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Gooferking Science
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When setting up a vacuum distillation, are there any precautions I should take to avoid damaging my vacuum pump? I'm afraid that vapor from the
distillation will get in the pump and damage it.
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gdflp
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That depends on what type of pump you have as well as what you're planning on distilling. I'm assuming that you're using a rotary pump, in which
case, and solvents or corrosive vapors will need to be trapped. The standard way of doing this is to use a liquid nitrogen trap, but LN is difficult
to come by for most. An alternative, is to use a dry ice/acetone trap, this will still condense most gases. If what you're distilling an aqueous or
other reasonably noncorrosive compound, the vacuum pump can be used without a trap, or with only a water trap, but I would change the pump oil quite
frequently, every 1-3 months depending on usage.
If you have a diaphragm pump, then you don't need to worry. Very few things can attack a diaphragm pump, I have never run into a situation where I
need to use a trap.
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kecskesajt
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What happens if I nitrate ascorbic acid?
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learningChem
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At what temperature does hydrated sodium bisulfate become anhydrous sodium bisulfate?
I heated the hydrate for a while and it boils and turns into a syrup-like liquid. Then at some point it mostly stops boiling and white fumes start to
appear. I'm wondering if at that moment the substance is anhydrous bisulfate, or rather pyrosulfate?
According to wikipedia the mp of anhydrous bisulfate is 315C but it also lists 315C as the decomposition point so I'm not sure if heating to 315C will
dry the bisulfate or decompose it.
[Edited on 19-7-2015 by learningChem]
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Zephyr
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I recently got an old Gast Rotary Vane vacuum pump, model 0522-V3-G180X.
Its not in very good shape, and hums without spinning when switched on.
Does anyone here know much about this pump or have any ideas on how to fix it?
Thanks!
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Texium
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Does anyone know what compound(s) are responsible for the characteristic smell of cork? I've always really liked the smell, which always seems to be
pretty much the same whether it's in the form of a cork stopper, a bulletin board, or the backing of my ruler. I wasn't able to find anything helpful
upon Googling it. Some results about "cork taint" in wine came up, although apparently that is not always caused by cork, and if it is, it is
irregular and unrelated to compounds found commonly in cork.
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Zephyr
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Finally got the pump working!
Huge thanks to Steve_hi for all his help.
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Oscilllator
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I'm no expert, but ascorbic acid is a decent reducing agent (it can reduce Cu(II) to Cu(0)) and Nitric acid is a strong oxidiser. So I don't think you
will actually get an ascorbic acid nitrate, more likely horrible mess.
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chemrox
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Back to your question: I would use an NaOH filter between the glassware and the pump. I don't have a cylinder large enough to make one and I stripped
an intermediate that had some organic acid and anhydride vapors in my vacuum oven. I changed my pump oil afterward. None of my tubing is big enough
and filter flask though thick walled are flat. Not sure about pulling 28 psi on one of these for 12 hours. It sure helped seal the door gasket ;^)
"When you let the dumbasses vote you end up with populism followed by autocracy and getting back is a bitch." Plato (sort of)
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j_sum1
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Is there a simple qualitative test for Al3+ ions in solution?
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kecskesajt
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Add NaOH solution.If Al ions are present,a goo will form.
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j_sum1
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Well, that's a nice idea. But it might not work in practice. I have some element wire that I have dissolved in acid. It appears that it is not
nichrome as I originally thought. I am wondering if it is Kanthal (Cr-Fe-Al). NaOH will also precipitate Fe (which I know is present) as well as the
Cr. Something a bit more selective than NaOH would be preferable.
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gdflp
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You could use the alizarin test as described here if you have alizarin.
Alternatively, you may be able to add a large excess of sodium hydroxide, then centrifuge the solution. Fe(OH)3 and Cr(OH)3 are
insoluble in this solution and will precipitate, but Al(OH)3 dissolves in an excess of sodium hydroxide to give sodium aluminate. After
centrifuging, decant the supernatant and slowly add a dilute solution of hydrochloric acid(or another acid). If a precipitate forms, then this should
be reasonable confirmation of the presence of aluminum, though this precipitate will redissolve if too much acid is added.
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j_sum1
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Thanks for that.
Alizarin looks to be reay useful and versitile as an indicator. This video mentions Cr, Fe, W, and group II as well as Al.
https://m.youtube.com/watch?v=IFlIi_Xk3FE
The Wikipedia article mentions Ca as well as the Mg mentioned in the vid. It looks like it takes some care and a bit of knowledge to use. I'd love to
know more.
I'm inspired by aga's current dissolving and analysis of rocks. This could be a good tool.
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DraconicAcid
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Quote: Originally posted by gdflp  | You could use the alizarin test as described here if you have alizarin.
