# Calculate sublimation rate from pressure rise

• flysa01
In summary, the conversation discusses the use of a pressure rise test on a chamber to calculate the rate of accumulation of vapor during freeze drying. The person is looking for suggestions on how to calculate the sublimation rate from the increase in pressure. Another person in the conversation mentions trying a combination of engineering and chemistry equations, but it did not work out correctly.
flysa01
Hi, I did a pressure rise test on a chamber, where I closed the isolation valve and measured the increase in pressure over 30 seconds.

I want to use this information to calcualte the rate of accumulation of vapour in the chamber. What I'm looking for is the sublimation rate during freeze drying, so how does this increase in pressure correlate to a sublimation rate?

Any suggestions are much appreciated!

Before giving my suggestion I would like to know if you have solved this as I am very late to replay here? If know then I would love to answer you.

powder coat

Hiya, I never got it worked out right, do you know how to do it?? In the end I combined a few engineering equations with some chemistry ones and hoped for the best but I knew it wasn't right!

## 1. What is sublimation rate?

Sublimation rate refers to the rate at which a solid substance transitions directly into a gas without going through the liquid phase. It is typically measured in units of mass per unit time, such as grams per second.

## 2. How is sublimation rate calculated from pressure rise?

Sublimation rate can be calculated from pressure rise by using the Clausius-Clapeyron equation, which relates the vapor pressure of a substance to its temperature and enthalpy of sublimation. By measuring the pressure rise over time, the sublimation rate can be determined.

## 3. What factors can affect the sublimation rate?

The sublimation rate can be affected by various factors such as temperature, pressure, surface area, and the properties of the substance itself (e.g. molecular weight, vapor pressure, etc.). These factors can impact the rate of sublimation by altering the energy required for the substance to transition from a solid to a gas.

## 4. How is sublimation rate important in scientific research?

Sublimation rate is important in scientific research as it can provide insights into the physical properties and behavior of substances. It is particularly useful for studying materials that undergo sublimation at low temperatures and pressures, such as dry ice and certain pharmaceuticals.

## 5. Can sublimation rate be controlled or manipulated?

Yes, sublimation rate can be controlled or manipulated by adjusting the environmental conditions, such as temperature and pressure, or by altering the properties of the substance itself. This can be useful in various industrial and scientific applications, such as freeze-drying and purification processes.

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