Cannizzaro, Stanislao atomic weights

One of the key components of such a scheme was provided in I860 by the Italian chemist Stanislao Cannizzaro, who announced at an international chemical conference in Karlsruhe that the work of his compatriot Amedeo Avogadro provided an improved list of the atomic weights of the elements. This list allowed an accurate ranking of the elements by weight, from the lightest (hydrogen) to the heaviest. 

But the potentiality of molecular structure could not be successfully pursued until the atomic weights were reliably established and the number of atoms in the molecules could be reliably known. This was not accomplished until fifty years later, by Stanislao Cannizzaro, through a rigorous application of Avogadros hypothesis first published in 1811. Since this long complex story does not involve any change in the compositional concepts introduced by Dalton, it is appropriate to offer only a brief account. 

CANNIZZARO, STANISLAO (1826-1910). Born in Italy, lie extended the research of Avogadro on the molecular concentration of gases and thus was able to prove the distinction between atoms and molecules. His investigations of atomic weights helped to helped lo make possible the discovery of the periodic law hy Mendeleyev. His research in organic chemistry led to the establishment of the Cannizzaro reaction involving the oxidation reduction of an aldehyde in the presence of concentrated alkali. 

Chiefly remembered for his reinstatement of Avogadro s hypothesis and his subsequent reform of atomic weights was the Italian chemist Stanislao Cannizzaro. His life and (especially) his work have been commemorated in a book by John Bradley, appearing in German86 and English87 editions. There have also been three volumes of Cannizzaro correspondence, edited by L. Paoloni88 90... 

Italian chemist Stanislao Cannizzaro, known for his theories on atomic weight. 

Mendeleev also attended the 1860 Karlsruhe Congress, the first international chemistry conference. Many of the leading chemists of the day were in attendance, and one of the central questions addressed was the appropriate method for calculating atomic weight. Different chemists used different systems, leading to widespread confusion over everything from nomenclature to chemical formulas. Mendeleev heard the Itafian chemist Stanislao Cannizzaro present Amedeo Avogadro s hypothesis that equal vol-tunes of gas under equal temperature and pressure contained equal numbers of molecules. 

The idea of chemical equivalents was stated by Henry Cavendish in 1767, clarified by Jeremias Richter in 1795, and popularized by William Wollaston in 1814. Wollaston applied the concept to elements and defined it in such a way that one equivalent of an element corresponded to its atomic mass. Thus, when Wollaston s equivalent is expressed in grams, it is identical to a mole. It is not surprising then that the word mole is derived from molekulargewicht (German, meaning molecular weight ) and was coined in 1901 or 1902. see ALSO Avogadro, Amedeo Cannizzaro, Stanislao Cavendish, Henry Gay-Lussac, Joseph-Louis. 

Stanislao Cannizzaro s method for determining atomic weights was not easy to apply to the metallic elements, as it required volatile compounds. Instead, other methods continued to be used for metals. One important way of obtaining atomic weights was through the 1819 law of Pierre-Louis Dulong and Alexis-Therese Petit. As discussed in chapter 2, these authors had found an approximate relationship between the specific heat and atomic weight of a sohd element to be ... 

Cannizzaro, Stanislao (1826-1910) Italian chemist. Cannizzaro was responsible for reviving interest in the ideas of Amedeo avogadro in a pamphlet published in 1858 and in an address to the Chemical Congress at Karlsruhe, Germany. His pamphlet clarified the concepts of atomic and molecular weights and also showed how the molecular weight (now termed relative molecular mass) of a compound could be determined by measuring its vapor density. He also discovered the... 

CannizzarO/ Stanislao (1826-1910) Italian chemist who showed that inorganic and organic chemistry were not basically different. He made the important distinction between atomic weights and molecular weights, and produced a table of weights with hydrogen as the unit. He established the use of atomic weights in chemical formulas and calculations. 

Bessemer converter for steel manufacture. German chemists Robert Bunsen and Gustav Kirchhoff discover the element cesium. Scottish physicist James Clerk Maxwell and Austrian physicist Eudwig Eduard Boltzmann independently develop statistics for analyzing the behavior of molecules in a gas. Robert Bunsen invents the magnesium light. Italian chemist Stanislao Cannizzaro convinces an international conference of chemists to use the value of atomic weights determined by Swedish chemist Jons Jakob Berzelius to standardize chemical formulas. 

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