False coin before Christ
2006/05/01 Elhuyar Zientzia Iturria: Elhuyar aldizkaria
A coin of two thousand years ago has captivated Italian chemicals. It is thought to be silver, but the analysis of the microscopic structure reveals that it is a false coin, of lead, but disguised as a thin layer of silver.
Counterfeiters also deceived current archaeologists, who gave the coin as silver in 1948, when they found Gallipoli near the city. The analyses carried out in 2003 were those that discovered the fraud. Counterfeiters have always existed, but the fine works found in this coin have surprised scientists.
Silver and lead are perfectly united in the coin, a result that is not achieved by heating two fine silver sheets with the coin, or by chemical reactions that give shape to silver. A result of this type is currently obtained by an electrolytic process, but the electrochemistry did not develop in the XIX. Until the twentieth century. How did they do it then?
The chemists of the Roman university of La Sapienza have found the solution, using techniques known two thousand years ago to achieve the same effect. The key was to submerge the coin in copper acetates and silver chloride. The first is obtained by deposition of a piece of copper in vinegar and the second by treatment with ammonia of a silver mineral. Ammonia itself was extracted from the urine.
This seems simple, but it must be taken into account that those forgers invented two thousand years ago a method equivalent to electrochemistry. Of course, at that time it could also easily be demonstrated that the currency is false, with only measuring the density, but in a market full of millions of coins could not analyze them all and the fraud would advance.
