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The rubber boom ((ポルトガル語:Ciclo da borracha) (:ˈsiklu dɐ buˈʁaʃɐ), 1879 to 1912) was an important part of the economic and social history of Brazil and Amazonian regions of neighboring countries, being related to the extraction and commercialization of rubber. Centered in the Amazon Basin, the boom resulted in a large expansion of European colonization in the area, attracting immigrant workers, generating wealth and causing cultural and social transformations. It encouraged the growth of cities such as Manaus, Porto Velho, and Belém, capitals within the respective Brazilian states of Amazonas, Rondônia and Pará; as well as the expansion of Iquitos in Peru. The rubber boom occurred largely between 1879 to 1912. There was heightened rubber production and associated activities from 1942 to 1945 during the Second World War. ==Background== Natural rubber is an elastomer, also known as tree gum, India rubber, and ''caoutchouc,'' which comes from the rubber tree in tropical regions. Christopher Columbus was the one of the first Europeans to bring news of this odd substance back to Europe, but he was not the only one to report it. Around 1736, a French astronomer recalled how Amerindians used rubber to waterproof shoes and cloaks. He brought several samples of rubber back to France. Rubber was used as an eraser by scientist Joseph Priestley in England. It was not until the 1800s that practical uses of rubber were developed and the demand for rubber began. The first factory for rubber products (suspenders (US) or braces (UK)) was in Paris, France, in the year 1803. However, the material still had disadvantages: at room temperature, it was sticky. At higher temperatures, the rubber became softer and stickier, while at lower temperatures it became hard and rigid. The South Amerindians first discovered rubber; sometime dating back to 1600BC. They used it in a ball in a game they called ''tlachtlic.'' The Amerindians in the Amazon rainforest developed ways to extract rubber from the rubber tree (''Hevea brasiliensis''), a member of the Euphorbiaceae family. A white liquid called latex is extracted from the stem of the rubber tree, and contains rubber particles dispersed in an aqueous serum.〔(【引用サイトリンク】 title=Rubber Technology )〕 The rubber, which constitutes about 35% of the latex, is chemically cis-1,4-polyisoprene ((C5H8)n). Latex is practically a neutral substance, with a pH of 7.0 to 7.2. However, when it is exposed to the air for 12 to 24 hours, its pH falls and it spontaneously coagulates to form a solid mass of rubber. Rubber produced in this fashion has disadvantages. For example, exposure to air causes it to mix with various materials, which is perceptible and can cause rot, as well as a temperature-dependent stickiness. Industrial treatment was developed to remove the impurities and vulcanize the rubber, a process that eliminated its undesirable qualities. This process gives it superior mechanical properties, and causes it to lose its sticky character, and become stable - resistant to solvents and variations in temperature. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Amazon rubber boom」の詳細全文を読む スポンサード リンク
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