Author Topic: Any tips on speeding up dissolving Ni/Cu alloy  (Read 1228 times)

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  • Guest
Any tips on speeding up dissolving Ni/Cu alloy
« on: June 02, 2003, 06:44:00 AM »
with strong aqueous acid ? I am using HCl with a small amount of H2SO4, about 100ml 37%HCl, 5ml 98% H2SO4, and some H2O - about another 75ml.
I am using this to dissolve pieces of a nickel/copper alloy (somehting like 75% Cu and 25 % Ni) but this is taking a very long time- after several days in the above solution it has dissolved approximately 2% of the pieces. They are about 2mm thick flat strip. Heating seems to speed it up very slightly, but I'm wondering if another inorganic ion might be more aggressive on this- such as nitric acid- it is very oxidising when concentrated. Any ideas ?

I wondered if there might be too little water for good hydrolysis, so I added about another 75ml. This may have had a slight positive effect but it has only been a few hours since this addition.  ::)


  • Guest
« Reply #1 on: June 02, 2003, 01:50:00 PM »
Reflux it in conc. sulfuric acid, or use nitric with hydrochloric acid.


  • Guest
Ah, much better Aziz
« Reply #2 on: June 03, 2003, 09:23:00 PM »
Thanks, it's working nicely.


  • Guest
What´s working nicely?
« Reply #3 on: June 04, 2003, 04:02:00 PM »
What´s working nicely? Would you care to describe the method you used?

 Here´s an interesting report on the subject, with some ideas on how to separate Ni from Cu, taken from

I've actually made efforts at isolating nickel from American nickels (which are made from a 25% Ni, 75% Cu alloy).

The first experiment was placing nickels in 37% HCl solution, as Ni metal reacts with HCl while Cu metal does not. After a week, I merely had a pale greenish solution. The reaction obviously was proceeding ridiculously slow. A few days later, a crack mysteriously developed in the beaker, and the contents leaked out. So that was the end of that experiment. The next experiment involved adding nickels to a solution of 27.5% H2O2 and H2SO4. Bubbles streamed from the coins, and the solution soon turned blue-green. I left it on the lab bench unattended for about an hour. Upon my return, I found blue-green solution strewn everywhere - all over the bench, my notes, the wall, and the floor. I donned my chemical warfare suit (nickel salts are very toxic!) and spent an hour cleaning up the mess. I moved onto dissolving nickels in 70% HNO3. At the initial reaction temperature of -10C, essentially nothing was happening. Upon gentle warming, though, the reaction started, billowing NO2 for several minutes, yielding blue-green crystals and solution. I then realized that aqua regia would be a good way to lower the amount of valuable 70% HNO3 I would have to use, and so gave that a whirl. Six nickels (30g) were added to a solution composed of 13mL 70% HNO3 and 50mL 37% HCl. As with dissolving in straight HNO3, the reaction proceeded exceedingly slowly until it was gently warmed (all of these experiments were being done outside, in -20C weather). The reaction was very exothermic and likely would have begun boiling violently had it not been for the cooling effect of the cold weather. A blue-green foam formed as the temperature rose past 50C. At 90C, the temperature leveled off, the blue-green foamed vanished suddenly, and a solution which appeared almost brownish remained. I boiled down the solution (leaving brownish crystals), added water (became blue-green), and then boiled for at least an hour with 17.1g Cu metal (to convert soluble cupric salts to insoluble cuprous saIts). After filtration, the copper wire weighed 16.5g, meaning that very little cupric salt was converted to cuprous salt. I soon learned that the reason for this trouble was the fact that nitrate ions were in solution, destabilizing cuprous cations. Cuprous nitrate is soluble, so it decomposes quickly in aqueous solution; cuprous chloride is not soluble, so it doesn't decompose in aqueous solution (at an appreciable rate, that is). I then boiled 44mL concentrated H2SO4 with 10 nickels until all of the H2SO4 was gone. Very little of the nickels were dissolved. I proceeded to try dissolving six nickels in a solution prepared by adding 36g NaNO3 to 100mL 37% HCl. The reaction proceeded similarily to the one previously mentioned, except it was considerably less exothermic - meaning it was much easier to control. I added an excess of NaOH solution, precipitating insoluble cupric hydroxide and nickelous hydroxide (small amounts of black nickelic hydroxide, the trivalent cation, were noted). The precipitate was washed with concentrated NaOH, in hope that cupric cations (which are soluble in strong alkaline solution, while nickelous/nickelic cations are not) would be washed out, leaving only the nickelous and nickelic hydroxides. The concentrated NaOH solution used for washing became only a pale blue, so I concluded that NaOH washing was not an effective method of isolating nickel.

