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Jor
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Quote: Originally posted by not_important  | In the presence of strong acids and/or heat formic acid decomposes into water and carbon monoxide; even pure +90% formic acid slowly decomposes so
storage containers need pressure relief to prevent explosions. You must use dilute acid, slowly add it to a solution of the formate, always have an
excess of format, and keep it cool. When finished, chill and filter off the hydrated sodium sulfate, the fractionate to get about 70% formic acid.
Supposedly it can also be had by mixing sodium formate and bisulfate and distilling under vacuum, but I've no details on that.
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Aha, so that is why we have PLASTIC Acros bottled with HCOOH at uni. That was the first plastic Acros bottle I have ever seen.
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querjek
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To prepare ~30% HBr in acetic acid, could I saturate some acetic acid with HBr gas generated by dripping H2SO4 onto NaBr?
it's all about chemistry.
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Nicodem
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Thread Split
26-3-2009 at 06:10 |
sakshaug007
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| Quote: Originally posted by querjek | | To prepare ~30% HBr in acetic acid, could I saturate some acetic acid with HBr gas generated by dripping H2SO4 onto NaBr? |
The sulfuric acid/NaBr reaction will work to produce HBr gas but is often not preferred since it is an oxidizing acid and therefore will inevitably
form bromine, sulfur dioxide, and H2O impurities. Its actually best to use non-oxidizing acids such as phosphoric acid or even acetic acid. I'm also
not sure how soluble HBr is in acetic acid I assume a little would dissolve but I don't know about 30%. Lastly, I could be wrong but what might also
happen is the acid could protonate the hydroxyl group and form acetic bromide compounds as by products. I hope this was helpful.
[Edited on 26-3-2009 by sakshaug007]
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sakshaug007
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Hello everyone,
I am interested in synthesizing methyl iodide and was wondering if the following reaction would work:
CH3OH + H2SO4 + KI ---> CH3I + K2SO4 + H2O (heat solution @ ~60°C to distill CH3I)
My HSC calculations show it to be favorable, but again I don't anything about the rate. Has anyone tried this? Or does anyone suspect it to work?
Thanks a lot
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Jor
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Yes, HBr can dissolve to certainly 30% in GAA.
Conc. H2SO4 on KBr will produce lots of bromine. Use phosphoric acid.
No you can't make MeI this way. Even cold, sulfuric acid will oxidises iodides to iodine, itself being reduced to sulfur dioxide, sulfur, hydrogen
sulfide, and possibly other sulfur-compounds.
The prefferred method uses red P/I2. These two react to form PI3, wich reacts with water forming phosphorous acid (H3PO3) and HI, and HI will react
with methanol, forming MeI.
I also recall (not sure) that if highly concentrated (it was more than 85%, i think 95%) is heated with methanol/KI, MeI is formed, but I'm really not
sure, and I can't remember where I read it.
Be careful, MeI is a nasty carcinogen.
[Edited on 26-3-2009 by Jor]
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sakshaug007
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| Quote: Originally posted by Jor |
No you can't make MeI this way. Even cold, sulfuric acid will oxidises iodides to iodine, itself being reduced to sulfur dioxide, sulfur, hydrogen
sulfide, and possibly other sulfur-compounds.
[Edited on 26-3-2009 by Jor] |
Would my reaction work substituting sulfuric acid for other non oxidizing acids? What are some other strong non-oxidizing acid besides H3PO3?
Thanks
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Paddywhacker
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| Quote: Originally posted by sakshaug007 | | Quote: Originally posted by Jor |
No you can't make MeI this way. Even cold, sulfuric acid will oxidises iodides to iodine, itself being reduced to sulfur dioxide, sulfur, hydrogen
sulfide, and possibly other sulfur-compounds.
[Edited on 26-3-2009 by Jor] |
Would my reaction work substituting sulfuric acid for other non oxidizing acids? What are some other strong non-oxidizing acid besides H3PO3?
Thanks |
Yeah, what about toluene sulphonic acid, or even a big handful of acid exchange resin that could be recovered afterwards?
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User
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I was wondering about boiling down hydrogen nitrate.
Years ago my only source for nitric acid was " Ph- " about 30% HNO3.
Well according to Wikipedia the water/nitric azeotrope boils at 121,8 degrees Celsius.
So a quite easy method of determining whether the concentrating has reached it's azeotrope or 68% would be watching the temperature stabilize at 121.8
degrees.
Well my question is how could a determine the concentration by an alternate way.
( has anyone a table of concentration/density versus mass )
[Edited on 27-3-2009 by User]
What a fine day for chemistry this is.
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UnintentionalChaos
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| Quote: Originally posted by User | I was wondering about boiling down hydrogen nitrate.
Years ago my only source for nitric acid was " Ph- " about 30% HNO3.
Well according to Wikipedia the water/nitric azeotrope boils at 121,8 degrees Celsius.
