Radiocarbon measurements, mainly on soil and water samples are being continued. Benzene samples are prepared as described earlier (Scharpenseel and Pietig, 1969; 1970). Radioactivity is measured in a single quartz vial, and also with 13 specially manufactured, low background Teflon/Duraluminium vials, similar to the system described by Polach (1971, pers commun).

The Radioisotopes Laboratory was established in January 1972, in order to supply radiocarbon measurements of various samples to several institutions. Active analyses commenced in June following the testing and evaluation of equipment and known samples for accuracy and reproducibility. During this time, data was accumulated for the statistical establishment of counting accuracy, particularly for background activity.

The Low-level Measurements Laboratory at AERE, Harwell was set up some years ago principally to measure natural levels of tritium in water for hydrologic applications. The measurement of 14C in groundwater carbonates was a logical development from this work. In the period 1971–73 the measurement system has been extended to include archaeologic samples and this is the first list of dates for samples submitted during that period.

14C dates listed in this report on geochemical, geologic, and archaeologic samples were obtained mainly from the beginning of 1971 to the middle of 1973. Techniques of measurement used are the same as described previously (Yang, 1972). Sample descriptions and comments for archaeologic samples were prepared in collaboration with collectors and submitters. For age calculation, 95% activity of NBS oxalic acid is used as the modern standard and the value of 5568 ± 40 years is used for the half-life of 14C. Dates are expressed in years bp (before ad 1950). The error (1σ) quoted is calculated from the uncertainty involved in counting background, NBS oxalic acid standard, and sample.

On two previous occasions we have published lists of 14C results of precisely dated wood samples in Radiocarbon as per mil deviations (R, 1965, v 7, p 179–186; R, 1969, v 11, no. 2, p 469–481). We have also published a list of 14C dates, consolidating all dated wood samples processed in our lab to July 1969 (Ralph and Michael, 1970).

This date list includes most of the archaeologic and geologic samples dated in this laboratory since publication of our last date list (R, v 13, p 367–381), as well as some samples dated previously, which lacked adequate sample information. Known-age samples are reported in Univ of Pennsylvania Radiocarbon Dates XVI, this issue. The bp ages are based on ad 1950, and have been calculated with the half-life value of 5568 yr. All samples were counted at least twice for periods of not less than 1000 min each. Errors quoted for each sample are derived from the measurement of the sample, the background, and several counts of our mid- 19th century standard Oak sample, but do not include the half-life error. All samples were pretreated with 3N HCL, and some, where noted, were given additional pretreatment with 2% NaOH for the removal of possible humic acid contaminants.

Preparation of samples, operation of counting systems, and calculation of results remain as described previously (Harkness and Wilson, 1973).

In September 1970, the laboratory moved into new premises on the ground floor of a new building. The measuring room is constructed of low radioactive limestone concrete and is lined with grounded copper plate. Air conditioning insures a working temperature of 20 ± 1°C and a relative humidity of 40%.

The dating equipment and operating conditions remain essentially as previously described. All samples are from Ireland unless specified.

Measurements have continued with the same proportional counter system, pretreatment procedure, methane preparation and measurement, and calculation using a half-life of 5568 ± 30 years, as described previously (R, 1970, v 12, p 298–318). Uncertainties quoted are single standard deviations originating from standard, sample, background counting rates and half-life. No 13C/12C ratios were measured.