Alternatively, you may be able to add a large excess of sodium hydroxide, then centrifuge the solution. Fe(OH)3 and Cr(OH)3 are
insoluble in this solution and will precipitate, but Al(OH)3 dissolves in an excess of sodium hydroxide to give sodium aluminate. After
centrifuging, decant the supernatant and slowly add a dilute solution of hydrochloric acid(or another acid). If a precipitate forms, then this should
be reasonable confirmation of the presence of aluminum, though this precipitate will redissolve if too much acid is added. |
Chromium(III) is also amphoteric, and will dissolve in excess sodium hydroxide. If your solution is not colourless, add hydrogen peroxide and heat it
to convert the chromium anion into chromate, then acidify.
[Edited on 25-7-2015 by DraconicAcid]
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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j_sum1
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I bought some oxalic acid from the hardware store. Is it likely to be anhydrous or dihydrate? It might make a difference if I want anything in a
stiochiometric ratio.
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gdflp
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It is most likely the dihydrate. In my experience, most MSDS's specify whether it is the dihydrate or anhydrous, and all I have seen have specified
the dihydrate. Anhydrous oxalic acid is typically unavailable unless you go to a lab supplier.
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Argentum
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I will be working with fuming nitric acid soon and I need some help with choosing my gloves. Nitrile and latex are not an option, but what about vinyl
gloves? I heard that (butyl?) Gloves work fine, but they are pretty difficult to find, and not cheap at all. Any other choice?
Safety first, always!
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Volanschemia
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Question
Does anyone know the solubility of Tin(IV) Nitrate and Tin(II) Nitrate?
"The chemists are a strange class of mortals, impelled by an almost insane impulse to seek their pleasures amid smoke and
vapor, soot and flame, poisons and poverty; yet among all these evils I seem to live so sweetly that may I die if I were to change places with the
Persian king" - Johann Joachim Becher, 1635 to 1682.
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omnilytic
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Hi guys,
I am trying to conduct capillary electrophoresis on salt water, and was wondering if you had any ideas for getting rid of the sodium and chloride?
So far viable options include using an ion exchange resin for chloride and applying complexing agent, such as a crown ether to the sodium.
Cheers.
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Gooferking Science
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I have a math course question. I am trying to decide whether I should take precalculus or trigonometry. I plan on doing calculus 1, 2, and 3 in the
future. Also, the trig class offered is not at my high school. It is at a local junior college and is called "Plane Trigonometry". The precalculus
class at my high school is an entire year. The trig class at the junior college is only two months, but is said to be a very rigorous course. My
question is: Would I be just fine taking trig then calculus, or would I be missing important concepts covered in precalc? Just FYI I took college
algebra this summer, so I have a good knowledge of college level algebra already. I have heard that precalc is considered to be trig + college
algebra, is this true? Sorry if this is a confusing post, but I'm kind of freaking out since school starts next week and my schedule is all messed up
still!
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solo
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.....take pre-calculus, there will be time for trig and plane geometry down the line....solo
It's better to die on your feet, than live on your knees....Emiliano Zapata.
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The Volatile Chemist
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Any opinions as to how easy it is to skip from AP Calc AB to BC? I know my derivatives...
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j_sum1
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Made something pretty by mistake.
Nice pink shade of crystalline solid. Totally unexpected in what I was doing. I was wondering if anyone could cast some light onto what it is.
I was distilling some paint stripper for dichloromethane. The MSDS says that it is methylene choride, toluene and methanol. The label is more specific: 870g/L methylene chloride, 130g/L methanol and
"contains toluene". The actual product evidently contains other things as well -- it is a viscous green gelatinous goop. I assume there is some kind
of dye in there as well.
Anyway, I distilled. Distillate was cloudy but uncoloured. I washed with sodium chloride solution, separated with a sep funnel and dropped it in a
flask containing a small quantity of anhydrous calcium chloride to remove the remaining methanol and water. Distillate came over at just under 40°C
as expected. Just at the last stage of distillation a pink/magenta coloration appeared on the calcium chloride. Like I said, not expected.
Later when I was cleaning up, I added a reasonable quantity of water to wash the flask. It occurred to me that the colour was reminiscent of
phenophthalein in basic solution. On a whim I added some to a test tube and added a drop of HCl. The pink colour disappeared. (The test tube also
filed with a white cloudy vapour.) I also tried adding some NaOH and (unsurprisingly) got a cloudy precipitate of Ca(OH)2. The pink colour remained.
Thinking that this might be worth investigating further I decided to boil my solution dry. The solution at this stage was pretty weak and the colour
was not vivid. On applying heat the colour disappeared completely from the solution. In the final stage of recrystallisation, a little pink
reappeared but not nearly as bright as my original crystals.
Unless I hit upon an enormous fluke I am guessing that I did not make phenolphthalein. But what I did produce has some similar properties. Any idea
what it might be?
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mayko
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Why does acetaldehyde seem to be so hard to come by? It don't know of it being a precursor, and I don't think it's as toxic as the widely-available
formaldehyde
al-khemie is not a terrorist organization
"Chemicals, chemicals... I need chemicals!" - George Hayduke
"Wubbalubba dub-dub!" - Rick Sanchez
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