njl
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NiCl2 Weirdness
I'm having some trouble with a batch of nickel chloride I just made. I did not follow a procedure really, just used background knowledge. The
important thing is that I end up with NiCl2. Here's what I did.
Into a Pyrex dish there was added 5 grams of nickel metal powder. The dish was then filled halfway with concentrated HCl. Then, 2 pre-weighed copper
sheet electrodes were added on either side, such that they did not touch the bottom of the dish or any nickel powder. A current was then run through
the cell, just enough to form bubbles on the electrodes, then dialed back ~20 percent. The cell was left overnight. In the morning I was greeted with
an emerald green solution. However, not all of the nickel dissolved and there was a fair amount of copper powder/flakes on the bottom of the cell
(presumably plated out overnight). I realized that the electrodes were being destroyed, so I set them aside and added 3 percent H2O2. The solution
then sat for about 2 weeks, with periodic swirling and addition of H2O2. Finally, I could see that there was little to no nickel metal left in the
cell, just copper powder. The solution was poured off into a second dish. The copper at the bottom was rinsed with water and set aside with the
electrodes. I was worried that there was significant copper contamination, but after weighing the electrodes and copper flakes only around .5 grams
was unaccounted for (still significant but not as bad as I thought). The solution was then set under a fan for several days to dry. When the solution
started to form crystals around the edge of the dish, I added excess sodium carbonate until bubbling subsided. The supernatent liquid was then
decanted, and the precipitate washed 5 times with warm filtered water. The dish was then placed under a fan again for several days until the surface
looked dry. The dish was then wrapped in aluminum foil. Ventilation holes were poked into the foil covering and the dish was placed in a 250 F
convection oven for 3 hours. When the foil was removed, a crackly surface remained, still not totally dry. The dish was placed back under the fan, and
the solid broken up into a moist slurry. Every few hours the slurry was mixed up, and it slowly dried to a very slightly damp solid. This solid was
broken up and left for 2 days under the fan. When it was mostly dry, the solid was removed and ground in a mortar. Still slightly clumpy, the mortar
was placed under the fan for one more night. Then, the solid was scraped out of the mortar and added back into the dish. There was then added excess
HCl until bubbling subsided. This is where I am right now.
The problem is that although the solution is strongly acidic with HCl, there is still a large amount of what looks like nickel carbonate on the bottom
of the dish. When some nickel carbonate that was stuck on the pestle was added, the solution bubbled like normal. What could be at the bottom of the
dish? The solid at the bottom of the dish was stirred, swirled, etc. and still no bubbling. Help?
I have a few notes as well. I know this procedure was silly and a big waste of time. I don't really know much about electrolysis and in hindsight that
whole step was probably pointless. Adding sodium carbonate to precipitate the nickel was also pretty much pointless.
Edit: It was a solubility issue. After adding more water and stirring the solution cleared up to a beautiful emerald green.
[Edited on 2-13-2021 by njl]
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Lion850
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Interesting read. If you extract nickel chloride crystals please post a photo.
On the very few times I wanted to dissolve nickel metal I used nitric acid.
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Boffis
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WTF! I don't think I have ever read such a ridiculously over engineered method to achieve anything in my life. Are you trying to make nickel chloride
hydrate?
If so just put nickel powder in dilute hydrochloric acid and stand for a couple of days /week filter off any undissolved material and evaporate slowly
and crystallise in stages. dilute H2O2 should speed up the process remarkably. If your nickel powder is pure you shouldn't have any problems. The
hydrochloric acid does not need to be concentrated, 10% is adequate. Nickel dissolves slowly in dilute HCl alone but the H2O2 should greatly speed up
this reaction.
There is no point trying to use electrolytic dissolution with copper electrodes that don't touch the nickel; whats that going to do except fill your
solution with copper? You now have a mixture of copper and nickel in solution and they are going to be a bugger to separate.
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RustyShackleford
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jesus, just put the nickel in HCl and stir it / bubble air through it for a few days or a week
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njl
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@Lion will do.
@Boffis lighten up a little... it's impossible to over engineer something done purely for fun. If you read the whole post you will find that I ended
up with exactly what I wanted. As I said in my post, the electrolysis was pointless. It absolutely filled the solution with copper (if your definition
of filled is less than 10 percent by mole fraction).
@Rusty I don't have a bubbler and Nickel is ferromagnetic so stirring is a pain in the ass.
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Panache
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nji,
Thanks for writing it up. 'negative' results are so useful for others doing things. i dont think boffis, nor any of the others were having a go at you
in any way, rather they were exasperating 'with' you. They perhaps just lacked nuance in their responses so think nothing of it.
So what happens if you put iron or nickel powder under an oscillating magnetic field like that of a stirrer? I have never tried it.
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Amos
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Your early precipitate sounds like copper(i) chloride or oxychloride. If you ever suspect you've got copper contamination in your nickel solution (and
of course you would have lots, using copper electrodes like that), just warm it up in the presence of nickel metal and it will plate out; I've made
copper plated nickels this way.
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njl
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@Panache Thank you. The point of stirring would be to create an even suspension of the metal in solution, but since there are several magnets right
next to the metal, a large amount just sticks to the sir bar as a clump and doesn't move anymore.
@Amos Good point. Part of my reasoning for using copper electrodes was that after the electrolysis process, when there was left over nickel powder,
that is exactly what would happen and the amount of copper contamination would decrease as nickel metal replaced copper in solution.
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