Rafter carbon dating
Often, submitted samples are divided and one portion retained as a reference in case the original sample is lost, or a further date required.
Sometimes, submitters perform basic pretreatments, usually involving a wash in distilled water and the removal of root material.
Pretreatments are designed to remove the contaminating substances that have affected the sample during its post-depositional history.Contamination may also be caused by humic acids circulating throughout the soil. They may exchange carbon or adhere to samples that have large surface areas and make any radiocarbon results too young.This surface exchange is termed 'adsorption' and is especially common in samples such as peats, charcoals and muds.Libby realized that the residual carbon 14 of some samples would be thus affected and suggested that some materials would be more accurate for dating than others.He predicted that charcoal would be the most effective, shell, the least.