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plante1999
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extract chromium from 18/0 stainless
recently i have make test on dollar store spoon witch is wrigthed 18/0 ss so i tried electrolisis of he spoon as an anode and a steel wire as a
cathode in sodium hydrogen sulfate and a red incredibly corrosive solution is formed , this solution corrod glass(and stain it)! so i abandond this
way. I make test and no nickel is present , vanadium also is not present. So im disolving it in HCl to make CrCl3 and FeCl3. how i can precipitate the
chromium (as a coupound), extract the chromium(or precipitate the iron as a salt)?
thanks!
i know many post have been posted on this subject but no one correspond to my way.
.... and please dont post comment like: it is impossible, you cannot , or other same thing, this topic is for improuvement not for regress.
[Edited on 21-3-2011 by plante1999]
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Jor
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Add a large excess of NaOH-solution. All the iron will precitipate a hydrated oxides, while chromium will dissolve as CrO3(3-) (or a hydrated
variant). Filter, and next, made the solution acidic again and add ammonia to precitipate Cr(OH)3, or just add enough ammonium chloride (or
sulfate/nitrate) to the basic solution.
But why don't you buy pure chromium from eBay. It's pretty cheap and you avoid the messy seperation.
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Polverone
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If there is no nickel or vanadium present, I suggest using the spoon as an anode in a sodium or potassium carbonate solution. The chromium will go
into solution as chromate and the iron will be left behind as insoluble basic compounds. I have done this myself, using toaster element wire rather
than spoons. If you need pure, solid chromium compounds or metal you can convert the mixed carbonate/chromate solution later.
Much of the electrical energy goes to making oxygen at the anode rather than dissolving the metal, so it is inefficient, but electricity is available
everywhere and leaves less waste to deal with than if you start out with dissolving stainless in hydrochloric acid.
PGP Key and corresponding e-mail address
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plante1999
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in fact i will do chromium chemistery because i have used all my titanium and zirconium coumpound , and i will order some other compound in 1month ,
and i want to make chemistery , and the only chemistery that i like that it is redily avaible is chromium.
ive read this on wikipedia:For the production of pure chromium, the iron has to be separated from the chromium in a two step roasting and leaching
process. The chromite ore is heated with a mixture of calcium carbonate and sodium carbonate in the presence of air. The chromium is oxidized to the
hexavalent form, while the iron forms the stable Fe2O3. The subsequent leaching at higher elevated temperatures dissolves the chromates and leaves the
insoluble iron oxide. The chromate is converted by sulfuric acid into the dichromate.[29]
4 FeCr2O4 + 8 Na2CO3 + 7 O2 → 8 Na2CrO4 + 2 Fe2O3 + 8 CO2 2
Na2CrO4 + H2SO4 → Na2Cr2O7 + Na2SO4 + H2O
The dichromate is converted to the chromium(III) oxide by reduction with carbon and then reduced in an aluminothermic reaction to chromium.[29]
Na2Cr2O7 + 2 C → Cr2O3 + Na2CO3 + CO
Cr2O3 + 2 Al → Al2O3 + 2 Cr
from wikipedia the online enciclopedia ,Chromium (element)
[Edited on 22-3-2011 by plante1999]
[Edited on 22-3-2011 by plante1999]
[Edited on 22-3-2011 by plante1999]
[Edited on 22-3-2011 by plante1999]
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plante1999
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sorry for the double post but , after disolving the stainless for 12hour i filtered the solution and tested the presence of iron with naoh , it seam
that no iron is present. also does anybody have an idee about the composition of the red solution.
the solution is realy dark green.
[Edited on 22-3-2011 by plante1999]
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blogfast25
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Firstly, for your photos, try a whitish background and get close up: the black ruins everything.
Secondly, no stainless steel without an iron base. Are you sure you used enough alkali? But the ‘red solution’ may indicate the Fe(OH)3.nH2O has
peptised, that is: gone into a colloidal state which runs right through the filter! Look up ‘colloid’ and ‘pertisation’, if needed. Fresh
Fe(OH)3.nH2O is prone to peptisation when washing the precipitate because by washing the ionic strength of the washing water starts to drop a lot. A
simple counter measure is not to wash too thoroughly (thereby losing small amounts of the target Cr…) or allowing the precipitate to mature
somewhat. You may also simmer the slurry (obtained by adding the alkali to the solution of SS 18/0 in HCl) for a while. Washing the precipitate with
strong NH4Cl (instead of water, thereby keeping the ionic strength high!) will also prevent peptisation.
