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j_sum1
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Discoloration of stannous chloride
I have been cleaning up some old stock solutions in my school lab and have come across some stannous chloride solutions that are quite discoloured. I
am used to SnCl2 being an off-white but this is something different.
The first solution was actually one I prepared myself about a year ago by dissolving some tin pellets in HCl. It has been stored in a PE dropper
bottle for over that time. It is now a bright yellow colour.
The second is in a glass reagent bottle dating back at least ten years. It seems someone inexpertly attempted to dissolve SnCl2 in neutral distilled
water. There is a thick white sludge on the bottom of the bottle. Stirring it up reveals some pale yellow discoloration. There are also some
greenish lumps in the very bottom of the sludge which I assume originate from the bottle not having been properly cleaned.
Anyway, I am curious as to what the yellow colour is. My intention is to purify and recycle if possible. there is quite a bit there.
Actually, advice on purification would be welcome too. I am predicting that it will be a bit of a dog to work with.
[Edited on 1-8-2017 by j_sum1]
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Sulaiman
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Could the yellow precipitate be insoluble lead stannate, Pb2SnO4, due to lead (plus O2 from air) contamination ?
https://en.wikipedia.org/wiki/Lead-tin-yellow
CAUTION : Hobby Chemist, not Professional or even Amateur
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j_sum1
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Lead contamination in the reagents used? Maybe. I'll check the source of the tin metal tomorrow. I have since mixed the two samples together but I
can test for lead -- I think. Ill have to work out a way of detecting trace lead and differentiating it from the tin.
It is likely that the sludge came from the one of the (very old) bottles of SnCl2 we have on the shelf. One is the dihydrate and the other anhydrous.
One might have an assay on it but the other is pre-metric and poorly labelled.
It's nice to have a little puzzle.
I will see if I can test the solution for lead.
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j_sum1
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Update.
All three sources of tin -- the granules I used, the SnCl2 and the SnCl2.2H2O te technical grade. Which means that
lead contamination is reasonably likely.
The 1 year old solution prepared from metal dissolved in HCl was a yellow solution with no precipitate. It was quite strongly coloured. I can't
figure out what this is yet. I am picking that Sn is in the +4 state as a stannate as a result of available oxygen but then it should precipitate if
lead is present. It certainly had sufficient time to settle out and so I am not thinking of fine particulate material.
I combined the two mixtures, partially boiled it down to get rid of water and left it to settle. What remains is a cream-yellow fine powder and a
slightly cloudy yellowish liquor. The liquid is highly acidic. It tests positive for chloride with AgNO3 (hardly surprising) and negative for
sulfates with Ba(NO3)2.
Testing with potassium iodide causes a deeper yellowing but no precipitate. This could easily be lead iodide at low concentrations. I am not seeing
any red/orange precipitate of tin(II) iodide.
Neutralising with NaOH gives interesting results. Cloudiness begins to appear at around pH 4. By the time it becomes alkaline the cloudiness
disappears and is replaced by a grey-green flocculant material. This resembles the greenish lumps that appeared in the sludge.
On filtering it separates into a yellow precipitate (Pb2SnO4? PBO?) and a small amount of grey material that settles last. The filtrate does not
appear to contain any lead when tested with a carbonate solution.
I would be tempted to think the grey material is metallic except that it was the last to settle in the filter paper. It looks pretty dark. It is
also extremely fine. Tin and lead convert from 2+ to elemental at almost the same reduction potential and so if it is metallic it could be both. I
am not picking what would have done the reduction though. Perhaps I am missing something obvious.
Returning to the original liquor, I have carefully adjusted the pH to 6 using NaOH. A white precipitate is slowly settling out. At least I think it
is white. It is a bit hard to tell in the presence of universal indicator. I intend to test the liquid portion with carbonate. If any lead remains
then it should be visible.
I think the conclusion is that Pb is likely in my original reagents and that I have a bit to learn about distinguishing between tin and lead.
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experimenter_
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Ammonium thiocyanate test colors
It is known that a qualitative test for iron ions (Fe+3) is the blood red color they form with a thiocyanate ( link )
Do you know any other metal that forms the same blood red color when reacted with a thiocyanate? (e.g. heavy metals, precious metals?)
I see this blood red color when adding thiocyanate in an Au chloride solution (Au was of .999 purity). Does this mean that the Au is contaminated with
iron?
(the acids used were tested and found to be free of iron)
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Cryolite.
