Jean Servais Stas
Stas, Jean Servais
Stas, Jean Servais
In 1837, reportedly after much trouble, Stas gained admission to French chemist Jean Baptiste Dumas' laboratory at the Ecole Polytechnique in Paris in order to continue research on phloridzin (a flavonoid compound found naturally in some foods), which he had begun earlier in an attic in his father's house.
In 1840, Stas left Paris when he was appointed the chair of chemistry at the Ecole Royale Militaire in Brussels. He became a professor and worked assiduously on determining atomic weights (i.e., relative atomic masses), including the atomic weights of oxygen and carbon, with more accuracy than had been previously accomplished. Stas produced the first modern table of atomic weights, using oxygen as a standard (set at number 16). Stas' practice of using the number 16 for oxygen on the periodic table as a reference point would continue well into the twentieth century, when chemists returned to basing atomic masses on carbon-12. In 1920, the English chemist Francis Aston (1877–1945) discovered, by means of the mass spectrograph , that all atomic masses (isotopes taken into account) are very nearly integral multiples of the same number, a number now taken to be 1/12 the mass of carbon-12, for which Aston received in 1922 the Nobel Prize in chemistry.
Stas also aimed to prove the hypothesis of English physicist William Prout (1785–1850), a hypothesis independently elaborated by the German Johann Ludwig Georg Meinecke, that all atoms were conglomerations of hydrogen atoms. Instead, Stas' results discredited Prout's hypothesis that all atomic weights are whole numbers, but provided the foundation for the work of Dimitri Mendelejew and others on the periodic system. Though Stas started with a predilection in favor of Prout's hypothesis, he was later led by the results he obtained and by his failure to find any evidence of dissociation in the elements to regard it as a pure illusion, and to look upon the unity of matter as merely an attractive speculation unsupported by proof.
Stas also worked in connection with the poisoning of Count Hippolyte de Bocarmé with nicotine in 1850, working out a method for the detection of the vegetable alkaloids, such as caffeine, quinine, morphine, strychnine, atropine, and opium. These poisons affect the central nervous system. Plant alkaloids leave no demonstrable traces in the human body, thus requiring relatively complicated methods of extraction before an analysis can be performed. Stas searched for three months for the agent, and eventually managed to isolate nicotine from the body tissues. Using ether as a solvent, which he then evaporated to isolate the drug, he found the potent drug that was, in fact, the murder weapon. The man's killer had extracted it from tobacco and force-fed it to the victim. With Stas's testimony, the killer was convicted.
Stas thus became the first person to develop a method to extract material containing plant alkaloids from the organic material of the human body, and for many years thereafter, with some modifications, this method was used as the standard. Other toxicologists then developed qualitative tests with the so-called Stas-Otto procedure to determine the presence of various alkaloids in the obtained extract. With his treatise "Forensic investigation on nicotine" Stas became a founder of modern toxicology and a pioneer in industrial pollution.
Stas' interests also included the humanities, and in 1851–52, together with Guillaume Claine, he gave a series of lectures at the Cercle artistique et littÕraire de Bruxelles on daguerreotype and its applications in art.
After more than a quarter of a century, but before he had served the thirty years necessary to secure a pension, Stas was obliged to resign in 1869 because of a malady that affected his speech. He then advised the Belgian government on military issues and was also appointed to a post in connection with the Mint. In 1872 he succeeded in preparing pure platinum and iridium, metals necessary to produce the standard measure. Stas was openly critical of the part played by religion in education. He spent the rest of his life in retirement in Brussels, where he died in 1891.
Jean Servais Stas' name is best known for his determination of the atomic weights of a number of the more important elements. His work in this field was marked by extreme care, and he adopted the most minute precautions to avoid error, with such success that the greatest variation of individual determinations for each element are reported to be from 0.005 to 0.01. Stas was one of the most skillful, chemical analysts of the nineteenth century and his measurements remained the standard of accuracy for over 50 years.
see also Isotopic analysis; Medicine; Spectrograph; Toxicology.