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Dr.Bob
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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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