Liquid scintillation counting is another radiocarbon dating technique that was popular in the 1960s.
A vial with a sample is passed between two photomultipliers, and only when both devices register the flash of light that a count is made.
The method does not count beta particles but the number of carbon atoms present in the sample and the proportion of the isotopes. Samples that have been radiocarbon dated since the inception of the method include charcoal, wood, twigs, seeds, bones, shells, leather, peat, lake mud, soil, hair, pottery, pollen, wall paintings, corals, blood residues, fabrics, paper or parchment, resins, and water, among others.
Physical and chemical pretreatments are done on these materials to remove possible contaminants before they are analyzed for their radiocarbon content.
The benzene is produced as follows: carbon dioxide, obtained by burning the sample, reacts with metallic lithium to form lithium carbide.
The lithium carbide is hydrolysed to acetylene which is subseqently converted to benzene by catalytic trimerisation.