Great Scientists and their Inventions

Louis Pasteur ( 1822 – 1895)

louis pasteur

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Louis Pasteur discovered that some molecules have mirror images – these can be described as left-handed and right-handed versions of a chemical compound.

He banished forever the concept of spontaneous generation in biology – the idea that bacterial life could just appear from nowhere in fruit or that maggots could appear spontaneously in meat.

Pasteur invented the process of pasteurization and patented it in 1862.

During pasteurization, farm and brewery products such as milk, wine and beer are heated briefly to a temperature between 60 and 100 °C, killing microorganisms that can cause them to go bad.

First Major Contribution in Chemistry

In 1849, Louis Pasteur was attempting to resolve a problem concerning the nature of tartaric acid—a chemical found in the sediments of fermenting wine. Scientists were using the rotation of polarized light as a means for studying crystals. When polarized light is passed through a solution of dissolved tartaric acid, the angle of the plane of light is rotated. Pasteur observed that another compound called paratartaric acid, also found in wine sediments, had the same composition as tartaric acid. Most scientists assumed the two compounds were identical. However, Pasteur observed that paratartaric acid did not rotate plane-polarized light. He deduced that although the two compounds had the same chemical composition, they must somehow have different structures.

Looking at the partartaric acid under a microscope, Pasteur observed there were two different types of tiny crystals. Though they looked almost identical, the two were actually mirror images of each other. He separated the two types of crystals into two piles and made solutions of each. When polarized light was passed through each, he discovered that both solutions rotated, but in opposite directions. When the two crystals were together in the solution the effect of polarized light was cancelled. This experiment established that just studying the composition is not enough to understand how a chemical behaves. The structure and shape is also important and led to the field of stereochemistry.

In 1854, Pasteur was appointed professor of chemistry and dean of the science faculty at the University of Lille. There, he worked on finding solutions to the problems with the manufacture of alcoholic drinks. Working with the germ theory, which Pasteur did not invent but further developed through experiments and eventually convinced most of Europe of its truth, he demonstrated that organisms such as bacteria were responsible for souring wine, beer and even milk. He then invented a process where bacteria could be removed by boiling and then cooling liquid. He completed the first test on April 20, 1862. Today the process is known as pasteurization.

Shifting focus, in 1865, Pasteur helped save the silk industry. He proved that microbes were attacking healthy silkworm eggs, causing an unknown disease, and that the disease would be eliminated if the microbes were eliminated. He eventually developed a method to prevent their contamination and it was soon used by silk producers throughout the world.

Pasteur's first vaccine discovery was in 1879, with a disease called chicken cholera. After accidentally exposing chickens to the attenuated form of a culture, he demonstrated that they became resistant to the actual virus. Pasteur went on to extend his germ theory to develop causes and vaccinations for diseases such as anthrax, cholera, TB and smallpox.


Pasteur had been partially paralyzed since 1868, due to a severe brain stroke, but he was able to continue his research. He celebrated his 70th birthday at the Sorbonne, which was attended by several prominent scientists, including British surgeon Joseph Lister. At that time, his paralysis worsened, and he died on September 28, 1895. Pasteur's remains were transferred to a Neo-Byzantine crypt at the Pasteur Institute in 1896.


In the fields of observation chance favors only the prepared mind.

Science knows no country, because knowledge belongs to humanity, and is the torch which illuminates the world.

Let me tell you the secret that has led me to my goal. My strength lies solely in my tenacity.