Home > Community > Tips for preparing crystals of nickel(II) chloride hexahydrate?
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Posted by
Mike Roberts

Tips for preparing crystals of nickel(II) chloride hexahydrate?

Deborah Denise Thomas  Follow
You said you are doing this outdoors and not standing downwind and not near anyone or anything that can be harmed?

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Badi DukviL  Follow
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no cross posting on our forum
Right, which is I why I meant I was going to cross post to other forums, i.e., on other websites besides CF.

Anyway, I got my hands on some oxalic acid (pKa 1.25, 4.14) and NaOH (pKa 14.56) which I combined dissolved in ~100 mL of water each and combined in a roughly 1:2 ratio to produce a solution of sodium oxalate hopefully close-ish to neutral (I don't have a pH probe). Adding this to the amber/black solution caused it to clear up and turn back to the vibrant green of a NiCl2·6H2O solution, as I suspected, but I also expected iron oxalate to precipitate out as a yellowish solid, and there was no precipitate and no cloudiness.

(Technically what I did was combine oxalic acid (aq) and NaOH (aq) in a roughly 1:1 ratio, added it to the black solution, it turned green but no precipitate, went back to my computer and looked up how to make sodium oxalate and apparently you need a 1:2 acid:base ratio, not 1:1, and that what I actually made was sodium hydrogenoxalate, so I made another batch of ~100 mL of NaOH (aq), added it to the now-green solution, still green and still no precipitate)

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Dennis Pasek  Follow
Ehhhhh... outside, yes, and if I boil it off during the night there won't be anyone else around but me to breathe in the fumes, but I don't know how to guarantee not standing downwind of it except by, say, going indoors to watch from a window until the fuel runs out.

(I decanted the saturated green NiCl2 solution and it turned extremely dark, almost black, overnight. Here's to hoping that's just absorbing moisture from the atmosphere, because if it's anything else I have no idea what happened or how to fix it)

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David Bell  Follow
If I remember Mason jars are used in canning where they are submerged in boiling water. Test a Mason jar with just water will work using something like a sand bath, thermometer and hot plate will work.

https://chem.libretexts.org/Bookshelves/Organic_Chemistry/Book%3A_Organic_Chemistry_Lab_Techniques_(Nichols)/1%3A_General_Techniques/1.3%3A_Heating_and_Cooling_Methods/1.3H%3A_Water%2C_Sand%2C_and_Oil_Baths

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Caren McElrea  Follow
Linseed oil is unhealthy.

It is one thing that made 19th century painters mad (the others being absinthe and alcohol).

Please be careful for real!

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Daniel Andrews  Follow
I apparently forgot oxalate can be a ligand. In that case, I guess it's likely that the green solution w/out precipitate was largely sodium ferrioxalate.

I prepared a sort of makeshift sand bath as suggested by placing the mason jar in a galvanized steel bucket and surrounding the jar on all sides + bottom with sand, and placing the whole bucket on top of a single-burner propane camp stove. I boiled most but not all of the water off (perhaps 2/3 - 3/4 of the water), but during the heating process the solution turned amber-colored. I left it to cool over night to see if it returns to green when cooled, but if not, I have no idea what I just made.

Aaaaanyway since this is veering a bit far from the original goal of making nickel chloride - the 2nd batch of nickel chloride (the one uncontaminated with iron) looks about saturated (i.e. not getting any greener); is it actually safe to boil the liquid off in a sand bath, since the fumes would contain a fair amount of HCl (g)?

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Blake Senftner  Follow
Quote from:
...
Last note: since I'm new to the forums, I'm not sure if this is the right board or it should've gone in Undergraduate (which I am, but ChemE major instead of Chem, and this isn't homework or anything) or Inorganic. I'll probably also cross-post this to a couple other forums besides Chemical Forums since I'm not sure how active this place is.

no cross posting on our forum
This is a forum policy.
Click on the link near the top center of the forum page.
Forum Rules: Read This Before Posting.
http://www.chemicalforums.com/index.php?topic=65859.0

I think
Citizen Chemist
is probably the best place for this post.

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Aminat Aregbe  Follow
Try to buy universal pH strips, they are cheap.

Precipitates won't show before you get past the solubility limit of a given salt or hydroxide (actually it is about getting past the solubility product, but let's keep things simple).

Oxalate is a good complexing agent, it complexes both iron and nickel. Iron complexes are much more stable, so my bet is that's what happened - you complexed iron.

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