February 22 is Johannes Brønsted’s birthday. Brønsted was a Danish chemist best known for developing a theory to explain acids and bases at the same time as English chemist Thomas Lowry.
The Brønsted-Lowry theory defines acids as any chemical that is able to donate a proton or hydrogen ion to a reaction. A base would then become any compound that gains or accepts a proton or hydrogen ion during a reaction.
This also introduces two other terms: conjugate acid and conjugate base. A conjugate acid is the particle remaining when a base accepts a proton in an acid-base reaction. A conjugate base is the particle left when the acid gives up the proton.
Acid + Base ↔ Conjugate Acid + Conjugate Base
HCl + H2O ↔ H3O+ + Cl–
Take hydrochloric acid in water for example.
HCl + H2O ↔ H3O+ + Cl–
The acid is HCl and water is the base. The proton (H) leaves HCl to join with a water molecule to form a hydronium ion, H3O+ and leaves a chlorine ion alone. The hydronium ion accepted the proton and became the conjugate acid. The hydrochloric acid gave up its proton and left the chlorine ion on its own making the chlorine ion the conjugate base.
Prior to this theory, an acid was any substance that dissociates in water to form hydrogen ions. A base was a substance that dissociates in water to form hydroxide ions (OH–). Brønsted-Lowry expands this definition to include substances that do not include hydroxides, like ammonia (NH3).
Hydrochloric acid in ammonia follows the reaction
HCl + NH3 ↔ NH4+ + Cl–
HCl is still the acid but ammonia is now considered a base because it accepts a proton in the reaction to form an ammonium ion. By the old definition of acids and base, ammonia is not a base. Brønsted-Lowry makes ammonia a base.
Another advantage of Brønsted-Lowry theory was it included reactions in solvents other than water. As long as a substance donated a proton it was an acid. If it accepted protons, it was a base.
While Brønsted is recognized for his work in chemistry, he also was active in politics. Denmark and Germany both claimed control of part of the Jutland peninsula known as Schleswig. The question of control came up again in 1947 and Brønsted decided to run for Denmark’s parliament. He won that election but died before he could take up his office the next year.
Notable Science History Events for February 22
1936 – J. Michael Bishop was born.
Bishop is an American microbiologist who shares the 1989 Nobel Prize in Medicine with Harold Varmus for the discovery of retroviral oncogenes, or how cancerous tumors form from normal cell genetic information. They discovered and identified the oncogene c-Src.
1914 – Renato Dulbecco was born.
Dulbecco was an Italian virologist who was awarded the 1975 Nobel Prize in Medicine with David Baltimore and Howard Temin for discoveries concerning the relationships and interactions between cell genetic material and tumor viruses. They showed how oncoviruses could incorporate their genetic code into healthy cells to produce mutations which could form cancer cells.
1949 – Félix d’Herelle died.
d’Hérelle was a French-Canadian microbiologist who was one of the discoverers of bacteriophages, or viruses that infect bacteria. He also pioneered the use of these bacteriophages to treat diseases. He used phages found in chicken feces to successfully treat typhus in chickens and cured a dysentery patient with another bacteriophage. He also used phages in the water supply to greatly reduce the death rate of a cholera epidemic in India.
1902 – Fritz Strassmann was born.
Strassman was a German analytical chemist who with Otto Hahn identified the smaller element barium when uranium was bombarded by neutrons leading to the discovery of the process of nuclear fission.
1901 – George Francis FitzGerald died.
FitzGerald was an Irish physicist who independently of Lorentz, proposed that moving bodies contract relative to the direction of motion. This would be called the Lorentz-FitzGerald contraction and lead to Einstein’s theory of general relativity.
His work verifying Maxwell’s equations for electromagnetic fields led him to propose a method of generating electromagnetic waves by oscillating electric currents. This method would eventually be used in the invention of wireless telegraphy.
1879 – Johannes Nicolaus Brønsted was born.
1857 – Heinrich Rudolf Hertz was born.
Hertz was a German physicist who first demonstrated a device to transmit and receive radio waves. The unit of frequency, Hertz was named after him. He also showed charged bodies slowly lose their charge when exposed to ultraviolet light which was later explained by the photoelectric effect.
1815 – Smithson Tennant died.
Tennant was an English chemist who first identified the elements osmium and iridium.
Tennant was investigating platinum metal samples. Platinum ores had always given mineralogists a difficult time because the metal was difficult to extract from the ore and had slightly different properties from different ores. Tennant dissolved his samples in aqua regia. Aqua regia is an acid that is a mixture of nitric acid and hydrochloric acid and is useful for dissolving noble metals.
After the samples dissolved, a black powder was left behind. He discovered this powder had different properties from platinum and therefore wasn’t platinum. It had to be something else. Further investigation showed the powder was actually a mixture of two new elements. The first element formed salts that would shine with many different colors. He named the element iridium, after the Greek goddess Iris who was symbolized by a rainbow. The second element gave off a strong pungent odor so he named it osmium from the Greek osme which means ‘odor’.
He also showed that diamonds are made of pure carbon.
1785 – Jean-Charles-Athanase Peltier was born.
Peltier was a French scientist who discovered the heating or cooling effect of a junction of two metals in a circuit is related to the electric current passing through the junction. Depending on the direction and strength of the current, heat energy could be gained or lost. This became known as the Peltier effect.
Peltier was also known for his studies in meteorology. He published papers on atmospheric electrical phenomenon, hurricane formation, waterspouts, and the effects of altitude on the boiling point of water.