Preparations to establish a radiocarbon dating laboratory at the University of Sydney were made in 1970 in the Department of Physical Chemistry, to support Ph.D. studies and to supplement existing dating services in Australia to the archaeologic and geologic communities.

Measurements reported in this paper were obtained in the Cambridge Radiocarbon Dating Laboratory during 1970–71. For most determinations, pure carbon dioxide at a pressure of 2 atm was used to fill the copper proportional counters, of 0.5 L or 1.5 L volume. The counters were protected by a massive lead shield and a plastic scintillation anticoincidence screen (Switsur, Hall, and West, 1970). Modern sample gas was obtained from the 1845 to 1855 growth rings of a locally grown oak tree which was felled in 1950. Background was prepared from Welsh anthracite. The contemporary standard is compared frequently with the activity of the International NBS oxalic acid standard. Sample ages are calculated using the conventional half-life of 5568 ± 30 years and the uncertainty stated in terms of one standard deviation of the counting statistics.

The following list covers some old measurements not included in previous lists and most of the samples measured at the Uppsala C14 laboratory since the last list (R., 1969, v. 11, p. 515–544); samples utilized for determining the increase of the C14/C12 ratio due to explosion of nuclear devices are omitted.

This date list covers most of the datings made during 1968 to 1970. Each sample is measured in one of the two counters described previously (R., 1970, v. 12, p. 205-237).

The radiocarbon laboratory in the Oceanography Department at Texas A&M University was established primarily for the examination of seawater samples, although other types of samples have been run. Emphasis has been placed on seawater samples of the Gulf of Mexico and adjacent areas. Most of the samples examined have been inorganic carbon, but some organic-carbon samples are being run, mainly wood and charcoal whose ages have been determined previously. More samples of known age will be run as a further check on the reliability of experimental methods and procedures.

The Radiocarbon Dating Laboratory of Tehran University Nuclear Centre began operation in autumn 1970. Benzene synthesis and liquid scintillation counting was chosen as the best method for processing a large number of archaeologic specimens most of whose ages are less than twice the half-life of C14. Advantage of benzene synthesis; ease of chemical processing light transfer properties, lack of isotopie fractionation and radioactive contamination, removal of radon, and improbability of cross-contamination, have been discussed (Noakes et al., 1964; Noakes, Stipp, and Hood, 1964; Kowalski, 1965).

This laboratory is now a branch of the Texas Memorial Museum of the University of Texas at Austin. This list reports C14 measurements made in projects completed between October 1969 and August 1971. A number of major projects are still in progress and are to be reported later. Age calculations are based on C14 half-life of 5568 yr and modern standard of 95% of NBS oxalic acid. Deviations reported are based on counting statistics of sample, background, and modern, and are ±1σ except that when sample count approaches either modern or background, 2σ limits are reported. Except where noted, C12/C13 measurements have not been made, and results are not corrected for C13 fractionation. The laboratory uses liquid scintillation counting of benzene, with Li2C2 and vanadium-activated catalyst in preparation; chemical yields average 88%. The counter is a Packard TriCarb Model 3002.

The following list of dates is compiled from samples prepared since publication of our last date list (R., 1971, v. 13, p. 468-474). The counting equipment and operating procedures are the same. Ages are quoted with a lσ counting error which includes statistical variation of the sample count as well as for the background and standard, using a.d. 1950 as the reference year and 0.95% NBS oxalic acid for C14 dating as the standard. The half-life value used is 5570 years.

Measurements have continued with the same proportional counter system, sample pretreatment procedure, methane preparation and measurement, and calculation using a half-life of 5568 ± 30 yr 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 C13/C12 ratios were measured.