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Chemistry 1808: the way we were…

Pictured below is a postcard my daughter brought back from the Science Museum (London). It is John Dalton’s Table of Elements (1808) and represents a great advance by the so-called ‘atomists’. The understanding that chemical elements are substances made up of the same types of atoms and how this explains why chemical compounds contain these elements in fixed ratios was an enormous stride forward for chemistry.

Some of the elements listed by Dalton clearly aren’t elements: Magnesia (modern: MgO), Lime (CaO), Soda (Na2CO3) and Potash (K2SO4) are all compounds. And by Barytes I think he intended BaSO4.

The numbers to the right, marked as ‘w’t’, presumably represent early atomic weights but not many fit to modern values, apart from the value of ‘1’ for hydrogen. Very much around that same period another giant of early chemistry, Jöns Jacob Berzelius, spearheaded a big push for the measurement of the atomic masses of the known elements. In it he assigned the value of 100 to oxygen. Maybe the numbers have to be seen in that light?

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