Harmon Northrop Morse

Harmon Northrop Morse (born October 15, 1848 in Cambridge , Vermont , † September 8, 1920 in Chebeague , Maine ) was an American chemist . Morse was the first to synthesize the drug paracetamol in 1878 . However, paracetamol only found widespread use as an ingredient in pain reliever and antipyretic drugs many years after his death. In the first half of the 20th century Morse was best known for his work on the measurement of osmotic pressure , for which he was awarded the Avogadro Medal in 1916 . The Morse equation for calculating osmotic pressure is named after him.

Avogadro Medal for HN Morse, Accademia delle Scienze di Torino, 1915. Obverse.

Avogadro Medal for HN Morse, Accademia delle Scienze di Torino, 1915. Reverse.

Education and life

Harmon Northrop Morse was a descendant of John Morse from England, who settled in New Haven in 1639 . His father, Harmon Morse, was a puritan farmer who rejected all kinds of leisure activities. Morse's mother died young, leaving Northrop, his brother Anson, and his sister Delia.

A donation from his grandmother enabled Northrop Morse to study chemistry at Amherst College . He began this course in 1869 and completed it in 1873. He then traveled to Germany to continue his studies, where he received his doctorate in chemistry from the University of Göttingen in 1875 and completed a degree in mineralogy . Morse's doctoral supervisor and director of the chemical institute was Hans Huebner . At this time Friedrich Wöhler was already retired , but still spent part of his time in the laboratory. A few students, mostly Americans, had the privilege of working with Wöhler. Hübner was a professor of organic chemistry, so Morse initially also worked in this field, later he turned to physical chemistry .

In 1875 Morse returned to the United States and took up a position as a research assistant at Amherst College. He worked there for a year under Harris and Emerson. When Johns Hopkins University began teaching in 1876 , Morse was Ira Remsen's assistant ; Emerson had recommended him for the job. Remsen and Morse jointly set up the chemical laboratory at Johns Hopkins. Morse's experiences from his time in Germany proved to be very valuable, since at that time the chemical institutes at the universities of the USA were still underdeveloped. Morse became assistant professor in 1883, full professor of inorganic and analytical chemistry in 1892, and finally director of the chemical laboratory in 1908. In 1907 he was elected to the National Academy of Sciences , in 1914 to the American Academy of Arts and Sciences . He retired in 1916.

Morse married twice and had four children - a daughter and three sons. His second wife, Elizabet Dennis Clark, helped him prepare scientific articles for publication. After his retirement, Morse withdrew, rarely left the house and his health deteriorated. He died during his annual residency in Chebeague Island, Maine . He was buried in Amherst , where he had a summer residence. In his obituary for Morse, Remsen described him as “calm and calm”.

Works

Although Johns Hopkins was a research university from the start, the chemistry department's early years were marked by few students and inadequate laboratory equipment. These conditions discouraged Morse at first, so that he turned mainly to teaching tasks. At the turn of the century he published a series of papers on the representation of permanganic acid . This gave rise to his interest in the phenomenon of osmosis and osmotic pressure, the field with which Morse's name was firmly connected during the first half of the 20th century. With financial support from the Carnegie Institution of Washington , he published a report entitled The Osmotic Pressure of Aqueous Solutions (German: The osmotic pressure of aqueous solutions ), who summarized his work from the years 1899-1913. For this work, the University of Turin (formerly: Academia della Scienze di Turino ), where Amadeo Avogadro had once taught, awarded him the Avogadro Medal. This medal was awarded once on the occasion of the hundredth anniversary of the formulation of Avogadro's law .

