Grey et al. (1969) have discussed the problems that arise when using the wet oxidation method for the preparation of CO2 from oxalic acid and suggest that, although offering an effective substitute, the dry combustion method also has problems.

The present date list describes the first stage of a co-operative study on the validity of dating secondary soil carbonates in arid and semi-arid environments of Australia. Because of the complex nature of the physical and chemical variables in a soil environment, many additional samples are being dated from stratigraphically controlled sites before final evaluation of carbonate reliability is possible.

The laboratory has continued to concentrate on soil and water dating, using the benzene method as outlined in Scharpenseel and Pietig (1969a).

This radiocarbon dating laboratory was established to complement the research activities in the field of archaeology and geology in Korea. The benzene liquid scintillation counting method (Noakes, Kim, and Stipp, 1965; Noakes, Kim, and Akers, 1967) is employed in this laboratory because of its compatibility with other dating methods and future possibility in application of this procedure to the biomedical research field. The chemical process for converting carbon from a sample to benzene used by this laboratory is briefly outlined below.

This list reports the first age determinations carried out by the Freiberg Radiocarbon Dating Laboratory. The preparation of samples and radiocarbon dates were done by the first two authors, who constructed the apparatus; sample descriptions and interpretations of dates were made by the third author.

The following list shows the age measurements made at Algiers by the Service des Applications Nucléaires using the C14 method. The laboratory was created in 1965 to answer the increasing demand of the archaeologic research in N Africa, and made its first measurements in 1967. The electronic apparatus employed was completed and calibrated in 1968 and the first tests were performed during the same year. Regular dating-test samples started in June, 1968. The electronic circuits are of commercial origin or made in the C14 Laboratory.

This list contains a selection of dates from analyses carried out during the past few years. Samples are grouped in geologic-palynologic, and archaeologic sections according to main problem. When influence of human activity on pollen diagrams has been observed it has been explicitly indicated. The descriptions and comments have been written in collaboration with collectors and submitters. For the samples from Switzerland, general reference has also been made to Welten (1958a) and to sections on palynology, geology, and archaeology in work edited by the Schweizerische Gesellschaft für Ur- und Frühgeschichte (1968-1970).

Both the 2-L counter, described in GSC I (Radiocarbon, 1962, v. 4, p. 13–26), and the 5-L counter (GSC IV, Radiocarbon, 1965, v. 7, p. 24–46) were operated routinely during the past year. Approximately half the determinations reported were obtained from each counter. The 2-L counter was operated at 2 atm except for August and September, 1968, when it was operated for the first time at 1 atm. This allowed for the counting of most small samples without the necessity of mixing with dead gas. The 5-L counter was operated at 1 atm, except for the same period when it was operated at 4 atm. Carbon dioxide is used as the counting gas, and both counters are of the proportional type.

This date list presents results of samples measured at ISOTOPES during 1968 and 1969 and several measurements made previously for which complete sample data has recently been received.

Measurements have continued with both the 1 L and 6 L counters. Results are not corrected for C13 fractionation. Errors quoted refer only to the standard deviation calculated from a statistical analysis of sample and background count rates and the Libby half-life of 5570 ± 30 yr. Pretreatment has been continued as described previously (Shotton, Blundell, and Williams, 1969).

The present list covers samples measured between 1963 and July, 1967. Three previous lists have been published in Leningrad I (Sovetskaya arkheologiya, 1961, p. 3); Leningrad II (The Absolute Geochronology of the Quaternary Period, 1963); and Leningrad III (New Methods in Archaeological Investigations, 1963, p. 9–56). The samples measured include charcoal from cultural layers and hearths, wood from barrows [kurgans] and cemeteries, wooden tools from peat deposits, and mounds, as well as peat and animal tissue.

This list includes selected dates of archaeologic samples from DDR, Czechoslovakia, Hungary and the Soviet Union made between 1966 and 1969. As in previous lists the major portion of dates are concerned with Neolithic and Early Bronze age period in Middle and SE Europe.

The measurements reported in this list were made in the Louvain C14 Dating Laboratory in 1968 with the 0.6L CH4 proportional counter. The counter generally operates at 3 atm pressure. Samples too poor to provide 2 L methane are measured at 1000 mm Hg pressure. Ages are calculated on the basis of a C14 half life of 5570 yr and are quoted with 1σ counting error. The description of each sample is based on information provided by the submitters.

The list given below contains the C14 dates obtained for only archaeologic samples, during 1966 and 1967; for the study of the geologic samples dated during the same period, cf. our previous list Gif-III (Radiocarbon, 1969, v. 11, p. 327-344). The same instruments and techniques have been employed.

This list contains mainly radiocarbon dates for Africa. Some results for samples from the ocean floor and from islands in the Atlantic and Indian oceans, as well as a few series of geophysical samples have also been included. The results are grouped into three categories: geologic, archaeologic, and geophysical, and arranged according to the country of provenance, passing roughly from N to S. Descriptions and comments are based on information supplied by the collectors and submitters and on the publications cited. In several cases insufficient information was available, but since it is improbable that it will be forthcoming, the dates have been included.

The following is a list of dates obtained since the compilation of List XII. 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 Michigan date lists up to and including VII, we quoted errors at least twice as great as the statistical errors of counting, to take account of other errors in the over-all process.

The laboratory routinely operates two proportional counters; one 2-L (Dyck and Fyles, 1962) and one 5-L (Dyck et al., 1965). CO2 is used as the counting gas. The 2-L counter is operated mainly at 2 atm. and the 5-L counter mainly at 1 atm. On occasion the 2-L counter is operated at 1 atm. and the 5-L counter at 4 atm. No changes have been made in the CO2 preparation and purification techniques described in previous GSC dating lists (Lowdon et al., 1969; Lowdon and Blake, 1970).

The following list comprises measurements made since those reported in Radiocarbon, 1969, v. 11, p. 130–136. No changes have been made in measurement technique or in the method of calculating the results described in Radiocarbon, 1965, v. 7, p. 156–161. It was necessary during 1968 to replace all the geiger counters used in the anti-coincidence rings, but the long term stability of background and standard count rates implicit in the use of a 20-week rolling mean has been maintained.

Natural C14 measurements have been performed at the Dept. of Physics, National Taiwan University since 1965, using a cylindrical proportional counter of 1000 ml (Hsu et al., 1965). The proportional counter is operated with CO2 as the filling gas at a pressure of 1216 mm Hg at room temperature of 20°C. Working voltage is 4.7 Kv, with a plateau length of more than 700 v and a plateau slope of ca. 1% per 100 v. Background is reduced to 5.1 counts/min and the counting rate of the NBS oxalic acid standard is 9.4 counts/min at the normal counting pressure of 1216 mm Hg.

A third radiocarbon counting system has been established in the Chemistry Department, University of Glasgow, since April, 1968. Operating conditions for the previous systems have remained essentially as described by Baxter et al. (1969).