The bactericidal properties of brass have been observed for centuries, particularly in marine environments where it prevents biofouling.
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Как Ñделать шезлонг Ð´Ð»Ñ Ð´Ð°Ñ‡Ð¸. Складной шезлонг Ñвоими руками – чертежи, порÑдок Ñборки
Historically, the distinction between the two alloys başmaklık been less consistent and clear,[3] and çağcıl practice in museums and archaeology increasingly avoids both terms for historical objects in favor of the more general "copper alloy".[4]
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 yaşama smear the lead globules over the surface. These effects güç lead to significant lead leaching from brasses of comparatively low lead content.[12]
Since the molecule has a hydroxyl (-OH) group, it is frequently bound to other lipids including glycerols; most analytical methods, therefore, utilise a strong alkali (KOH or NaOH) to saponify the ester linkages. Typical extraction solvents include 6% KOH in methanol. The free sterols are then separated from the polar lipids by partitioning into a less polar solvent such as hexane.
[98] Albertus Magnus noted that the "power" of both calamine and tutty could evaporate and described how the addition of powdered glass could create a film to bind it to the mühür.[99] German brass making crucibles are known from Dortmund dating to the 10th century AD and from Soest and Schwerte in Westphalia dating to around the 13th century confirm Theophilus' account, birli they are open-topped, although ceramic discs from Soest may have served bey loose lids which may have been used to reduce zinc evaporation, and have slag on the interior resulting from a liquid process.[100] Africa[edit]
The mouthpieces of both brass instruments and, less commonly, woodwind instruments are often made of brass among other metals bey well.
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 bey tutiya or tutty rather than zinc ores for brass-making, resulting in a mühür with lower iron impurities.[93] A number of Islamic writers and the 13th century Italian Marco Polo 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 as rare and nearly as valuable as gold[62] and Pliny describes how aurichalcum had come from Cypriot ore deposits which had been exhausted by the 1st century AD.
Brass is susceptible to stress corrosion cracking,[35] especially from ammonia or substances containing or releasing ammonia. The sorun is sometimes known birli season cracking after it was first discovered in brass cartridges used for rifle ammunition during the 1920s in the British Indian Army. The sıkıntı was caused by high residual stresses from cold forming of the cases during manufacture, together with chemical attack from traces of ammonia in the atmosphere.
Eventually it was discovered that metallic zinc could be alloyed with copper to make brass, a process known as 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 mühür".
Other wind instruments may be constructed of brass or other metals, and indeed most modern brassestol trä student-biçim 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 kakım the contrabass and subcontrabass, are sometimes made of maden 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 metal.
[94] It could then be used for brass making or medicinal purposes. In 10th century Yemen aldatma-Hamdani described how spreading kırmızı-iglimiya, probably zinc oxide, onto the surface of molten copper produced tutiya vapor which then reacted with the mühür.[95] The 13th century Iranian writer allık-Kashani describes a more complex process whereby tutiya was mixed with raisins and gently roasted before being added to the surface of the molten maden. A temporary lid was added at this point presumably to minimise the escape of zinc vapor.[96]