EthidiumBromide
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Some chemistry pictures from a long time forum lurker
Hello!
A bit of background - I've been a home chemist since the early 2010s. I've been aware of this forum's existence around 2012-2013, at the same time I
discovered Woelen's website. I don't know why, but I hesitated to create an account here, until now. In an academic sense, I'm more involved with
biotechnology (genetic engineering) and molecular biology. This year I recieved my master's degree. But I still enjoy chemistry as a hobby. I do most
of my chemistry on a small scale and in aqueous solutions, I don't have the equipment to do things like distillations or syntheses which require
prolonged heating and reflux systems (but I do want to invest in a hotplate with stirring this year or next, so that might change).
I've rambled about my self long enough, time to show you the pictures. Woelen has already seen them in emails, but encouraged me to show them to all
of you, so here they are:
Ferrate(VI)
I've made some ferrate(VI) with the usual Fe salt + alkali + hypochlorite route. I think it's still nice to look at this more unusual oxidation state
of iron, in its beatiful purple color. Here is ferrate(VI) next to samples of Fe(III) and Fe(II):
Vanadium oxidation states (II-V)
A classic experiment, nothing too special. NH4VO3 was dissolved in 10% HCl, and then split across 4 test tubes. To one I added
sulfite to obtain the blue VO2+ and to the next two, Zn powder (with some heating) to get V3+ and V2+
Chromium(II) in solution and as crystallized solid
I made a very concentrated chrome alum solution in 10% HCl, which I reduced with Zn powder. As the solution went to a beautiful blue color, I secured
the top of the test tube with mineral oil, to cut off contact with the air. I then put this in the refrigerator overnight. The next day I was pleased
to find that some of the Cr(II) had crystallized out of solution as a blue salt. I used chrome alum and used Zn powder as a reducing agent, so it's
likely that this salt was contaminated with other ions. I'd like to revisit this experiment, using CrCl3 and Cr powder or shavings to
hopefully produce pure CrCl2 hydrate crystals. The black stuff is the leftover Zn powder.
Manganese oxidation states(II-VII)
I consider these one of my best photos yet. I wanted to create a side-by-side comparison of all the oxidation states of manganese which can be created
in a home lab without exotic chemicals or specialized equipment.
The starting materials were KMnO4 and MnSO4. For Mn(VI) I heated dilute KMnO4 in 5 M KOH. Mn(IV) was created as
MnO2 by reducing permanganate with sucrose. Mn(III) was obtained by oxidizing Mn2+ with BrO3- in
H2SO4. Mn(V) was a challenge. I initially tried obtaining the hypomanganate by trying the first two methods described in the
potassium hypomanganate wikipedia page. I used ~10 M KOH in both attempts, but these didn't work for me. I then discovered Bedlasky's thread about
obtaining hypomanganate with thiosulfate. This proved successful, so thank you very much Bedlasky for saving this experiment and allowing me to snap
these neat photos:
Belousov-Zhabotinsky experiments
I did the BZ experiment in two variants - one with the classic blue/red oscillation (ferroin), the other with the often described but almost never
seen green/blue/red oscillations (ferroin + cerium).
These photos were done in poor lighting so perhaps they're not the greatest. I'd love to do it again in a bigger petri dish with better lighting and
make a timelapse video of the ferroin + cerium variant, because seemingly nowhere can you find a video of these oscillating tricolored waves. Also, if
any of you know recipies for adding even more or different colors to the BZ reaction, I'd love to hear about them.
That would be all I have for now, but perhaps I'll collect some more photos to share. Cheers!
[Edited on 28-9-2020 by EthidiumBromide]
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Metacelsus
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Very pretty! I especially like the B-Z reaction.
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woelen
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Welcome! Very good to see you here on sciencemadness. Your contributions will be appreciated!
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Bedlasky
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Welcome on Sciencemadness!
You can make CrCl2 just with Cr metal and HCl.
Cr + 2HCl --> CrCl2 + H2
But if you use CrCl3 + Cr, it is probably cheaper way. CrCl3 can be made from chrome alum, which is quite cheap, so you need less Cr metal.
Quote: Originally posted by EthidiumBromide  |
Mn(V) was a challenge. I initially tried obtaining the hypomanganate by trying the first two methods described in the potassium hypomanganate
wikipedia page. I used ~10 M KOH in both attempts, but these didn't work for me. I then discovered Bedlasky's thread about obtaining hypomanganate
with thiosulfate. This proved successful, so thank you very much Bedlasky for saving this experiment and allowing me to snap these neat photos:
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You are welcome  . You have really nice clean solution! I sometimes had cloudy
solution because of Na2CO3 contamination or because of NaOH started to crystallize out after cooling.
Btw. your Mn3+ solution is quite interesting! I never heard, that bromate can oxidize Mn(II) to Mn(III), before! I few times prepare some Mn(III)
complexes, which are stable in aqueous solution - complexes with EDTA, phosphate and pyrophosphate, all are red. Woelen also recently mention reaction
between KMnO4/MnO2 and HCl (and also MnCl2 and chlorate/ClO2) - in this reaction green chloride complexes of Mn(III) and Mn(IV) are formed.
https://www.sciencemadness.org/whisper/viewthread.php?tid=15...
