How was the Kelvin Scale created?

Question

How was it found that if we go 273°C below 0, we would reach absolute zero. What experiment gave this result.
Charles' law states that volume is directly proportional to the absolute temperature. Was the Kelvin perhaps created as scale in which temperature and pressure of a gas are proportional?
I tried to find absolute zero in this manner with experimental data from this video.

This is my work:
$v_1$ = 112mL
$t_1$ = 23°C
$v_2$ = 138mL
$t_2$ = 100°C
Let's define x as the quantity to add to °C measurement's to satisfy Charles' law. In other words -x°C would be absolute zero. \begin{equation} \frac{v_1}{v_2} = \frac{x + t_1}{x + t_2} \\ \frac{112}{138} = \frac{x + 23}{x + 100} \\ 26x = 112*100 - 138*23 \\ x = 308.69 \end{equation} I also tried other values but I am not getting the desired answer. Is there a flaw in my reasoning or does this have nothing to do with the Kelvin scale at all? If so, then how was the Kelvin scale formulated.

Answer 1

You reasoning and method is totally correct. Your final answer is almost correct. The problem is that you are looking at high temperatures and trying to find a number which is far away. This means that a little rounding in your numbers will have a huge impact on your answer. For example, if you try these numbers,

v1 = 111.1mL,
t1 = 23.9°C,
v2 = 138.9mL,
t2 = 99.1°C,

You will end up with 276.629 which is much closer to absolute zero.