Editing Three-age system (section)

=== Measurement of chemical change ===
Any material sample contains elements and compounds that are subject to decay into other elements and compounds. In cases where the rate of decay is predictable and the proportions of initial and end products can be known exactly, consistent dates of the artifact can be calculated. Due to the problem of sample contamination and variability of the natural proportions of the materials in the media, sample analysis in the case where verification can be checked by grand layering systems has often been found to be widely inaccurate. Chemical dates therefore are only considered reliable used in conjunction with other methods. They are collected in groups of data points that form a pattern when graphed. Isolated dates are not considered reliable.