Brass was produced by the cementation process where copper and zinc ore are heated together until zinc vapor is produced which reacts with the copper. There is good archaeological evidence for this process and crucibles used to produce brass by cementation have been found on çingene period sites including Xanten[77] and Nidda[78] in Germany, Lyon in France[79] and at a number of sites in Britain.[80] They vary in size from tiny acorn sized to large amphorae like vessels but all have elevated levels of zinc on the interior and are lidded.
Although forms of brass have been in use since prehistory,[48] its true nature birli a copper-zinc alloy was not understood until the post-medieval period because the zinc vapor which reacted with copper to make brass was hamiş recognised bey a mühür.[49] The King James Bible makes many references to "brass"[50] to translate "nechosheth" (bronze or copper) from Hebrew to archaic English. The Shakespearean English use of the word 'brass' can mean any bronze alloy, or copper, an even less precise definition than the çağcıl one.
Знай и умей
During the later part of first millennium BC the use of brass spread across a wide geographical area from Britain[66] and Spain[67] in the west to Iran, and India in the east.[68] This seems to have been encouraged by exports and influence from the Middle East and eastern Mediterranean where deliberate production of brass from metallic copper and zinc ores had been introduced.[69] The 4th century BC writer Theopompus, quoted by Strabo, describes how heating earth from Andeira in Turkey produced "droplets of false silver", probably metallic zinc, which could be used to turn copper into oreichalkos.
The pattern the globules form on the surface of the brass increases the available lead surface area which in turn affects the degree of leaching. In addition, cutting operations hayat smear the lead globules over the surface. These effects birey lead to significant lead leaching from brasses of comparatively low lead content.[12]
The cartridges were stored in stables and the ammonia concentration rose during the hot summer months, thus initiating brittle cracks. The sıkıntı was resolved by annealing the cases, and storing the cartridges elsewhere. Types[edit]
The concentration of brassicasterol in a core sample from Loch Striven, Scotland. Highest values may be seen in the bütünüyle sections of the sediment, which decrease with depth. However, the cholesterol behaves in a similar manner, and the ratio brassicasterol/cholesterol is fairly uniform at all depths, indicating either a comparable degradation rate with no change in source or different degradation rates and a change in source. Multivariate analysis[edit]
"copper alloy (Scope note)". British Museum. The term copper alloy should be searched for full retrievals on objects made of bronze or brass. This is because bronze and brass have at times been used interchangeably in the old documentation, and copper alloy is the Broad Term of both.
The cementation process continued to be used but literary sources from both Europe and the Islamic world seem to describe variants of a higher temperature liquid process which took place in open-topped crucibles.[92] Islamic cementation seems to have used zinc oxide known as tutiya or tutty rather than zinc ores for brass-making, resulting in a maden with lower iron impurities.[93] A number of Islamic writers brassestol trä and the 13th century Italian Marco çevgen describe how this was obtained by sublimation from zinc ores and condensed onto clay or iron bars, archaeological examples of which have been identified at Kush in Iran.
By the 8th–7th century BC Assyrian cuneiform tablets mention the exploitation of the "copper of the mountains" and this may refer to "natural" brass.[59] "Oreikhalkon" (mountain copper),[60] the Ancient Greek translation of this term, was later adapted to the Latin aurichalcum meaning "golden copper" which became the standard term for brass.[61] In the 4th century BC Plato knew orichalkos bey rare and nearly birli valuable birli gold[62] and Pliny describes how aurichalcum had come from Cypriot ore deposits which had been exhausted by the 1st century AD.
To enhance the machinability of brass, lead is often added in concentrations of around 2%. Since lead başmaklık a lower melting point than the other constituents of the brass, it tends to migrate towards the grain boundaries in the form of globules bey it cools from casting.
Eventually it was discovered that metallic zinc could be alloyed with copper to make brass, a process known birli speltering,[109] and by 1657 the German chemist Johann Glauber had recognised that calamine was "nothing else but unmeltable zinc" and that zinc was a "half ripe metal".
Other wind instruments may be constructed of brass or other metals, and indeed most çağcıl student-model flutes and piccolos are made of some variety of brass, usually a cupronickel alloy similar to nickel silver/German silver. Clarinets, especially low clarinets such birli the contrabass and subcontrabass, are sometimes made of metal because of limited supplies of the dense, fine-grained tropical hardwoods traditionally preferred for smaller woodwinds. For the same reason, some low clarinets, bassoons and contrabassoons feature a hybrid construction, with long, straight sections of wood, and curved joints, neck, and/or bell of maden.
[94] It could then be used for brass making or medicinal purposes. In 10th century Yemen düzen-Hamdani described how spreading tuzak-iglimiya, probably zinc oxide, onto the surface of molten copper produced tutiya vapor which then reacted with the metal.[95] The 13th century Iranian writer hile-Kashani describes a more complex process whereby tutiya was mixed with raisins and gently roasted before being added to the surface of the molten mühür. A temporary lid was added at this point presumably to minimise the escape of zinc vapor.[96]