Temperature Required to Dehydrate a Hydrated Compound

[Curtis15]

Hey Guys,

I am looking for information related to the dehydration temperatures of hydrated compounds, particularly silica compounds.

For research I am working on, we are trying to figure out at what temperature will the water molecules in a certain compound begin to leave the structure.

I do not want to make the assumption that it would be at around 100 C, because that seems too obvious and I feel like it would depend on how specifically the molecules are bound and how many there are.

The information in my general chemistry textbook is literally only a paragraph on the subject, so I was wondering if anyone here could either tell me directly how to go about calculating something like this or direct me to a place where I can start to look for information.

The compound of interest is hydrated SiO2 if that helps any.

Thanks all.

 

[Mike H]

Silica gel - which is basically SiO₂ - is often used as a desiccant, and can be regenerated by an hour or so in an oven at ~ 150°C. While I haven't used silica gel for much of anything since my undergrad days, other desiccants (Drierite is my oldest and best friend on this count, and is basically anhydrous calcium sulfate) are also regenerated by such a protocol, although you typically want to hit at least 200°C in that case.

Let me know if the above serves as a starting point.

 

[Curtis15]

Thank you very much. Your answer is along the lines of what I am looking for. However, the SiO2 was just a starting point. Besides remembering temperatures from your experience, would you know of a place where this information is given for a wide variety of compounds?

There is also one thing I forgot to add. Our setup includes a vacuum chamber where pressures will be on the order of 10^-7 Torr. Do you believe this will greatly affect the dehydration temperature?

 

[Mike H]

It's been a while since I've had a copy at my fingertips, but there is a "drying agents" brochure put out by Merck that describes the use of various desiccants. I am certain it is Google-able.

You have a vacuum setup? Yes, that can impact things. Often, vacuum drying is used to remove trace amounts of liquids from desiccants. Insofar as a simple and quantitative way of calculating these processes in more detail, I don't have anything for you off the top of my head. (I wish I could say I'd be happy to help further, but I'm already running around in my increasingly rare free time doing things for my research beyond working hours.)

You might want to poke around the chemical engineering literature on this, as drying processes are something that have been written about in some detail as memory serves.

 

[Curtis15]

Thank you for the fantastic replies, I totally appreciate it.

 

[Borek]

Do you know what thermogravimetric curve is?