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I recently purchased a Corning PC220 hot plate stirrer off eBay. The stirring functions normally, but when I turn the heating on it makes a loudish
buzzing noise when starting up. This noise subsides as the unit warms up. Is this anything I should worry about? I did remove the ceramic top before
powering it on to clean out some accumulated dust.
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agent_entropy
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Question and Answer
I recently received 5 kg of cobalt (II) sulfate heptahydrate as a gift. Any ideas for interesting things to do with it? I'm not too keen on messing
around with heavy metal salts (cumulative toxicity makes me nervous), but this seems like too large a quantity to ignore if there is anything worth
doing with it.
Edit: Cryolite, I wouldn't worry too much about the buzzing unless parts other the ones that are supposed to are heating up. The oscillating magnetic
field induced by the alternating current can cause slight vibrations in the conductors/resistors that result in audible frequencies.
[Edited on 3-8-2017 by agent_entropy]
[Edited on 3-8-2017 by agent_entropy]
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j_sum1
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Cobalt chemistry is fascinating -- lots of complexes and interesting colours and a couple of oxidation states. But 5kg is a lot to play with. More
than you would need. If it was me I would keep 500g and barter the rest.
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FireLion3
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Does water aspirator flow rate affect max vacuum, or only the rate the vacuum is pulled?
Googled, didn't see anyone else asking this. I understand that the maximum vacuum is related to the vapor pressure of the liquid at the given
temperature, but does the flow rate of the liquid have an effect on the vacuum?
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XeonTheMGPony
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Yes it does, you need the pressure to push the flow to 5gpm for mine any ways it is the brass one sold from deschem.
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Texium
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Threads Merged
6-8-2017 at 07:20 |
bobjgalindo
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Making esters from butyric acid
In the spirit of making odors by combining carboxylic acids (ie propanoic acid) and alcohols (ie ethanol) with a drop of sulfuric acid, is the
following combination safe to mix:
Butyric acid (abt 10 drops)
Octanol (abot 10 drops)
Sulfuric acid
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Texium
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Yes
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Texium
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Threads Merged
9-8-2017 at 10:51 |
Ramium
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Making benzyl alc from polystyrene
I thought I might try producing benzyl alcohol from polystyrene just for fun.
To accomplish this, I was thinking:
Step 1. Depolymerize polystyrene to give styrene, this can be done by distilling the polystyrene. Use immediately in step 2 to prevent
repolymerization
step 2. Reflux styrene with dilute sulfuric acid solution and sulphur (inhibits the polymerization of styrene). The styrene should undergo addition
with water to produce the benzyl alcohol.
step 3 isolate the benzyl alcohol
Sound potentually feasible?
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JJay
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Hydration of styrene would typically result in 1-phenylethanol. You'd have to demethylate it somehow.
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Ramium
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Thank for the respones.
Oh yeah your right, forgot about markovnikov's rule. 1-phenylethanol would be the major product, and phenethyl alcohol the minor.
1-phenylethanol is a secondary alcohol and should be easily oxidized to give the corrosponding ketone, Acetophenone! which is very useful. This is
even cooler then making benzyl alcohol .
Polystyrene could be a very cheap source of acetophenone.
I don't know much about hydration reactions in practice. Is a reflux with water and a bit of sulphuric acid enough to hydrate an alkene?
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myristicinaldehyde
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So I made some isopropyl bromide (9.0g total). My next planned step is to try to see if I can alkylate salicylic acid with it.
I have 2 options for reaction conditions- anh. K2CO3 in butanone (never bothered getting acetone- but I might for this rxn) or I could try lithium
isopropoxide in isopropanol, similar to sodium methoxide in methanol: the pKa's arent wildly different, and I have a lot of IPA. I could also try
magnesium methoxide in methanol, lithium methoxide, or magnesium isopropoxide. I would rather not use methanol, as I am running low but I could always
buy more.
Which is better? The pKa of salicylic acid's phenol is 13.6 so an alkoxide might be the better option. Or am I completely off-base here?
If we don't study the mistakes of the future we're doomed to repeat them for the first time.
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JJay
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Quote: Originally posted by Ramium  | Thank for the respones.
Oh yeah your right, forgot about markovnikov's rule. 1-phenylethanol would be the major product, and phenethyl alcohol the minor.
1-phenylethanol is a secondary alcohol and should be easily oxidized to give the corrosponding ketone, Acetophenone! which is very useful. This is
even cooler then making benzyl alcohol.
Polystyrene could be a very cheap source of acetophenone.
I don't know much about hydration reactions in practice. Is a reflux with water and a bit of sulphuric acid enough to hydrate an alkene?
