Determination of aluminum in nonferrous materials

Abstract

This is the third of a series of papers dealing with the composition of copper alloys used in the classical world.Although a few isolated examples of prehistoric copper alloys containing several per cent of zinc are known, notably from Cyprus, it was not until the first millennium BC that the deliberate production of brass commenced, probably in Asia Minor. From the 7th century the Greeks commented upon brass, but always as an expensive, exotic metal not produced in Greece, and this is borne out by the absence of zinc in the great majority of Greek bronzes. Similarly, of the many Etruscan bronzes analysed, only two from the 5th and 3rd centuries BC respectively were of brass and these contained about 11% zinc with less than 3% tin (see below).By the 1st century BC the Romans were using the cementation process for producing brass. Initially it seems to have been used for coinage, but rapidly became popular in other fields, especially decorative metalwork where it largely replaced bronze. During the 2nd and 3rd centuries AD the zinc content of the coinage fell, and brasses with a high zinc content ceased to be used, although brass continued to be as popular as ever accounting for about 30% of Roman copper alloys. By the 3rd century an alloy of copper with a few per cent each of lead, zinc and tin (modern “leaded gunmetal”) was in regular use, and has remained so ever since.From the time of the King James Bible of 1611 in which all copper alloys are called “brass” irrespective of composition, the early development and use of brass has been confused, and learned books, both ancient and modern have often tended to increase rather than decrease this confusion! The origins of both terms “Brass” and bronze are obscure, but it seems that in medieval times brass was applied to all copper alloys, and only from the Renaissance the term bronzo was used in Italy to denote copper alloys specifically alloyed with tin. However the terms continued indiscriminately in use in England until the 19th century; Johnson defines bronze as brass in his Dictionary. However amongst the many works on the subject, those by Caley (1964) and Werner (1972) are very useful and shed much light on what is otherwise a rather dark area.By combining the information in these books with the new analyses, particularly those of the Roman period to be published in subsequent parts of this work, a much more complete picture of the early history of brass from its inception until the end of the Roman Empire can be built up.For the purposes of this review brass is taken to mean an alloy of copper to which zinc has been deliberately introduced. In pre-Roman brasses the zinc normally replaces tin, but in Roman brass the two metals are often both present in the alloy.