Little_Ghost_again
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Registered: 16-9-2014
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Washing?/drying calcium sulphate
Hi.
I started with sea shell's (Calcium Carbonate) dissolved in hydrochloric acid so I guess this is then calcium chloride, I will point out that I did
this in a large container and kept adding shells until non dissolved anymore, as they dissolved a layer formed on the bottom which I assume is the
calcium chloride becoming saturated in solution and dropping out as its formed.
The solution has been kept acidic with hydrochloric acid and the powder on the bottom has a nice clean thick layer and on the top of this a dirty grey
very fine layer (all the organic crap I guess).
Anyway from this I took some of the saturated solution and dropped small amounts into a beaker of conc sulphuric acid and a small amount of water, a
very very fine white precipitate drops out the solution and sinks to the bottom, if only left for a day or so it remains very much a non clumped layer
on the bottom of the beaker, but I am guessing that after a while water is absorbed and the the calcium sulphate starts to clump (I assume its calcium
sulphate).
What I would like to do is filter off the powder before it absorbs water and store it, but what do I wash the acid off with? and how do I go about
drying the powder? I dont want to leave it to air dry and I am pretty sure the sulphuric acid is keeping it very dry for a while. Anyway how do I was
and dry the calcium sulphate and then store it?
I will also do the same with some of the calcium chloride powder after I have filtered the crap out of it.
Sorry its a basic question but I kind of want to get this right as in one way or other this has actually been a bit of a nightmare to get this far, I
over did it collecting the shells and was sick for days after blah blah blah. I know there is some magnesium carbonate in the shells as well but I am
ignoring that  , the oyster shells were the best and dissolved great producing a
really nice white precipitate, the main vessel is 10 litre demi john type container as I need a fair bit of chloride and sulphate for drying out stuff
in the desiccator. I could of got it on ebay but its been fun making it and got me out the house and on the beach for a couple of days!
Dont ask me, I only know enough to be dangerous
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aga
Forum Drunkard
Posts: 7030
Registered: 25-3-2014
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If water isn't an option, how about toluene or acetone ?
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Little_Ghost_again
National Hazard
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I will get hold of some acetone and hope its dry .
Not so sure now why I am bothered about using water, I can always heat it back up and dry it as I only want to wash the acid off it
Dont ask me, I only know enough to be dangerous
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Darkstar
Hazard to Others
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Registered: 23-11-2014
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Why not just wash with water and then dry in the oven at 220°C for a couple of hours? You can air dry first to remove as much water as possible to
make the dehydrated products easier to deal with. Heating heavily hydrated salts too fast tends to leave you with a rock-hard cake because the salt
ends up dissolving in its own water of hydration during heating. This is especially problematic with CaCl2. If you'd prefer not to have to deal with a
caked-up mess in the end, just heat slowly and in stages, gradually increasing the temperature over time. The more surface area the better. Stirring
every 30 minutes or so helps, too. If it starts getting white and crumbly, you can just go ahead and jump straight to 220°C if you're not already
there. The idea is to slowly drive off as much water as you can at first so there's not enough of it later for it to cake up when the heat is
increased. Again, this is especially the case when heating CaCl2.
Your dehydrated salts will be extremely dry and very close to being completely anhydrous. The microwave works too, and is faster, but the oven is
always a reliable method and never fails.
[Edited on 21-1-2015 by Darkstar]
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Little_Ghost_again
National Hazard
Posts: 985
Registered: 16-9-2014
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Mood: Baffled
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Thanks for that I will give it a go, I have both the chloride and sulphate to do. Considering I started with sea shells I am pleased with the results
so far. at the moment its been left in conc H2SO4 and seems fine with no clumpy at all
Dont ask me, I only know enough to be dangerous
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hyfalcon
International Hazard
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Registered: 29-3-2012
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Has anyone seen LG since this post? I'm worried about his health.
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violet sin
International Hazard
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Location: Daydreaming of uraninite...
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Nope, I was wondering the same thing when I saw this post towards the top of the daily happenings. Hoped he was checking in 
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macckone
Dispenser of practical lab wisdom
Posts: 2168
Registered: 1-3-2013
Location: Over a mile high
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He had that little legal issue as well. Hoping the legal issue is what is keeping him away rather than his health. And hoping the legal issue gets
cleared up.
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