After separation you then obtain a solution of sodium chromite [+III] (NaCr(OH)4), treat this with HCl, to about pH = 7 to obtain
Cr(OH)3.nH2O, wash thoroughly and semi-calcine (>500 C) to dry to Cr2O3. At to low pH you’ll obviously redissolve to CrCl3.
Pure chromium is prepared industrially via aluminothermy from Cr2O3. I’ve done this myself and the metal forms as beautiful reguli of clean skinned
metal You’ll need Al powder and fluorite (CaF2) for this reaction.
[Edited on 22-3-2011 by blogfast25]
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plante1999
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Quote: Originally posted by blogfast25  | Firstly, for your photos, try a whitish background and get close up: the black ruins everything.
Secondly, no stainless steel without an iron base. Are you sure you used enough alkali? But the ‘red solution’ may indicate the Fe(OH)3.nH2O has
peptised, that is: gone into a colloidal state which runs right through the filter! Look up ‘colloid’ and ‘pertisation’, if needed. Fresh
Fe(OH)3.nH2O is prone to peptisation when washing the precipitate because by washing the ionic strength of the washing water starts to drop a lot. A
simple counter measure is not to wash too thoroughly (thereby losing small amounts of the target Cr…) or allowing the precipitate to mature
somewhat. You may also simmer the slurry (obtained by adding the alkali to the solution of SS 18/0 in HCl) for a while. Washing the precipitate with
strong NH4Cl (instead of water, thereby keeping the ionic strength high!) will also prevent peptisation.
After separation you then obtain a solution of sodium chromite [+III] (NaCr(OH)4), treat this with HCl, to about pH = 7 to obtain
Cr(OH)3.nH2O, wash thoroughly and semi-calcine (>500 C) to dry to Cr2O3. At to low pH you’ll obviously redissolve to CrCl3.
Pure chromium is prepared industrially via aluminothermy from Cr2O3. I’ve done this myself and the metal forms as beautiful reguli of clean skinned
metal You’ll need Al powder and fluorite (CaF2) for this reaction.
[Edited on 22-3-2011 by blogfast25] |
1:in 2hour in half i will re made picture.
2:i think used enoug alkaly , but is this possible that this appen (take note that a precipitate of grayis powder have formed in the beaker).
FeCl3 + Cr -} CrCl3 + Fe
when i was talking about the red solution i was talking about the first experiment i made, with electrolisis in NaHSO4. The solution is clear dark red
and corrod most metal including copper , iron, aluminium and it also corrod glass!!!! in fact if possible i wich to have 50g+ of solid green chromium
trichloride hexahydrate. if i find a good way witch use cheap otc chemical i will made a prepublication , a video and a raport of my experimentation
witch i will post on this topic.
and I know that the desk is really dirty but this is not my desk, I worked with my poratativ lab (which is in a steel suitcase) in my grandfather
house.
@blogfast: for your question about ZrF4 i will send you in 1-2 day a complete report of all the experimentation with picture , at this time i have a
lot of work.
[Edited on 22-3-2011 by plante1999]
[Edited on 22-3-2011 by plante1999]
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blogfast25
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Cr (0) === > Cr3+ + 3e …. E = + 0.744 V
Fe3+ + 3e === > Fe(0) …. E = - 0.037 V
+ 0.744 + (- 0.037) = + 0.707 V, reaction is possible. But where would the elemental Cr come from??? Your gray stuff could be some magnetite: Fe3O4...
I’d forget about electrolytic dissolution, if I were you: Cr dissolves readily in strong HCl as does Fe. Then precipitate with excess NaOH, allow to
stand so the Fe2+ oxidises to Fe3+ in air or add H2O2 or bleach. Proceed as above…
[Edited on 22-3-2011 by blogfast25]
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plante1999
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wath apen if naocl is mixed with crcl3?
