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Author: Subject: Violuric acid salts (fantastic colors and variety)
RustyShackleford
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shocked.gif posted on 16-12-2020 at 12:49
Violuric acid salts (fantastic colors and variety)


Screenshot 2020-12-16 214303.png - 70kB

Violuric acid can be prepared from barbituric acid (via NaNO2) or from alloxan (via hydroxylamine chloride). Barbituric acid can be prepared from condensation of diethyl malonate and urea, but i have not tried this, i simply purchased the barbituric (from S3 chemicals).

To make the violuric acid i followed the preparation on illumina from barbituric acid: https://illumina-chemie.de/viewtopic.php?t=5502

"
Procedure:
Sodium violurate:
6.40 g (50 mmol) of barbituric acid were dissolved in 100 ml of hot water in a beaker. A solution of 3.80 g (55 mmol) of sodium nitrite in 10 ml of water was added to the hot solution, and it immediately turned deep purple. A large amount of sodium violurate precipitated when it cooled down. To complete the reaction and precipitation, 10 g of sodium chloride (because of the addition of equal ions) as well as 1 g of sodium acetate and 3 ml of acetic acid were added to bring the pH to approx. 4-5 (the reaction is de facto complete in the pH range) and stirred for about 1-2 hours at room temperature. The pH was then brought back to the weakly basic range (lowest solubility) with 2.5 g of NaOH and allowed to crystallize in the refrigerator for a few hours.
The product was suction filtered and washed with a little cold water and air dried for a few days.
Yield: 9.85 g of sodium violurate dihydrate (84.5% of theory)


violuric acid, from sodium violurate:
7.8 g (33.5 mmol) of sodium violurate dihydrate were suspended in 20 ml of water and 10 ml of conc. Hydrochloric acid added. The deep violet suspension turned brown-pink in color. It was stirred well for about 1 hour at room temperature, suction filtered and washed thoroughly with dilute HCl, the color becoming a little lighter (cream-colored). The product was air dried for a few days.

Yield: 5.70 g of violuric acid monohydrate (88.2% of theory)
Note: if you touch the damp precipitate with a metal spatula, blue-violet spots will appear at the point of contact after a short time. Obviously, even the smallest traces of metal lead to a salt / complex formation."

I found that i got 86% yield on converting barbituric acid to violuric acid.


Most of the salts themselves were produced by simply heating the acid with the corresponding base in water and evaporating dry, but some (like barium and ethylene diamine) were prepared by adding salts of them to the solution of sodium violurate left behind in the preparation of the acid.

So far i have made: Na, K, Fe, Cu, Ba, ethylene diamine, hexamine, Sn, NH4, Mn, Zn and creatinine.

im planning to make: Sr, Ca, Pb, Al, aniline, benzylamine and quinoline

Let me know if there are particular salts youd want to see, so far it has made great colors with everything i have tried

Screenshot 2020-12-16 211809.png - 1.8MB

Screenshot 2020-12-16 211930.png - 1.4MB

Screenshot 2020-12-16 212001.png - 1.4MB

My favorites are these: Ethylene diamine, Mn and hexamine (bottom to top)
IMG_20201203_233709.jpg - 3.2MB
as well as the copper one.
IMG_20201203_233849.jpg - 2.1MB

The iron one isnt bad either, has a rich dark blue color in solution, but solid is so dark its almost black, not very fun

IMG_20201216_213811.jpg - 2.9MB
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ShotBored
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[*] posted on 16-12-2020 at 13:13


Those colors are awesome, dude. Only iron compound I've ever seen blue like that is Prussian blue. I'd be interested in seeing Pb, Sr, or guanidine salts! Or anything further on this subject really. These colors are astounding.
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RustyShackleford
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[*] posted on 16-12-2020 at 13:20


Quote: Originally posted by ShotBored  
Those colors are awesome, dude. Only iron compound I've ever seen blue like that is Prussian blue. I'd be interested in seeing Pb, Sr, or guanidine salts! Or anything further on this subject really. These colors are astounding.

