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The INTERNET Database of Periodic Tables

There are thousands of periodic tables in web space, but this is the only comprehensive database of periodic tables & periodic system formulations. If you know of an interesting periodic table that is missing, please contact the database curator: Mark R. Leach Ph.D.

Use the drop menus below to search & select from the more than 1300 Period Tables in the database: 

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Year:  1858 PT id = 1047

Cannizzaro's Letter

Letter of Professor Stanislao Cannizzaro to Professor S. De Luca: Sketch of a Course of Chemical Philosophy given in the Royal University of Genoa, Il Nuovo Cimento, vol. vii. (1858), pp. 321-366.

Read the full letter/paper, in English translation, here.

Many thanks to Carmen Giunta, Professor of Chemistry Emeritus, Le Moyne College who provided the information about, and link to, Cannizzaro's Letter. See a list of other classic chemistry papers.

Cannizzaro writes:

"I believe that the progress of science made in these last years has confirmed the hypothesis of Avogadro, of Ampère, and of Dumas on the similar constitution of substances in the gaseous state; that is, that equal volumes of these substances, whether simple or compound, contain an equal number of molecules: not however an equal number of atoms, since the molecules of the different substances, or those of the same substance in its different states, may contain a different number of atoms, whether of the same or of diverse nature."

From the Science History of Science Institute:

"In 1858 Cannizzaro outlined a course in theoretical chemistry for students at the University of Genoa,where he had to teach without benefit of a laboratory. He used the hypothesis of a fellow Italian, Amedeo Avogadro, who had died just two years earlier, as a pathway out of the confusion rampant among chemists about atomic weights and the fundamental structure of chemical compounds."

Mark Leach writes:

"Before a periodic table of the chemical elements – which orders the elements by atomic weight and then groups them by property – could be developed it was necessary to know the atomic weight values. However, to deduce the atomic weights was a problem as it was necessary to know the ratios of how the elements combined, the stoichiometry.

"Tables of atomic weight data by Dalton (1808), Wollaston (1813) and Daubeny (1831) show progress, but the 1858 Cannizzaro letter was the first where the atomic weight data is more or less both complete and accurate.

"I have extracted the element atomic weight data from the paper, and given the % error with respect to modern atomic weight/mass data. Only titanium is significantly out! It is clear that Cannizzaro knew that hydrogen, nitrogen, oxygen, chlorine, bromine & iodine existed as diatomic molecules."

Element Symbol Cannizzaro's Weight Modern Weight/Mass % error
Hydrogen H 1 1.008 -0.8%
Boron B 11 10.81 1.7%
Carbon C 12 12.011 -0.1%
Nitrogen N 14 14.007 0.0%
Oxygen O 16 15.999 0.0%
Sodium Na 23 22.99 0.0%
Magnesium Mg 24 24.305 -1.3%
Aluminium Al 27 26.982 0.1%
Silicon Si 28 28.085 -0.3%
Sulphur S 32 32.06 -0.2%
Phosphorus P 32 30.974 3.2%
Chlorine Cl 35.5 35.45 0.1%
Potassium K 39 39.098 -0.3%
Calcium Ca 40 40.078 -0.2%
Chromium Cr 53 51.996 1.9%
Manganese Mn 55 54.938 0.1%
Iron Fe 56 55.845 0.3%
Titanium Ti 56 47.867 14.5%
Copper Cu 63 63.546 -0.9%
Zinc Zn 66 65.38 0.9%
Arsenic As 75 74.922 0.1%
Bromine Br 80 79.904 0.1%
Zirconium Zr 89 91.224 -2.5%
Silver Ag 108 107.87 0.1%
Tin Sn 117.6 118.71 -0.9%
Iodine I 127 126.9 0.1%
Platinum Pt 197 195.08 1.0%
Mercury Hg 200 200.59 -0.3%
Lead Pb 207 207.2 -0.1%
Diatomic Molecule Formula Cannizzaro's Weight Modern Weight/Mass % error
Hydrogen H2 2 2.016 -0.8%
Oxygen O2 32 31.998 0.0%
Sulphur S2 64 64.12 -0.2%
Chlorine Cl2 71 70.9 0.1%
Bromine Br2 160 159.808 0.1%
Iodine I2 254 253.8 0.1%
Molecule Formula Cannizzaro's Weight Modern Weight/Mass % error
Water H2O 18 18.015 -0.1%
Hydrochloric Acid HCl 36.5 36.458 0.1%
Methane CH4 16 16.043 -0.3%
Hydrogen sulphide H2S 34 34.076 -0.2%
Diethyl ether CH3CH2OCH2CH3 74 74.123 -0.2%
Carbon disulphide CS2 76 76.131 -0.2%
Chloroethane CH3CH2Cl 64.5 64.512 0.0%
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