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Author: Subject: The Short Questions Thread (4)
elementcollector1
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[*] posted on 15-2-2014 at 13:56


I know about the passivation from concentrated nitric acid, but what about dilute? Copper metal seems to follow much the same rules, and it reacts vigorously when in *dilute* nitric acid.



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papaya
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[*] posted on 15-2-2014 at 14:06


I'm afraid even dilute acid won't work.
https://en.wikipedia.org/wiki/Al%28NO3%293
I can't figure out any clean route myself. Maybe if Al(OH)3 is obtained first, it could be dissolved in HNO3? But hydroxide is a gel as far as I know and will entrap all kind of ions (if for example obtained by AlCl3 + NaOH route) inside.
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Etaoin Shrdlu
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[*] posted on 15-2-2014 at 14:42
Question


methyl anthranilate + undecanal --> Schiff base

Is there any simple chemical method to check for the presence of leftover reactants? Short of a GC analysis I'm stumped. (Yes, I know they'll be there.)
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Brain&Force
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[*] posted on 15-2-2014 at 16:09


papaya, dissolve it in HCl first, then add an excess of nitric acid to the aluminum chloride. The acidic solution of nitrate and chloride will convert to nitrosyl chloride, and eventually there will be no more chloride in solution, just nitrate. Do it in a fume hood for safety.
Or why not make aluminum carbonate?




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alexleyenda
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[*] posted on 15-2-2014 at 17:07


A little bit out of subject, but I have to tell it, it is too funny: The first time I read your message ( I am very tired tonight and english is not my first language so I make connections slowly, and I didn't read the previous posts before ), I thought you told someone to dissolve a papaya in HCl and add HNO3 to the produced aluminium chloride etc... and I was really strongly thinking what the hell, meditating in front of my screen, trying to understand XD I had never seen that someone is called papaya before. I laughed a lot when my brain decided to go back to work :p
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papaya
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[*] posted on 16-2-2014 at 00:13


Quote: Originally posted by Brain&Force  
papaya, dissolve it in HCl first, then add an excess of nitric acid to the aluminum chloride. The acidic solution of nitrate and chloride will convert to nitrosyl chloride, and eventually there will be no more chloride in solution, just nitrate. Do it in a fume hood for safety.
Or why not make aluminum carbonate?


AlCl3 + nitric acid looks interesting, if you are absolutely sure that it will work. Do I need anhydrous AlCl3 and conc. HNO3 or aqueous solutions will do? Is it that easy to get rid of all chloride or it'll be still impure? Some details (or references) please.
Also I thought Al carbonate cannot be made from water solutions since it'll tend to hydrolyze , wiki is not clear about that
https://en.wikipedia.org/wiki/Aluminium_carbonate
but if it works (Na2CO3 + Al salt) then I would like to go this way.
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Brain&Force
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[*] posted on 16-2-2014 at 01:06


https://www.youtube.com/watch?v=u4Ha1SJrazY
Just keep the solution acidic.




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[*] posted on 18-2-2014 at 11:03


Does sodium/potassium metabisulfite degrade over time (say, 2-3 years), releasing SO2 and leaving behind the sulfite? I have a bank of K2S2O5 that has gotten quite lumpy and hard to dissolve in water.
Also, S2O5 + H2O -> 2HSO3 in solutions. Does any other anion, other than the bisulfite, exist in aqueous solution? I'll be buying new metabisulfite, but I wonder if it's also worthwhile to get what is sold as bisulfite (how can it be a dry powder?).

[Edited on 18-2-2014 by Nickdul]
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bismuthate
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[*] posted on 18-2-2014 at 15:10


I tried the briggs-rauscher oscillating iodine reaction but I replaced the H2SO4 with a stoichiemetric amount of NaHSO4. The mixture did nothing why is this?



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Zyklon-A
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[*] posted on 19-2-2014 at 06:54
Question


Does chlorine attack rubber stoppers?
For my element collection I have decided to store some chlorine now. I'm putting it in a big test tube, so the color will be visible, but will it disintegrate the stopper over time?




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confused
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[*] posted on 19-2-2014 at 07:27


yes, it'll cause the rubber to become brittle and eventually disintegrate the stopper, you might want to ampoule it, i recommend practicing a few times before storing the sample
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Zyklon-A
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[*] posted on 19-2-2014 at 08:20


Well I can't ampule it, but I have a roll of Teflon tape, So I'll rap the stopper with a few layers of that.



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[*] posted on 19-2-2014 at 08:35


Honestly for something like chlorine the only way I would say you can safely store and be completely comfortable is ampouling. You can make an ampoule using a glass pipette. I know NurdRage has a video on it but I can't link to it right now.



