title, "The New Digester." It was subsequently published in Paris. This was a vessel with a safety valve, which can be tightly closed by a screw and a lid. Food can be cooked along with water in the vessel when the vessel is heated, and the vessel's internal temperature can be raised by as much as the pressure inside the vessel will permit safely. The maximum pressure is limited by a weight placed on the safety valve lever. If the pressure exceeds this limit, the safety valve will be forced open and steam will escape until the pressure drops sufficient for the weight to close the valve again. It is probable that this essential attachment to the steam boiler had previously been used for other purposes; but Papin is given the credit of having first made use of it to control the pressure of steam. In 1787, Antoine Lavoisier, in his Elements of Chemistry, refers to "Papin's digester" as an example of an environment where high pressure prevents evaporation when he explains that the pressure caused by evaporation of fluid prevents further evaporation. See also Steam engine History of thermodynamics References External links Papin's Digester - Good Quality Image Robert Boyle - has drawing of Papin's digester French inventions Steam power Thermodynamics