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I've never hydrated an alkene, but I think typically they use high temperatures and pressures to make the reaction proceed at a reasonable rate. It
may be possible to do it by simply putting dilute sulfuric acid and styrene in a test tube, putting it in an iron pipe, sealing both ends, and heating
the pipe in a metal bath; I don't know. Magpie could do it: http://www.sciencemadness.org/talk/viewthread.php?tid=14652
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Velzee
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Anyone know what the energy of a Cl=O double bond is?
Check out the ScienceMadness Wiki: http://www.sciencemadness.org/smwiki/index.php/Main_Page
"All truth passes through three stages. First, it is ridiculed. Second, it is violently opposed. Third, it is accepted as being self-evident."
—Arthur Schopenhauer
"¡Vivá Cristo Rey!"
—Saint José Sánchez del Río |
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xfusion44
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Is nickel resistant to HCl and H2SO4? I'm trying to find out if what I've ordered really is nickel... There was no reaction between it and
hydrochloric acid (31%) but it was slowly reacting when I added 30% H2O2 (water turned green and there was strong smell of chlorine). With H2SO4 there
was something to see (nickel turned dark gray but H2SO4 color hasn't changed and reaction was very slow).
Thanks!
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Zephyr
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| Quote: Originally posted by xfusion44 | Is nickel resistant to HCl and H2SO4? I'm trying to find out if what I've ordered really is nickel... There was no reaction between it and
hydrochloric acid (31%) but it was slowly reacting when I added 30% H2O2 (water turned green and there was strong smell of chlorine). With H2SO4 there
was something to see (nickel turned dark gray but H2SO4 color hasn't changed and reaction was very slow).
Thanks! |
Yep, that's nickel. If you heat it to boiling in HCl it will react as well. Another way to identify it is using a magnet, it's one of the few
ferromagnetic metals.. (Although I think it's weaker than iron?)
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xfusion44
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| Quote: Originally posted by Zephyr | | Quote: Originally posted by xfusion44 | Is nickel resistant to HCl and H2SO4? I'm trying to find out if what I've ordered really is nickel... There was no reaction between it and
hydrochloric acid (31%) but it was slowly reacting when I added 30% H2O2 (water turned green and there was strong smell of chlorine). With H2SO4 there
was something to see (nickel turned dark gray but H2SO4 color hasn't changed and reaction was very slow).
Thanks! |
Yep, that's nickel. If you heat it to boiling in HCl it will react as well. Another way to identify it is using a magnet, it's one of the few
ferromagnetic metals.. (Although I think it's weaker than iron?) |
Thank you very much! Yes, it is attracted by a magnet. One more question: why the chlorine was produced when it reacted with HCl and H2O2? And at the
same time the green color appeared - nickel chloride? But why chlorine and chloride at the same time? Or was it some other compound?
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Geocachmaster
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Acidic solutions of H2O2 are strong enough to oxidize chloride into chlorine. The green color can be attributed mostly to
dissolved chlorine, although I'll bet there's some nickel chloride in there as well. The HCl and H2O2 react to make chlorine and
HCl reacts with the Ni to make NiCl2 (Edit: although the latter reaction should be pretty slow at room temp)
[Edited on 8/17/2017 by Geocachmaster]
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physics inclination
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Would urea and a strong base react to make ammonia and/or methanol from the urea molecule? I wonder because bases are proton donors, and it seems you
could split the urea molecule into 2 ammonia molecules and 1 methanol molecule if you "add" enough hydrogens.
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Crowfjord
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| Quote: Originally posted by physics inclination | | Would urea and a strong base react to make ammonia and/or methanol from the urea molecule? I wonder because bases are proton donors, and it seems you
could split the urea molecule into 2 ammonia molecules and 1 methanol molecule if you "add" enough hydrogens. |
Bases are proton acceptors. Acids are proton donors. In Bronsted-Lowrey theory at least. Urea hydrolysis would give ammonia and carbonate in base, and
ammonium salt and carbon dioxide in acid.
For methanol to form, electrons as well as protons would need to be added to that carbon. That is, a reduction would need to take place.
[Edited on 18-8-2017 by Crowfjord]
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TheNerdyFarmer
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Question
Hello.
Does anyone know of a good way to test for hydrofluoric acid?
The only method that I have seen is by treating calcium carbonate with it and it produces an insoluble precipitate. But I'm not sure how well this
works. Would be a tremendous help if someone could mention a great way to test for the presence of it so I could further preform a titration to
determine the concentration. Thanks!!
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