Violuric acid salts (fantastic colors and variety)

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







My favorites are these: Ethylene diamine, Mn and hexamine (bottom to top)

as well as the copper one.


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

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.

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.

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 . 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

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.

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.

Thanks for the post! I will be making some

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

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]

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

Quote: Originally posted by valeg96

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

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"?

Quote: Originally posted by valeg96

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.

Quote: Originally posted by valeg96

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".

Today i produced some more salts.
Sadly had to borrow the calcium one from Diachrynic because my calcium source i attempted it with was impure.
Very nice to see such good variety in the 2 group


I also produced some new amine ones, the color of the benzylamine salt is quite close to the Sr interestingly enough.


I also attempted to produce a urea salt, aswell as previously attempted a biuret salt. Neither of these worked, the violuric just crashes out alone, but in solution they are both a dark purple.

[Edited on 17-12-2020 by RustyShackleford]



[Edited on 17-12-2020 by RustyShackleford]

Quote: Originally posted by valeg96

What about Co, Ni, W, Cd, Hg, Pb? I'd like to try them myself but I don't want barbituric acid in my lab lmao Also, I'm wondering what these compounds look like structurally. They can't be all just simple ionic salts, some are probably coordination compounds. Also, are these compounds perfectly soluble, or do they crash out at some point?

Quote: Originally posted by valeg96

I'd like to try them myself but I don't want barbituric acid in my lab lmao

Quote: Originally posted by Tsjerk

Barbituric acid is very friendly toxicity wise, the toxicity is so benign the LD50 for rats is usually given to be > 5 gr/kg (read: couldn't be determined). It is the derivatives you have to be careful with.

Quote: Originally posted by Tsjerk

] Barbituric acid is very friendly toxicity wise, the toxicity is so benign the LD50 for rats is usually given to be > 5 gr/kg (read: couldn't be determined). It is the derivatives you have to be careful with.

Read: "barbituric acid causes death by indigestion"

Here are some photos of violurate salt crystals.

Barium violurate note the two different forms

Strontium violurate, again note the two forms

Calcium violurate, brick red spherules and bow-ties but sometime orange rhombs form, the yellow blades are UO2++ violurate, the greenish colour cause by Fe2+ contamination of the mineral.

Sodium violurate forming at the edge of an evaporating drop

Its worth noting that it seems rather difficult to grow only one specific form so Rusty's compounds may not be pure hence the colours may vary. I am not sure what the difference is between the spherulitic or coralloid form and the euhedral crystals is. But I do remember from the Hantzsch paper that some form "acid" and normal salts while other sometimes form hydrates. I will try and find the Hantzsch paper that I translated years ago.
[Edited on 17-12-2020 by Boffis]

[Edited on 17-12-2020 by Boffis]

Quote: Originally posted by woelen

[...]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

Quote: Originally posted by woelen

I do not know any other anion, which gives such striking different colors when e.g. Na(+) is exchanged with K(+).

Quote: Originally posted by clearly_not_atara

Amazing work, had no idea this anion even existed, or that it was so colorful. Quote: Originally posted by woelen   I do not know any other anion, which gives such striking different colors when e.g. Na(+) is exchanged with K(+). indeed, it seems Li+ would be a particularly interesting continuation

Quote: Originally posted by Justin Blaise

Really cool that these are nicely colored and easily isolated. Do you have any Ce, Nd, or Bi salts to try to make some complexes?

Quote: Originally posted by Lion850

Advice needed please. My source did not have barbituric acid but he did have diethyl barbituric acid. So I got some to try. I dissolved 5g diethyl barbituric acid in 100g hot water (with difficulty), and 3.5g sodium nitrite in 12g water. I added the sodium nitrite solution to the diethyl barbituric acid solution......and nothing. No purple color change; the solution stayed clear. I left it stirring. I have zero knowledge of organic chemistry so help will be appreciated. The obvious question being can diethyl barbituric acid be a starting point to arrive at sodium violurate?

I probably can't help you, but are you talking about 1,3-diethylbarbituric acid or 5,5-diethylbarbituric acid ?

If it's the latter, I dun think the oxime will form at the 5th position cos the acidic alpha hydrogen is gone? My very limited knowledge ....

If it's the former, maybe 1,3-diethylvioluric acid will form? Just guessing.

Quote: Originally posted by Lion850

Hi Artemov it only says Standard Diaethylbarbitursaure / Diethyl-barbituric acid and a formula (C2H5)2CCONHCONHCO. A Swiss product made by Fluka AG Buchs SG.

Quote: Originally posted by Lion850

Artemov thanks for the feedback. It will be returned to the source, no use to me then.

Erm ... you might want to wait for verification from more knowledgeable members, cos I might be wrong

Much requested cobalt violurate turned out to be quite bad, just brown.
6-methyl-quinoline turned out quite nice, light pink-red and acetone solution of it is a deep orange.

