IAEA‑C7 and IAEA‑C8 Oxalic Acids were prepared by M. Le Clercq and J. van der Plicht, by using industrially oxalic acids, one produced using the carbohydrate oxidation route in India by the Vaishali firm, Aurangabad, and synthetic oxalic acids produced using the alkaline CO_H2O synthesis by the company Rhône‑Poulenc, Switzerland. Both materials, one containing modern 14C levels and the other one being free of 14C, were mixed both together in desired ratios by dissolution and re‑crystallization at Chemie Uettikon GmbH, Lahr, Germany , in quantities of 150 kg for each product.
The recommended value of this quality control material is the result of the statistical evaluation of an interlaboratory comparison [2, 3].
Reference date for decay correction: 1991-01-01
* Marked value is expressed as standard uncertainty (1-σ level)
** Marked value is standard uncertainty at 1-σ level, calculated from the data given in the respective literature
LE CLERCQ, M., VAN DER PLICHT, J., GRÖNING, M., New 14C reference materials with activities of 15 and 50 pMC, Radiocarbon 40 1 (1998) 295-297.
ROZANSKI, K., Consultants' group meeting on 14C reference materials for radiocarbon laboratories. February 18-20, 1991, Vienna, Austria. Internal Report, IAEA, Vienna (1991).
ROZANSKI, K., STICHLER, W., GONFIANTINI, R., SCOTT, E. M., BEUKENS, R. P., KROMER, B., VAN DER PLICHT, J., The IAEA 14C Intercomparison exercise 1990, Radiocarbon, 34 3 (1992) 506-519.