Botched a Simple Synth :(

I have tried to make a purple-colored copper complex as described in the following video:
https://www.youtube.com/watch?v=aYprYEYesbs
The synthesis is supposed to be straightforward: Dissolve some pool tablets in water in one beaker, dissolve copper sulfate in another, mix the two together, wait, then filter. I have checked to make sure that the pool tablets used are sodium dichloroisocyanurate, so this isn't a problem of accidentally using the wrong reagents.
There were two attempts to make this: The first was by using stoichiometric amounts as indicated by the equation CuSO₄ + 4 Na(C₃N₃O₃Cl₂) → Na₂[Cu(C₃N₃O₃Cl₂)4] + Na₂SO₄
(Taken from the Wikipedia article: https://en.wikipedia.org/wiki/Sodium_dichloroisocyanurate)
The second attempt used equal masses of reagents. Both attempts failed. In both cases, I mixed the solutions together and then waited until a precipitate formed. Things started going downhill from there. Yes, the solution changed color, but it was not to the purple color shown in the video. Instead, the color changed to a dark blue-green.There was aggressive bubbling and granules of purple precipitate occasionally floated to the surface. I waited until the bubbling stopped and the precipitate settled down. Then I filtered the liquid through a cheesecloth that had been folded several times (I didn't have normal filters at the time).
The total volume of solutions for both attempts was 100ml.

However, instead of getting the nice, purple powder that I was hoping for, I instead got an insoluble paste (Well, probably just a wet powder; I am writing this only minutes after my second attempt) in which streaks of purple could be seen upon very close inspection.



What could I have possibly done wrong and how could I avoid botching this simple reaction in the future?
Moreover, what could the oddly-colored, insoluble residue be?

[Edited on 9-3-2019 by Volitox Ignis]

[Edited on 9-3-2019 by Volitox Ignis]

I suspect that if you add the copper sulphate solution to the complexing agent solution in small increments,
(rather than adding complexing agent to copper sulphate solution)
then the complexing agent will intitally be in massive excess and you can judge progress by colour changes - I guess.

EDIT: I just tried TCCA (I have no NaDCC) with 1M copper sulphate solution and saw no immediate 'reaction'
so I tried lowering the pH with 1M H₂SO₄ - to no effect.

I tried 1M ammonia solution instead ( just to check my stock CuSO₄ solution) and got the expected deep blue complex.
I guessed that TCCA might work as its structure is so similar - to my naieve/untrained eye - but obviously I am wrong

[Edited on 9-3-2019 by Sulaiman]

Quote: Originally posted by Sulaiman

I suspect that if you add the copper sulphate solution to the complexing agent solution in small increments, (rather than adding complexing agent to copper sulphate solution) then the complexing agent will intitally be in massive excess and you can judge progress by colour changes - I guess. EDIT: I just tried TCCA (I have no NaDCC) with 1M copper sulphate solution and saw no immediate 'reaction' so I tried lowering the pH with 1M H2SO4 - to no effect. I tried 1M ammonia solution instead ( just to check my stock CuSO4 solution) and got the expected deep blue complex. I guessed that TCCA might work as its structure is so similar - to my naieve/untrained eye - but obviously I am wrong [Edited on 9-3-2019 by Sulaiman]

Quote: Originally posted by Sulaiman

I suspect that if you add the copper sulphate solution to the complexing agent solution in small increments, (rather than adding complexing agent to copper sulphate solution) then the complexing agent will intitally be in massive excess and you can judge progress by colour changes - I guess. EDIT: I just tried TCCA (I have no NaDCC) with 1M copper sulphate solution and saw no immediate 'reaction' so I tried lowering the pH with 1M H2SO4 - to no effect. I tried 1M ammonia solution instead ( just to check my stock CuSO4 solution) and got the expected deep blue complex. I guessed that TCCA might work as its structure is so similar - to my naieve/untrained eye - but obviously I am wrong [Edited on 9-3-2019 by Sulaiman]

Quote: Originally posted by Σldritch

I have never seen pool tablets made of NaDCC. They only seem to be made of TCCA or BCDMH which dissolve much slower than NaDCC or Ca(OCl)2 which are sold as granules (likely for just that reason). What you got looks like Calcium Sulfate with some copper in it, what colour is your filtrate? CuSO4 + Ca(OCl)2 ---> Cu(OCl)2 + CaSO4 Cu(OCl)2 ---> CuCl2 + O2 Which should be green. That is the best explanation i can come up with.

My particular tablets have "Dichloroisocianurato de sodio", which is just Spanish for NaDCC, listed as the main ingredient. MSDS also says that sodium carbonate and sodium chloride are used as filler. The liquid that passed through the cloth smells like pool chlorine and its color is like a lighter version of this:



By the way: Yeah, I forgot to account for the fact that the tablets are mostly filler , I'll keep that in mind and try this synth again tomorrow when I buy some decent filters. I'm still curious what the sludge is, though.

[Edited on 10-3-2019 by Volitox Ignis]

I tried this experiment today and the result was beautifull:



I used 100% Sodium dichloroisocianurate dihydrate as can be seen in the label:



Maybe ading just a little bit of acid to the mix will improve your results as I did see the formation of some copper hydroxide.

Quote: Originally posted by Σldritch

Volitox Ignis: If it contains Sodium Carbonate your precipitate is Copper Carbonate.

