Sciencemadness Discussion Board - Metal Identification

Metal Identification

KaliyaK - 26-1-2021 at 17:54

I recently recycled a few mercury vapour lamps and noticed that the suport frames (wires that go from one eletrode to the other outside the arc tube) were not magnetic, silver in colour, some maliable and easy to bend others more tarnished were very britle.

So i made some chemical test and the results were the foloing:

37% HCl (cold) -> no reaction
37% HCl + 3% H2O2 (Cold) -> formation of a black layer on surface easly removed by scrubing
98% H2SO4 (cold and hot) -> no reaction
60% HCLO4 (cold and hot) -> no reaction
Con. aq. NaOH (cold and hot) -> no reaction
70% HNO3 (cold) -> yellow solution at start with gradual turn to orange. Formation of orange scales on the metal surface that would flake off as a powder. With time, solution became green with a orange powder on bottton. The adition of 3% H2O2 made the solution orange with the dissolution of the orange percipitate.
70% HNO3 (hot) -> energetic reaction of the metal leaving a clear orange solution. The adition of sodium hydroxide to the final orange solution resulted in a clear bright yellow solution with no percipitate formation.

Did a flame test on the metal and shlowed as a pale green yellow (photo in attachments)

All the sings indicate (to me) for the metal to be tunsten (flame test and nitric acid atack) but feels to light and doesnt make sense to use expensive tunsten as suport frames... Any ideas? More tests?

Lamp is question are "Osram powerstar hqi-t 2000w/d/i MSDS"

[Edited on 27-1-2021 by KaliyaK]

[Edited on 27-1-2021 by KaliyaK]

ChemTalk - 26-1-2021 at 20:01

Good luck, and let us know what you find out.

This article may, or may not, be of some use: https://products.gecurrent.com/sites/products.currentbyge.co...

woelen - 27-1-2021 at 00:05

The orange color also may be due to the presence of vanadium. Hydrous V2O5 is orange and only sparingly soluble. On addition of H2O2 a red/brown complex is formed, which in dilute form may look orange. In alkaline solution, vanadium produces pale yellow vanadates, and at really high pH, colorless orthovanadates are produced. Maybe there is a mix of metals, vanadium being one of them.

Bedlasky - 27-1-2021 at 04:23

It's deffinitely not a tungsten. Tungsten dissolves quite easily in H2O2, peroxide complex in acidic solution is colourless. Tungstate and polytungstates are colourless and not yellow/orange.

KaliyaK - 27-1-2021 at 09:45

Quote: Originally posted by ChemTalk

Good luck, and let us know what you find out.

This article may, or may not, be of some use: https://products.gecurrent.com/sites/products.currentbyge.co...

it mentions nickel coated steel and i have recycled some lamps where the support frames are indeed magnetic, but this ones are not and that's what catched my interest

KaliyaK - 27-1-2021 at 09:53

Quote: Originally posted by woelen

The orange color also may be due to the presence of vanadium. Hydrous V2O5 is orange and only sparingly soluble. On addition of H2O2 a red/brown complex is formed, which in dilute form may look orange. In alkaline solution, vanadium produces pale yellow vanadates, and at really high pH, colorless orthovanadates are produced. Maybe there is a mix of metals, vanadium being one of them.

Vanadium metal does seem to be a nice guess as it is very resistant to acid atack but i read ir reacts with hot sulfuric and my sampled did not. Also if it is an alloy, the remaining metals either did not dissolve or dont form insoluble hydroxides (iron and many other metals)

For it to be pure vanadium is very weird...

Fantasma4500 - 28-1-2021 at 02:45

i know that silver doesnt react with nitric acid at room temperature, but first when its heated up. why dont you dissolve it in some acid and ppt it as (likely) chloride salt? might give off some color. if its silver you can decompose it using sunlight- or at least whatever portion of it is silver
youre most likely dealing with an alloy of some sort

rockyit98 - 28-1-2021 at 05:56

run a current in it. if white smoke appears ( obviously don't breath it) while yellow hot it's Molybdenum or one of it's alloys. quoting from wiki "Molybdenum can withstand extreme temperatures without significantly expanding or softening, making it useful in environments of intense heat, including military armor, aircraft parts, electrical contacts, industrial motors, andsupports for filaments in light bulbs ".

KaliyaK - 29-1-2021 at 04:04

Quote: Originally posted by rockyit98

run a current in it. if white smoke appears ( obviously don't breath it) while yellow hot it's Molybdenum or one of it's alloys. quoting from wiki "Molybdenum can withstand extreme temperatures without significantly expanding or softening, making it useful in environments of intense heat, including military armor, aircraft parts, electrical contacts, industrial motors, andsupports for filaments in light bulbs ".

Found the answer! Connected a piece of wire though my arc welder and as soon as it became yellow hot a dense white cloud of smoke emerged from the wire! And while researshing the reaction of molibdenum metal with nitric acid (the only acid that atacked my sample) found an old post in this forum looking for an answer to the composition of the stage orange percipitate the same one i got! http://www.sciencemadness.org/talk/viewthread.php?tid=10582

ChemTalk - 29-1-2021 at 14:08

Very cool KaliyaK, we are glad you figured it out. Now the question is, what will you do with your new molybdenum compounds?