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plante1999
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sorry for the double post. today i experienced the joy of the stiking iron II hydroxide , but befor explaning it i will start from the begining , ok i
will start with my steel suitcase(portable lab). look to the yamaha phaser clutch (my father hoby).
here the suitcase
here the first batch of chemical i have all time with my.
a zoom of my favorite compound:
and the second batch (look to the realy dirthy acetone):
finnaly the third batch:
with this chemical wath can i do for precipitate the iron?
so i disolved the stainless spoon in the hydrochloric acid with reflux.
and after i filter (i take my young sister white board).
than i ad sodium hydroxide to 10 ml of it the realy stiky iron II hydroxide form and the chromium hydroxide is contained inthe iron hydroxide. so i
need an other way for precipitate the iron (the picture of my portable chemical is for that).
i ave thinked of :
the solution + H2O2
the second solution + naocl , but i dont know if naocl afect the crcl3.
I never asked for this.
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S.C. Wack
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I would check the pH of that solution. IIRC everything should precipitate without drama though I may recall this with some nickel in there and perhaps
heat. I suspect this subject has been covered pretty well before.
I would NOT count on NaOH in any quantity to dissolve much Cr in the presence of so much Fe. That blue-gray precipitate holds a lot of Cr, and NaOH. I
dare anyone to find this used in the analytical lit. for the separation of Cr and Fe; naturally I say this without looking - let's see how that goes.
Barring the use of an oxidizer with the alkali of course. I used H2O2 with the boiling well-stirred sludge and did obtain considerable quantities of
Cr+6, but do not recommend this. For one thing among many is that excess NaOH seems necessary with makes isolation less simple.
You're on the right track with a chromite process, but I would target the immediate preciptitate as is.
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blogfast25
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Hypochlorite cannot oxidise Cr3+ to chromate (Cr [+VI]) in alkaline conditions (see reduction potentials). H2O2 would oxidise it to Cr [+VI] but I
don’t see the point here.
| Quote: Originally posted by S.C. Wack | I would NOT count on NaOH in any quantity to dissolve much Cr in the presence of so much Fe. That blue-gray precipitate holds a lot of Cr, and NaOH. I
dare anyone to find this used in the analytical lit. for the separation of Cr and Fe; naturally I say this without looking - let's see how that goes.
Barring the use of an oxidizer with the alkali of course. I used H2O2 with the boiling well-stirred sludge and did obtain considerable quantities of
Cr+6, but do not recommend this. For one thing among many is that excess NaOH seems necessary with makes isolation less simple.
You're on the right track with a chromite process, but I would target the immediate preciptitate as is. |
Whether or not there are references to the separation of Fe and Cr in the anal. lit. (I’m pretty sure there are) is immaterial: Cr3+ IS amphoteric,
Fe2+/Fe3+ IS NOT and that makes separation possible. My experience shows that 'fresh' Cr(OH)3.nH2O dissolves in NaOH solutions very readily, much like
Al(OH)3.nH2O.
Firstly, complete dissolution of the metal in the acid has to be achieved of course, it’s not clear to me whether that’s the case or not in
plante's effort. Then precipitate the whole lot with strong NaOH, using some excess to get the Cr3+ as Cr(OH)6(3-) (chromite). Filter and wash
precipitate with strong NaOH to get all the chromite out.
Neutralise the filtrate carefully with HCl solution until Cr(OH)3.nH2O appears, filter and wash carefully. To ensure getting rid off all sodium,
redissolve in medium HCl and reprecipitate with WEAK ammonia (avoiding Cr-NH3 complexes which would form with strong, excess ammonia solution) as
Cr(OH)3. Filter and wash carefully. Drying and calcinating the hydrated chromium [+III] oxide will get rid of any ammonia/ammonium.
[Edited on 23-3-2011 by blogfast25]
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blogfast25
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Chromium’s [III] amfoterism:
Below three identical test tubes with some K,Cr [III] alum solution:
After treatment with alkali:
1 = control
2 = after adding sufficient NaOH 1 M, Cr(OH)3.nH2O drops out as a greenish precipitate.
3 = after creating the same precipitate as in 2 and then adding a small amount of NaOH 4 M: the precipitate redissolves effortlessly to an emerald
green solution of Na3Cr(OH)6.
The pix don’t really do it justices (too concentrated solutions, I think…)
[Edited on 23-3-2011 by blogfast25]
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S.C. Wack
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| Quote: Originally posted by blogfast25 |
Whether or not there are references to the separation of Fe and Cr in the anal. lit. (I’m pretty sure there are) is immaterial
|
I thought said separation was the subject of this thread. Your reaction of the hydroxide without massive amounts of iron present is immaterial.
