The Original Presentation of Boyle’s Law

Abstract

The original presentation of what we know as Boyle’s law has several interesting features. First, the technical difficulties of the experiment were considerable, because Boyle used a glass tube full of mercury that was nearly 2.5 m long, and the large pressures sometimes shattered the glass. Next, Boyle’s table of results contains extremely awkward fractions, such 10/13, 2/17, 13/19, and 18/23, which look very strange to us today. This was because he calculated the pressure for a certain volume of gas by using simple multiplication and division, keeping the vulgar fractions. Boyle was not able to express the numbers as decimals because this notation was not in common use at the time. Finally, his contention that pressure and volume were inversely related depended on the reader’s comparing two sets of numbers in adjacent columns to see how well they agreed. Today we would plot the data, but again orthogonal graphs were not in general use in 1662. When Boyle’s data are plotted by using modern conventional methods, they strongly support his hypothesis that the volume and pressure of a gas are inversely related.

Appendix

For people whose arithmetic is rusty, here is the calculation keeping the vulgar fractions.

• The original expression is (29 2/16 × 48)/38.

• Converting the numbers inside the brackets to 16ths gives

• (29 × 16 + 2) x 48 or 22368

• Dividing this by 16 gives 1398.

• Dividing this by 38 gives 36 + 30/38 or 36 15/19