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Author: Subject: Crystallization Questions
Fidelmios
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[*] posted on 28-4-2016 at 23:53
Crystallization Questions


Hello all,

Recently I've gotten into crystallization as a hobby. I've since acquired Copper Sulfate and Iron Sulfate. My question is, if I make solutions of the two, and mix them, will I make a double salt? I don't see anything on the web about this topic so far.

Also, I am having a heck of a time dissolving some copper carbonate I synthesized, any suggestions? I've tried ammonia and all I made was a copper tetrammine complex with a really beautiful color.

Thanks for the help in advanced (Finals week)
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Detonationology
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[*] posted on 29-4-2016 at 06:10


Mohr's Salt is your closest option.

http://www.sciencemadness.org/talk/viewthread.php?tid=29738
http://www.sciencemadness.org/talk/viewthread.php?tid=20058

[Edited on 4-29-2016 by Detonationology]




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Chemist_Cup_Noodles
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[*] posted on 29-4-2016 at 06:16


Alright so first and foremost, basic copper carbonate is a BITCH to dissolve. I've never been able to do it successfully. Some people say it is "soluble" in weak acidic solution, but that's because it's basic and it reacts to form soluble compounds.
Let me direct you to the Crystal Growing Topic. It's a great thread, give it a skim through and you may learn a lot.

So you refer to creating a "double salt". You clearly know what complexes are, so I guess you're not trying to refer to that. But since you have two sulfates, are you perhaps trying to refer to the alums? Also, is your iron sulfate ferric (Iron III) or ferrous (Iron II)? There is an important difference if your goal is to make a "double salt". If your iron sulfate is ferrous (which it likely is), you can make Mohr's salt with it and ammonium sulfate. If you have any relatively strong sulfuric acid accessible, react with ammonia to get ammonium sulfate. Then react the ammonium sulfate and ferrous sulfate in equimolar amounts in a solution slightly acidified with sulfuric acid. The resulting salt isn't too pretty, but oh well.

If you want to get some practice on crystallizations, just try making a saturated solution of your copper sulfate first, and cool it gently and let the water evaporate.

Edit: Ah, Detonationology beat me while I was typing my post! Oh well, he's linked you to a scimad thread on Mohr's salt which will likely be more helpful than a wikipedia page.

[Edited on 29-4-2016 by Chemist_Cup_Noodles]




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Fidelmios
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[*] posted on 29-4-2016 at 09:43


Thank you both, I've actually got the reagents for Mohr's Salt, and I just wanted to play with my excess Ferrous Sulfate. Last night I tried to crystallize them, and after some time I got a very nice seed layer (and a very cloudy solution filled with oxides). I decided to mix some of the remaining solutions together ( Copper Sulfate and Ferrous Sulfate) and left them over night. I still got a thin oxide layer but the solution is a mixture of the blue and green I expected. However, I think I am getting a seperation of the two layers, though it may be too early to tell.
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