S. PL SØRENSEN: BIOGRAPHY, CONTRIBUTIONS TO SCIENCE - BIOGRAPHIES - 2025

SPL Sørensen (1868-1939) was a Danish-born chemist whose main contribution to science was the creation of the pH scale. This measures the acidity of any substance and is currently used in multiple fields. This work, in addition to other contributions, earned him several Nobel Prize nominations, although he never won it.

Sørensen, from a humble family, decided to study chemistry at the University of Copenhagen thanks to the influence of SM Jorgensen, a scientist specializing in this field. In 1899 he managed to finish his doctorate and began working at the Carlsberg Laboratory, a prestigious biochemical research center closely linked to beer production.

SPL Sorensen in a laboratory. Photo Credit: Photo Agency

It was in this laboratory that Sørensen made his main findings. In 1909, when he was investigating the effect of ion concentration on proteins, he invented an easier way to express hydrogen ion concentrations. This was the basis of the pH scale, an acronym for "hydrogen potential."

After working in the same laboratory for more than 30 years, the scientist was abandoned his research. Despite this, he continued to write articles and collaborate to the best of his ability with science until his death in February 1939.

Biography

In addition to being the creator of the pH scale, Sørensen is also recognized by the scientific community for his works on biological problems. His life was dedicated to knowledge, and his studies covered areas such as fermentations, proteins or the synthesis of amino acids.

According to biographers, Sørensen had a natural talent for chemistry, although they also highlight his work so that human beings achieve greater well-being, as well as his determination that his discoveries had practical effects in medicine.

All of the above earned him to be nominated for the Nobel Prize on up to 13 different occasions: five of them in medicine and another eight in chemistry. However, he never managed to win the prestigious accolade.

Studies

The scientist, whose full name was Søren Peter Lauritz Sørensen, came to the world on January 9, 1868, in the town of Havrevjerg, near Slagelse (Denmark). His family was very humble, since his father was a farmer. However, he always had family support to study.

After completing his primary education, Sørensen entered a secondary school in Sorø. Later, at the age of 18, he began studying Medicine at the University of Copenhagen. However, there he came into contact as Sophus Mads Jorgensen, a well-known chemist who was researching complex inorganic compounds.

It was Jorgensen who convinced Sørensen to change careers and study Chemistry. Already during his years of study, the young scientist began to prove his worth and received two gold medals for his work. The first for an essay on chemical radicals and the second for another writing on strontium compounds.

Doctorate

Sørensen successfully completed college in 1881. Upon graduation, he began work on his doctorate. However, this effort to complete his education did not prevent him from pursuing other activities.

Thus, he participated in research on geology, worked as an assistant in the laboratory of the Danish Polytechnic Institute and was an advisor for the shipyards of the Royal Navy of his country.

Finally, in 1889, he finished his doctorate. His thesis was dedicated to the chemistry of cobalt oxides.

First jobs

Sørensen spent his first ten-year career researching inorganic synthesis at the Technical University of Denmark. His boss in this first job was Jorgensen, the same professor who had convinced him to study chemistry. At the end of this period, the scientist began to work in the laboratory to which he would dedicate the rest of his life: the Carlsberg.

In 1876, the founder of the Carlsberg Brewing Company, Jacobsen, had decided to open a laboratory for chemical research. In 1900, the until then head of the investigations, J. Kjeldahl, passed away and it was necessary to look for a replacement.

Facade of the Carlsberg Laboratory. Public Domain, The person chosen for the position, head of the Carlsberg Laboratory Chemistry Department, was SPL Sørensen, who had already acquired great prestige in his country thanks to his research.

Carlsberg Laboratory

Although the Carlsberg Laboratory had been designed to experiment and improve brewing, Sørensen's arrival at the management level gave it new impetus. Thus, in a short time it became one of the most prestigious study centers in Europe, to the point of attracting researchers from all over the planet.

At first, the laboratory and Sørensen himself specialized in the study of protein chemistry, especially in the application of thermodynamics. At this stage, the scientist dedicated himself to studies how the concentration of ions affected proteins, as well as the importance of hydrogen in them.

It was there, in the course of one of his investigations, that Sørensen created his pH scale. This, still in force, is used to measure the acidity of any substance.

Help from his wife

Although it has been frequently forgotten, Sørensen's wife, also a scientist, was an indispensable collaborator in his discoveries.

Margrethe Høyrup Sørensen, named after the scientist's wife, participated in research on lipoproteins or carbon monoxide compounds.

Both scientists, in 1917, were the first to crystallize egg white during a laboratory experiment.

