DeAdFX Posted March 17, 2007 Posted March 17, 2007 Damn it... I feel bad asking such a simple question but . Ok I need some help preparing copper (II) nitrate xH2O in crystaline form. I first started out by dissolving 1/10th of a mol of copper (II) sulfate in 100mL of water. I then added in 1/5th a mol of potassium nitrate. I let the solution sit around for awhile until all the potassium nitrate dissolved. I decanted the solution [i assume the potassium and copper ions did their thing as there was a fine white perciptate] after leting it cool for awhile. I heated the solution again ( what I believe to fairly pure Cu(NO3)2 in water) in the hope of ending up with powdered copper (II) nitrate. What I end up is with this powdered green crap. I have a feeling it is very fine copper metal which is surprising because I don't this stuff should decomose in hot water.... Am I decomposing the copper (II) nitrate or am I doing this right?
Mumbles Posted March 17, 2007 Posted March 17, 2007 If possible I would obtain some Calcium nitrate and go from there. They will form the rather insoluble Calcium Sulfate.
asilentbob Posted March 17, 2007 Posted March 17, 2007 A good portion of CaSO4 will usually pass through coffee filters.
pa_pyro Posted March 18, 2007 Posted March 18, 2007 I don't think it is possible to get a crystals of copper nitrate by heating the solution. Copper nitrate is highly hygroscopic(to the point of being deliquiscent),and if you were to try to heat off the moisture the copper nitrate wold decompose. IIRC you can leave the copper nitrate sol. in a dessicator to dry it out and eventually get crystalline copper nitrate.
Mumbles Posted March 18, 2007 Posted March 18, 2007 Copper nitrate decomposes at reasonably high temperatures. Around 400-500C. It's possible to heat and dehydrate them. I am not sure how anhydrous you could get it, but dry at least. 100-150C should probably do the trick. Decomposition of Copper nitrate is a good way to form fairly pure NO2 I believe it is.
DeAdFX Posted March 18, 2007 Author Posted March 18, 2007 Hmm... While I tried heating the solution at 70-100C to accelerate the drying process. After an hour or so I ended up with a green and blue sludge with a slight NO2 smell. I think a vacuum and a slightly lower temp will be needed to get a less decomposed product. The green product is most likely basic copper nitrate. From the sources I have read copper nitrate should decompose at a slightly higher temp of ~180C or so. I wonder if the residual potassium sulfate is lowering the decompisition point hmm... I will see if I can make a trip down to the local fertilizer store for some Ca(NO3)2... no 50lbs bags please THe basic copper nitrate seems to be less hydroscopic than pa_pyro's description of copper nitrate... Prehaps it might be more useful than just plain ol copper nitrate in pyro.
rocket Posted March 18, 2007 Posted March 18, 2007 Well I thought that I would give this a go as I have a 25kg bag of Ca(NO3)2. I used a 1:1 mol ratio of Ca(NO3)2 and CuSO4, I added them to together in a hot water solution and the CaSO4 formed which was good. I then filtered it till the CaSO4 was white. I then boiled the filtrate down as much as I could (I think it was staring to decompose). Now it’s a blue slug that I’m trying to dry with CaCl2.
Crazy Swede Posted March 20, 2007 Posted March 20, 2007 ...THe basic copper nitrate seems to be less hydroscopic than pa_pyro's description of copper nitrate... Prehaps it might be more useful than just plain ol copper nitrate in pyro.It is correct that basic copper nitrate is non hygroscopic and useful in some applications like gas generators for example. Ordinary Copper (II) nitrate however is way too hygroscopic to be used in pyrotechnics at all!
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