Loschmidt, Johann

Loschmidt, Johann Josef (1821-1895) Austrian professor of physical chemistry at the University of Vienna in 1868. 

In 1861 Johann Josef Loschmidt who was later to become a professor at the University of Vienna pri vately published a book con taming a structural formula for benzene similar to the one Kekule would propose five years later Loschmidt s book reached few readers and his ideas were not well known... 

The work on gas theory had many extensions. In 1865 Johann Josef Loschmidt used estimates of the mean free path to make the first generally accepted estimate of atomic diameters. In later papers Maxwell, Ludwig Boltzmann, and Josiah Willard Gibbs extended the rrratherrratics beyorrd gas theory to a new gerreralized science of statistical mechanics. Whenjoined to quantum mechanics, this became the foundation of much of modern theoretical con-derrsed matter physics. 

The third innovator of the early 1860s was the Austrian physicist Johann Josef Loschmidt, who, despite his work in chemistry, is not widely appreciated as a chemist. A portrait of him is shown in Figure 8. Loschmidt was bom in Pocena and began his university education at the German University of Prague. He completed his education at Vienna, but was unable to procure a teaching position there. He... 

Figure 8. Johann Josef Loschmidt (1821-1895) LOSCHMIDT1861 MODERN FORMULAS... 

The history of benzene is one of the most intriguing in science. It started in 1825 with the isolation of benzene by Michael Faraday from the condensed phase of pyrolyzed whale oil. Its planar cyclic structure was first proposed in 1861 by the Austrian physicist and physical chemist Johann Josef Loschmidt [1—5]. However, it was only fully understood some 70 years later, around 1930, with the advent of the modem theories of aromaticity, i.e. the theory of molecular orbitals (Hiickel s theory) [6-8] and the theory of resonance [9-12]. 

Johann Josef Loschmidt (1821-1895) attended Prague University, and then at 21 went to Vienna to study first philosophy and mathematics, and then the natural sciences, physics and chemistry. After industrial ventures making potassium nitrate and oxalic acid among other products, he returned to Vienna as a concierge in the early 1850s, and then became a school teacher. Always attracted by theoretical problems, he is also known for his calculation in 1865 of the number of molecules in one mL of gas (the Loschmidt number ). In 1866, he became Privatdozent at the University... 

Johann Joseph Loschmidt, born Mar. 15, 1821, in Putschirn (Pocerny), Czech Republic, died Jul. 8, 1895, in Vienna. 

Johann Josef Loschmidt first calculated the value of Avogadro s number often referred to as the Loschmidt number in German-speaking countries Loschmidt constant now has another meaning). 

In 1861 the Austrian chemist Johann Josef Loschmidt represented the benzene ring with a circle, but he made no attempt to indicate how the carbon atoms were actually arranged in the ting. 

Figure 1.2 Johann Josef Loschmidt (15 March 1821-8 Juiy 1895).

With the mean free path thus calculated, it was possible to obtain a value for the number of molecules in unit volume, provided the diameter of the molecule was known. A method of estimating molecular diameters was suggested in 1865 by Johann Joseph Loschmidt (1821-1895), and the value he calculated for the number of molecules per cubic centimetre is sometimes called the Loschmidt number. It is now known that Loschmidt s value is too small by a factor of 30, This was due to Loschmidt using Mayer s value for the mean free path. Although Mayer s work was more recent than Maxwell s, his value for the mean free path was less accurate. 

Austrian chemist Johann Joseph Loschmidt introduces the practice of using a single line for single bonds, a double line for double bonds, etc. into organic chemistry. 

Amedeo Carlo Avogadro (1776-1856) was an Italian chemist, most noted for his contributions to the theory of molarity and molecular weight. In 1811, he declared the hypothesis of what we now call Avogadro s law Equal volumes of gases, at the same temperature and pressure, contain the same number of molecules. Hence, the gas laws of Boyle, Mariotte and Cay-Lussac in combination with Avogadro s Law can be generalized by the ideal gas law. The Avogadro constant Na, that is, the number of molecules in one mol is 6.022 x 10 mol is named in his honor. The numerical value of /Va was first estimated in 1865 by Johann Josef Loschmidt (1821-1895), an Austrian scientist. 

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