Zsigmondy Invents the Ultramicroscope Summary

  • Last updated on November 10, 2022

Richard Zsigmondy’s development of the ultramicroscope allowed scientists to measure and identify individual particles in colloid solutions.

Summary of Event

Richard Zsigmondy’s invention of the ultramicroscope grew out of his interest in colloidal substances. Colloids Colloids are tiny particles of a substance finely dispersed throughout a solution of another material or substance (for example, salt in water). Zsigmondy, whose father, Adolf, was a noted inventor of dental surgical equipment, first became interested in colloids while working as an assistant to the physicist Adolf Kundt at the University of Berlin in 1892. Although originally trained as an organic chemist, in which discipline he took his Ph.D. at the University of Munich in 1890, Zsigmondy became particularly interested in colloidal substances containing fine particles of gold that produce lustrous colors when painted on porcelain. He subsequently abandoned organic chemistry and devoted his career to the study of colloids. Ultramicroscope Inventions;ultramicroscope [kw]Zsigmondy Invents the Ultramicroscope (1902) [kw]Ultramicroscope, Zsigmondy Invents the (1902) [kw]Invents the Ultramicroscope, Zsigmondy (1902) Ultramicroscope Inventions;ultramicroscope [g]Germany;1902: Zsigmondy Invents the Ultramicroscope[00350] [c]Science and technology;1902: Zsigmondy Invents the Ultramicroscope[00350] [c]Chemistry;1902: Zsigmondy Invents the Ultramicroscope[00350] [c]Inventions;1902: Zsigmondy Invents the Ultramicroscope[00350] Zsigmondy, Richard Siedentopf, H. F. W.

Zsigmondy began intensive research into his new field of interest in 1893, when he returned to Austria to accept a post as lecturer at the Technische Hochschule at Graz. He became especially interested in gold-ruby glass, the accidental invention of the seventeenth century alchemist Johann Kunckel. While pursuing the alchemist’s chimera of transmuting base substances into gold, Kunckel discovered instead a method of producing glass with a beautiful deep-red luster through the suspension of very fine particles of gold throughout the liquid silica before it was cooled to become glass. Zsigmondy also began studying a colloidal pigment called purple of Cassius, Purple of Cassius the discovery of another seventeenth century alchemist, Andreas Cassius.

Zsigmondy soon discovered that purple of Cassius was a colloidal solution and not, as many chemists believed at the time, a chemical compound. This fact allowed him to develop techniques for glass and porcelain coloring with potentially great commercial value, which led directly to his 1897 appointment to a research post with the Schott Glass Manufacturing Company in Jena, Germany. With the Schott Company, Zsigmondy concentrated on the commercial production of colored glass objects. His most notable achievement during this period was the invention of Jena milk glass, still prized by collectors throughout the world.

Richard Zsigmondy.

(The Nobel Foundation)

While Zsigmondy was studying these substances, many European chemists insisted that purple of Cassius was a chemical compound. Zsigmondy devised experiments that convinced him that it was not a chemical compound but instead a colloidal substance. When he published the results of his research in professional journals, however, they were not widely accepted by the scientific community. Other scientists were not able to replicate Zsigmondy’s experiments and consequently denounced them as flawed. The criticism of his work in the technical literature stimulated Zsigmondy to make his greatest discovery, the ultramicroscope, which he developed to prove his theories regarding the colloidal nature of purple of Cassius.

Between 1900 and 1907, Zsigmondy pursued private research. During this period, he completed most of the work for which he was awarded the 1925 Nobel Prize in Chemistry. Nobel Prize recipients;Richard Zsigmondy[Zsigmondy] In pursuing his investigations into colloids, he encountered a number of problems that were unresolvable with the scientific equipment available to him. Up to that time, scientists had attempted to study colloidal particles in organic solutions by observing a cone of scattered light, called the Faraday-Tyndall cone, Faraday-Tyndall cone[Faraday Tyndall cone] shone into a solution. This method, however, did not permit the observer to see the individual particles suspended in the solution. Using the facilities and assisted by the staff (especially H. F. W. Siedentopf, an expert in optical lens grinding) of the Zeiss Glass Manufacturing Company of Jena, Zsigmondy developed an ingenious device that permitted direct observation of individual colloidal particles.

This device, which its developers named the ultramicroscope, made use of a principle that was already known. Sometimes called dark-field illumination, Dark-field illumination[Dark field illumination] the method utilizes a light (usually sunlight focused by mirrors) that is shone through the solution under the microscope at right angles from the observer, rather than directly from the observer into the solution. The resulting effect is similar to that seen when a beam of sunlight is admitted to a closed room through a small aperture. An observer standing back from and at right angles to such a beam can see, even with the unaided eye, many dust motes suspended in the air that otherwise are not visible. Zsigmondy and those who assisted him made a number of refinements and improvements in dark-field illumination procedures, and the result was the ultramicroscope.

