JEAN-SERVAIS STAS Atomic mass of the elements, phlorizin, and toxicology

Abstract

Jean-Servais Stas (1813-1891), a Belgium physician and brilliant analytical chemist, isolated (together witch de Koninck) phlorizin from the roots of wild apple, determined the physical and chemical properties of this new glucoside, and prepared the derivatives phloretin, phloretic acid, and phlorizein. The latter was proposed as a possible substitute of the dye orcein. Stas determined with Dumas the correct value of the atomic mass of carbon using carbon originating from three different sources: natural graphite artificial graphite, and diamond, and also determined the atomic mass of nitrogen, chlorine, sulfur, potassium, sodium, and silver and their relation to the atomic mass of hydrogen.  The final results proved conclusively that Prout's hypothesis (all the atomic masses are multiples by a whole number of the atomic mass of hydrogen taken as 1) was wrong. Stas also showed that the composition of any given compound was independent of the procedure used for synthesizing it and that the ratio in which its elements combined to generate it was independent of the pressure and temperature. This principle also implied that the molecular mass of any compound was constant. Stas developed a new synthetic procedure for acetal and showed that Liebig's results were incorrect. Stas and Dumas gave a detailed explanation of the action of KOH on alcohols and their main ethers and provided chemists with a simple tool to synthesize the equivalent acid.