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Zyklon-A
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[*] posted on 19-2-2014 at 08:44


I know I've seen the video, I need all my glass pipets right now, getting an ampule isn't the problem either, sealing it is, my torch recently broke.:mad:
I think the Teflon will work, I have stored chlorine before for about 3 months in a vial, as mentioned here.




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[*] posted on 19-2-2014 at 12:11


at Nickdul


dissoc_2.jpg - 89kB
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[*] posted on 19-2-2014 at 13:20


Quote: Originally posted by bismuthate  
I tried the briggs-rauscher oscillating iodine reaction but I replaced the H2SO4 with a stoichiemetric amount of NaHSO4. The mixture did nothing why is this?


This reaction includes many equilibrium reactions that must all take place for the reaction to succeed. Quote from wikipedia "IO3− + 2H2O2 + CH2(COOH)2 + H+ → ICH(COOH)2 + 2O2 + 3H2O"

NaHSO4 being a neutral salt, it does not provide the H3O+ ions needed for the step cited above.


[Edited on 19-2-2014 by alexleyenda]
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DraconicAcid
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[*] posted on 19-2-2014 at 13:55


Quote: Originally posted by alexleyenda  
Quote: Originally posted by bismuthate  
I tried the briggs-rauscher oscillating iodine reaction but I replaced the H2SO4 with a stoichiemetric amount of NaHSO4. The mixture did nothing why is this?


This reaction includes many equilibrium reactions that must all take place for the reaction to succeed. Quote from wikipedia "IO3− + 2H2O2 + CH2(COOH)2 + H+ → ICH(COOH)2 + 2O2 + 3H2O"

NaHSO4 being a neutral salt, it does not provide the H3O+ ions needed for the step cited above.

Incorrect. NaHSO4 is hardly a neutral salt, being more acidic (Ka = 1 x 10-2) than phosphoric acid (K1 = 7 x 10-3). However, because it's not a strong acid, the solution will not be as acidic as a solution of sulphuric acid, which means that reactions that have hydronium ion in their rate law will go at a much different rate, thus mucking up the expected oscillation.




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[*] posted on 19-2-2014 at 16:00


My bad, it is sodium sulfate that is a neutral salt, I confused both. At least I had part of the answer :) By the way I salute your knowledge Draconic, you always have the righ precise and well explained answer to everything ;)
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[*] posted on 20-2-2014 at 21:24


Not really an information-seeking question, more an opinion-seeking one.
I have a 1 troy oz. bar of .999 silver. I want to cut off a bit and put it in an ampoule. However, doing so would make me unable to sell the bar as anything other than bulk silver (which I guess is not so bad, but collector's value can be a powerful thing). Should I use this bar as my source for silver, or should I obtain it from another source and use that?

Bar is Pan American, and was bought about 5-6 years ago.




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[*] posted on 21-2-2014 at 06:19


My opinion would be to keep it as an investment. If it is for an element collection, 1g bars are going for a decent price and (again, my opinion) are very cute :D The same goes for 1g gold bars.
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Zyklon-A
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[*] posted on 21-2-2014 at 07:24


Keep it, I regret selling all of my silver.



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Zyklon-A
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[*] posted on 26-2-2014 at 20:20
Filter nitric acid


I made some dilute nitric acid according to this reaction:
Ba(NO3) + H2SO4 → 2HNO3 + BaSO4 ↓.
(26.1 g Ba(NO3) + 9.9 g H2SO4 + 7.0 g H2O → 23.3 g BaSO4 ↓ + 12.6g HNO3 + 7 g H2O.)
12.6g HNO3 + 7 g H2O = 19.6 g 66.3% HNO3 = .2 mol HNO3.
So my question is, How can I filter off the barium sulfate?
I have disposable coffee filters, a synthetic filter, and a filter made out of copper mesh.
Obviously, the copper will react, but would a disposable coffee filter work? Or will it react, I know con. sulfuric acid reacts with paper. There is slight excess sulfuric acid, because I wanted to make sure that all the nitrate would react, and form insoluble sulfate. Nitric acid + sulfuric acid + cellulose → potential nitrocellulose? Would that happen with 66% nitric acid and ~2% sulfuric acid?


[Edited on 27-2-2014 by Zyklonb]




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S.C. Wack
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[*] posted on 26-2-2014 at 20:29


Sand. Glass wool.



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DraconicAcid
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[*] posted on 26-2-2014 at 20:37


Or let it settle, and remove it with a pipette.




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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Zyklon-A
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[*] posted on 27-2-2014 at 06:40


Ok, thanks. I don't have any glass wool, non do I have pure sand. I'll use a pipette.



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