Quote: Originally posted by Bedlasky

I think that cobalt salt is Co(III) violurate. 6-methyl-quinoline violurate look really nice.

Quote: Originally posted by Bedlasky

Brown colour isn't typicall for Co(II) salts. If some cobalt salt is brown, it have usually some higer oxidation state. Some cobalt complexes (especially wtih N donor ligands) have tendency to get oxidized by aaerial oxygen quite easily. For example [Co(NH3)6]2+ is slowly oxidized by oxygen to [Co(NH3)6]3+. Or Co(OH)2 is slowly converted by oxygen in to CoO(OH). [Co(CN)6)]4- is oxidized even by water to [Co(CN)6]3-. [Edited on 24-12-2020 by Bedlasky]

Quote: Originally posted by Bedlasky

Brown colour isn't typicall for Co(II) salts. If some cobalt salt is brown, it have usually some higer oxidation state. Some cobalt complexes (especially wtih N donor ligands) have tendency to get oxidized by aaerial oxygen quite easily. For example [Co(NH3)6]2+ is slowly oxidized by oxygen to [Co(NH3)6]3+. Or Co(OH)2 is slowly converted by oxygen in to CoO(OH). [Co(CN)6)]4- is oxidized even by water to [Co(CN)6]3-. [Edited on 24-12-2020 by Bedlasky]

Did some aminoguanidine violurate using the violuric acid RustyShackleford sent me.

I reacted
136mg (1mmol) aminoguanidine bicarbonate
and
175mg (1mmol) Violuric acid
in some warm dH2O and it precipitated out.

Quote: Originally posted by TheMrbunGee

Hey, Do You have alloxan procedure, You mentioned? Colors look amazing, could try alloxan route, since I have sample with no use.

I would try the improved procedure by Guinchard from 1899:

Quote: Originally posted by Diachrynic

Quote: Originally posted by TheMrbunGee   Hey, Do You have alloxan procedure, You mentioned? Colors look amazing, could try alloxan route, since I have sample with no use. I would try the improved procedure by Guinchard from 1899: Quote: Violuric acid (or rather, pseudovioluric acid) For the preparation of violuric acid I recommend the following, more convenient and higher yielding modification of the impractical method by Ceresole; 20 g alloxane (1 mol weight) and 10 g hydroxylamine hydrochloride (1.5 mol weight) [translators note: this is not a 1:1.5 molar ratio, it is more a 1:1.1 molar ratio] are dissolved in 150 g of water and heated for 1 hour on the water bath, after cooling one obtains 12.5 g of pure violuric acid directly in glittering, almost colorless crystals and another 2 g from carefully evaporating the mother liquor. [Edited on 5-1-2021 by Diachrynic]

Today i have produced some more salts of violuric acid thanks to SM user Tsjerk.
The ceasium salt, like the potassium, forms a blue hydrate, a slight bit darker than the potassium. On dehydration it turns to a nice teal, while the potassium turns purple.
The nickel salt is quite crummy, its a dirty light green, significantly worse than copper which in comparison was a wonderful moss green

This is the Rb salt. It slowly hydrates on air and turns blue like the K salt.

Here it is.

Ethanolaminium Violurate

here it is compared to the aminoguanidinium one:



[Edited on 7-2-2021 by h0lx]

Quote: Originally posted by Housane

What amazing colours, I want to try and make sum but I can't find any sodium nitrite over here as it is a restricted chemical, could it be substuted for any easier to obtain chemicals here in the UK?

Quote: Originally posted by vano

Where did you buy this acid? Its salt's have very nice colours.

Quote: Originally posted by vano

I gladly tried the following metals. Scandium, cadmium, mercury 1 and 2, Gallium, indium, copper 1, samarium, silver, beryllium and others. Probably all is possible. Is it possible to send a parcel from your country to my country?

Quote: Originally posted by Housane

Ok thanks, where did you find your nitrite? As it is a explosives precursor here

Quote: Originally posted by RustyShackleford

if you want another route you can go from diethylmalonate via sodium metal and hydroxylamine.

Quote: Originally posted by Housane

What amazing colours, I want to try and make sum but I can't find any sodium nitrite over here as it is a restricted chemical, could it be substuted for any easier to obtain chemicals here in the UK?

Quote: Originally posted by Amos

I don't believe I've seen anyone post an aniline salt yet, that would be neat. Piperidine too if anyone has it. Thanks a bunch for bringing this to everyone's attention, Mr. Gribble

I received some violuric acid from RustyShackleford yesterday in order to test what colours its rare earth salts have - thanks!. It's already after midnight now, but I could not resists the temptation to do one test.

