The C14 measurements reported here were carried out by the Radiocarbon Laboratory, Dept. of Geophysics and Geochemistry, A.N.U., between Jan. and Aug. 1967. Laboratory equipment consists of a Beckman methane gas-proportional unit (ANU I) supplemented in Dec. 1966 by an automatic 3-channel Beckman model LS-200 liquid scintillation spectrometer. Synthesis of methane and benzene is the same as used in ANU I and described by Polach and Stipp (1967). Treatment of samples remains a 2N hot acid (HCl) wash unless otherwise specified. Where applicable, fractional separation follows procedures reported by Olson (1963), Berger et al. (1964), Tamers and Pearson (1965), and Krueger (1966). In the treatment of bone samples, physical or mechanical cleaning could not completely remove sedimentary material often filling the structural pores. This material, if present, was retained with the fraction referred to as “collagen”. Since we are not dealing with pure collagen, we prefer to call it “acid-insoluble” bone fraction, a name describing the treatment. These dates are reported as equal to or greater than given age. Table 1 summarizes all dated fractions.

The dates detailed below are based on measurements made from September 1962 to August 1964. Work was often seriously interrupted due to difficulties with electronic equipment and also, from the late summer of 1963, high levels of tritium in the local water supplies used in the synthesis of acetylene (from nuclear weapons tests) made it difficult to obtain accurate measurements with acetylene as a filling gas for the proportional counter. The gas preparation equipment was therefore modified for the preparation of high purity CO2, and from Sample BM-165 onwards, the proportional counter was operated with CO2 as the filling gas at a pressure of 210 cm Hg at 22°C. instead of 140 cm Hg pressure of acetylene at 22°C. as reported previously (British Museum I). Background and net modern count rates under these conditions are 3.59 c.p.m. and 8.35 c.p.m., respectively. (In practice these values are taken as the rolling mean of the past 20 weeks’ measurements and are very constant.) The calculations of age are based on the half-life of 5570 yr and error terms are widened to include contributions of ± 80 yr for possible isotopic fractionation effects and ± 100 yr for de Vries-effects. Safeguards against inaccuracies are as described previously (British Museum I).

Measurements have continued with the 6 L counter which has proved reliable at pressures as high as 2.6 atm and as low as 0.3 atm. It has now been enclosed in a double ring of 27 geiger tubes which has reduced the background count to 10 cpm at 2 atm. So far, we have had no success with the 1.5 L Oeschger-type proportional counter. Failure to obtain steady readings is probably due to continued outgassing from the teflon insulation. All insulating parts have now been remanufactured from the same source of teflon as was used in the 6 L counter, and the Oeschger counter is being reassembled.

Results are still given without correction for δC13. Errors quoted refer only to the standard deviation calculated from a statistical analysis of count rates and the Libby half-life of 5570 ± 30 yr.

The 2-L counter (GSC I) and the 5-L counter (GSC IV) were operated routinely during the past year. The 5-L counter was operated at 1 atm, except for February-March 1967, when it was operated at 4 atm. Approximately half the determinations reported were obtained from each counter.

The laboratory started dating in 1966 using liquid scintillation techniques. Considerable effort has been expended on improvements in both sample preparation and detection (Pietig and Scharpenseel, 1964 and 1966). Yields now approach 100% and 4 to 6 samples are completed each week. A solution of 3 cc synthesized benzene and 1 cc “dead” commercial toluene is employed for ordinary measurements. Toluene contains PPO and POPOP scintillators that give final concentrations of 0.4% and 0.01%, respectively, when diluted with sample benzene. The counting arrangement with normal shielding gives a net modern count rate of 25.6 cpm (78% efficiency) with a background of 9.7 cpm. A special counter equipped with 5 cm mercury and 10 cm lead shielding as well as an anti-coincidence “umbrella” of polystilbeneplastic scintillator has considerably better characteristics. In addition to reduced background, samples as large as 100 cc can be accommodated. The exceptional performance obtained here is presently reserved for natural radioactivity measurements, such as T-3 and C1–36.