In 1887 Jacobus Henricus van 't Hoff published his pioneering work on the analogy of gas pressure and osmotic pressure of solutions, for which, among other achievements, he was awarded the first Nobel Prize in Chemistry in 1901 . In it he developed a formulation analogous to Gay-Lussac's law , which describes the dependence of osmotic pressure on temperature. The measurement data that the German botanist Wilhelm Pfeffer had published 10 years earlier under the title Osmotic Investigations - Studies on Cell Mechanics served as a basis . Pfeffer had developed an osmometer , the Pfeffer cell , to measure the osmotic pressure of aqueous solutions , in which a semipermeable membrane made of copper (II) hexacyanoferrate (II) closes the porous walls of a clay cell. After van 't Hoff's theory was published, other experimenters found it difficult to repeat Pfeffer's measurement results. The main reason for this was the quality of the clay cells used, whose inadequate stability and uneven density meant that the precipitation membranes were inadequately supported when the pressure rose - a problem that pepper had already struggled with. Morse was also able to show that the membranes of the Pfeffer's cell became permeable to dissolved substances at higher pressures. His most important experimental contribution was a method of applying the material of the semipermeable membranes to the walls of the clay cells by means of electrolysis . This procedure allowed him to confirm and improve van 't Hoff's theory.

In its modern version, van 't Hoff's law reads:

${\displaystyle \Pi \cdot V=n\cdot R\cdot T}$

Here Π is the osmotic pressure, V is the volume of the solution, R is the universal gas constant and T is the temperature in Kelvin . This equation can be transformed as

${\displaystyle \Pi ={\frac {n}{V}}\cdot R\cdot T=c\cdot R\cdot T}$

( van 't Hoff's law ), where c = n / V is the molarity in mol · m ⁻³ . Morse showed experimentally that the calculated values ​​correspond better to the measurements if the molarity in the above equation is replaced by the molality m (mol kg ⁻¹ ):

${\displaystyle \Pi =m\cdot R\cdot T}$

( Morse's Law ) With the help of these equations, the molecular mass of a compound can be calculated from the osmotic pressure.

Individual evidence

1. ↑ Morse, HN: About a new method of representing acetylamidophenols . In: Reports of the German Chemical Society . 11, No. 1, 1878, pp. 232-233. doi : 10.1002 / cber.18780110151 .
2. ^ Johns Hopkins Alumni Magazine (1916) , pp. 227 and 320.
3. ↑ ^{a b c d e f} Ira Remsen: Harmon Northrop Morse (1848–1920) . In: Proceedings of the American Academy of Arts and Sciences . 58, No. 17, Sep., 1923, pp. 607-613.
4. ↑ ^{a b c} The Avogadro Medal and the Work of Professor Morse . In: The Scientific Monthly . 2, No. 6, June 1916, pp. 619-620.
5. ↑ ^{a b} Patrick J. Sinko, Alfred N. Martin: Martin's Physical Pharmacy and Pharmaceutical Sciences: Physical Chemical and Biopharmaceutical Principles in the Pharmaceutical Sciences . Lippincott Williams & Wilkins, 2005, ISBN 0-7817-5027-X , pp. 137-141.
6. ↑ ^{a b} Ira Remsen: Harmon Northrup Morse . In: Science, New Series . 52, No. 1352, November 26, 1920, pp. 497-500.
7. ^ Biographical data, publications and academic family tree of Harmon Northrop Morse at academictree.org, accessed on January 3, 2019.
8. ^ ^{A b} Harmon Northrop Morse: The Osmotic Pressure of Aqueous Solutions: Report on Investigations Made in the Chemical Laboratory of the Johns Hopkins University During the Years 1899-1913 . Carnegie institution of Washington, 1914, p. 222.
9. ↑ JH van 't Hoff (1887), The role of osmotic pressure in the analogy between solutions and gases Website Uri Lachish (English, PDF; 187 kB). Physical Chemistry Journal . 1, 481-508
10. ^ Wilhelm Pfeffer : Osmotic investigations - studies on cell mechanics . Wilhelm Engelmann, Leipzig 1921, p. 10.
11. ^ Harmon Northrop Morse: The Osmotic Pressure of Aqueous Solutions: Report on Investigations Made in the Chemical Laboratory of the Johns Hopkins University During the Years 1899-1913 . Carnegie institution of Washington, 1914, pp. 77-78.

Web links

• Vera V. Mainz, Gregory S. Girolami: Entry Harmon Northrop Morse in the Chemical Genealogy Database (PDF, 7 kB) 1998. Retrieved on August 1, 2008 (English).