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What is the Periodic Table Showing? Periodicity

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. The database holds information on periodic tables, the discovery of the elements, the elucidation of atomic weights and the discovery of atomic structure (and much, much more).

   Use the drop menus or search box (below) to Select or Search the 1400 entries in the database: 

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Year:  1814 PT id = 1034, Type = formulation

Wollaston's Physical 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 Wollaston, a leading chemist and natural philosopher during the early 19th century.

"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"

Wollaston uses a decimal scale in which oxygen is defined as having an atomic weight (relative atomic mass) of 10.00 rather than the modern value of 15.999.

Read more here and here, and an entry concerning chemical slide rules:

Mark Leach writes:

"I have edited the image above, setting the scale to zero:"

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What is the Periodic Table Showing? Periodicity

© Mark R. Leach Ph.D. 1999 –


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