Twospoons
International Hazard
Posts: 1324
Registered: 26-7-2004
Location: Middle Earth
Member Is Offline
Mood: A trace of hope...
|
|
chrome alum from Cr(III) acetate
Trying to make some chrome alum ( KCr(SO4)2 ) for crystal growing.
I have a couple of small jars of Cr(III) acetate, and access to some common sulfates ( NH4, K, Mg, Cu) - but not sulfuric acid.
Solubility data dredged up so far: (@20C, g/100g in water)
KCr(SO4)2 : 24
Cr acetate : 67.5
Cr sulfate : 220
K acetate : 286
K sulfate : 13
So i'm looking at this and wondering if simply combining the cr acetate with K sulfate will result, at some point, with KCr(SO4)2 crystalizing out,
leaving the acetates in solution? This isn't something i've ever tried to work out before, and to be honest i'm not really sure how.
Advice appreciated . Alternative route suggestions also appreciated.
I have nitric acid ( lots of it - but no sulfuric *sigh*), so going via nitrates is possible.
[Edited on 3-4-2017 by Twospoons]
Helicopter: "helico" -> spiral, "pter" -> with wings
|
|
|
diddi
National Hazard
Posts: 723
Registered: 23-9-2014
Location: Victoria, Australia
Member Is Offline
Mood: Fluorescent
|
|
Sulfuric acid can be purchased at most auto stores as top up for car batteries. It is clean and does not need processing like the drain cleaning
products.
Beginning construction of periodic table display
|
|
|
Twospoons
International Hazard
Posts: 1324
Registered: 26-7-2004
Location: Middle Earth
Member Is Offline
Mood: A trace of hope...
|
|
Ah, this might be simpler:
CuSO4 : 32 g/100g
Cu acetate : 7.2 g/100g
So combining CuSO4 with Cr acetate, I should get copper acetate crytalizing out first, leaving Cr sulfate in solution?
I've looked for battery acid in auto shops, and never found any. Seems to be harder to find in NZ.
[Edited on 3-4-2017 by Twospoons]
Helicopter: "helico" -> spiral, "pter" -> with wings
|
|
|
Dmishin
Harmless
Posts: 32
Registered: 5-10-2015
Member Is Offline
Mood: No Mood
|
|
I am pretty sure that mixing chromium acetate with excess of univalent sulfate will let you crystallize alum. Did not tried exactly this process, but
did similar things several times.
I would recommend trying NH4 sulfate, since it is more soluble than K2SO4
|
|
|
woelen
Super Administrator
Posts: 8014
Registered: 20-8-2005
Location: Netherlands
Member Is Offline
Mood: interested
|
|
There may be one issue which spoils things with acetate. The acetate ion is a good coordinating agent and I expect it to be tightly bound to the
chromium ion. The salt actually is an acetato complex of chromium(III).
Adding H2SO4 most likely (slowly) breaks away the acetate from the Cr(3+) ion and makes acetic acid, but I expect that adding CuSO4 to Cr-acetate does
not lead to much useful. I think that most of the acetate will remain attached to the chromium ion.
|
|
|
CharlieA
National Hazard
Posts: 646
Registered: 11-8-2015
Location: Missouri, USA
Member Is Offline
Mood: No Mood
|
|
Please enlighten me...what is univalent sulfate? A sulfate salt of a univalent cation?
|
|
|
Fantasma4500
International Hazard
Posts: 1681
Registered: 12-12-2012
Location: Dysrope (aka europe)
Member Is Offline
Mood: dangerously practical
|
|
certainly will still be Cr Ac impurities if you just try to crystallize out most, maybe if you form large crystals you can sort out the crystals
supposing both compounds wont cocrystallize
i would suggest --> carbonate / hydroxide, then dissolving that in acid
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
