Brass calamine

If we accept a date of around AD 1000 for the commencement of the distillation of zinc on a large scale, then, following the work of Craddock (1978), all earlier brasses should contain less than 28% Zn, as this is the approximate upper limit for the calamine process at around 1000 °C. Above this temperature, the process is more efficient, but it is said that the brass produced melts and the active surface area for the process is thus reduced. By granulating the copper and therefore increasing the surface area, the maximum can be pushed to around 33% Zn, but it is unlikely that this was done in Europe until the 18th Century (see Section 6.4). This model is supported by the analytical data Craddock s work on Roman brass indeed shows an upper limit of about 28% zinc. 

In the closing years of the production of calamine brass, the following grades of brass are recorded by Aitken (1866) ... 

Zinc is another earhest known metal. Use of its alloy, brass, dates back to prehistoric times. The metal was produced in India in the 13 century by reducing calamine (a sihcate mineral of zinc) with wool. Marggraf produced the metal in 1746 by reducing calamine with charcoal. The element took its name from the German word zink meaning of obscure origin. Lohneyes first used this name in 1697. 

In about 1830 an unsuccessful attempt was made to determine the nature of a peculiar ore from die Saucon Valley near Bethlehem, Pennsylvania. Mr. W. T. Roepper, who afterward became the first professor of mineralogy at Lehigh University, identified it as calamine, zinc hydrosilicate, and produced brass by smelting it with native copper (110). The history of early zinc works in die Lehigh Valley has been ably presented in die Journal of Chemical Education by R. D Billinger (110). 

Zinc, as previously stated, was not recognized by the ancients as a distinct substance. As its ores (calamine) were much used in the manufacture of brass, it is difficult to conceive that it was never obtained in the metallic state, owing to the readiness with which its ores are reduced. But if obtained, it is probable that it was not considered as other than a variety of lead or tin, not well adapted to the uses made of these metals. 

Whether brass, however, is found as a native metal or not cannot be ascertained with any surety. We only know of the artificial brass, which consists of copper tinted with the colour of the mineral calamine, and yet if any should be dug up it would be a proper metal. Black and white copper seem to be different from the red kind. Metal thcre-... 

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