British Museum natural radiocarbon measurements III.

Abstract

The third series of radiocarbon measurements made at the British Museum Research Laboratory is reported in the following list. Equipment and method used are as described previously (British Museum 1) [GeoScience Abstracts 1-1681] and, as in previous lists, the error terms are not based solely on counting statistics, but are widened to include contributions of + or -80 years for possible isotopic fractionation effects and + or -100 years for the deVries effect. Ages are calculated on a half-life of 5568 + or - 30 years. NBS oxalic acid is now used as a reference standard in place of 100-yr.-old oak. The latter gave an age-corrected value almost exactly 95% of the oxalic-acid activity, and thus no corrections are required to our previous date lists to bring them into line with the new standard. One of the laboratory's long-term projects is an investigation into the reliability of bone and antler as source materials for dating. A number of measurements on such materials are reported here. In all cases, only the organic fraction of the sample was used as a source of carbon, and the procedure adopted was as follows: Sample was broken into small pieces, either by coarse grinding or pounding in a mortar, and was treated with cold dilute hydrochloric acid in order to remove carbonates and to decalcify the material. Resulting granular gel was washed thoroughly by repeated soaking with cold water and was finally dried, prior to combustion.