Here is a classroom demonstration of how to estimate absolute zero. Charles Law and absolute zero. https://www.youtube.com/watch?v=wkWo-8tY8cY
Btw, if the temperatures and volumes of other gases are measured and plotted you will get lines with different slopes, but they will all converge on the same value of absolute zero. However, this is based on a _extrapolation_. Maybe the volume of a gas and its temperature don't maintain this linear relationship as the volume approaches zero. William Thomson (Lord Kelvin) first proposed that this linear extrapolation was reliable. The demonstrator quotes him at about seven minutes into the video: << ...infinite cold must correspond to a finite number of degrees of the air-thermometer below zero; if we push the strict principle of graduation, stated above, sufficiently far, we should arrive at a point corresponding to the volume of air being reduced to nothing, which would be marked as -273° of the scale (-100/.366, if .366 be the coefficient of expansion); and therefore -273° of the air-thermometer is a point which cannot be reached at any finite temperature, however low. >> footnote 6 from https://zapatopi.net/kelvin/papers/on_an_absolute_thermometric_scale.html I think it is illogical to propose a linear relationship exists all the way down to absolute zero. Air with no volume is an oxymoron. Linearity may be an excellent approximation over most scales, but I would say below some small but finite volume the linear assumption breaks down with or without appeals to quantum mechanics. Harry