Since I am not completely inept and suspect you know nothing about this and have never done it you may want to read rather than disregard the
literature. I'm pretty sure the iron prevented solution fairly well but not entirely. In fact I recall considerable iron being present (it's rather
conspicuous after a time in air) in the alkali, and chrome in the precipitate. Indeed the precipitate was soaked and washed many times with NaOH, and
it still contained Cr. However I probably did add solid NaOH in my larger experiments with the acid solution that I still remember some, which is
likely a no-no. I expect many books at Google Books to have available full text detailing separation of the two; as a rule not involving extraction
with alkali, since my efforts were not drawn out of thin air.
Oxidizers are used in the literature. You say hypochlorite is no good yet there are many references to alkali and chlorine.
But if the green solution really is strongly basic, and precipitates the hydroxide on boiling, you've got chromite. If the solution turns chromate
yellow on adding H2O2, and dichromate orange on addition of acid, well that's what it is.
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blogfast25
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@ S.C. Wack:
Okay, keep your hair on. No one said you’re inept. Your condescension is uncalled for.
You claim iron prevents chromium from dissolving (if I understand you correctly)? How, prey tell? A this point I don’t know whether (plante’s)
dissolution is complete either, of course, as I stated. If the Cr doesn’t dissolve, the separation could be achieved this way. If it can then
separation based on amfoterism must be possible. Give me one good reason why it shouldn’t. And better solvents for SS may also be available.
I said that based on half potentials, ClO- isn’t capable of oxidising Cr3+ to chromate in alkaline conditions. Based on tabled reduction
potentials. Look it up. But I’ll gladly test it myself.
Oh, I’ve got chromite alright, you bet! How else to explain the Cr(OH)3.nH2O dissolves readily in (actually fairly weak) NaOH? Done it may times
before, including addition with H2O2 to get yellow chromate. Also on this forum.
Edit:
On hypochlorite + Cr3+, I seem to have misread a table (http://web.archive.org/web/20070518092613/http://www.northla...), which gives:
Reduction: ClO- + H2O + 2e === > Cl- + OH- …. E = + 0.81 V
Oxidation: Cr(OH)3 + 5 OH- === > CrO4(2-) + 4 H2O + 3e …. E = + 0.13 V
So the cell potential would be + 0.94 V.
I’ll verify that experimentally tomorrow.
[Edited on 23-3-2011 by blogfast25]
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S.C. Wack
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My last post did not refer to your post immediately before it in any way. I still speak of the original green solution.
There are other experiments. Not always fact filled but relevant:
http://books.google.com/books?id=erMKAAAAYAAJ&pg=PA334
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plante1999
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how can i precipitate iron sulfide and chromium sulfide?
ive read that reaction work:
2FeCl3 + FeS -> 3FeCl2 + 1/8S
and
6FeCl3 + Cr2S3 -> 2CrCl3 + 6FeCl2 + 3/8S
this one is not favorable.
[Edited on 23-3-2011 by plante1999]
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blogfast25
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Two experiments
1. Comparison of H2O2 (3%) with commercial bleach as oxidisers for chromite solutions:
Two tubes with approx. 0.1 M Cr3+:
After adding 4 M NaOH and (left) H2O2 and (right) hypochlorite:
At first the hypochlorite didn’t seem to do anything but after heating some Cr(OH)3.2H2O dropped out and the yellow chromate colour developed in the
supernatant liquid.
2. Fe-Cr separation experiment based on chromite formation:
For this a 0.1 M solution of Mohr’s Salt (Fe[+II]) was prepared and an equal volume amount of the 0.1 M Cr3+ solution was added. The resulting
solution is thus about 0.05 M Cr3+ and 0.05 M Fe2+. Since as the atomic weights of Fe and Cr aren’t miles apart the weight ratio of both elements is
roughly 1.
Three test tubes were filled with this broth:
After treatment:
Left: no treatment.
Middle: treated with 4 M NaOH. Turns emerald green but with precipitate.
Right: same as middle but after filtration (filter not shown). The filtrate runs a perfectly clear emerald green, about as intensive as the middle
tube. It filters slowly. I didn’t wash.