The development of a C14 laboratory within the physical laboratory of the “Institut royal du Patrimoine artistique” was begun by Dr. I. Elskens and D. Gausset (A.I. Br.).

The electronic apparatus was delivered in 1963 and routine counting on gas of petrochemical origin began in 1964. By December 1965, methane gas was prepared from pure commercial CO2 and, in February 1966, the first test samples were burnt.

This list presents dates on a portion of the samples measured at ISOTOPES since publication of Isotopes V, and for previously analyzed samples for which complete sample data are now available.

Samples were analyzed by gas proportional counting of carbon dioxide at 3 atm pressure in counters of 1 1. volume. Each sample was assayed twice, in different counters and on different days.

Procedures employed in sample preparation and age calculations have been described previously (Isotopes V).

Plans for a radiocarbon dating laboratory at the University of Lund were initiated by Tage Nilsson and Holger Arbman in 1962. Work was begun in 1964 and at the end of 1965 most of the dating equipment was installed. Dating began in 1966 after careful testing of counting electronics and counters.

The dating system has two 1-L copper-walled proportional counters of Östlund-Engstrand construction (for details see Stockholm V. p. 204, Fig. 1) surrounded by 2.5 cm of selected lead, followed by a ring of 23 cosmic-ray Geiger counters (model HZ-100, Zentralwerkstatt Göttingen). On all sides are at least 20 cm of iron. Above and on both long sides of the counters are 10 cm of paraffin wax with about 12% boric acid between the iron layers.

The following list comprises a selected number of measurements made up to October, 1967. Age calculations are based on 95% of the activity of the NBS oxalic-acid standard, and on a half-life for C14 of 5570 yr. Results are reported in yr before 1950, and in the A.D./B.C. scale.

Errors quoted include standard deviations of the count rates for the unknown sample, contemporary value, and background. Because possible errors arising from isotopic fractionation in the plants, or from the de Vries effect, have not been included, calculated errors smaller than 100 yr have been increased by rounding to that figure as a minimum.

Sample descriptions have been prepared in collaboration with collectors and submitters.

The following list comprises a selected number of measurements made during 1966–67 with CH4 at 3 atm pressure in a 0.6 L proportional gas-counter as previously described. The B.P. ages are based upon a.d. 1950 and are calculated with a half-life of 5570 yr. The quoted error consists of experimental standard deviation including the counting variations of the unknown sample, the modern standard, and the background.

Most of the measurements have been obtained with a 4.5-L CO2 counter (Kiel I). Dates given are not corrected for C13/C12 except Ulmus series. Error corresponds to 1σ of statistical variations of sample net counting rate including variance of reference and background, but does not include the uncertainty in C14 half-life and in secular C14 variations. Half-life is 5570 yr and a.d. 1950 is zero point of b.p. scale.

The following is a list of dates obtained since the compilation of List XI in December 1965. The method is essentially the same as described in that list. Two CO2-CS2 Geiger counter systems were used. Equipment and counting techniques have been described elsewhere (Crane, 1961). Dates and estimates of error in this list follow the practice recommended by the International Radiocarbon Dating Conferences of 1962 and 1965, in that (a) dates are computed on the basis of the Libby half-life, 5570 yr, (b) A.D. 1950 is used as the zero of the age scale, and (c) the errors quoted are the standard deviations obtained from the numbers of counts only. In previous Michigan date lists up to and including VII, we have quoted errors at least twice as great as the statistical errors of counting, to take account of other errors in the over-all process. If the reader wishes to obtain a standard deviation figure which will allow ample room for the many sources of error in the dating process, we suggest doubling the figures that are given in this list.

We wish to acknowledge the help of Patricia Dahlstrom in preparing chemical samples and David M. Griffin and Linda B. Halsey in preparing the descriptions.

The C14 dates given below are a continuation of the work presented in our previous list (RIKEN III), and have been obtained by counting CO2 at ca. 2 atm pressure in a 2.7 L stainless steel counter. Results obtained mainly during 1967 are described.

