The following list of dates contains the majority of measurements made during 1975, ie, since our last list (R, 1975, v 17, p 255-275).

Radiocarbon measurements are carried out mainly on soil samples and soil organic matter fractions. Benzene samples are prepared as described earlier (Scharpenseel and Pietig, 1969; 1970). Radioactivity is measured in a single quartz vial, using a Packard Tri Carb Model 3075 as well as a Berthold Betascint BF 5000. Most equipment has been transferred from Bonn University Radiocarbon Dating Lab to Hamburg, where operation of former Bonn Radiocarbon Lab will be continued.

Most of the 14C measurements reported here were made between October 1974 and October 1975. Equipment, measurement, and treatment of samples are the same as reported previously (R, 1968, v 10, p 36-37) except for bone samples (see below).

This list includes dates measured from January 1974 to June 1975 with previously described CO2 proportional counters (Alessio et al, 1970b). All archaeologic and geologic samples except for Arslantepe series come from Italian territory. Chemical apparatus for CO2 preparation and purification is unchanged (Alessio et al, 1970b). Data recording devices have recently been replaced with integrated circuits built entirely at the Lab. The logic of the circuitry was also modified to provide more stable devices and a higher relative figure of merit A/√B of each counter (A = net activity of modern standard, B = background). Consequently, the resolution of age measurements has increased appreciably. Present values of A/√B for the 4 counters in use are shown in Table 1.

The present list includes 35 dates of geologic samples analyzed at the Geobiochemical Laboratory of the Institute of Zoology and Botany, Academy of Sciences, Estonian SSR. Benzene synthesized from wood dating from 1850 ± 10 yr served as a reference standard. All radiocarbon dates have been calculated using 5568 ± 30 yr before ad 1950 as the half-life of 14C.

The Radiocarbon Laboratory under the Chair of Nuclear physics of Tbilisi State University is engaged in studies of radiocarbon variation in the atmosphere and mineral waters and determination of the absolute age of archaeologic, geologic, botanical, and other samples. This list reports dates of archaeologic and geologic specimens only. Gas counting and liquid scintillation methods are used for dating.

The following list of dates is compiled from samples prepared and catalogued since publication of our last date list (R, 1975, v 17, p 99-111). The counting equipment and operating procedures are the same. Ages are quoted with a 1σ counting error which includes statistical variation of the sample count as well as for background and standard, using ad 1950 as the reference year and 95% NBS oxalic acid for 14C dating as the standard. The half-life value used is 5570 years.

The following radiocarbon measurements are a partial list of geologic samples from S Florida dated during the summer of 1975. The technique used is liquid scintillation counting of wholly synthesized benzene as indicated in R, v 16, p 402-408 and R, v 18, p 210-220. Dates are calculated using a 14C half-life of 5568 yr and errors are reported as one standard deviation. Before conversion, shell material was etched with HCl to remove all soft or powdery material. All wood and peat samples were treated with NaOH.