0
$\begingroup$

What pressure does liquid nitrous oxide need at -45°C to remain liquid? How can I calculate it's pressure required for other temperatures?

$\endgroup$
2
$\begingroup$

This document provides a formula for the vapour pressure of $N_2O$:

$$ log_e \left(\frac{p}{p_c}\right) = \frac{1}{T_r}\left[b_1(1-T_r) + b_2(1-T_r)^{3/2} + b_3(1-T_r)^{5/2} + b_4(1-T_r)^5\right]$$

where $p$ is the pressure you want to solve for, $p_c = 7251$kPa, $b_1 = -6.71893$, $b_2 = 1.35966$, $b_3 = -1.3779$, $b_4 = -4.051$, $T_r = T / 309.57$K, and $T$ is the temperature.

This is valid over the range $T = -90$ to $36^o$C ($183.15$ to $308.15$K).

There might well be simpler ways to get an approximate answer from molecular theory / thermodynamics, but if you just practically want to calculate it this looks like it would be okay.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.