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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: 

  Text Search:       

Year:  1814 PT id = 1034

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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