In that case, it looks like I'll need to separate the NaDCC from the Carbonate. I'm considering separating them by density. My first thought was to use acetone, dump the crushed up tablets in, and keep whatever floats to the top. However, I checked and found that I don't have any acetone and I don't feel like going to the store just to buy a bottle of it, but I do have three liquids to choose from. Here is some data on them from the MSDS
Paint Thinner:



Density is 1.0165 g/ml
Motor Oil:


Density 0.86 g/ml


Considering that the ingredients listed are either insoluble in water or are barely soluble, is it safe to assume that the paint thinner doesn't have any water (Or at least a negligible amount) in it that could dissolve my NaDCC?
More importantly, will NaDCC react with any of the ingredients listed?

Now, the third liquid is denatured alcohol which is between 30-60% ethanol and 30-60% methanol, but I am wary of using it since it probably has water in it as well.

[Edited on 10-3-2019 by Volitox Ignis]

Quote: Originally posted by Σldritch

j_sum1: Actually it does work without. My TCCA contains boric acid and Copper Sulfate, after i had use it for chlorine generation it became purple. However it is probably not exactly the same complex but one with more hydrogen and less chlorine. Volitox Ignis: If it contains Sodium Carbonate your precipitate is Copper Carbonate. Felab: be careful with the acid, do not use hydrochloric or you will get chlorine gas. I would use dilute sulfuric with much care.

Quote: Originally posted by Volitox Ignis

More importantly, will NaDCC react with any of the ingredients listed?

Quote: Originally posted by Σldritch

Quote: Originally posted by Volitox Ignis   More importantly, will NaDCC react with any of the ingredients listed? It may very well with paraffin and it definitively will with alcohols and acetone. Acetone and chlorine forms dangerous lachrymators and some alcohols may very well do it too. If you only want to make the copper complex i suggest you do as Felab said and add some acid which will only react with the Sodium Carbonate making it unable to interfere with the reaction. I think the easiest one to use is Sodium Bisulfate which is sold as pH lowering agent for pools.

Quote: Originally posted by Volitox Ignis

Thanks for the heads up. However, wouldn't sodium bisulfate react with sodium chloride in the filler and produce HCl, which will in turn react with the NaDCC? I remember seeing some video on Youtube where the author made HCl by mixing bisulfate and table salt. If that's the case, components would still need to be separated somehow. [Edited on 13-3-2019 by Volitox Ignis]

Quote: Originally posted by Felab

Quote: Originally posted by Volitox Ignis   Thanks for the heads up. However, wouldn't sodium bisulfate react with sodium chloride in the filler and produce HCl, which will in turn react with the NaDCC? I remember seeing some video on Youtube where the author made HCl by mixing bisulfate and table salt. If that's the case, components would still need to be separated somehow. [Edited on 13-3-2019 by Volitox Ignis] Just do a small scale titration to see how much sodium carbonate is in your NaDCC. Ad a dilluted solution of NaHSO4 in a well kown concentration and in mesaured ammounts (use a graduated pipet) to a solution with a known percentage of NaDCC. Ad the Bisulphate slowly with stirring while mesuring out the pH of NaDCC solution. When the pH starts becoming acidic stop adding the NaHSO4 and mesaure how much you have added. With some math you can calculate how much sodium carbonate is in a given portion of NaDCC, and ad the bisulphate accordingly in a larger batch without risk of releasing chlorine. [Edited on 13-3-2019 by Felab]

Unfortunately, the exact amount of NaDCC can't be known. I just read the MSDS, and this is what it says:

Are you sure about titrating it? Wouldn't the bisulfate mostly react with the NaCl, which will then produce HCl, which will then either react with the carbonate or the NaDCC?


[Edited on 15-3-2019 by Volitox Ignis]

Quote: Originally posted by Volitox Ignis

Quote: Originally posted by Felab   Quote: Originally posted by Volitox Ignis   Thanks for the heads up. However, wouldn't sodium bisulfate react with sodium chloride in the filler and produce HCl, which will in turn react with the NaDCC? I remember seeing some video on Youtube where the author made HCl by mixing bisulfate and table salt. If that's the case, components would still need to be separated somehow. [Edited on 13-3-2019 by Volitox Ignis] Just do a small scale titration to see how much sodium carbonate is in your NaDCC. Ad a dilluted solution of NaHSO4 in a well kown concentration and in mesaured ammounts (use a graduated pipet) to a solution with a known percentage of NaDCC. Ad the Bisulphate slowly with stirring while mesuring out the pH of NaDCC solution. When the pH starts becoming acidic stop adding the NaHSO4 and mesaure how much you have added. With some math you can calculate how much sodium carbonate is in a given portion of NaDCC, and ad the bisulphate accordingly in a larger batch without risk of releasing chlorine. [Edited on 13-3-2019 by Felab] Unfortunately, the exact amount of NaDCC can't be known. I just read the MSDS, and this is what it says: Are you sure about titrating it? Wouldn't the bisulfate mostly react with the NaCl, which will then produce HCl, which will then either react with the carbonate or the NaDCC? [Edited on 15-3-2019 by Volitox Ignis]

Soooo I finally got around to attempting the experiment, and the results were much better!
First, I crushed up the tablets and added the powder to a mason jar. I then added vinegar, which caused bubbling when the liquid touched the powder. I kept adding vinegar until the bubbling stopped, and then added some more. I then added a solution of copper (II) sulfate and waited. The purple precipitate formed and there were no impurities. All I need to do now is filter off the liquid.

(A sample of the precipitate before filtration).
Thanks for the help.

[Edited on 28-3-2019 by Volitox Ignis]