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Abbe Nollet and Osmosis

In 1748, while studying the behaviour of liquids under reduced pressure, Jean-Antoine Nollet discovered osmosis. This discovery would have a greater influence on modern scientific activity than all of Galileo's astronomical discoveries from the century before. The concept of Osmosis is important to Cell Biology, Medicine, Agricultural Science, Botany, and Chemical Engineering. We will look at how Osmosis works, why its important, and why Abbe Nollet is not better known.

Abbe Nollet's Experiment.

Jean Antoine Nollet was a Catholic priest from the eighteenth century who was a major advocate for the study and teaching of science in France. He became known as Abbe Nollet. His main area of study and experimentation was electricity. In 1748, Abbe Nollet conducted an experiment where he took a vial of alcohol, covered it securely with some pig's bladder then submerged it into a container of water. Abbe Nollet was careful to purge the alcohol of any air. Upon returning 6 hours later, he noticed that the piece of pig's bladder was bulging. On pricking the bladder, liquid from inside the vial shot 1 foot (30 cm) into the air. Suspicious that heat might somehow involved, he retried the same experiment accounting for temperature, and discovered that heat was not a factor. [_1_] .

The importance of the experiment is not obvious. Dissecting the experiment might help. Firstly, there seemed to be a net movement of water from the outside container into the vial of alcohol. Secondly, this was happening against some resistance and building considerable pressure along the way. And all this seemed to happen without an external input of energy (e.g. heat).

This experiment was tremendously important. A means of moving water without an external input of energy had been discovered. The movement of water in biological systems is very important. Human beings,like many animals, are 50-70% water. The phenomenon was also capable of generating considerable pressure. There was a hidden benefit that wasn't so obvious. What if the water contained the minerals and other chemicals that could be either essential to life or toxic to life. This process, osmosis, could be used to regulate our internal environment; moving nutrients to where they are needed and flushing out toxins.

Examples of Osmosis

We might know osmosis by other names; dialysis and kidney function. The compelling advantages of osmosis to biological systems means that it is used almost everywhere in animals and plants. The following examples illustrate why osmosis is so important:

  1. Explains how plant roots are able to overcome the resistance of the soil.
  2. Explains how roots are able to absorb water from the soil.
  3. Explains how the flow of gases into and out of leaves is regulated (osmosis acting through stomata and guard cells). This is used in the regulation of photosynthesis and respiration.
  4. Explains the state of a plant's stem, branches and even leaves (e.g rigid or wilting).
  5. Explains how organelles in the cell and the cell itself can maintain a consistent chemical environment conducive to chemical reactions in biological systems.
  6. Explains much of Kidney function.
  7. Explains why salt-water fish die in freshwater and freshwater fish die in salt-water.
  8. Explains why sugar can be used to preserve fruit and why salt can be used to preserve meat,fish and vegetables.
  9. Explains why brine is an effective agent to adjust the moisture content of cheese.
  10. Explains some types of hemolysis (bursting of blood cells).
  11. Explains why intravenous drug delivery must be done using saline solutions. Intravenous delivery of drugs with ordinary water could cause hemolysis.
  12. Forward osmosis (the one Abbe Nollet discovered) is used to desalinate water.
  13. A process associated with osmosis, reverse osmosis, is used widely in the chemical, desalination and sanitation industries. Some of you reading this may be drinking water that has been purified by reverse osmosis.
  14. And many, many more.

Osmosis Light

Osmosis is achieved through the use of semi-permeable membranes. These are membranes with 'pores' that allow some molecules through and block or repulse other molecules. What happens in osmosis is that solute (e.g. salt or sugar) molecules cannot pass through the membrane but solvent molecules (e.g. water) can. This can't explain osmosis on it's own. Remember that the Abbe noticed a net increase in solvent in one direction. Solvent molecules can pass through the pores in a semi-permeable membrane as easily in one direction as the other. This should mean that over time an equal number of solvent molecules go in either direction. With osmosis this is not what is happening.

So what is happening? In the diagram below, Side B has only solvent molecules, and Side A has solvent and solute molecules. Lets also say that there are the same number of solvent molecules on either side. If the levels on Side A and Side B donot stay the same it might mean that the solute (e.g. salt) is interfering in some way with the ability of solvent (e.g. water) on Side A to enter the pore. In fact, solvent molecules will attach to the solute molecules. This means fewer free solvent molecules are available at the pores on Side A. The availability of solvent at the pores on Side B hasn't changed. Over time this imbalance means that solvent (water) will build up on side A.

Osmosis Diagram

Abbe Nollet and Galileo

The most famous experiment in popular histories of science is probably Galileo's Tower of Pisa experiment. But which experiment is really more important, Galileo's or Nollet's? The answer is actually very easy, Abbe Nollet's Wine Spirits experiment. That is because Galileo's Tower of Pisa experiment is a modern myth (see Galileo Myths , Myth 1). Popular histories of science are not very reliable. They ignore many scientists and scientific discoveries and they sometimes propagate myths. Abbe Nollet was one of many Catholic clergy that made important contributions to the various disciplines in science (see List of Catholic Clergy Scientists). Besides Gregor Mendel very few of these are ever mentioned.



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Copyright Joseph Sant (2017).
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1. , John Hinton Publishers, 1755., Universal Magazine for Knowledge and Pleasure. Vol. 16, , pp. 72
This early encyclopedia published only eight years after Abbe Nollet's experiment contains a good description of Abbe Nollet's experiment. Full access is available at Google Books,
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