Last decades

During the last decades of his life, the scientist began to spend less time on his work in the laboratory. Despite continuing to publish studies and articles in various journals until 1934, he increasingly paid more attention to administrative and organizational tasks.

These tasks were not only related to the Carlsberg Laboratory, as he was a member of various boards of directors. Sørensen, for example, was one of the promoters of the creation of the Wheat Committee in 1929, a body that aimed to improve the quality of the flour that the Danes used to obtain their bread.

Similarly, in 1934 he was one of the founders of the Danish Air Force Association.

Retirement and death

Sørensen stepped down as head of the laboratory's Department of Chemistry in 1938. He was subsequently appointed president of the Royal Danish Science Society.

His presidency, however, was short-lived. On February 12, 1939, when he was 71 years old, he died in the Danish town of Charlottenlund.

Contributions to science

Sørensen, as noted, developed the vast majority of his work at Carlsberg Laboratories, owned by the beer brand of the same name. His most outstanding research was the one that studied how acidity affected fermentation enzymes.

In an article called Enzyme Studies II The Measurement and Meaning of Hydrogen Ion Concentration in Enzymatic Processes, published in 1909, the scientist considered that the method used until then to calculate the degree of acidity in a solution was not the most appropriate. According to his studies, the end result was not correct.

For this reason, Sørensen began to study another way to measure and classify acidity. The result was the pH scale, the achievement for which it went down in the history of science.

PH scale

The presentation of the pH scale created by the Danish scientist was made in 1909. The initials pH come from “pondus hydrogenii”, hydrogen power in Spanish. Today, however, "hydrogen potential" is often used instead.

Before Sørensen made his pH scale public, there was no single way to express what the concentration of nitrogen ions was. His proposal was to create a scale in which pH 7 would be neutral, while 1 and 14 would be the extremes of acidity and alkalinity respectively.

PH indicator - Source: Ariadna.creus

The scientific community immediately accepted Sørensen's proposal, not only because of its accuracy, but also because it enabled the measurement criteria to be unified.

A German chemist and physician, Leonor Michaelis, was primarily responsible for the rapid acceptance of the pH scale. This scientist published a work in 1914 that dealt with the concentration of hydrogen ions, which allowed Sørensen's idea to reach the knowledge of more researchers.

Measurement methods

Sørensen's contributions in this field were not limited to the pH scale. Similarly, the scientist invented two new methods to measure acidity. One of them was based on the use of electrodes, while the other included the comparison of sample colors and some preselected indicators.

In addition, he was the author of the formula that allows to handle whole numbers in the pH of each substance.

What is pH for

Since Sørensen invented his scale to measure the alkalinity and acidity present in a substance, its use has been increasing.

As noted, this scale establishes that the lower the pH number, the higher the acidity and while the values ​​get closer to 14, the higher the alkalinity.

Today this way of measuring is used in many ways. Among these, for the treatments of the cultivation land, since the pH of the soil moisture is related to the nutrients present.

Similarly, pH measurement is used to check the acidity of the water. PH values ​​between 6 and 8 indicate that a lake or river is in good condition.

The system has proven its worth even in the field of health. Today, any blood test includes pH measurement, as it can warn of the presence of some infections or diabetes.

Other contributions

In addition to the pH scale, the Danish scientist was also the author of the formol titration or Sørensen method. This is used to measure the hydrolysis of a protein caused by a certain amount of enzyme.

On the other hand, Sørensen encouraged many of his colleagues to visit his laboratory to find solutions to medical problems. Similarly, he collaborated in some studies on various topics, from chemical technology to the explosives industry.

References

1. BBC Mundo newsroom. Who was Soren Peter Lauritz, the chemist who coined the concept of pH and why the Google doodle honors him. Retrieved from bbc.com
2. López, Alberto. SPL Sørensen, the Danish biochemist who got us familiar with pH. Obtained from elpais.com
3. FONDECYT. SPL Sørensen, the Danish biochemist creator of the hydrogen potential (pH). Obtained from fondecyt.gob.pe
4. Irfan, Umair. SPL Sørensen invented the pH scale by experimenting with beer. Retrieved from vox.com
5. Complete Dictionary of Scientific Biography. Soren Peter Lauritz Sorensen. Retrieved from encyclopedia.com
6. Barnes, Tom. SPL Sørensen: Five things you should know about the groundbreaking Danish chemist. Retrieved from independent.co.uk
7. Haigh, Phil. Google Doodle remembers SPL Sorensen, the inventor of the pH scale - what you need to know about him. Retrieved from metro.co.uk
8. Science History Institute. Søren Sørensen. Retrieved from sciencehistory.org