The precipitate on the filter: right from the start the greenish precipitate started to discolour to reddish/brown. W/o a shimmer of a doubt this is
Fe(OH)2.nH2O oxidising to hydrated rust:
This experiment says nothing much about actual separation percentages, yet shows that separation between Fe and Cr is possible, based on Cr [III]’s
ampfoterism.
It says nothing about the solubility of stainless steel in strong HCl either. That will be tested separately.
As an aside:
In at least one case, industrially iron and chromium are separated from each other by fusing Chromite ore, FeCr2O4, with KOH, lime and air, to form
potassium chromate, CaCO3 and Fe2O3. Leaching of the ground frit followed by acidification then yields dichromate.
[Edited on 24-3-2011 by blogfast25]
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blogfast25
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Well, well. Looks like SC Wack may well be right or at least partly right about the difficulty of separation Cr and Fe using chromite to keep Cr in
solution...
Here’s are the experiments.
56 g of a stainless steel object (a bathroom beaker) were dissolved in about 27 w% HCl and 300 ml of solution were obtained and filtered. It took
about 2 h. Dissolution was near complete with just a little brownish-blackish residue left on the filter (more about that below).
100 ml of that solution was first iced and then neutralised with 3 M NaOH to pH 13 to 14. The precipitate formed was very dark (blackish, really) and
was filtered off on a coffee filter. To my surprise, the filtrate ran clear and almost colourless, no green (chromite) to be seen (see photo, RIGHT).
The filtrate was then tested for chromium by boiling a 20 ml sample with some twenty ml bleach, with extra NaOH added. No precipitate, no green, no
yellow, nothing!
Then two teaspoons of the still very wet precipitate were mixed with some more NaOH and bleach added. Immediately the colour of the precipitate
changed to the familiar reddish-brown (of Fe2O3) and this suspension was boiled for about 5 mins, topping up with bleach once. This was filtered and
now the chromium showed up as green chromite (see photo, LEFT):
Treating the green solution with H2O2 (9 %) yielded chromate yellow.
From this result I tentatively conclude that on this occasion, in clear contradiction with the previously obtained test tube results, the
chromium had co-precipitated in its entirety with the Fe2+, the majority constituent.
Other tests were carried out, some ongoing.
Some of the precipitate was dried in a steel pan on my lab gas cooker and 8 g of this (see photo, MIDDLE) very dark powder was mixed with 8 g KOH and
2 g KClO3 and fused for 15” to a dull red heat. Water was then added after cooling and this will be filtered tomorrow.
Also 2 teaspoons of the still wet precipitate have been mixed with 50 ml water and 25 ml NaOH. This will be left to stand overnight and filtered. No
oxidiser (other than air) is present.
Then a test tube test. To a few ml of the SS steel solution was added the same amount of the Cr3+ solution used in the test tube experiments in the
post above. 4 M NaOH was then added in excess. Again the filtrate ran clear and colourless, indicating that the Cr had co-precipitated with the iron.
Is it possible that in some conditions something akin to Chromite ore, FeCr2O4 (FeO.Cr2O3), precipitates and that only oxidation of
the Fe [II] to [III] ‘breaks’ this ‘complex’ (or ‘double oxide’)?
Finally, a couple of tests on the brownish-blackish filter residue. It dissolves in 50/50 w/w % NaOH, with evolution of gas, which would point to
carbon or silicon. With hot, 38 w% nitric acid no dissolution occurs but the residue is ‘bleached’ (??!?) No nitric soluble metals like Ni or Cu
(for instance) appear to be present in the HCl insoluble residue.
Final results tomorrow.