Purple aqua and sulfato complexes can be made by oxidizing MnSO4 with KMnO4 in conc. sulfuric acid (use just small quantities, KMnO4 form in conc.
H2SO4 unstable Mn2O7). Something similar should work in conc. H3PO4 (I don't try it yet, but I read about it).
https://www.sciencemadness.org/whisper/viewthread.php?tid=15...
Mn(III) can be also make by oxidizing Mn(II) acetate by KMnO4 in glacial acetic acid.
I read about preparation of K3[Mn(C2O4)3], but it is quite unstable (unlike his Fe analogue).
| Quote: Originally posted by EthidiumBromide |
I did the BZ experiment in two variants - one with the classic blue/red oscillation (ferroin), the other with the often described but almost never
seen green/blue/red oscillations (ferroin + cerium). |
Cool! 
Have you ever tried Briggs-Rauscher reaction?
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EthidiumBromide
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| Quote: Originally posted by Bedlasky |
Btw. your Mn3+ solution is quite interesting! I never heard, that bromate can oxidize Mn(II) to Mn(III), before! I few times prepare some Mn(III)
complexes, which are stable in aqueous solution - complexes with EDTA, phosphate and pyrophosphate, all are red.
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If the BZ reaction is done with Mn2+ catalyst, you get oscillation between Mn(II) and Mn(III). So by this logic, if I take out the bromide
and malonic acid for reduction, I should just get simple oxidation of Mn2+ to Mn3+. I prepared a solution of KBrO3 in
20% H2SO4 (the same I used to prepare the Mn3+ earlier), to which I added dropwise a solution of MnSO4. As
you can see, in low concentration Mn3+ has a salmon color, but as it gets more concentrated, it shifts to a red-amaranth (it doesn't show
well on the pictures, but it has a slightly more purple tint in person).
Mn3+ isn't very stable in this form, it needs very acidic enviroment. If the acid solution isn't concentrated enough, Mn(III) quickly
disproportionates to Mn(IV) and Mn(II). A similar result occurs if you dilute the concentrated Mn3+ with pure water, no acid added, as I
did here - I took a few drops of the concentrated Mn(III) and added some distilled water.
Though even in concentrated acid, the color of solution shifts to a more brownish red color after a day of storage at room temp, indicating that it's
not very stable, unless complexed, as you've mentioned.
Yes, I have done it a few times, but I don't have yet a magnetic stirrer, so I had to mix the reaction myself, by swirling the flask. It still worked,
oscillating between colorless, amber and dark blue.
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Bedlasky
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Still, there must be some sort of complexation. [Mn(H2O)6]3+ ions aren't stable in aqueous solution - only in nearly water free environment (like in
conc. sulfuric acid). You need some water for formation of aqua complexes, but too much water leads to quick disproportionation.
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MidLifeChemist
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Ethidium, well done, this is outstanding!
It is really nice to see your results. I actually just finished putting together my home lab and I have all of these reactions / products on my
experiment list. I appreciate you posting this and can't wait to try all of these as I have all of the reagents necessary except for one.
I see Bedlasky's thread on hypomanganate here: https://www.sciencemadness.org/whisper/viewthread.php?tid=14...
Did you simply follow his steps exactly?
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EthidiumBromide
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Yes, the only difference is I used KOH instead of NaOH, but that shouldn't have any effect on the end result. I did filter my hypomanganate solution
after I took it out of the refridgerator though, as some MnO2 had formed that made it opaque and obscured the blue color. Once filtered, it was indeed
a very bright blue, maybe a bit turquoise, but very distinct from the green manganate(VI).
[Edited on 28-9-2020 by EthidiumBromide]
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Bedlasky
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That's strange. This never happend to me. If solution is cool and hydroxide is strong enough, there shouldn't be any disproportionation. I once try to
made manganate in cold 20% NaOH using Na2S2O3 as reductor and I accidentaly got hypomanganate. So concentration of hydroxide can be lower than 40%
(but hypomanganate in 40% is more stable than in 20% NaOH).
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EthidiumBromide
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Perhaps my thiosulfate is not the best quality? It is quite old, so maybe some impurities caused some of the hypomanganate to decompose? I'll be
ordering fresh thiosulfate soon as I'm almost out anyway.
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Bedlasky
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| Quote: Originally posted by EthidiumBromide | | Perhaps my thiosulfate is not the best quality? It is quite old, so maybe some impurities caused some of the hypomanganate to decompose? I'll be
ordering fresh thiosulfate soon as I'm almost out anyway. |
Yes, this maybe cause the problem. Old samples contain some sulfate and polythionates, this shouldn't be a problem, but some other impurities can.
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B(a)P
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Welcome to the forum and thanks for sharing. You have done some great work!
It is a great reminder that you really don't need a lot of equipment to do some really interesting things.
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TriiodideFrog
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Thts ann interesting B-Z reaction. I have only seen the blue/red oscillation but never the green/red/blue ones.
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