Xenos
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Oxalic, Benzoic and Nitric acids
I was wondering if there was any way to make Oxalic or Benzoic acid with HCl or H2SO4. I have sodium compounds of both. Dave said that oxalic acid is
difficult. I dont have a CRC handbook, yet, so i cant look up the solubilities. I was just wondering if anyone had a good method. Also, that 'nitric
acid' that i attemped to make a week or two ago has seperated from the white percipitate. I dont have the pH info for nitric acid, and i dont know any
other tests to see if it is really nitric acid. Btw, I only have about 5ml of it. Any help would be great.
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Polverone
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So you have sodium oxalate and sodium benzoate and you would like to obtain the acids? Preparing benzoic acid is easy. Just dissolve the sodium
benzoate in a minimal amount of cold water and drip in hydrochloric acid. Benzoic acid has very low solubility in cold water and should instantly
appear as the acid is added. When no more white solid appears upon the addition of further HCl, you're done. Separate the solid benzoic acid.
Oxalic acid is trickier. It will be attacked by concentrated H2SO4. It doesn't have such a sharply defined difference in solubility compared to its
salts. It does sublime, though. Perhaps heating powdered sodium oxalate with powdered citric acid and collecting the material that sublimes? That's
just a first guess, not a verified procedure.
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Polverone
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Whoops, I forgot to address the nitric acid issue. Try placing a drop of the liquid you think is nitric acid on a piece of copper metal and gently
heating the metal. If it is HNO3, it should attack the copper with the evolution of reddish-brown gas (gas color may not be visible in smaller
quantities). Evaporate a drop of the liquid on a glass surface to see what it leaves behind (how much in the way of dissolved impurities it contains).
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Xenos
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I tried the Benzoic acid, and it worked as described. Im letting it dry overnight. Now, how do i make benzoates? I would guess you mix Benzoic acid
with the salt, lets say KNO3, in water and heat it to get potassium benzoate and HNO3??
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Xenos
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Oh, and about the 'nitric acid'. I tried the copper test and the acid just boiled and turned the copper black. The apperance looks similar to HCl, but
i used H2SO4 and Ba(NO3)2 so that cant be right. It also fummed white when i took the cork off the test tube.
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Polverone
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Hmmm
You converted sodium benzoate to benzoic acid so you could convert it to potassium benzoate? Are you after a particular flame color? Is that why you
needed the potassium salt insteaad?
Benzoic acid isn't strong enough to produce HNO3 when heated with KNO3. You need to react it with potassium carbonate, bicarbonate, or hydroxide to
get potassium benzoate (well, there are other potassium compounds that would work, but they're rarer and/or more dangerous).
It sounds like you should have HNO3, but your description of the copper test sounds a little odd. For one thing, you say that HCl turns your copper
black?! It should make the copper appear very shiny and bright, strip everything off the surface. And you should certainly be able to notice a
difference between the action of HCl and HNO3 on copper unless the acids are very diluted.
One other test might be to neutralize a tiny amount of your suspect acid with some potassium carbonate/bicarbonate/hydroxide and then see if the
resulting salt supports/accelerates combustion.
PGP Key and corresponding e-mail address
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Polverone
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One other thing
You might want to check your assumed nitric acid and see if it still contains any sulfate ions. Mix a drop with a solution of a soluble barium or lead
salt and see if you get a precipitate.
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