Lavoisier

Analyse du Gypse. 1765.

1768 · 44940 — Paris L'Imprimerie Royale 1768. 4to. Extract from "Mémoires fe Mathematique et de Physique Présentés à l'Academie des Sciences par divers Savans" Tome V. With tittlepage to vol. 5. Pp. 341-357. Clean and fine. <br/><br/><em>First appearance of Lavoisier's FIRST PUBLISHED CHEMICAL PAPER introducing quantitative methods in chemistry and in which he for the first time brought a hydrometer in use to measure the specific gravities of components of a chemical solutions. Lavoisier defended the originality of his approach in the following words: "It is to the art of combination that the knowledge of the specific gravities of fluids can bring most light. This aspect of chemistry is much less advanced than we thought we possess barely the rudiments of it." "This first paper which in so many respects embodies the quantitative methods Lavoisier was to employ in his later work had in fact been largely anticipated by others notably by Marggraf who had already discovered the composition of gypsum and shown that it contained water phlegm. Yet Lavoisier’s work was more through; and his paper his first contribution to the Academy of Sciences read to the Academy on 25 February 1765 appeared in 1768. The paper offered. - Lavoisier’s earliest chemical investigation his study of gypsum was mineralogical in character; begun in the autumn of 1764 it was intended as the first paper in a series devoted to the analysis of mineral substances. This systematic inventory was to be carried out not by the method of J. H. Pott "who exposed minerals to the action of fire" but by reactions in solution by the "wet way." "I have tried to copy nature" Lavoisier wrote. "Water this almost universal solvent "is the cheif agent she employs; it is also the one I have adopted in my work." Using a hydrometer he determined with the care the solubility of different samples of gypsum samples of selenite or lapis specularis some supplied by Guettard and Rouelle. He made similar measurements with calcined gypsumplaster of paris. Analysis convinced him that this gypsum was a neutral salt a compound of vitriolic sulfuric acid and a calcareous or chalky base. Not content with having shown by analysis the composition of the gypsum Lavoisier completed his proof by a synthesis following as he said the way that nature had formed the gypsum. He further demonstrated that gypsum when transformed by strong heating into plaster of Paris gives off a vapor which he showed to be pure water making up about a quarter of the weight of gypsum. Conversely when plaster of Paris is mixed with water and turns into a solid mass it avidly combines with water. Using the expression first coined by Rouelle he called this the "water of crystallization." DSB.Partington III pp. 378-79. - </em> unknown