iloveloli
Harmless
Posts: 21
Registered: 8-8-2015
Member Is Offline
Mood: No Mood
|
|
about copper(ii) azide
i mix potassium azide and Copper(II) sulfate solution together.
it turn green like copper(ii) chloride solution. is that because Cu2+ and N3-complex together??
other there are another reason??
|
|
|
Tdep
National Hazard
Posts: 516
Registered: 31-1-2013
Location: Laser broken since Feb 2020 lol
Member Is Offline
Mood: PhD is done! It isn't good but it's over lol
|
|
Well this is a badly asked question but having tried this experiment, I know what you're asking.
Mixing an excess of copper sulfate and sodium azide results in the red insoluble primary copper azide and sodium sulfate, as well as excess of copper
sulfate. Given this, the solution above the red precipitate should be the typical blue copper sulfate however the filtrate is green.
Never considered it to be a complex, put the colour down to impurities in the sodium azide, given it wasn't exactly technical grade.
It's hard to see in this photo as there's the deep red suspension of Cu azide but you can see the slight copper chloride type green.
[Edited on 8-8-2015 by Tdep]
|
|
|
nezza
Hazard to Others
Posts: 324
Registered: 17-4-2011
Location: UK
Member Is Offline
Mood: phosphorescent
|
|
I have tried this with dilute solutions. I get some brownish precipitate and an intense yellow green solution, even at very dilute concentrations.
If you're not part of the solution, you're part of the precipitate.
|
|
|
Tdep
National Hazard
Posts: 516
Registered: 31-1-2013
Location: Laser broken since Feb 2020 lol
Member Is Offline
Mood: PhD is done! It isn't good but it's over lol
|
|
Did you use technical grade azide Nezza? If so, are there known impurities?
Any small amount of nitrite that made its way into the azide would account for the colour I think, copper(II) nitrite has that deep green (so yellow
green at low conc) colour. Just a theory, seriously doubt it's to do with the azide ion though, given the very low solubility of both copper(I) and
copper(II) azide.
|
|
|
woelen
Super Administrator
Posts: 7977
Registered: 20-8-2005
Location: Netherlands
Member Is Offline
Mood: interested
|
|
I can confirm Tdep's observation. Copper(II) ions and azide ions give a dark red/brown precipitate, which is amazingly explosive. I took some of the
wet slimy material, put this on a spatula and heated in in a flame. It exploded with a loud high-pitched report.
The material is notoriously unstable and may easily explode, even when stored under water. Destroy it by adding sufficient acid (any dilute strong
acid will do). The liquid becomes clear in that case and then it is safe again.
|
|
|
Tdep
National Hazard
Posts: 516
Registered: 31-1-2013
Location: Laser broken since Feb 2020 lol
Member Is Offline
Mood: PhD is done! It isn't good but it's over lol
|
|
Did you observe a green coloration to the solution Woelen?
Also, adding acid will produce hydrogen azide possibly? On milligram scales it wouldn't matter sooo much if you were prepared for it I guess. I'm a
big fan of the nitrite/nitrous acid cleanup for azides
|
|
|
woelen
Super Administrator
Posts: 7977
Registered: 20-8-2005
Location: Netherlands
Member Is Offline
Mood: interested
|
|
I did not have a green solution. Mixing a blue copper sulfate solution with the azide resulted in formation of the dark red/brown precipitate, with a
pale blue solution over it (hence, I had excess copper(II)).
I know of the nitrite cleanup of azides, but for destruction of the red compound I first add acid to get free copper ions again and free (dilute) HN3
and eliminate the risk of explosion.
|
|
|
Tdep
National Hazard
Posts: 516
Registered: 31-1-2013
Location: Laser broken since Feb 2020 lol
Member Is Offline
Mood: PhD is done! It isn't good but it's over lol
|
|
Well with the assumption that Woelen used an azide of a known high purity without green colouration, i'm going to say the answer to OP's question is
nitrite impurities. Not that I think OP will be back or really care, but something something starfish back into the ocean whatever.
|
|
|
woelen
Super Administrator
Posts: 7977
Registered: 20-8-2005
Location: Netherlands
Member Is Offline
Mood: interested
|
|
I used a commercial sample of NaN3 of general lab grade quality. This has good purity.
|
|
|
iloveloli
Harmless
Posts: 21
Registered: 8-8-2015
Member Is Offline
Mood: No Mood
|
|
i just use KN3 that make from the reaction. and i didn't wash it. i think it contain NO-.
|
|
|
Boffis
International Hazard
Posts: 1836
Registered: 1-5-2011
Member Is Offline
Mood: No Mood
|
|
I decided to try an experiement with copper and azide ions to see what happens if azide is in excess and the solution fairly concentrated.
