Instituto Venezolano de Investigaciones Cientificas Natural Radiocarbon Measurements II

Abstract

The dates reported in this list were measured from December, 1964 to November, 1965. The laboratory continues to employ liquid scintillation techniques with synthesized benzene; however, the chemical yield has been improved to the point where it is now between 80 and 100%. For most of the measurements listed here, a 4 cc counting vial was used with 3 cc benzene and 1 cc commercial toluene containing PPO and dimethyl-POPOP scintillators. The counting efficiency is 72%, which gives a net modern count of 23.5 cpm, and the background is 8.2 cpm. The detection limit (48 hours counting, 2σ statistics) with ordinary size samples is 43,000 yr using the 4 cc vial and 52,000 yr with a 20 cc vial. Errors introduced by the laboratory procedure are less than ½% (Tamers and Pearson, 1965a). A detailed review of the methods being used has been published recently (Tamers, 1965b).