Zsigmondy’s device shines a very bright light through the substance or solution being studied. The microscope then focuses on the light shaft from the side. This process enables the observer using the ultramicroscope to view colloidal particles ordinarily invisible even to the strongest conventional microscope. To a scientist viewing purple of Cassius, for example, colloidal gold particles as small as one ten-millionth of a millimeter in size become visible. After Zsigmondy publicized his findings, scientists in a variety of disciplines adopted the ultramicroscope, finding many uses for it in fields as disparate as medicine and agriculture. It remains an important tool in many fields of scientific research.


After Zsigmondy’s invention of the ultramicroscope and his subsequent observations concerning colloidal solutions, in 1907 the University of Göttingen appointed him professor of inorganic chemistry and director of the university’s Institute for Inorganic Chemistry. Using the ultramicroscope, Zsigmondy and his associates quickly refuted all the critics who had denounced his research on purple of Cassius, proving that it is indeed a colloidal substance. That finding, however, was the least of the spectacular discoveries that resulted from Zsigmondy’s invention. In the next decade, Zsigmondy and his associates found that color changes in colloidal gold solutions result from coagulation—that is, changes in the size and number of gold particles in the solution caused by particles bonding together. Zsigmondy found that coagulation occurs when the negative electrical charge of the individual particles is removed through the addition of salts. Coagulation can be prevented or slowed by the addition of protective colloids.

These observations also made possible the determination of the speed at which coagulation takes place, as well as the number of particles in the colloidal substance being studied. With the assistance of the theoretical physicist Max von Smouluchowski, Zsigmondy worked out a complete mathematical formula of colloidal coagulation that is valid not only for gold colloidal solutions but also for all other colloids. Colloidal substances include milk and blood, which both coagulate, thus giving relevance to Zsigmondy’s work in the fields of medicine and agriculture. These observations and discoveries concerning colloids—in addition to invention of the ultramicroscope—earned Zsigmondy the 1925 Nobel Prize in Chemistry.

After his appointment at Göttingen University, Zsigmondy assembled a research team and began intensive research into colloids using the ultramicroscope. He and his team developed another tool for their investigations, which Zsigmondy called ultrafiltration. Using the ultramicroscope and ultrafiltration, the scientists undertook a detailed study of gels, particularly silica and soap gels (which are essentially coagulated colloidal solutions). This research led to many important discoveries with numerous commercial applications, including the development of products such as shampoo, shaving cream, cold cream, suntan lotion, and deodorant soap.

In later years, other scientists using the ultramicroscope and Zsigmondy’s ultrafiltration techniques succeeded in ascertaining the electrical conductivity of colloidal particles. This process led to the development of a method for separating colloidal solutions from the admixed electrolytes, not only in gold solutions but also in other colloidal solutions. These new methods have had numerous commercial applications that have improved the quality of life for humankind. Ultramicroscope Inventions;ultramicroscope

Further Reading
  • citation-type="booksimple"

    xlink:type="simple">Hatschek, Emil, ed. The Foundations of Colloid Chemistry. London: Ernest Benn, 1925. Places Zsigmondy in the context of his predecessors. Intended for readers with some background in chemistry.
  • citation-type="booksimple"

    xlink:type="simple">Hauser, Ernst. Colloidal Phenomena. New York: McGraw-Hill, 1939. Explores the status of colloid research up to the late 1930’s. Requires a working knowledge of chemical terms and concepts.
  • citation-type="booksimple"

    xlink:type="simple">Kruyt, H. R. Colloids. London: Ernest Benn, 1930. A standard reference in colloid chemistry. Discusses Zsigmondy’s contributions to the field.
  • citation-type="booksimple"

    xlink:type="simple">McBain, James W. Colloid Science. Boston: D. C. Heath, 1950. Includes an extensive and admiring overview of Zsigmondy’s work and his contributions to the field of chemistry. Intended for readers with background in chemistry.
  • citation-type="booksimple"

    xlink:type="simple">Sherby, Louise S. The Who’s Who of Nobel Prize Winners, 1901-2000. 4th ed. Westport, Conn.: Oryx Press, 2001. Provides detailed information on all winners of the Nobel Prize in the twentieth century, including Richard Zsigmondy. Each article includes a description of the laureate’s life and career, summarizes his or her important achievements, and provides a list of his or her publications as well as biographical resources on the individual. Four indexes enable readers to find laureates by name, education, nationality or citizenship, and religion.
  • citation-type="booksimple"

    xlink:type="simple">Zsigmondy, Richard Adolf. Colloids and the Ultramicroscope. Translated by Jerome Alexander. New York: Wiley, 1909. Zsigmondy’s account of the development and uses of the ultramicroscope. Somewhat technical, but a valuable source.

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