Pb and Sr are in the works, guanidine i do not currently have, but maybe some day. maybe put a thing in your calendar to check back in a week or two, ill update the post as i produce new salts.
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DraconicAcid
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[*] posted on 16-12-2020 at 13:24


Gorgeous! I'm interested in seeing the nickel complex.



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[*] posted on 16-12-2020 at 13:31


Quote: Originally posted by RustyShackleford  

Pb and Sr are in the works, guanidine i do not currently have, but maybe some day. maybe put a thing in your calendar to check back in a week or two, ill update the post as i produce new salts.


Derp for me, reading comprehension helps since you clearly state which ones you are working on above...oops.

Other compounds I would think would have interesting colors would include Cr and Mn...and As, though I usually stay away from As compounds myself. Hydrazinium might have vibrant colors too.

Finally, I did a lot of work with Nickel coordination chemistry in college. I always thought Nickel compounds had incredibly beautiful hues, mostly greens and deep reds are what I saw.
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RustyShackleford
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[*] posted on 16-12-2020 at 13:43


Quote: Originally posted by ShotBored  

Other compounds I would think would have interesting colors would include Cr and Mn...and As, though I usually stay away from As compounds myself. Hydrazinium might have vibrant colors too.


Mn i already did lol :D. Cr probably not hard, hydrazine might also be possible, but if i could make it from the sulfate that would be best, the freebase is kind of a pain to deal with and make pure.
Ni i would certainly do, just need to get some.
I basically want to make the violurate salt of every cation i have or can reasonably get
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[*] posted on 16-12-2020 at 14:33


Nice! Differences in colours of Na, K and NH4 salts are quite unusual. I would like to see Co2+ salt, cobalt salts in general have very nice colours.



If you are interested in aqueous inorganic chemistry look at https://colourchem.wordpress.com/main-page/

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[*] posted on 16-12-2020 at 14:35


@Rustyshackleford, I did a load of work on these compounds years ago and posted a few microphotographs of the the crystals. Most M+ and M2+ metals form amazing coloured salts. They were the subject of much research back in the early 1900s because of the tendency of the colourless violuric acid to form strongly coloured slat with ions that normally form white salts. There are a few interesting exception Fe2+ forms a deep blue complex and cobalt and orange one. The shape of the crystals under the microscope is also highly characteristic. I used to use these reactions to identify alkali and alkaline earth metals in easily soluble minerals and Mn oxides.

The barium and Strontium salts are quite stunning under the microscope.
http://www.sciencemadness.org/talk/viewthread.php?tid=14644&...

I will have to dig out the other photos from a back-up disc. I even tried to encourage a thread dedicated to this type of microchemical test but to no avail.

I also starting preparing barbituric acid derivatives N-methyl, N,N'-dimethyl, thio- etc. and also related isonitroso-isoxazoles. Interesting to see that someone else is finally interested in these most unusual salts.
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RustyShackleford
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[*] posted on 16-12-2020 at 15:30


Quote: Originally posted by Boffis  
@Rustyshackleford, I did a load of work on these compounds years ago and posted a few microphotographs of the the crystals.


Thats very cool! with the amazing colors this acid produces im suprised its not more widely known about.
Do you have any tips for me in preparing these salts or the derivatives of the acid?
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[*] posted on 16-12-2020 at 15:50


Quote: Originally posted by Bedlasky  
Nice! Differences in colours of Na, K and NH4 salts are quite unusual. I would like to see Co2+ salt, cobalt salts in general have very nice colours.

Different colours for the alkali metals is special indeed!
@RustyShackleford What about Caesium?
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[*] posted on 16-12-2020 at 17:30


Thanks for the post! I will be making some :)
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[*] posted on 16-12-2020 at 21:13


Well, nice!

What about ammonium? Or silver? Cadmium? Mercury 2+?
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[*] posted on 17-12-2020 at 00:56


This is really remarkable. I missed this thread up to now, but what most strikes me is the different colors for different alkali metals and ammonium. I do not know any other anion, which gives such striking different colors when e.g. Na(+) is exchanged with K(+).

It's also interesting to see Ba(2+) vs. Sr(2+) vs. Ca(2+). Usually, salts of these three anions also have more or less the same color.