Shell samples were treated with 1% HCl to remove the outer 10%. Calcareous deposits on the surface, when observed, were removed by mechanical means.

Dates were calculated on the basis of the C14 half-life of 5568 yr and 95% NBS oxalic acid as modern standard. No correction was applied even for fresh water shell samples.

The following list comprises measurements made since those reported in NPL IV.

No changes have been made in measurement technique or in the method of calculating results

The Radiocarbon Dating Laboratories of the Oak Ridge Associated Universities (ORAU) has previously published radiocarbon dates under the Oak Ridge Institute of Nuclear Studies (ORINS) name. ORINS has recently changed its name to ORAU and its laboratories and programs have accordingly assumed this new name. The ORINS prefix, which previously designated the published radiocarbon dates of this laboratory, will be continued to minimize confusion in the literature.

The radiocarbon dating program carried out at this laboratory is primarily concerned with assisting the ORAU Special Training Program in its teaching and research activities. Radiocarbon dates which appear in this paper represent samples submitted from research groups associated with the 41 universities which make up ORAU and by other college and university personnel who do not have access to radiocarbon dating facilities.

Carbon samples are chemically synthesized to liquid benzene and their C14 activity determined by liquid scintillation spectroscopy. Samples are first converted to lithium carbide and then to acetylene gas as described by Barker (1953). The acetylene is catalytically trimerized to benzene by a method described by Noakes et al. (1965). Chemical yields for the synthesized benzene routinely approach 90% with no evidence of chemical impurities or carbon isotope fractionation occurring in the chemistry.

A Packard Tricarb Model 314 D.C. liquid scintillation spectrometer, which has been modified for low level counting, is used to count the benzene samples. Counting efficiency is 50% when operating at a voltage of 800 with discriminator setting of 100-800-1000. Background count rate is 1.7 c/m with a 5 cc benzene sample. Shielding consists of 4 in. of lead with coincidence and anticoincidence systems.

The modern reference standard is 0.95% activity of NBS oxalic acid standard which is 6.82 c/m/g carbon. Ages are calculated on a C14 half-life of 5570 yr as suggested by Godwin (1962). The statistics quoted are compiled as one standard deviation (1σ) of the uncertainty involved in counting background, standard, and sample.

This paper is a list of the first results of age determinations made at the Centre de Recherches Radiogéologiques de Nancy (CRR). The Center is the result of a convention between the Commissariat à l'Energie Atomique (CEA) and the University of Nancy. It is part of a group of research laboratories of Earth Sciences headed by Prof. M. Roubault.

The list includes age measurements carried out from December 1966 and November 1967. All samples both of archaeologic and geologic interest are drawn from Italian territory.

Chemical techniques have remained unchanged (Bella and Cortesi, 1960). Two counters have been used for dating: the 1st, of 1.5 L, already described (Bella and Cortesi, 1960; Alessio, Bella, and Cortesi, 1964), the 2nd, of 1 L, recently assembled, is identical to the previous 1 L counter (Alessio, Bella, and Cortesi, 1964), its anticoincidence system was realized by a plastic scintillator and photomultipliers. Background 6.15 ± 0.08 counts/min, counting rate for modern carbon 24.49 ±0.15 counts/min. Higher efficiency of electronic recording was obtained by reducing pulse length and by a few other changes. All samples are usually measured by both counters.

The errors quoted, as in previous measurements, are 1σ statistical error. Age has been calculated using Libby's half-life of 5568 ± 30 yr, with 1950 as the standard year of reference. As in all previous measurements, the same modern wood, grown near Rome between 1949 and 1953, has been taken as modern standard: its activity has once again been carefully checked and judged satisfactory.

The following list includes samples dated between 1956 and 1961. Wood dating from A.D. 1850 ± 10 yr is used as a contemporary reference standard. Background sample is synthesized from anthracite. All radiocarbon dates were calculated with the hall-life of C14 being equal to 5568 ± 30 yr. All dates are calculated from the year 1950.

This series reports some of the measurements made since publication of the previous list. Equipment and methods are described in Saskatchewan II.