Coins of the Roman Republic

Chemical Composition of Copper-Based Coins of the Roman Republic,... 

Twenty-two copper-based coins of the Roman Republic were analyzed for Fe, Co, Ni, Cu, Zn, As, Ag, Sn, Sb, and Pb by using X-ray fluorescence according to the procedures described by Carter and Booth (11). Generally, X-ray fluorescence determines elements only in a thin surface layer, about 5-10 xm deep, so it was necessary to clean coins for analysis in such a way that the surface layer was as representative of the entire coin as possible. First, the coins were cleaned by electrolytic reduction in a hot solution of sodium carbonate. Next, the coins were abraded in an air stream containing finely divided aluminum oxide powder to remove about 10 to 15 xm of metal. Carter and Booth described the cleaning procedure in detail as well as the X-ray fluorescence parameters (11). 

Twenty-two coins from the years 217 to 31 B.C. of the Roman Republic were analyzed by X-ray fluorescence for Fe, Co, Ni, Cu, Zn, As, Ag, Sn, Sb, and Pb. No evidence was found for widespread remelting of coins. The early coins are remarkable for their relatively high Co contents. Several coins have exceptionally high Pb, As, or Sb contents. Generally, the compositions of these Roman Republican coins are very different from those of Roman Imperial coins. Although few coins were analyzed, their compositions correlate reasonably well with time. Further analyses are required to determine whether composition varies with denomination and whether coins may be dated to within a few years by their chemical compositions. Microstructures of two Roman Republican coins containing lead are presented. 

The earliest Roman bronzes that have come down to us date from the fifth century b.c. and contain tin about 7 per cent, and lead from 19 to 25 per cent. This was the alloy used for casting the large coin (8 to 11 oz) of the Republic, known as the As. These ternary alloys were continued in use as coinage until 20 b.c. but from that date until two centuries later lead is seldom found in Roman coins except as an accidental impurity. The lead was no doubt added partly to increase the fusibility of the alloy and also because of its cheapness as compared with copper and tin. Roman bronze statues often contain 6 to 12 per cent of lead. Gowland states that the Japanese were accustomed to add lead to bronze, not merely for cheapness and increased fluidity but also to enable the development, under suitable treatment, of a rich brown patina J. Pliny gives a tip to the house-wife. When bronzes are cleaned,... 

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