And that's as far as I've gotten. Right now, I think the best method would be dissolving the coins in NaNO3/HCl solution, precipitating insoluble hydroxides with addition of NaOH solution; converting to chlorides with HCl, then boiling with Cu metal, precipitating insoluble cuprous chloride; then finally filtering out the insoluble cuprous chloride, leaving a solution of nickel chloride.


  • Guest
That's a solid bit of work. Thanks.
« Reply #4 on: June 05, 2003, 12:36:00 AM »
That's a solid bit of work. Thanks. The info about different salts' salubilities especially- all is useful. Can't quite match it, but....

Allow me to retort  :P

To a 500ml flask, ~60g of Cu/Ni 75%/25% alloy was introduced, which is about 1 mole, and 60g  aq. HCl  370g/L (~33%) was added, followed by an additional 10g 98%sulfuric acid. The reaction was very slow with slight bubble formation over minutes, even with heating. The solution turned slightly green.
The heat was removed, and roughly 40g KNO3 was then added to the vessel, and an additional 50ml H2O. Most of the potassium nitrate dissolved, and gentle heat was re-applied such that the solution was barely refluxing. The solution quickly developed a greenblue colour which darkened over the next 3 hours to a drty coca-cola colour. When the vessel was removed from the heat and allowed to cool, a small amount of dirty white solid crystalline precipitate formed (NiCl2?).
The heat was re-applied for another 3 hours, and then the vessel was allowed to cool and placed in storage for 3 days. Continued refluxing would have accelerated the process further, but was not possible at this time. When it was examined again the solution was a very dark dirty coca-cola, the alloy was mostly dissolved (~75%), and there were beautiful large blue crystals of copper sulfate forming, mostly on the alloy pieces. It may be that a significant amount of the copper has actually separated this way all by itself. They will be collected and weighed to explore this. There is also a dirty-white powdery crystalline  sediment.

During heating additional water was added to replace that lost through evaporation, twice. After cooling additional water had evaporated, leaving around 125ml solution.

Additional heating will follow, after physically extracting the large CuSO4.5H2O crystals.

Looking forward....

It would be interesting to preprare more than one catalyst type from this.

Having read the Urishibara prepration notes, an Al/Ni system- U-Ni-AB seems ideal, for the intended purpose, and the preference for producing primary amines by U-Ni-NH3 is very cool indeed.

Also with interest it is noted, under U-Ni-C preparation (a more highly activated form) :

"To reduce the particle size of the precipitated nickel, it is necessary to retard the velocity of the ion exchange reaction; that is, to retard the speed of deposition of nickel."

It strikes me that there is room for a lot of fleshing out here.
For example, How about this:

# preparing a U-Ni-BA aggregate, but using NH3  as the base;

# preparing a U-Ni-BA aggregate, then further processing it as per U-Ni-C to increase activity;

# preparing a U-Ni-BA aggregate, but using NH3  as the base; then further processing it as per U-Ni-C to increase activity...

and so on.

maybee someone can add to this.

The last one looks particularly cool. It takes a bit of extra preparation but the if end result is freely, economically available and achieves the desired effect, mercury can be replaced with something that's a bit too common to List.
If they ban Nickel, they'll have to ban lignin too.

It is also being considered, using some of the crude copper/nickel solution as-is, and investigating whether the competing precipitation of Cu and Ni also produces a reduced particle size and (depite the presence of the far less-active Cu variant) may very well produce an active product.

One of Ni catalyst letdowns is a less-than-perfect durability i catalytic activity- yet can be regenerated (or even somewhat revitalised with U-Ni).

For Further down the track, to test the catalyst..... 
Some dill apiole is also being extracted from seeds; The expected oil qty will not be large, but should be enough for a couple of runs. ;D  ;D