moviez
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Ni + HNO3 = something red?
Hi folks, I’m trying to make a small amount of Nickel nitrate and I reacted a few grams of nickel strips with 35% HNO3 solution (azeotrope HNO3 :
H2O =1:1). To my surprise it ended up with a brick red solution (see picture).
The nickel is battery-grade (>99% per manufacturer but I’m not sure now). They attract to magnets well. Nitric acid is from JSP (I’ve used some
from the same bottle before, and there was no issue).
I’ve tried a few things but they don’t make sense so far. I’ve boiled the solution to drive off dissolved NO2, and diluted the solution with
more water, but the solution remains red.
I still have a few things to try:
(1) add a small amount of H2O2
(2) perform qualitative identification tests such as Prussian blue test for iron and see what other potential metals are there
(3) repeat this experiment again with even more diluted nitric acid
I’m wondering if anyone had seen this before? Even if my starting materials aren’t as pure as they advertised, it shouldn’t be this bad. Any
inputs are highly appreciated.
[Edited on 13-11-2025 by moviez]
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moviez
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Here is a video of this reaction
Attachment: ScreenRecording_11-12-2025 20-15-19_1.mov (5.4MB)
This file has been downloaded 33 times
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Radiums Lab
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I think this Fe+3 impurities. As you know your solution should end up in an emerald green colour.
Water is dangerous if you don't know how to handle it, elemental fluorine (F₂) on the other hand is pretty tame if you know what you are doing.
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Radiums Lab
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This has a less chance but you might have Co nitrate too which is magenta in colour.
Water is dangerous if you don't know how to handle it, elemental fluorine (F₂) on the other hand is pretty tame if you know what you are doing.
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moviez
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My first thought was iron impurities as well. I’ll do some confirmatory tests and update here.
The chance of cobalt impurity is low since cobalt is much more expensive than nickel, and they usually don’t come in the same ores. But I’ll check
cobalt as well.
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Deathunter88
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A lot of pure nickel battery tabs from eBay/China are actually just nickel plated steel. I'm guessing 99% of their users wouldn't tell the difference.
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woelen
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Your solution looks remarkably much like a solution you get when you dissolve pure iron in HNO3, which I did a few years ago. Most likely
Deathunter88's post gives the best explanation.
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moviez
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Quote: Originally posted by Deathunter88  | | A lot of pure nickel battery tabs from eBay/China are actually just nickel plated steel. I'm guessing 99% of their users wouldn't tell the difference.
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You’re probably correct. I thought they were pure nickel since they were attracted to magnets, but apparently iron with a thin nickel coating does
the same.
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moviez
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| Quote: Originally posted by woelen | | Your solution looks remarkably much like a solution you get when you dissolve pure iron in HNO3, which I did a few years ago. Most likely
Deathunter88's post gives the best explanation. |
Thank you for the input. When the nitric acid was added, it indeed turned green momentarily (which is probably from the nickel coating) and then
turned blood-red color right after.
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moviez
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Update:
Thank you all for the input. These are, indeed, just iron strips coated with a thin layer of nickel. See below for the thiocyanate test and Prussian
blue test.
After the metal strips were dissolved in nitric acid, the mixture was diluted to ~300 ppm (by weight, so 0.0003 grams of metal ions per mL) before
performing these tests. I didn’t do a quantitative analysis, but just based on the results, we can say the metal is mostly just iron.
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