It was with great pleasure that we were able to present a poster devoted to the historical instruments of the collection of the Department of Chemistry and Industrial Chemistry (DCCI) at the University of Pisa, during the Chemistry for Future 2025 conference, hosted by the Department itself [View Poster]. Our participation in a meeting dedicated to the new frontiers of scientific research reinforces our mission: namely, to employ the study of past scientific instrumentation—considered within its historical and social context—as a means of fostering sensitivity towards scientific inquiry, while simultaneously promoting familiarity with laboratory apparatus and the technical competencies required for the operation of modern scientific instrumentation.
Even in the early stages of research, compelling discoveries have already emerged. Among these is an autograph letter written in 1836 by Giuseppe Branchi to the Rector of the University of Pisa, listing the scientific instruments then available in the chemistry laboratory. Giuseppe Branchi may well be regarded as the first scholar to have received an academic education in chemistry in Pisa. He was trained by his father, Nicola Antonio Branchi (1723–1810), a physician by profession, who had been appointed the first holder of the Chair of Chemistry established at the University of Pisa in 1753. Both father and son were particularly engaged in the study of the behaviour of inflammable gases and of phosphorus, with a special focus on the interaction between light and certain substances. This may help to explain why the collection of the Department of Chemistry and Industrial Chemistry is especially rich in instruments designed for the investigation of matter through the agency of light.
Among the artefacts presented from the collection was the Universal Refractometer, manufactured by Carl Pulfrich and datable to around 1927. Pulfrich’s refractometer determines the refractive index of solids and liquids by analysing the critical angle (ε) of total internal reflection between a prism of known refractive index and the unknown sample. The sample is brought into contact with a glass prism of known index, N, through which the light passes. By observing the boundary between the illuminated and shaded zones, one may directly read from the instrument the critical angle, denoted as i. From this, by means of a simple mathematical relation, the refractive index of the unknown sample, n, may be determined.
Pulfrich’s refractometer admirably met the analytical needs of many when it was first commercialised, owing to its remarkable versatility (it could analyse both solids and liquids) and to the possibility of controlling the temperature of operation. Yet, it did not withstand the test of time: the excessive complexity of the apparatus, coupled with the difficulty of maintenance, eventually led practitioners to favour less versatile, but far simpler, instruments—such as Abbe’s refractometer—which, in its modern incarnations, continues to be employed in analytical laboratories to this day.
Much more might be said: of Pulfrich, who collaborated with Max Planck in the editing of Rudolf Clausius’s posthumous works; of Ernst Abbe, who, while dividing his time between political engagement as a socialist and the invention of his refractometer, also discovered the chi-square distribution. Much remains to be told about these somewhat neglected figures of science; such accounts, however, will be reserved for forthcoming contributions on our website.