I do have diethyl malonate. Up to now I did not have any real use for it, I obtained it as part of a package of old chemicals, years ago, and it still is in its unopened bottle. Now I have a use for that :D




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[*] posted on 17-12-2020 at 01:13


How about caesium as the cation? If you don't have any I could send you send you some CsOH for shipping costs. In what part of the world are you located?

[Edited on 17-12-2020 by Tsjerk]
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[*] posted on 17-12-2020 at 01:55


Quote: Originally posted by Tsjerk  
How about caesium as the cation? If you don't have any I could send you send you some CsOH for shipping costs. In what part of the world are you located?
[Edited on 17-12-2020 by Tsjerk]

i sent you a U2U, hopefully we can work something out!
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[*] posted on 17-12-2020 at 02:23


Incredible colors! I'm adding this compound to my todo list

Rubidium would be cool to see as well if you are going for cesium!

Also, if you have an interesting results with Al3+, maybe the rare earth would be interesting to investigate. They usually all react the same way and form pale-colored compounds, so a difference from this would be noteworthy.
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[*] posted on 17-12-2020 at 02:38


The colours you see can vary a lot even with a single cation depending on the hydrate and the ratio of acid to cation, pH, temperature etc. There are a whole series of papers on these salts by Hantzsch and others from 1909-1910. I hhave translated some of them but I can't find them just at the moment. Caesium forms a pure blue salt under warm neutral conditions. I spent a lot of time looking at organic buffers to try and find one that doesn't form a coloured salt with violuric acid. In the end the best was anion exchange resin beads washed with NaOH then acetic acid. Lithium is another interesting one, normally a bright red salt but then occasionally an insane fushia pink! Mn, Zn and some other divalent transition cations also react, but Cu2+, Fe2+ and Co react to produce soluble coloured complexes that are hard to crystallise. Interestingly UO2++ also reacts to form intensely yellow blades. I orginally examined this reagent as a microchemcial reagent for investigating secondary uranium minerals and Mn oxides both easily soluble in dilute acetic acid (the best medium for salt formation)
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[*] posted on 17-12-2020 at 07:18


What about the lanthanides? I'm also curious about unusual metals such as U, Th and the likes.




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[*] posted on 17-12-2020 at 07:41


Quote: Originally posted by valeg96  
What about the lanthanides? I'm also curious about unusual metals such as U, Th and the likes.

I myself do not have any pure lanthanides nor U or Th. I only have the mixture from dissolving lighter flints. If you have lanthanides or U/Th , i could send you some violuric acid, as long as you promise to post pics in this thread :P
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[*] posted on 17-12-2020 at 08:20


I wonder what violurate esters might look like. Also, metal complexes as the cation might be interesting. There's always so many possibilities with interesting ions.



Nuclear physics is neat. It's a shame it's so regulated...

Now that I think about it, that's probably a good thing. Still annoying though.
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[*] posted on 17-12-2020 at 08:51


Out of curiosity, can you post a full procedure for the preparation of the metal salts?




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RustyShackleford
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[*] posted on 17-12-2020 at 08:57


Quote: Originally posted by valeg96  
Out of curiosity, can you post a full procedure for the preparation of the metal salts?

i just measured stoichiometric metal base and violuric acid by mass, heated together in water solution and evaporated dry with heat. wasnt really anything advanced. I was doing 2-3 at a time.
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[*] posted on 17-12-2020 at 11:53


Is that a proven procedure, backed up by literature? Where do the anions go? What do you mean with "metal base"?




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[*] posted on 17-12-2020 at 11:56


Quote: Originally posted by valeg96  
Is that a proven procedure, backed up by literature? Where do the anions go? What do you mean with "metal base"?


A metal base would be a metal carbonate or a hydroxide. Do you need us to explain to you where the anions go when you react an acid with a metal hydroxide or carbonate?




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[*] posted on 17-12-2020 at 12:05


Oh, well, it makes sense then. I'm just not used to call CuCO3 or Cu(OH)2 a "metal base", and I believe I've never heard anyone call transition metal hydroxides or carbonates "bases".

You're called DraconicAcid but you're caustic as hell today, bruh.





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