Vacuum at different altitude I have tried to find this searching the internet and I am not sure if I understand it. I want to turn water from solid to gas without going into the liquid phase - Sublimation.

The altitude above sea level is 1500 meter about 5000 feet. I have small 1 stage vacuum pump and a cheap vacuum gauge. The pump is rated to 5Pa (at sea level). Atmospheric pressure is around 85kPa. The vacuum gauge reads 20 inHg but what is that in Pascal, if I convert it using Google or the calculator it give me a value of 67kPa.

Two questions:
1. Can sublimation occur at an altitude of 1500 meter above sea level and atmospheric pressure of around 85kPa


How does one convert vacuum inHg into pascal


I am not chemist nor a chemist student and just like experimenting with stuff
Because you are manipulating the pressure using a vacuum pump, the altitude change should not matter. If you look at the phase diagram for water in the attached link, you can see that if you keep your system below 0C, say at -10C, than you will cross the solid-vapor equilibrium line and your ice will start to vaporize when the vacuum pump decreases the pressure to ~200 pa.

https://en.wikipedia.org/wiki/Phase_diagram#/media/File:Phase_diagram_of_water.svg

To convert from pa to in Hg, I suggest searching for the conversion factor. From google: 1 in Hg = 3386.39 pa. So if you have a reading of say, 2 in Hg on your gauge then: $ 2 inHg*(3386.9 pa)/(1 in Hg) = 6772.78 pa $