Violuric acid is sparingly soluble in cold water, but much better in hot water. I noticed a somewhat sweetish smell coming off the warm solution (~60C).

0.291g of violuric acid was dissolved in ~15ml warm water, giving a clear purple solution (the dry salt is off white). This was added to a solution of 0.229g EuCl3.6H2O in a few ml water, yielding an orange solution!



The solution is evaporating in a desiccator over NaOH. I'm charging up my UV lamp batteries to see whether the solution still fluoresces. EuCl3 solution (as well as the solid compound) fluoresces with a reddish colour.

Remade the aniline violurate with distilled clean amine, its a very dark red.
Anthranilic acid violurate is a light orange.
Im planning to make some substituted anilines and try with those (N- acetyl, N-benzyl, N-benzylglycine)



Side note: i have noticed that the color of the salts seem to "develop" over time. Like for example the Ni salt i made is now a more consistent and nicer shade of green than it was when i initially made it. No good idea of what the cause is.



[Edited on 7-3-2021 by RustyShackleford]

Adding violuric acid to solutions of rare earth chlorides proved not a good idea. I had hoped to evaporate the HCl in solution over NaOH in a desiccator and obtain the rare earth violurates, but this did not happen. Instead, the Eu-violurate shown in my 7 March post lost its colour and a creme coloured solid was obtained.

So I continued to combine carbonates and hydroxides with violuric acid instead of chlorides. Sm2(CO3)3 gave a deep red solution which on drying gave red-brown granular crystals. I assumed the carbonate to be a 2.5 hydrate as posted here (bottom of page 8), but seeing I have some Sm-carbonate coloured residue, my carbonate may just have been dry.

Pr(OH)3 also gave a deep red solution. Pr(OH)3 was added in excess and intensely stirred for 15 minutes on a 70C hotplate. The solution was then filtered using a fine fritte. It's is now drying in a desiccator over NaOH.

Li2CO3 gave a strongly permanganate coloured solution, which on drying gives an intense almost fluorescent pink solid.



Edit: fixed link

[Edited on 12-3-2021 by Bezaleel]

Updates

Samarium
I redissolved the Sm violurate and filtered off the undissolved carbonate, obtaining a warm clear solution. As it cooled down, a beige film formed on the flask. The solution was poured off and dried in a desiccator over NaOH, forming a deep red solid.



Praseodymium
A new sample was made using Pr(OH)3. The hydroxide was stirred powerfully with demiwater, filtered again and then used. 0.300g of violuric acid was added to an excess of Pr(OH)3 and the undissolved hydroxide filtered off. When left to crystallise over NaOH, an orange-yellow film formed on the walls of the beaker and after everything had dried up completely, a mix of dark red and yellow-orange crystals had formed. As far as possible, the dark crystals were separated and the rest was redissolved - the yellow crystals did not dissolve on heating, but the red ones did. The solution is now crystallising again.



A comparison between the Sm and Pr salts is in the last picture. It looks like the colour of the compounds is mainly caused by interactions inside the violuric acid ligand and not so much by the metal-ligand interactions. In particular the weak green of the Pr forbidden transitions seems to be retained, and causes a minor difference in colour of the salt as compared to Sm.



Indium
0.096g of indium were dissolved in 10% HCl. This took a long time, although the acid was heated to near boiling. The indium was precipitated with ammonia solution and the supernatant liquid pipetted off 3 times. 300mg of violuric acid were added. The solution turned purple immediately, which suggests that not all of the ammonium had been removed, although the pH of the solution with the In(OH)3 was 8.
On heating hardly any of the precipitate dissolved. The beaker was covered with cling film and put on a stirrer at 1200 rpm and heated at 70C plate temperature and stirred for 1 hour. Still much In(OH)3 remained undissolved, but the mix had obtained a colour resembling molybdenum blue.



It seems that indium is chemically too basic to easily form a salt with violuric acid. My estimate is that this will count all the more for Re, Mo and W. I decided that I will not make the uranyl salt, because of the precautions necessary to safely work with it. I consider cerium, which is interesting because it is a coloured RE and also has a stable +IV oxidation state, and aluminium.

Quote: Originally posted by DraconicAcid

So violuric acid is made from barbituic acid....I wonder if something similar could be made from Meldrum's acid (which seems easier to make than barbituic). https://en.wikipedia.org/wiki/Meldrum%27s_acid

Hi. RustyShackleford gave me violuric acid and will make some violurates. Today i made scandium violurate, i used scandium carbonate. Nice yellow- brown colour.

Quote: Originally posted by vano

Hi. RustyShackleford gave me violuric acid and will make some violurates. Today i made scandium violurate, i used scandium carbonate. Nice yellow- brown colour.

Thanks. This is indium violurate. Brown- dark red colour. I used indium carbonate. Carbonates are better.




[Edited on 27-3-2021 by vano]