I dissolved 0.1g of sodium azide in 2ml of water and added 6 drops of saturated copper sulphate solution. The initial precipitate quickly dissolved
producing an intense deep brown solution. A couple of drops were placed on a microscope slide and allowed to evaporate slowly. A very intimate mass of
microscopic brown, colourless and yellow crystals formed. The brown compound is very soluble so a couple more drops of the solutions were mixed with a
drop of 5% caesium chloride solution and allowed to evaporate. As expected a rather less soluble caesium copper compound crystallised as stout
plain-chocolate brown prisms after an hour or so.
These reactions are reminiscent of chloride and bromide ions and suggest that copper forms a brown azidocuprate ion. The ratio of copper to azide
cannot be deduced from these experiments but the valency of the copper is probably II since there is no evidence of any reduction products. The
initial precipitate therefore is probably copper II azide.
|
|
|
nezza
Hazard to Others
Posts: 324
Registered: 17-4-2011
Location: UK
Member Is Offline
Mood: phosphorescent
|
|
Sorry about the delay in replying TDep. It was commercial sodium azide of good purity. I will have a look at different ratios of azide/copper and
copper/nitrite.
If you're not part of the solution, you're part of the precipitate.
|
|
|
nezza
Hazard to Others
Posts: 324
Registered: 17-4-2011
Location: UK
Member Is Offline
Mood: phosphorescent
|
|
Right. A few observations. As I get older I'm getting more paranoid about safety and copper II azide is reputed to be treacherous stuff so precautions
:-
1. I used small amounts of dilute (0.1M and 0.05M solutions).
2. The azide and copper II were mixed behind a perspex screen.
3. I had an excess of acidified nitrite available for the destruction of the azides post reaction.
Using ratios of 2:1 (Azide/copper) to 1:2 all gave a brown gelatinous precipitate with a dark brown/green/yellow solution.
That's about as much as I want to do with copper azide.
If you're not part of the solution, you're part of the precipitate.
|
|
|
bismuthate
National Hazard
Posts: 803
Registered: 28-9-2013
Location: the island of stability
Member Is Offline
Mood: self reacting
|
|
I do think that it is quite possible that copper would form a [Cu(N3)4]2- ion under the right conditions though, since the azide ion is a
pseudohalogen and will likely form complexes with copper like halides do.
|
|
|
Boffis
International Hazard
Posts: 1836
Registered: 1-5-2011
Member Is Offline
Mood: No Mood
|
|
Well nezza's results seem to confirm my observations so I decided to make up some standard 0.1M solutions of NaN3 and various salts of copper, cobalt
and nickel. I used the sulphate, acetate and sulphate respectively. I haven't yet retried the copper experiment but I did try cobalt and nickel.
Cobalt acetate:sodium azide 1:4 gave a deeper crimson coloured solution than the original cobalt. I divided it in two and left one half to evaporate
on a microscope slide and mixed the other with a couple of drops of 6% H2O2, this caused the solution to turn golden brown. Again it is evaporating
slowly.
Nickel sulphate:sodium azide 1:2 gave a pale yellowish green not much darker than the original but slightly yellower, I then left it to evaporate.
I'll try the the copper again tomorrow with various ratios and I'll also try adding Cs to the above mixtures if I don't get nice crystals.
@bismuthate, Yes my thinking too but the simple halides such as copper form several chlorocuprate II ions with different ratios of chloride to copper,
in the presence of Caesium the less chloride rich compound forms brown prisms with the other forms deep yellow prisms. I was trying to see if azide
does the same but the experiments were too crude. I try again tomorrow with controlled ratios. There is a thread on the copper chloro complexes.