[Edited on 26-3-2011 by blogfast25]
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blogfast25
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The result of the fusion with KOH was leached by adding cold water and standing overnight, it was then filtered. The filtrate is very dark green with
potassium chromite:
The result of the test where only a lot of extra alkali was added wasn’t worth filtering: it can be seen that the supernatant liquid is clear and
colourless:
Yet another experiment was conducted by oxidising 30 ml of the stainless steel solution with about 5 ml of 38 w% nitric acid:
FeCl2(aq) + 1/3 HNO3(aq) + HCl (aq) === > FeCl3(aq) + 1/3 NO(g) + 2/3 H2O(l)
The oxidation was carried out in a large test tube on steam bath:
The cooled solution was then neutralised to pH 13 - 14 and filtered: much to my surprise the filtrate ran clear and colourless:
Heating the slurry obtained above made no difference but adding bleach to the hot slurry cause the filtrate to run yellow:
Conclusions:
1. It would appear that in some conditions iron and chromium co-precipitate. This wasn’t observed at low concentrations (0.05 M) and low Fe/Cr molar
ratios (about 1) but it was observed at high concentrations (about 3 M) and high Fe/Cr molar ratios (8 - 9). Whether a Cr/Fe complex precipitates or
whether this is a case of chemisorption, in one instance merely oxidising the Fe [+II] to Fe [+III] wasn’t enough to ‘free’ the chromium.
2. There are various ways to recover chromium from scrap stainless steel but at bench level I’d suggest the following:
• Dissolve scrap in strong HCl, then precipitate with strong alkali as mixed oxide.
• Filter off precipitate (washing is optional) and dry it to a paste or powder.
• Add about the same amount of KOH (this may be overkill but it worked for me) and fuse the mixture. After cooling add water and allow to soak
overnight.
• Filter: the filtrate should contain the chromium, in my case as potassium chromite (but oxidation state of the Cr may depend on duration of
fusion). No guarantees about the degree of separation can be given.
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S.C. Wack
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| Quote: Originally posted by blogfast25 |
Is it possible that in some conditions something akin to Chromite ore, FeCr2O4 (FeO.Cr2O3), precipitates and that only oxidation of
the Fe [II] to [III] ‘breaks’ this ‘complex’ (or ‘double oxide’)? |
When using 3-10% H2O2, only a small amount of Cr would extract at once, only on boiling even after the iron looked like it was all oxidized and lots
of peroxide had been added (much seemed wastefully decomposed instantly). It took several repetitions to get all the Cr out. And the filtered, clear,
chromate/NaOH solution contained unseen iron, which did not all precipitate at once on slow concentration in air.
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blogfast25
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| Quote: Originally posted by S.C. Wack | | When using 3-10% H2O2, only a small amount of Cr would extract at once, only on boiling even after the iron looked like it was all oxidized and lots
of peroxide had been added (much seemed wastefully decomposed instantly). It took several repetitions to get all the Cr out. And the filtered, clear,
chromate/NaOH solution contained unseen iron, which did not all precipitate at once on slow concentration in air. |
True, but in all these experiments I've only ever used H2O2 (3% but I've now got 9%) to show the green was due to chromite, never to oxidise anything
else. It's far too precious for that, IMHO.
What I also found surprising is that the fusion with KOH seemed to yield chromite only. But it was a very short run (15")...
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plante1999
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does it will work with impure NaOH containing NaNo3 for making sodium chromite.
the way: disolve the stainless in hot HCl when no acid is present boil the solution in a stainless mud , you will have calcined oxide.
than take sodium hydroxide and melt it in and lets it for a long time . digest it and filter , now you have sodium chromite. (does it will be pur?) if
yes
boil it in stainless to get the oxide , if no , i dont have any idee.
thanks!!
I never asked for this.
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blogfast25
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1st question: I don't see why not. Using 'toilet drainer', eh? 
If you wanted to to purify the chromite, best way would probably to use KOH rather than NaOH, thus obtaining the K chromite. Oxidise this to K
chromate, then acidify with H2SO4, this converts the chromate (CrO4(2-)) to potassium dichromate (K2Cr2O7), which is only sparingly soluble in cold
water (Wiki: 4.9 g/100 g water @ 0 degrees C). So simmer in your solution, then ice. Recrystallise once for good purity. Na2Cr2O7 could probably be
displaced to K2Cr2O7 with KCl and ice.
The dichromate can be converted to Cr3+ salts by reduction with alcohol (methylated spirits, wine, vodka, whatever)
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cyanureeves
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plante1999 what is the make up of that dg spoon?i got a custom belt buckle made for a navy officer and i haven't a clue what its made of.it looks like
s.steel with with gold plate outline of an american eagle.with all due respect to servicemen i will boil some of it in hcl acid and electrolyze a
portion in sodium carbonate.anyhow what test did you use for nickel test?ammonium hydroxide?
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