The steam digester (or bone digester, and also known as Papin’s digester) is a high-pressure cooker invented by French physicist Denis Papin in 1679. It is a device for extracting fats from bones in a high-pressure steam environment, which also renders them brittle enough to be easily ground into bone meal. It is the forerunner of the autoclave and the domestic pressure cooker.
Artificial vacuum was first produced in 1643 by Italian scientist Evangelista Torricelli and further developed by German scientist Otto von Guericke with his Magdeburg hemispheres. Guerike's demonstration was documented by Gaspar Schott, in a book that was read by Robert Boyle. Boyle and his assistant Robert Hooke improved Guericke's air pump design and built their own. From this, through various experiments, they formulated what is called Boyle's law, which states that the volume of a body of an ideal gas is inversely proportional to its pressure. Soon the ideal gas law was formulated.
Based on these concepts, in 1679, an associate of Boyle's named Denis Papin built a bone digester, which is a closed vessel with a tightly fitting lid that confines steam until a high pressure is generated. Later designs implemented a steam release valve to keep the machine from exploding. By watching the valve rhythmically move up and down, Papin conceived of the idea of a piston and cylinder engine. He did not, however, follow through with his design. In 1697, independent of Papin's designs, engineer Thomas Savery built the world's first steam engine. By 1712 an improved design based on Papin's ideas was developed by Thomas Newcomen.
Boyle speaks of Papin as having gone to England in the hope of finding a place in which he could satisfactorily pursue his favorite studies. Boyle himself had already been long engaged in the study of pneumatics, and had been especially interested in the investigations which had been original with Guericke. He admitted young Papin into his laboratory, and the two philosophers worked together at these attractive problems. He probably invented his "Digester" while in England, and it was first described in a brochure written in English, under the title, "The New Digester." It was subsequently published in Paris.
This was a vessel, B, capable of being tightly closed by a screw, D, and a lid, C, in which food could be cooked in water raised by a furnace, A, to the temperature due to any desired safe pressure of steam. The pressure was determined and limited by a weight, W; on the safety valve lever, G. 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" and discusses how the strong compression of water and other liquids in it, which is able to sustain a red heat, creates artificial atmospheres, which may potentially be able to soften or liquefy stones, salts, and the various parts of the earth.
- Papin’s steam digester, Science and Society – Picture Library.
- A Treatise on the Steam Engine, Historical Practical and Descriptive, John Farey, London 1827, page 109. The book proves that Savery's invention was independent of Papin's research, but that in French literature of the time, Papin was usually attributed as the original inventor of the steam engine, and Savery was referred to as having borrowed Papin's ideas.
- A Treatise, page 127
- Growth of the Steam Engine - B.C. 200 to A.D. 1650, Steam Engine Library, University of Rochester.
- Lavoisier, Antoine. (1787). Elements of Chemistry. New York: Dover Publications.