Sciencemadness Discussion Board

Whats the impurity?

RU_KLO - 2-12-2023 at 16:08

I bought some Iron powder, which was advertized as "Iron mineral powder" by a someone that wan´t sure what was selling. On asking if it was grinded Iron, she replied that it was not, that it was "mineral" iron. As it was really cheap (200grs for 1/2 usd - Argentinean exchange rate), bought it.
I need fine Iron powder for making FeS. (and was tired from filing a block of iron...)

Its a black magnetic powder. On dissolving in HCl (5M aprox) a yellow solution is obtained. (first test tube)
For testing if Iron, on adding NaOH/KOH a black precipitate is formed. On adding Ammonium oxalate an orange precipitate is formed.
I think its Iron.

But also a non dissolved leftover was found - did not weight it, but its small compared to the Iron powder. (lets say 1 - 2%) Lets call it "unknown".
The unknown was decanted, HCl removed by suction, and more HCl was added. It was boiled for 2 min. Did not dissolved. (I do not have concentrated HCl, only 5-6M (20%) muriatic acid. The solution was almost clear - faint yellow. This was done to remove leftover Iron.

The unknown is not magnetic (tested with a neodymium magnet). It was washed, decanted, and heated to remove leftover water. (small picture on the right) Its a silverish powder.

Then 2cm3 HCl (20%) was added + 2cm3 of HNO3 (60%) and boiled for 2 minutes. Did not dissolved.(the solution became opaque yellow - second test tube.

Acids were removed by suction, washed by decanting 2 or 3 times with water. Water removed by heat.

Then 1 cm3 of concentrated (almost clear) H2SO4 was added. Boiled for 2 minutes. It did not dissolved. Solution became grayish opaque (3rd test tube)

Acid were removed by suction, washed by decanting 2 or 3 times with water. Water removed by heat.

NaOH pellets were added, melted and boiled for 2 minutes. (as this is my first time with boiling NaOH, and know that boiling alkaly eats glass, did not push more time)

the 4th test tube shows the unknown not dissolved in hardened NaOH.

So:
1) Do I really have Iron Powder? (my understanding is yes)
2) Its possible to determine what the unknown should be?
3) What other test could I perform?
4) Maybe do the same experiment but boil it longer?

also:
3) How do you work with concentrated acids solutions to find if anything is dissolved?
a) conc. H2SO4
b) aqua reggia
(diluting 1/10 to work with not so concentrated acids? But also as these quantities are small, maybe I could not detect anything...)

Thanks







UNKNOWN.jpg - 534kB

Rainwater - 2-12-2023 at 16:37

"mineral iron" sounds like magnetite.
if you leave it out in open air, it will turn into red hematite.
if so the remaining insoluble stuff would be quartz.

[Edited on 3-12-2023 by Rainwater]

averageaussie - 3-12-2023 at 14:25

"Iron(III) chloride is a yellow solid. It dissolves in water to make a colloid of iron(III) oxide, making the water look muddy. When it is dissolved in an acidic solution, it is bright yellow."
Simple wikipedia for iron (III) chloride.
checks out considering you dissolved it in HCl.
you could try extracting the chloride, and then dissolving it water, and adding aluminium foil and some salt.
if that doesnt work, you could try different iron III salts, or just a thermite reaction with the original stuff.
I dont know if iron powder is cheaper than aluminium powder though, so buying it might be your best bet.

j_sum1 - 3-12-2023 at 17:31

Oxalic acid will precipitate iron as iron(II) oxalate dihydrate. Roasting tgis will give you finely divided iron powder. So fine it is pyrophoric. I d9n't know if that is helpful for you.
But it is fun.

RU_KLO - 5-12-2023 at 01:30

Quote: Originally posted by j_sum1  
Oxalic acid will precipitate iron as iron(II) oxalate dihydrate. Roasting tgis will give you finely divided iron powder. So fine it is pyrophoric. I d9n't know if that is helpful for you.
But it is fun.


its iron or iron oxide?

RU_KLO - 5-12-2023 at 04:21

Quote: Originally posted by Rainwater  
"mineral iron" sounds like magnetite.
if you leave it out in open air, it will turn into red hematite.
if so the remaining insoluble stuff would be quartz.

[Edited on 3-12-2023 by Rainwater]


I think Rainwater is correct, after seeing pictures of magnetite its the same color (black). so its not iron but iron oxide. Regretfully I cannot use it for FeS making. ( this confirms why when heating with sulfur did not produce FeS).

So Im waiting if I can transfrom it to iron with the oxalate route.

RU_KLO - 5-12-2023 at 04:50

Quote: Originally posted by RU_KLO  

I think Rainwater is correct, after seeing pictures of magnetite its the same color (black). so its not iron but iron oxide. Regretfully I cannot use it for FeS making. ( this confirms why when heating with sulfur did not produce FeS).

So Im waiting if I can transfrom it to iron with the oxalate route.


found the answer in wiki:
"When heated, it dehydrates and decomposes into a mixture of iron oxides and pyrophoric iron metal, with release of carbon dioxide, carbon monoxide, and water.[4]"

I dont know how much iron I can get, but it seems possible to get iron for FeS making, from this.

Is there a procedure to get more Iron than oxides? Im thinking in a closed pipe - to avoid oxigen to get in, and to get a carbon dioxide atmosphere, but dont want it to explode like a granade...


[Edited on 5-12-2023 by RU_KLO]

Rainwater - 5-12-2023 at 21:12

At round 750c pipe in CO
Commonly done with a down draft furnace. Google smelting.

Youtube "primitive technology" shows how to do this.
Turn closed captions on, he doesn't speak but writes
https://youtu.be/Fn9tmm-_yAI?si=MNlL8K4aah-u9J85

Aqueous electroplating works to purify iron from iron chloride.
i know a place that does it to make four nines sheets
But i have never gotten good results.

I have made iron powder from scrap steel very easily, it was pyroforic and set my
table on fire. Required controlled atmosphere, iir i used co2,
https://www.sciencemadness.org/whisper/viewthread.php?tid=15...
Has a detailed procedure using scrap iron.