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Dr.Bob
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Registered: 26-1-2011
Location: USA - NC
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I use a base bath frequently for glassware, it does not hurt it or bother the joints. The amount of glass removed is atoms thick, not measurable.
Only a very long time (days to months) there will ever remove enough glass to matter. HF on the other hand will etch glass in a few hours, and it
does not ever look the same again. I have a few flasks that HF was a byproduct in, and they all look bad when wet, and worse when dry. They look
sand blasted or such.
Scotch bright pads are good for cleaning the joints if they get dirty. The rubber septa will sometimes leave a film of goo on them, especially after
exposure to acid.
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Sir_Gawain
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Can anyone with some geology experience verify if this is actually cinnabar? https://www.etsy.com/listing/1705692311/australian-rough-cin...
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Rainwater
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Distill a sample at 600c. Not efficient but its worked for 10⁴ years
"You can't do that" - challenge accepted
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yobbo II
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How can the Alpha and the Beta CaSO4:0.5H20 have different solubilities (in the long term)?
Perhaps the study did not wait for days/weeks for all to dissolve, ie. the Beta is slower???
Yob
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4-Stroke
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Sulfur Chlorides Using HCl instead of Chlorine
I know this might be a dumb question, but I was wondering if HCl gas (which is easier and cheaper to prepare than chlorine) could be used instead of
chlorine in the synthesis of sulfur chlorides? Thanks.
Ukrainium
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j_sum1
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Just a quick one.
My daughter has extracted some pigment from brown onion skins to use for an art project.
I am curious. What class of compounds would be giving the colour?
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bnull
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Anthocyanins (https://pmc.ncbi.nlm.nih.gov/articles/PMC9363841/). By the way, the pigment can also be extracted from dried skins that are discarded by the
grocers.
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j_sum1
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| Quote: | | Anthocyanins are the flavonoid compounds responsible for the purple/red color of onion and are highly concentrated in the skin |
She used brown onions, so I don't think it is anthocyanins. Also, the pigment does not respond to changes in pH.
I had thought it was probably a tannin of some kind. But then I wondered about the possibility of sulfur compounds.
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bnull
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Well, that's odd.
I took a few bits of brown onion skin and tried to extract the pigment with boiling ethanol and with boiling water. Alcoholic
solution: almost colorless, no reaction with oxalic acid, yellow precipitate on addition of saturated NaOH solution that dissolved on
addition of HCl (10%). It looked like iron oxalate but paler. Aqueous solution: this one is funny. Persistent yellowish color at pH
neutral to low, orange color at high pH. Addition of hydrogen peroxide (3%) to acidic and basic solutions made no change. The funny bit is that, while
I was neutralizing the base in one of the tubes, it went from orange to wine red (burgundy or darker) and then yellow.
I still think the pigment is related to the anthocyanins, most probably a degradation (oxidation) product. If I find my red onion extract, I'll see if
reacts in a similar way.
Acidic (left) and basic (right) aqueous solutions of brown onion pigment.
By the way, what solvent did you use?
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j_sum1
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My daughter used water.
She separated inner skins from outer ones and so got two different shades. My suspicion is that the two are just different concentratikns but
essentially the same. One batch dhe boiled down until a solid started to appear.
This was a kitchen activity and I did not do any rigorous testing. Just used vinegar and sodium bicarb to test for pH colour changes.
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bnull
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| Quote: | | My suspicion is that the two are just different concentratikns but essentially the same. |
Nope. It is two different substances related to quercetin. I knew it had something to do with leuco dyes and stuff after the peroxide reaction.
Y. Ito etc al., Cepaic acid, a novel yellow xanthylium pigment from the dried outer scales of the yellow onion Allium cepa, (https://doi.org/10.1016/j.tetlet.2009.04.093).
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yobbo II
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What it the most reactive metal that you can cathodically protect by using it as a cathode is a water solution of (say) salt?
Cheers,
Yob
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j_sum1
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Gadolinium chemistry - unexpected transient yellow compound
I was just starting a project preparing some Gd salts. Initial step was to dissolve some metallic Gd in 20% HCl.
The reaction should produce a clear solution corresponding to a near colourless salt. However, I notices a distinct yellow appearance when the
reaction started, and persisting in a kind of halo around the Gd pieces. Some kind of intermediate I presume.
Anyone know what the yellow is? Maybe some unstable Gd2+ ions?
Just curious.
J.
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Sulaiman
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recently released gadolinium video you may like
https://youtu.be/YIxjFKBl5eg?si=bqoQy0tJmsGEKPig
CAUTION : Hobby Chemist, not Professional or even Amateur
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j_sum1
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Thanks Sulaiman. I did see that.
Coming back after a couple of hours out of the house, and the last fragments are still dissolving in the acid. When I left, the mixture was milky
looking with very fine bubbles. Now it is yellow. And cloudy rather than clear.
But online pictures show GdCl3 as off-white.
Anyway, I am kind of enjoying the subtle pastel shades of the lanthanides. I just bottled up some praseodymium carbonate.
I will see how it all goes.
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Fery
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How much pure is your Gd? Content of small amount of Fe in it?
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j_sum1
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Gd was sourced from onyxmet, sold as an element. It sholld be pretty good.
I have a chloride solution and a nitrate solution: both are a pale yellow. This is exactly what I expected until I started looking at online pictures
that showed both salts as nearly pure white.
The observation I thought was interesting was the strong yellow around the metal pieces whlle reacting with HCl - even though the solution was
colourless at that stage.
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