|| The apparatus at the left was designed by Walter Ahrens
of Englewood High School in Chicago. It came into the catalogue of the
Central Scientific Company of Chicago in 1918.
The catalogue copy reads, in part, "The apparatus is arranged for obtaining readings of volume of a definite quantity of air and the corresponding pressure in pounds per square inch. The air is confined in a tube of heavy glass adjacent to which is mounted an adjustable metric scale by means of which the length of air column, which is proportional to the volume, is read. A pressure gage, adjusted to read absolute pressures... is connected to the pressure reservoir. The latter is an iron cylinder partly filled with oil. and provided with a stop-cock with hose nipple at the top through which air can be pumped in by means of an ordinary bicycle pump. As the pressure increases in the cylinder the oil rises in the glass tube and the gage indicates the pressure."
Experiments could be done with pressures above and below atmospheric pressure. The catalogue shows a hyperbolic graph of typical PV data, and also the straight line obtained when P was plotted as a function of 1/V.
This apparatus is at Kenyon College in Gambier, Ohio
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