QUANTITATIVE NON‐DESTRUCTIVE NEUTRON ACTIVATION ANALYSIS OF SILVER IN COINS

Abstract

INTRODUCTION Historians concerned with the ancient and medieval' worlds have tended to rely solely on written evidence, neglecting the most abundant historical artifacts available4oins. When turning to numismatic evidence, the historian generally concerns himself only with the enscribed dates and names of rulers. However, the sheer quantity of coins available provides an opportunity for the historian, and particularly the economic historian, to study the coins for what they are-a money. In many cases coins are the most important, if not the only source of information about significant monetary and economic changes. Thus. the historian must go beyond the mere surface details of the coins, as valuable as these may be to him, and concern himselE with the composition of the coins. Although the quantity of gold in gold coins can be approximated by determining the specific gravity, silver coins may be debased with varying amounts of lead so that the specific gravity measurements can be totally meaningless. The elemental composition OF probably no more than 1500 ancient and medieval coins have been reported in the literature. The reason is obvious; the analysis of the composition of a coin meant the destruction of an irreplaceable object. Even the use of small scrapings for spectroscopic studies has been limited because of the reluctance of curators and collectors to allow any permanent damage to the coins. Neutron activation analysis, however, offers the possibility of making available to historians fundamental information about changes in the composition of coins without resorting to destructive analysis methods. Yet very little research on coins has been done using this technique. One of the mos,t extensive studies using neutron activation analysis was performed at Oxford University where 500 5th century B.C. Greek silver coins were analysed for their copper and gold impurities (Emeleus 1958, Kraay 1959, Thompson 1960, Aitken et. al. 1962). Wyttenbach and Herman (1966) reported on the determination of the Cu and Ag contents of 400 15th century Swiss coins. Other studies include Norman and Suebic gold coins (Meloni and Maxia 1962). 3rd-8th century B.C. electrum coins from Lydia and Carthage (Das and Zonderhuis 1964, 1965). ancient Roman copper coins (Zuber 1966, Ravetz, 1963), 4th-6th century B.C. Greek silver coins (Bluyssen and Smith 1962). and recent Japanese silver coins (Kusaka 1959). In the present study we have been concerned with the development of a rapid non-destructive method OF analysis of the silver content of coins. We wished to base the analysis method on the short half-life isotopes of silver (lo8Ag-2.4 min.