The fact that the cobalt solution turns brown, indicating Co3+, with H2O2 also suggests that a complex has formed but it is possible that it is the
acetate ions that ore forming the complex and not the azide. Any ideas for an anion that doesn't form complexes with transition metals?
[Edited on 18-8-2015 by Boffis]
|
|
|
Tdep
National Hazard
Posts: 516
Registered: 31-1-2013
Location: Laser broken since Feb 2020 lol
Member Is Offline
Mood: PhD is done! It isn't good but it's over lol
|
|
This is turning interesting. There is a cobalt azide complex salt (of perchlorate) mentioned in the Exotic Primaries thread, was obviously quite the
primary explosive. An anion I'd choose would be the sulfate ion, good solubility with transition metals and can't think of it forming complexes, not
like a chloro would or so,etching.
|
|
|
woelen
Super Administrator
Posts: 7977
Registered: 20-8-2005
Location: Netherlands
Member Is Offline
Mood: interested
|
|
Sulfate indeed is a good choice in this case. Perchlorate also does the job. In aqueous solutions it is one of the most inert anions.
The azide-complexes must be very dangerous to deal with, so use very small amounts. Especially if you allow salts of them to crystallize, be it
sulfate or perchlorate, they must be very sensitive and may explode without apparent reason. Please be careful! The used anion will only have minor
influence on the danger, it is the azide-complex which makes it dangerous!
|
|
|
Boffis
International Hazard
Posts: 1836
Registered: 1-5-2011
Member Is Offline
Mood: No Mood
|
|
Latest update:
On the microscope slide cobalt II gave a lacy dendritic crystalline product that under the microscope appears colourless but with the slide on white
paper is just visibly pink. When water was added the material appears reluctant to re-dissolve so it is probably sparingly soluble. The presence of
caesium does not affect the outcome so on balance it appears that Co2+ forms a sparingly soluble azide rather than a complex. The cobalt sample that
had been treated with H2O2 dried to give a glassy amorphous skin containing colourless crystals. When a fresh drop of water was added the crystals
dissolved but the brown skin did not.
Both compounds were suspended in water and then applied to small spots on filter paper, when dry they were heated in a spirit lamp flame; the Co2+
compound "phuts" all at once but the brown Co3+(?) compound only crackles.
I repeated the Cu2+ experiment using Cu sulphate:Na azide:CsCl in the ration 1:3:1 and 1:6:3. Both mixtures gave the same compound, small agregates of
well formed brown monoclinic prisms but the first gave a quicker precipitate and more abundant crystals suggesting that the extra azide and caesium
chloride solutions simply dilute the reaction mixture and that the compound is fairly insensitive to azide concentration. A 1:1 mixture of copper and
azide gives an amorphous brown ppt and a 1:3 mixture in the absence of caesium gives only a deep brown solution and no crystals.
To me these reaction indicate that copper forms an azidocuprate complex similar to the chlorocuprate complex except that there appears to be only one
stable ration of azide to copper in aqueous solution (there are at least two chlorocuprate II ions).
The fact that a 1:3 ratio gives a homogenous solution suggests that the ion is {Cu(N3)3}-. However, I seem to recall that the chloro complex analogue
is a trinuclear complex.
@Woelen don't worry I do these experiments on a microscope slide under a microscope. Apar from the safety aspect there is also the fact that you can
see the difference in the nature of a precipitate. For instance in this case the amorphous copper azide and the caesium copper azide compound would
look practically identical without a microscope.
|
|
|
Tdep
National Hazard
Posts: 516
Registered: 31-1-2013
Location: Laser broken since Feb 2020 lol
Member Is Offline
Mood: PhD is done! It isn't good but it's over lol
|
|
Any chance of pictures Boffis? Loving your analysis
|
|
|
nezza
Hazard to Others
Posts: 324
Registered: 17-4-2011
Location: UK
Member Is Offline
Mood: phosphorescent
|
|
Here are a couple of pictures of my observations. Very dilute solutions of Copper(II) and Azide mixed with a large excess of one or the other.
If you're not part of the solution, you're part of the precipitate.
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