So a quite easy method of determining whether the concentrating has reached it's azeotrope or 68% would be watching the temperature stabilize at 121.8
degrees.
Well my question is how could a determine the concentration by an alternate way.
( has anyone a table of concentration/density versus mass )
[Edited on 27-3-2009 by User] |
titrate. It answers everything 
Department of Redundancy Department - Now with paperwork!
'In organic synthesis, we call decomposition products "crap", however this is not a IUPAC approved nomenclature.' -Nicodem
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User
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Well just in case iam not in the possession of a buret any alternate ideas.
What a fine day for chemistry this is.
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DJF90
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You could do a crude titration using syringes.
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Paddywhacker
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With a cheap 0.01g balance you could do weight/weight titrations. Just weigh everything before and after and use a dropper to do the titration.
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sakshaug007
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Does anyone know where to get chloroform? (I don't want to make it). I want to electrolyze it for poly(hydridocarbyne) synthesis.
Thanks
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DJF90
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Try a chemical supplier. I dont think there are any OTC sources of chloroform, although I have seen DCM (at a ridiculous price, about 8 quid for
250mls! It was some kind of hob cleaner IIRC).
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Aubrey
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I attempted the synth of Cyclopentanol from cyclopentanone using Al Isopropoxide. I kept distilling until the vapor temp was 84.5 degrees and have
about 300ml of clear liquid in my receiving flask (now in a bottle).
The method calls for reacting the prcpt in the flask with H2SO4 until acidic. now the problem is that if they are talking of the reaction flask rather
than the receiving flask, i have a black mess in there from which i cannot even measure the ph because it tuns the litmus black! Should I filter this
fist or distill the lot across? I guess i could dip in my digitla ph meter into this mess but im not too keen on that idea.
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User
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For the record.
I don't know if ur purposely giving this guy incorrect info but DCM is not chloroform.
That would be TCM (trichloromethane) not DCM ( Dichloromethane ).
[Edited on 28-3-2009 by User]
What a fine day for chemistry this is.
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DJF90
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I know the difference between chloroform and DCM. I was merely stating that I have not seen chloroform OTC, but I have seen DCM albeit at a ridiculous
price. In some cases it may be possible to use DCM in place of chloroform.
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kclo4
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| Quote: | | I want to electrolyze it for poly(hydridocarbyne) synthesis. |
wow that stuff sounds really interesting! From wiki: Upon thermolysis in argon at atmospheric pressure and temperatures of 110°C to 1000°C,
decomposition of poly(hydridocarbyne) results in hexagonal diamond (Lonsdaleite).
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panziandi
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I just thought I'd share a nice photo of NaK with you all. Hope you like it. The second photo is a closeup of one of the globules. The NaK was
prepared by melting potassium and sodium under pre-dried paraffin, it was transfered to a vial, extruded into paraffin under argon from a pipette to
remove surface oxide contamination.
 
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sakshaug007
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| Quote: Originally posted by kclo4 | | Quote: | | I want to electrolyze it for poly(hydridocarbyne) synthesis. |
wow that stuff sounds really interesting! From wiki: Upon thermolysis in argon at atmospheric pressure and temperatures of 110°C to 1000°C,
decomposition of poly(hydridocarbyne) results in hexagonal diamond (Lonsdaleite).
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Yep that's what I plan to do, I want to diamond coat carbon electrodes for electrolysis experiments. But I need to figure out a way to dope the
material to make it conductive. Perhaps in situ during electrolysis using some kind of boron compound but I'm not sure which compound to use.
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dann2
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Hello,
Can anyone suggest another indicator, (more easy to get) other than Sodium Diphenylamine Sulphonate as a redox indicator.
Thanks, Dann2
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Paddywhacker
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| Quote: Originally posted by dann2 | Hello,
Can anyone suggest another indicator, (more easy to get) other than Sodium Diphenylamine Sulphonate as a redox indicator.
Thanks, Dann2 |
Fe[III]/thiocyanate, KI/starch
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DJF90
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Nice NaK panziandi! It does look very shiny...
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sakshaug007
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Hello everyone,
I am going to attempt the electrolysis of chloroform in acetone solvent, and I wanted to ask what ionic salts you would suggest for an electrolyte,
(i.e., readily soluble in acetone). I understand that I can just use a small amount of NaCl but if I end up doing a lot of this in the future I would
prefer a salt that can dissolve in higher concentrations in acetone.
Thanks a lot.
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Nicodem
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Lithium perchlorate can and is commonly used as electrolyte in organic solvents. It is soluble in all solvents that are at least slightly basic,
including acetone, and it does not get destroyed by oxidation at the anode like NaCl (which is not soluble in acetone anyway). But where did you saw
acetone can be used as solvent? I would imagine methanol or something like that, but not acetone which reacts at both electrodes.
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