How to dehydrate a solid crystal?

In summary, the process of dehydrating a solid crystal involves removing the water molecules from the crystal lattice through exposure to heat and low humidity. This can be achieved through various methods such as air-drying, oven-drying, or using a desiccant such as silica gel. It is important to follow proper safety precautions and to monitor the crystal closely during the dehydration process to prevent it from cracking or losing its crystal structure. Once the crystal is completely dehydrated, it can be stored or used for various applications such as inorganic chemistry experiments or as a decorative item.
  • #1
Panthera Leo
109
0
How to dehydrate a solid crystal?

I have a solid crystal with structural channels in it which are filled with water molecules. The size of each channel is 2.5 to 5 angstrom and a water molecule is 2.7 angstrom on its longest side. What is the best way to dehydrate it?
I have tried heating it and its been a good process but not good enough to fully dehydrate it...

Thanks in advance :)
 
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  • #2


Drying over molecular sieves? Concentrated sulfuric acid or P2O5?

Compare http://www.mercury-ltd.co.il/admin/userfiles/image/Information/Drying%20Agents.pdf .
 
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  • #3


Borek said:
Drying over molecular sieves? Concentrated sulfuric acid or P2O5?

Compare http://www.mercury-ltd.co.il/admin/userfiles/image/Information/Drying%20Agents.pdf .

A very very informative pdf Thanks a lot :)

Just one question; some of these channels have a diameter less than the 2.7 angstrom and these drying agents won't be able to enter such channels... The water in these channels are probably trapped during crystallization. How to get these molecules in touch with the drying agents?!

Immersing the crytal in Sulfuric acid or P2O5 and heating it to few hundred degrees can help? perhaps because of expansion of channels and increased kinetic motion of the molecules?

Thanks again
 
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  • #4


No no, you don't immerse the crystal. You keep it in a closed container above the drying agent. The idea is that water leaves the crystal and gets absorbed by the drying agent, as both processes are in equilibrium, you end with most of the water trapped where it is thermodynamically more stable (in the drying agent, if it is properly selected).

Immersion is for drying solvents (liquids), but then it is a matter of putting drying agent into liquid. I haven't heard about drying done the other way (that is, putting dried substance into liquid that is a drying substance).

No idea what to do if the water is trapped in such a way it can't leave the crystal. At the same time, I don't think crystal is so rigid water molecules can't diffuse to the surface, it just needs time. Elevated temperature will for sure speed up the process.
 
  • #5


I see! Thanks for the info :)

Just one last question; is it safe to place sulfuric acid in a sealed crucible and heat it to 300Celcius (can I go even higher like 850C?)?

I have an electric furnace and can sustain the temp accurately for long durations, but I'm not sure if the preasure build up may cause any damage or not?
 
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  • #6


Actually the temperature things is tricky. For sure elevated temperature will help water leave the crystal, but I am not sure it will speed up the dehydration process, as it will also affect equilibrium at the other end (increasing water vapor pressure). Could be some initial increase in temperature followed by the cold period will be best, but I am just guessing.

Compare http://en.wikipedia.org/wiki/Desiccator
 
  • #7


You are right... I guess I have to keep cookin & lookin lol

I was thinking... This is a silicate crystal so its soluble in H2SO4 & HF acids... Can I somehow "enlarge" those channels without much damage to the xtal itself?!

What kind of setup can you think of which may enlarge the structural channels, by dissolving its walls in acid but keeping the main bulk of the xtal safe?

Many thanks in advance Borek :)
 
  • #8


I doubt you will be able to modify the crystal this way, I am afraid modification will mean destruction of the structure.
 
  • #9


What about immersing the xtal in HF for a very short interval? because the structural channels are sorrounded by SiO3...

Here is how the structure looks like: http://youtu.be/-kS4zWyYLJk
 
  • #10


It won't work, you will etch the surface, but not channels. Just like water needs time to get out, HF won't be able to get in.
 
  • #11


What if I use an electric stiring device and stir the acid around the crystal with a very high speed?

I mean; can stirring with high speed limit the reaction between the surface and the acid in order to provide enough time for HF (which is less than 2 angstrom, Right?) to enter channels?

Thanks again :)
 
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  • #12


Won't work.
 
  • #14


chemisttree said:
You may need to http://www.springerlink.com/content/h3207l1705645633/" First dehydration peak at 600C!

Interesting paper... Thanks Chemisttree :)

Actually I have tried heating at 700C for 12 hours, but can't get all the type 2 water molecules (the ones prependicular to the direction of channel) out!

Type 1 molecules can be dehydrated by heating but not the type 2s :(

Thats why I was hoping to find a chemical process by acids etc which might increase the diameter of the channel just a little bit to accelerate the process. HF sounds good because its only 2 angstrom in size, & beryl is solluble in HF but as Borek suggested there are problems... Do you know any chemical process which might cause a partial destruction of channels but not the rest of the xtal?

Btw the crystals are worthless and I have a bunch of them so please tell me whatever comes to your mind :)

Thanks again :)
 
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  • #15


The only idea I have, and I haven't researched it, is to try and find a wavelength of radiation that the Al-O-Si-H2O absorbs and hit the crystal with that frequency while trying to dehydrate. Get that bond length oscillating and I'm thinking that the water will more loosely held and easier to remove. Right now you're doing that with heat but there might be a special frequency that excites just that bond. Don't know what the EM absorption spectrum is for your beryl might be. Library time!
 
  • #16


That's an interesting idea chemistree :)

But still considering beryl in trade & markets makes me think people are using certain chemicals to dehydrate natural beryl without disclosing. I found this bixbite (Red color Beryl) on eBay which was for sale & parts of the surface look like chemically etched!

There's no reason to immerse a "polished" beryl in some chemical of this sort unless they want to cause partial destruction of the channel in order to "dye" the channels. If you look at the other pictures of this same stone, the color is neither even nor "zoned"...

What do you think?

This the bixbite I am talking about:

http://i.ebayimg.com/00/$(KGrHqIOKnUE4Ky8qwPGBODH9ZVz!w~~0_3.JPG
 
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1. How does dehydrating a solid crystal work?

Dehydrating a solid crystal involves removing water molecules from the crystal lattice structure through heating or exposure to a desiccant. This process causes the crystal to lose its water content and become a dry solid.

2. What are the benefits of dehydrating a solid crystal?

Dehydrating a solid crystal can increase its stability and shelf life, reduce its weight, and prevent it from reacting with moisture in the air. It can also improve the crystal's optical clarity and make it easier to handle and store.

3. Can any type of solid crystal be dehydrated?

Not all solid crystals can be dehydrated. Some crystals, such as salts, are hygroscopic and will readily absorb moisture from the air. These types of crystals cannot be effectively dehydrated. Other crystals, such as metal sulfates, may undergo chemical changes when dehydrated, altering their properties.

4. What is the best method for dehydrating a solid crystal?

The best method for dehydrating a solid crystal will depend on the type of crystal and its properties. Heating in an oven or using a desiccant are common methods, but they may not be suitable for all crystals. It is important to research the specific properties and requirements of the crystal before attempting to dehydrate it.

5. Is it possible to reverse the dehydration process and rehydrate a solid crystal?

In some cases, it is possible to rehydrate a dehydrated solid crystal by exposing it to moisture or adding water back into the crystal lattice structure. However, this process may not always be successful and could alter the properties of the crystal. It is important to carefully consider the purpose of dehydrating a crystal before attempting to rehydrate it.

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