THE INFLUENCE OF CORROSION AND DIFFUSION ON THE PERCENTAGE OF SILVER IN ROMAN DENARII

The exact chemical composition of an ancient coin in its present state can be determined at present by means of non-destructive methods; in particular the method of activation analysis seems to be becoming more widely used in the study of ancient coins. Yet, in numismatics, an important problem has to be dealt with: to what extent is the chemical composition of a coin, in its present state, representative of the chemical composition of this coin at the time of its minting‘? We shall concern ourselves with this problem in the case when the coins are copper-silver alloys. After having pointed out the causes which may produce a difference between the original and the present compositions, we shall discuss quantitatively the variations of the percentage of silver and the average frequency of these variations.