lead borate as decomposing agent
5.2.2.1 Principle
The sample is heated together with lead borate in a stream of oxygen in a resistance tube furnace to convert the carbon to carbon dioxide by combustion. The sample mass and the details of the combustion depend on the method of determination used. The combustion gases are conducted through a tube containing percarbamide to absorb the oxidation products of the sulfur contained in the sample. The carbon dioxide is absorbed in an alkaline medium and determined either coulometrically, gravimetrically, conductometrically or by infrared absorption.
5.2.2.2 Reagents
Use only reagents of analytical grade.
5.2.2.2.1 Oxygen, 99,99 % or 99,5 %.
NOTE Oxygen 99,99 % is used if the instrument does not have an oxygen-refining capability. Oxygen 99,5 % is used if the instrument has oxygen-refining ability.
5.2.2.2.2 Lead borate, 2 PbO B2〇3, prepared by melting 45 g of analytical grade lead oxide, PbO, together with 7 g of analytical grade boron trioxide,巳2O3, for 10 min at (950 °C 土 25) °C, cooling the melt by pouring it onto a clean aluminium plate and then pulverizing it