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2019 has been designated the International Year of the Periodic Table as it is the 150th Anniversary of the formulation of Mendeleev's Tabelle I

Internet Database of Periodic Tables


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

Use the buttons below to select from the 1000+ Periodic Tables in the database:

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1814

Wollaston Slide Rule of Chemical Equivalents

From the Science Museum in the UK collection, the Wollaston slide rule of chemical equivalents:

"Three sliding scales of chemical equivalents, all with same manuscripts marks, published by W Cary, devised by W H Wollast.

"William Hyde Wollaston was a leading chemist and natural philosopher during the early 19th century. In 1813 he invented a chemical slide rule to illustrate his paper published the following year entitled: A synoptic scale of chemical equivalents. He was interested in the ratio of weights of various substances used up in reactions.

"Positioning the slider with the weight of the substance set against it will show you the weights of other substances which will react with it. This fundamental ordering based on measurement paved the way for the periodic table of the elements":

Mark Leach writes:

"I have editied the image above, so as to set the scale to zero, below:"

On inspection, it will be observed that many of the atomic weights are rather different to our modern understanding. My readings for some of the atomic weights are:

10 H 12.5 H 1.25 (1.008)
10 C 75 C 7.5 (12.011)
    O 10 (15.999)
    P 17.5 (30.974)
azote = N   N 17.5 (14.007)
    S 20 (32.06)
    Ca 26 (40.078)
    Mg 25 (24.305)
    Na 29 (22.990)
    Fe 35 (55.845)
muriatic acid   HCl 35 (36.45)
    Cu 41 (63.546)
    Cl 45 (35.45)
    Hg 128 (200.59)
    Pb 132 (207.2)
    Ag 138 (107.87)

Nagayasu Nawa writes and provides an explanation as how the slide rule is used:

"It is very interesting slide rule for me. Because we actually used slide rule in 1960s. There were not the electronic calculator in the world.

"I think it would be used as a simple slide rule of The Law of Definite Proportions by J.L.Proust 1799.

  • '10 water', for example, may be hydrating water in chemical compound

  • 'Chlorine' may be HClO: HCl(35) + O(10) = HClO(45), etc.

Click image to enlarge:

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Periodic Table, What is it showing?
Binary Compounds

© Mark R. Leach 1999-


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