How Coins Are Tested

Manawatu Times, Volume LIII, Issue 6631, 9 June 1928, Page 4 (Supplement)

How Coins Are Tested

The testing of the fineness of British coins is far removed from the rush and turmoil of their manufacture.

The assayers do their work in a subdued atmosphere in laboratories to which the public is not admitted. Often the tinkle of a tiny stream of liquid falling from a glass tap into a bottle is the loudest sound to be heard. Here some of the most precise measurements known to chemistry are made. With siver the dosity of a faint opalescent cloud in a clear liquid is measured by the eye, and the last decimal place in the amount of silver in a coin is deduced (writes Sir Thomas Eoso, in the ‘Daily Mail'). Silver is a sore subject at the Mint. For hundreds of years the standard of the coin was 925 of silver and 75 of copper in 1,000 parts. It is true that Henry VIII. and his successor debased the coinage until three-quarters of the shilling consisted of copper. But rctributiop soon came. The surface was a thin film of pure silver, as is is now, but in circulation the silver was soon worn away, and the coppery colour appeared on the outstanding parts. Bluff King Hal was seen to have a red nose, and the standard of 925 was restored and maintained for 350 years more.

Then the war came and silver became scarce and dear. A shilling was worth more if melted down than when passed as currency. It was only for a brief period of springtime in 1920, but it was enough to frighten the timid. The Mint again had to make coins half silver and half copper. Various dopes have been tried to preserve the Eoyal effigy from the fate of its Tudor ancestor, and perhaps the coins of 1928 will stand the test of time. At any rate economy is still the order of the day, and the restoration of the old standard seems as far off as ever. After all, half the countries of Europe have given up silver altogether, nad make their coins of cheaper metals—France of aluminiumbrnze, lire f nickel, and so on. Gold is different. The Mint has never debased god. It is assayed by cupellation, which as practised by the Greeks at Laurium at least 2,500 years ago. In cupellation metals are melted in a porus cup, which absorbs the base elements but leaves gold and silver untouched. So the ancients called them the noble metals. They would not stand fire. The silver is dissolved away by boiling nitric acid, but gold resists even that, and the pure metal left behind is the amount in the original sample.