National Physical Laboratory Radiocarbon Measurements I

The dating equipment at the National Physical Laboratory was completed by the summer of 1960. A series of calibration and intercomparison measurements was undertaken however, using the NBS oxalic acid reference standard, a modern wood standard (1850 oak tree) and other material before starting routine measurements toward the end of 1961. All results have been obtained using a 4.5 L copper proportional counter filled with CO2 at a constant density corresponding to standard conditions of 22°C and an absolute pressure of 150 cm Hg. The counter is shielded by 8 in. of steel, 6 in. of paraffin wax containing boric oxide, 23 Geiger counters arranged as two independent groups and finally by 1 in. of mercury.

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National Physical Laboratory Radiocarbon Measurements II

Radiocarbon ◽

10.1017/s0033822200010523 ◽

1964 ◽

Vol 6 ◽

pp. 25-30 ◽

Cited By ~ 7

Author(s):

W. J. Callow ◽

M. J. Baker ◽

Daphne H. Pritchard

Keyword(s):

Standard Deviation ◽

Standard Error ◽

Half Life ◽

Research Programme ◽

National Physical Laboratory ◽

Reference Standard ◽

Best Value ◽

Physical Laboratory ◽

The Difference ◽

Absolute Age

The following list comprises measurements made since those reported in NPL I and is complete to the end of November 1963.Ages are relative to a.d. 1950 and are calculated using a half-life of 5568 yr. The measurements have been corrected for fractionation and referred to 0.950 times the activity of the NBS oxalic acid as a contemporary reference standard. The quoted uncertainty is one standard deviation derived from a proper combination of the parameter variances, viz. those of the standard and background measurements over a rolling twenty-week period, of the sample measurements from at least three independent fillings, of the δC13 measurements and of the de Vries effect (assumed to add an additional uncertainty equivalent to a standard deviation of 80 yr). Any uncertainty in the half-life has been excluded so that relative C14 ages may be correctly compared. Absolute age assessments, however, should be made using the accepted best value for the half-life and the appropriate uncertainty included. If the net sample activity is less than 4 times the standard error of the difference between the sample and background activities, a lower limit to the age is reported equivalent to a sample activity of 4 times the standard error of this difference.The description of each sample is based on information provided by the person submitting the sample to the Laboratory.The work reported forms part of the research programme of the Laboratory and is published by permission of the Director.

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Measurement of the 14C Activity of the ANU Sucrose Secondary Standard by Means of the Proportional Counter Technique

Radiocarbon ◽

10.1017/s0033822200004501 ◽

1979 ◽

Vol 21 (3) ◽

pp. 321-328 ◽

Cited By ~ 8

Author(s):

Dušan Srdoc ◽

Bogomil Obelic ◽

Nada Horvatincic ◽

Adela Sliepcevic

Keyword(s):

Oxalic Acid ◽

Ambient Temperature ◽

Tree Rings ◽

Proportional Counter ◽

Barometric Pressure ◽

Secondary Standard ◽

Oak Tree

A systematic crosschecking of the NBS oxalic acid standard, the ANU Sucrose secondary standard, and the RB oak tree rings grown in 1858 ± 5 and 1890 ± 5 has been performed using the proportional counter technique. Details on the counter gas (methane) purification are given. Corrections of count rates due to changes of barometric pressure and ambient temperature are applied and discussed. Results of measurements are presented and the ratios between mean activities of the NBS oxalic, ANU sucrose and RB oak samples are given.

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The behaviour of polar molecules in solid paraffin wax

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1940.0055 ◽

1940 ◽

Vol 175 (961) ◽

pp. 253-254

Keyword(s):

Relaxation Time ◽

Chain Length ◽

National Physical Laboratory ◽

Paraffin Wax ◽

Polar Molecules ◽

Solid Paraffin ◽

Physical Laboratory ◽

Chain Compounds ◽

Long Chain

A paper by R. W. Sillars of the National Physical Laboratory was published under the above title in 1938. Sillars showed how the relaxation time of long-chain esters embedded in a paraffin wax medium depended upon the chain length of the ester. It is well known that many properties of long-chain compounds alternate according as the number of carbon atoms is odd or even. Accordingly, Sillars was careful to use only esters with an even number of carbon atoms in order to reduce the number of possible variables affecting his investigations. He hoped the esters with an odd number would be examined later, and accordingly the work described in this paper was undertaken for the purpose of filling in an obvious gap in Sillars’s experiments and to be complementary to them.

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