Revolutionary Instruments: Lavoisier's Tools as Objets d'Art

Detail of a plate from Traité elementaire de chimie, drawn by Madame Lavoisier. Roy G. Neville Historical Chemical Library. Photo by Douglas A. Lockard

By Horton A. Johnson

In 1788, just as the stage was set for revolution, France’s most celebrated scientist met with France’s most celebrated artist. This sitting for a portrait of the illustrious scientist and his wife may not have been an entirely cordial meeting. The scientist, Antoine-Laurent Lavoisier (1743– 1794), was one of the king’s men; the artist, Jacques-Louis David (1748– 1825), would four years later vote for the king’s execution. The rencontre yielded an immense canvas still regarded as one of the greatest portraits of the 18th century.

Antoine-Laurent Lavoisier (1743–1794) and His Wife, Marie-Anne Pierrette Paulze, (1758–1836) became an icon of the Enlightenment and now hangs in the Metropolitan Museum of Art. The painting shows Lavoisier and his wife and partner in science, Marie Anne Pierrette Paulze (1758–1836). Behind Mme. Lavoisier is a folio, indicating that she is an artist. (As a younger woman, Mme. Lavoisier had studied painting under David’s tutelage, and she may have been the one who instigated the meeting between her husband and her teacher.) In the background of the painting are several pilasters, a signature of David’s neoclassical style. But the most important symbols of Lavoisier’s career are the pieces of chemical equipment. Never mind that they belong in the laboratory and look strangely out of place on a writing desk. They are shown prominently in Lavoisier’s studio so that the viewer knows that this elegant man was a chemist.

It would be interesting to know how the specific pieces of equipment depicted in the portrait were chosen. One can imagine the Lavoisiers showing David their nearly 200 pieces of scientific equipment, many of them beautifully crafted by Nicolas Fortin, Lavoisier’s instrument maker since 1783. Lavoisier and his wife might have chosen pieces for their scientific significance, but David was likely also looking for pieces that would contribute to the overall composition of the portrait. He might also have wanted to paint instruments that would showcase his own skill as a painter at representing reflective surfaces —and this they certainly accomplish. The viewer has no doubt that the glass is glass, the brass is brass, the water is water, and the mercury is mercury.

It may be that the work on Lavoisier’s desk is the manuscript of Traité élémentaire de chimie, which one year after the painting was created would introduce to the world the basic concepts and nomenclature of modern chemistry. The scientific community recognized its importance immediately. Published first in Paris in 1789, it was quickly translated into English as Elements of Chemistry, and Lavoisier became the acknowledged leader of the Chemical Revolution. The popularity of the Traité led to a second edition, published in Paris in 1793, less than a year before Lavoisier stepped up to the guillotine on 8 May 1794. His chemical revolution was well under way as his head and body were carted off to a mass grave.

In the first of the two volumes of the Traité, Lavoisier presents the conclusions and principles derived from his experiments. The second volume describes his experimental methods in detail. Appended to the second volume are 13 plates that show some 170 pieces of laboratory equipment finely drawn to scale by Mme. Lavoisier. Most of these flasks, bottles, jars, siphons, furnaces, tables, and basins do not grace David’s portrait, and those that do are probably the best-known pieces of laboratory glassware in the art world. They also were vital components in several of Lavoisier’s experiments —experiments in which he discovered scientific principles that lie at the very center of modern chemistry.

Mass of Reactants = Mass of Reaction Products

As one might strengthen a rectangular gate with a diagonal brace, David strengthened his rectangular portrait with strong diagonals from the upper left-hand corner to the lower right. Mme. Lavoisier’s right arm, Lavoisier’s quill, the bright fold in the table cover, Lavoisier’s unnaturally long leg, and a beam of light coming from the upper left window all point to a glass balloon on the floor at the lower right of the canvas. The gleaming balloon shows David’s skill to great effect, but it is also important for its use in the establishment of the law of the conservation of mass.

Lavoisier was a superb quantitative chemist, a master of the volumetric flask, the beam balance, the barometer, and the thermometer. Most of his quantitative experiments were performed in closed systems and involved either the consumption or production of gases, which were measured in volumes. In order to balance his equations, the volumes of gases had to be converted to masses. To determine the mass per volume of atmospheric air, nitrogen, oxygen, hydrogen, and carbon dioxide, he weighed the gases in glass balloons, like the one in David’s painting, with capacities of about 17 liters. Each balloon had a brass cap cemented to its neck, through which a metal tube with a stopcock was soldered. Lavoisier measured the balloon’s precise volume by weighing it first empty and again filled with water. He then dried the balloon and evacuated it as much as possible using a brass air pump, visible in the painting. He then closed the stopcock and screwed it to a reaction vessel that contained the gas to be weighed. As the stopcock was opened, the gas rushed into the balloon. Lavoisier then closed the stopcock and weighed the balloon again with, as he writes in the Traité, “the most scrupulous exactitude.” He subtracted the weight of the evacuated balloon and made corrections for temperature, pressure, and incomplete evacuation by the air pump. It is remarkable that the ratios of his measured weights of various gases are not very different from the ratios of their molecular weights, of which Lavoisier had no knowledge. Once established, his volume-to-mass conversion factors would allow him to compare masses of reactants and reaction products.