Question about long-term storage of blue sphere silica gel

[cdzfan]

I have blue sphere silica gel if I store it long term saturated in pink color will it break and release water or liquid inside the shoe box?

 

[berkeman]

Welcome to PF.

I have blue sphere silica gel if I store it long term saturated in pink color will it break and release water or liquid inside the shoe box?

Sorry, I'm not understanding the question. Are you saying that if you try to store blue silica gel spheres long-term in a shoebox, that it turns pink and releases liquid? Or are you saying something else?

 

[cdzfan]

I asked if I keep silica gel blue sphere that saturated to pink color in the long term storage in pink color will the silica gel break and release water and absorbed moisture? pink silica gel pink has liquid water

 

[Borek]

Just storing is not enough - unless you store it an a very dry air. Which in a way is how the typical way of drying the silica gel with elevated temperature works. Warm air gets "dryer" (in terms of relative humidity, not the absolute one), so the water from the gel dries out till the systems reaches the new equilibrium.

 

[cdzfan]

I store it at room temperature and humidity but the silica gel sphere is pink so it has liquid moisture inside it. Will it break and leak to release water at some point?

 

[Tom.G]

Will it break and leak to release water at some point?

No.
Silica Gel absorbs water (almost) the same way a paper towel or a sponge does, just not as much water.

So there are no worries about the Gel 'breaking'.

If the Gel was sitting in liquid water the excess liquid on the surface could get the shoe box wet, but they would both dry to the touch over time.

If you want to use the Gel again in the future, spread it out in the oven and let it 'cook' at just below boiling temperature (212F, 100C) until it turns Blue again. Let it cool and it is good to reuse.

Have Fun!
Tom

 

[berkeman]

Sorry, a non-chemist question if I may. Why is the OP mentioning blue turning to pink?

 

[Tom.G]

There is an indicator in many brands of Silica Gel that changes color with humudity. That way the user knows when it is saturated and needs replacing/rejuvenation. Same general idea as litmus paper for acid/alkali detection.

There used to be desktop hygrometers that had patches that changed color with changing humidity... haven't seen any in decades though. Very sturdy, no damage when they hit the floor.

 

[Borek]

Sorry, a non-chemist question if I may. Why is the OP mentioning blue turning to pink?

Property of a cobalt chloride - when anhydrous it is blue, when converted to hexahydrate it becomes pink.

Many substances crystallize as hydrates. This is particularly true for salts (especially those of transition metals). Number of water molecules involved is never an exactly constant thing and it depends on the humidity and temperature, but some hydrates are quite stable and number of water molecules they contain in typical conditions is "always" the same, while in some hydrates it is highly variable.

In transition metal salts these water molecules surround cations, and when present, split energy levels of the d orbitals. Split (apart from other things) depends on the number of water molecules and their spatial arrangement, different splits mean different energy difference between them, so different wavelength of light emitted when electrons jump between these split orbitals (and they do it all the time). There is plenty of fine prints here though, in most cases some water molecules are very tightly bonded to the cation and they are responsible for the color, and additional water molecules don't change much.

Cobalt chloride is a lucky case where the anhydrous and hydrated forms exist in a range of temperatures and humidities that are quite common in everyday life, and these forms also have visibly different colors. So it is often added to silica gel as an indicator (but also used in some gadgets, like the ones mentioned by Tom).

This is actually material for a fascinating popular chemistry lecture, touching on equilibrium processes (different hydrates in different conditions) and ligand field theory (explaining these different colors).

 

[cdzfan]

I have many shoeboxes and inside them I have blue sphere silica gel sachets but the silica saturated and turned pink so I thought that if I keep these sachets inside the box the pink sphere silica gel will break and release water and liquid inside the box. box wetting everything

 

[Borek]

I have many shoeboxes and inside them I have blue sphere silica gel sachets but the silica saturated and turned pink so I thought that if I keep these sachets inside the box the pink sphere silica gel will break and release water and liquid inside the box. box wetting everything

No, that's not how it works. Water is not there in liquid form, it is absorbed in the crystalline structure of the solid, the only way it can leave it is by a slow evaporation.

 

[cdzfan]

what is the name of this type of absorption of the blue sphere silica gel that there is no risk of leaking to release liquid? I thought it held liquid inside it and if the silica gel ruptured it would release the liquid outside.

I have many sachets of blue silica gel that turned pink in storage

 

[DrJohn]

It's actually a chemical reaction - the water is chemically bonded to the metal cation. It forms a different compound. The name given to this type of reaction is hydration of the ion.

CoCl2 +nH2O -> CoCl2(H2O)n where n = 1 or 2 or 6 (6 is the pink one)
blue + some water -> pink hydrated Co ions

It is not absorbed the way a sponge or paper towel or piece of cloth works, where you can squeeze out the water trapped in spaces between the fibres.

Oh, and heat reverses the reaction - it's not evaporation of water - and the stuff can be used again and again to keep things water free, usually electronic devices in storage boxes.

If I was keeping the packets for future use, I'd warm them up as stated earlier, wait for the colour to return to blue, and when cooled to room temperature, I'd stick them in one of those sealable plastic bags. Storing them in a cardboard box but open to the air means they can absorb moisture again and turn pink again.

 

[cdzfan]

What is the name of the absorption process of silica gel spheres?

 

[DrJohn]

Hydration

Because when the blue form reacts with the water to turn pink, CoCl2 now has water acting as a ligand and bonding with the Co ion.

 

[Borek]

Hydration

Because when the blue form reacts with the water to turn pink, CoCl2 now has water acting as a ligand and bonding with the Co ion.

Sometimes there are small differences between nomenclature in different languages, so I am not going to argue - but to me hydration is what happens to the cobalt chloride which is an indicator. I would not use the word "hydration" to describe absorption of water by the gel, it is much less "chemical" process.

Which is just another interesting case for discussion about gray area between physical and chemical changes.

 

[TeethWhitener]

Which is just another interesting case for discussion about gray area between physical and chemical changes.

I wouldn’t call this particular case a gray area. Silica physisorbs water because of its high surface area and strongly hydrophilic—but non-covalent—interaction with water. Cobalt chloride chemisorbs water because it forms coordinate covalent bonds with water molecules.

 

[Nik_2213]

IIRC, cooling 'analysis' crucibles in silica-gel dessicators (vented) meant having to replace the silica-gel from time to time. The 'bake-outs' back from weary pink to good blue eventually took a toll on gel structure, which progressively crumbled to dust..

The spare blue stuff had to be stored in a sufficiently air-tight container, think big Kilner, 'preserves' or 'coffee' jar...

FWIW if, due 'exigencies', too big a hot crucible was cooled in the 'wrong' sort of dessicator, a small-ish un-vented type, and its 'book-mark' fell out, the partial vacuum that ensued often clamped lid to base beyond 'finger-tight'. Sometimes, if sufficiently silicone-greased, they could be warily slid apart. Else, the cry of 'Nik !!' went up. Stretching a large rubber band around the seam before putting in vacuum oven, I'd very, very warily pump that down until the lid shifted, the rubber band pulled into gap and held that ajar...
Could sometimes take several tries...
;-)