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woelen
Super Administrator
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Registered: 20-8-2005
Location: Netherlands
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Making calcium perchlorate from calcium chloride is not that easy. If you electrolyse CaCl2, then at the cathode you get hydroxide ions, but these
lead to precipitation of Ca(OH)2. Ca(OH)2 is soluble in water, but not very well. In a concentrated solution of CaCl2 its solubility is even lower.
Carbon dioxide from the air makes things even worse. You'll get turbidity from CaCO3 in your solution as well. I can tell you from experience. I tried
electrolysis of CaCl2, BaCl2 and MgCl2 and all of them were a pain in the ass. If you add a little HCl to the solutions, then your solution remains
clear, but in that case, the Cl2, produced at the anode simply escapes as gas, too little hydroxide is formed to get chlorate (and at a later stage
perchlorate).
So, in practice, electrolysis of CaCl2 is not a good route to Ca-chlorate or Ca-perchlorate.
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underground
National Hazard
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Registered: 10-10-2013
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To avoid the decomposition of chlorate while adding HCL in order to dissolve CaCo3/Ca(OH)2, you have you use low concentration of HCL, like 3%.
Concentrated HCL will decompose chlorate, even in solution. In KCL cell intentionally i add a small amount of CaCL2 as a buffer in order to keep the
ph close to neutral. While OH is forming, Ca(OH)2 ppt out, keeping ph neutral for max efficiency. If no CaCL2 is used, KOH will form and dissolve into
eletrolyte making it basic, lowering your efficiency. Once I saw Ca(OH)2 ppt at the cathode, i add dilute HCL to dissolve it back. I have much better
yields that way.
[Edited on 19-5-2025 by underground]
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yobbo II
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There is a Japanese paper here
https://www.sciencemadness.org/whisper/viewthread.php?tid=16...
regarding Ca chlorate by electrolysis.
To stop Ca hydroxide from building up on the cathode and stopping the current flowing you should use an amphotheric metal cathode.
Ti will fit the bill.
Use good stirring.
I believe it will work OK.
I have made Ca chlorate using two graphite electrodes and current reversal (reversed current every 60 sec approx). I could not recommend this method.
You should be able to go from chlorate to perchlorate using Pt anode & Ti cathode..
Then use Ca perk & ammonium sulphate to get ammonium perk plus insoluble Ca sulphate.
Yob
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