Chemical Match Output

Number:32

Maker:Wollaston Chemical
PHOTO

Length: 12 x 2.56"

Gauge Marks:

Scales Front: Chemical Scales

Scales Back:

Info: Discussed:
The Wollaston Chemical Slide Rule Conrad Schure JOS Vol 5. No. 1
Chemical Slide Rules Re-visited Andries de Man Slide Rule gazette 2019
Wollaston's 1814 slide rule used oxygen = 10 as its base value, the figure chosen as a matter of convenience.
Wollaston was yet to be convinced by John Dalton's new atomic theory, calling it "purely theoretical" and, therefore, of no use to the "formation of a table adapted to most practical purposes". Not desirous of "warping my numbers according to an atomic theory", Wollaston thus made oxygen the decimal unit of his scale because oxygen was the most common reactant in numerous important chemical reactions and the number ten was a simple figure to manipulate in calculations.
The rule shows that Wollaston used the formula HO for water instead of H₂O or that he used for hydrogen the molecular weight of H₂ instead of the atomic one.