# What pressure does liquid nitrous oxide need at -45°C?

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

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).