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Chemistry Forums for Students => Inorganic Chemistry Forum => Topic started by: shiffdaddy on January 09, 2017, 11:36:43 PM

Title: Vanadium/HNO3
Post by: shiffdaddy on January 09, 2017, 11:36:43 PM

I'm really into safely making/experimenting with my excess metals from my periodic table of the elements collection. I decided I had enough Vanadium so I wanted to test against the acids (HCl, H2SO4, HNO3) so I set up 3 tests tubes and the only one that reacted with with nitric acid.

The solution was a blue color, into a darker blue with sludge on the top.  Once the powder was completely dry I thought maybe I have vanadium nitrate. The powder was insoluble in water and made sort of an orange stain wherever it touches

any thoughts?

Ben

Title: Re: Vanadium/HNO3
Post by: cutelab on January 10, 2017, 11:41:35 AM

Hey Ben, what is the source of vanadium here?

Title: Re: Vanadium/HNO3
Post by: Enthalpy on January 12, 2017, 06:18:20 PM

My two cents, just to seed the thread:

• Your observations match Wiki's claims
• If nitric acid corrodes but others don't, then nitric probably acts as an oxidizer there rather than a plain acid
• In such a case, the main product wouldn't be a nitrate
• Its standard electrode potentials don't qualify vanadium as a noble metal. It's said to resist corrosion thanks to its oxide layer. Though, such metals with a good oxide layer tend to withstand nitric acid better than hydrochloric, so the situation is somewhat unexpected.

Wish you get better answers.

Title: Re: Vanadium/HNO3
Post by: Corribus on January 13, 2017, 11:29:24 AM

Vanadium complexes exhibit a variety of colors depending on the oxidation state of the V center. The oxides take on a number of colors, and V₂O₅ is notably orange.

https://en.wikipedia.org/wiki/Vanadium%28V%29_oxide

In solution, hydrated vanadium complexes are also variably colored, and the +2 aqua complex is intensely blue.

Be aware, vanadium complexes and salts are mildly toxic, so I hope you are using gloves and other suitable protection. Which of course you should be doing whenever you play around with chemicals.

Title: Re: Vanadium/HNO3
Post by: shiffdaddy on January 24, 2017, 08:10:47 PM

Thanks for the responses, been busy! Yeah what I was thinking is that I made some sort of vanadium oxide rather than the nitrate.  My vanadium is cheap crap probably, got 100g from a Chinese ebay source and yes i'm quite paranoid about always having gloves and goggles on.  Especially since recently I've been into nickel salts as well which are also quite toxic.

I am wondering if me heat evaporating the nitric acid off has anything to do with its decomposition, maybe if I allowed it to air dry? probably doesn't matter all that much though.

Ben

Title: Re: Vanadium/HNO3
Post by: snorkack on February 19, 2017, 03:13:57 AM

Vanadium(II) is blue, but so is vanadium(IV).
So, the likely candidate might be something like VO(OH)₂, oxidizing to VO₂OH in air.