Studies on the temperature dependence of electric conductivity for metals in the Nineteenth Century: a neglected chapter in the history of superconductivity (Estudos sobre a dependência com a temperatura da condutividade elétrica de metais no século XIX: um capítulo menosprezado na história da supercondutividade)Simón Reif-Acherman Two different lines of research had significant contributions to the discovery of superconductivity: the liquefaction of gases and the studies of the temperature dependence of the electrical conductivity, or resistance, of pure metals and alloys. Different publications have described and discussed the achievements in the first one of these subjects. The second subject had not received, however, the same attention. This article tries to fill this gap by presenting an account showing details of the evolution of the ideas, the first essentially experimental contributions to the subject and their corresponding responsible persons. Keywords: superconductivity, electrical resistance, temperature, dependency relation, history, metals, alloys.Duas diferentes linhas de pesquisa deram significativa contribuiçãoà descoberta da supercondutividade: a liquefação de gases e os estudos da dependência da condutividade ou resistência elétrica com a temperatura, em metais puros ou ligas. Diferentes artigos descrevem e discutem as conquistas da liquefação ao passo que a segunda não recebeu, contudo, a mesma atenção. Este artigo busca preencher esta lacuna, apresentando um histórico detalhado da evolução de idéias, das primeiros resultados experimentais e dos pesquisadores nelas envolvidos. Palavras-chave: supercondutividade, resistência elétrica, dependência com a temperatura, história da supercondutividade em metais e ligas.
IntroductionThe traditional accounts about the discovery of superconductivity, whose first century is commemorated this year, show it as a consequence, in some way accidental, of the experimental researches on the liquefaction of the by then so called 'permanent' gases. A previous article on this subject is mainly focused on the historical evolution of these events [1]. This conception is, however, historically incomplete, since parallel achievements developed in a different line of research made equally significant contributions to the identification of the new phenomenon. The necessity for disposing of appropriate thermometric instruments for the each time more extreme and limited regions of low temperature in order to replace those, by then, unpractical gaseous ones, forced the carrying out of researches focused on the application of different physical principles and materials in order to fill this objective. The studies on the electrical conductivity, or resistance, of pure metals and alloys and their temperature dependence aroused the interest of scientists of different nationalities in the second half of the nineteenth century and the first half of the twentieth century, and contributed not only to the understanding of the electrical properties of those materials but also to t...