Thinking I should really get round to starting work on preparing some pure, highly concentrated fuming nitric acid.
I've been needing some copper (II) salts, for producing zero-valent copper nanoparticles, the nitrate itself probably isn't suitable, but from there I can make other cupric salts from the nitrate, going via oxides, hydroxides etc. and treatment with other acids, after roasting the nitrate with a blowtorch to decompose it (and ideally capturing the NOx gases, hopefully to make nitrite salts, and recycle what otherwise would be toxic waste gas)
Its just a bit of a pain, as I otherwise have no copper salts, I used the very last few hundred milligrams of the copper (II) chloride I possessed for a test of the reaction I have been looking into a little while ago, running it on just a 10mmol scale, (of substrate the reaction was being tested on, which works out to a bit over a gram, and using a bit over 200mg of the CuCl2), and copper metal is fairly unreactive, it doesn't dissolve in hydrochloric acid, phosphoric acid that I know of, IIRC it will dissolve if electrolyzed in hot, concentrated sulfuric acid to give copper sulfate, but I tried and it seemed to form some sort of passivating layer on the electrodes very quickly that prevented all current from flowing, my decent power supply is busted, so I had to use a car battery charger, which just wasn't good enough.
None of the other acids I have to hand attack copper, that I know of, sulfamic acid might but I don't know, haven't tested it. But I DO know with absolute certainty that nitric acid attacks copper very aggressively and quickly dissolves it to yield Cu(NO3)2, cupric nitrate. This can be thermally decomposed to give some or other oxide of copper, I'd have to look up exactly which.
This can then be treated with strong hydrochloric acid to afford me the CuCl2 that I badly need at the moment. Tested it in-situ, using concentrated sulfuric acid (98-99% H2SO4) and sodium nitrate, on a small sample of copper metal, as fine copper dust, just to confirm it works. Although it left behind sodium sulfate or bisulfate (haven't checked which yet), which is an unwanted contaminant, that may have unpredictable effects on the formation of the nanoparticles, since nanotechnology can be highly dependent on the reaction conditions, solvents, rates of addition of a material, stirring/agitation, heat, all sorts of factors can alter the end result when working with nanotechnology based processes. So the sodium or sulfate cation and anion respectively, could well have negative effects, especially given the fact that copper (II) sulfate is reported to work for formation of the nanoparticulate copper metal but the yields when cupric sulfate is used instead of cupric chloride for that part of the reaction are lower than when CuCl2 is used.
So, I'm going to again, react concentrated sulfuric acid and sodium nitrate, but this time, rather than my tests where I simply mixed the two, and added copper powder in a 25ml beaker, I'll use a liter or so of 98-99% H2SO4 and an equimolar amount of NaNO3, and distill it to give pure, highly concentrated fuming nitric acid. And that'll give me loads of WFNA to work with, once I subject the product to vacuum to remove dissolved NOx gases if the result is red fuming nitric rather than white fuming nitric acid. Another acid, and a very useful strong oxidizing acid as well as nitrating agent, an ingredient for making aqua regia, for my lab stockroom, so its all ready for use, rather than my having to make up batches as I need HNO3, I can just keep a bottle of strong white fuming nitric on the shelves ready to grab and start dissolving metals, oxidizing things, nitrating stuff etc.
Saves mixing up acid and nitrate salts and distilling every time I want some damn HNO3)
The nitrate (copper (iI) nitrate that is, sodium nitrate is just a white powder) looks really nice too, has a lovely turquoise blue-slightly green hue when it is in it's hydrated form, although IIRC the anhydrous form is white. The hydrates are very pretty to look at, I'll post a picture in a moment of a solution of Cu(NO3)2 from my initial in-situ testing to ensure the HNO3 did indeed attack copper as desired. Was pretty sure but I didn't want to commit lots of resources until I knew for definite.
Soon as I've gone for a cigar, I'll upload the picture. Looks nice.
