Sciencemadness Discussion Board

Reduced iron powder question

mechem - 29-2-2008 at 15:58

Hi
Some organic synthesis require reduced iron powder. Is there any practical way of making reduced iron powder out of ordinary iron powder other then heating it to 900-C in hydrogen.

Klute - 29-2-2008 at 17:06

Would that be the same as "activated" iron? In that case a simple trituration with aq. HCl does the job well enough IIRC.

LSD25 - 29-2-2008 at 18:34

If you want to reduce the iron itself, you don't apparently need 900C:
Quote:
Orginally posted by Magpie in the Phosphorus topic:

I have no experience with gas-solid reactions. I did see on TV (of all places) a demonstration of the deoxygenation of an iron oxide using hydrogen. The oxide was placed in a boat and the boat was placed in a glass tube. H2 was passed through the tube as the tube was heated using a bunsen burner. Apparently this was successful as demonstrated by the magnetizability of the the iron product. % yield wasn't determined, however.

Did you weigh the residue remaining in the tube? If your stoichiometry is correct this could be a method to determine how much P was released. Can you do any quantitative analyses that would indicate the degree of reaction completion, such as a determination for phosphate?


Unless the glass tube was vycor or something similar, and the burner was something other than a bunsen, it would appear that the reaction you want with hydrogen can be run under much lower temperatures.

chemrox - 29-2-2008 at 18:43

Commercially its done electolytically, hence the name...its pretty cheap too. Another approach wouyld be to get some cast iron, sand off the Fe(O)x and grind it up under N2.

mechem - 1-3-2008 at 08:22

As I do not have any cast iron powder either, any idea how it is made electrolytically. Would it be a simple matter of just putting some iron powder in a beaker of water, making it the cathode and passing current through it, or is that to simple.

I did notice reduced iron powder cost about twice as much as ord. iron powder from lab suppliers.

not_important - 1-3-2008 at 09:13

The electrolytic process is in effect electroplating irom at high current densities. As you raise the current at first you start getting rough, less coherent and less adherent plating, then a granular or even powdery product. The hydrogen being formed at the same time diffuses into the iron, making it somewhat brittle, so the washed product often can be crushed to get a finer powder.

Use massive iron, like scrap pipe, as the anode, a sheet of aluminum or thin iron as the cathode. The anode should be free of grease and the like. Electrolyte would be about 30 to 40 grams of Fe(II) per liter, using ferrous sulfate, and enough ammonium sulfate to give a molar ratio NH3:Fe(II) of about 2:3 (2/3 mole of NH3 per mole of ferrous iron). Bath temperature 35 to 50 C, current is 2 to 3 amps per square decimeter (100 sq cm). A trace of chloride doesn't seem to hurt.

You'll want to have a bag around each electrode to catch pieces that fal or flake off. The anode will release carbon and other gunk dissolved in the metal that you don't want to get in the iron product.

You'll still have to crush the iron formed, in some cases it forms as splintery flakes the crush fairly easily, at other times it's tougher. Experiment a bit to try for the best result. I've done this using ferrous chloride from scrap iron and cheap HCl, and ammonium sulfate from fertiliser; it worked OK 2 times but crapped out once, so I'm not sure that a high concentration of chloride is OK or not.



[Edited on 1-3-2008 by not_important]

stoichiometric_steve - 1-3-2008 at 09:47

there is also iron powder made from Iron pentacarbonyl. i had a very cheap supplier for this stuff but somehow they dont have this product anymore.

mechem - 1-3-2008 at 10:38

Thanks not_important, does the iron form around the cathode and then needs to be scraped off. In order to dry it is it a matter of just warming it up slightly to dry. Is it air sensitive and what yield can I expect from a 1 litre batch.

bio2 - 1-3-2008 at 12:49

There is a procedure for electrolytic Iron in the "Kings Chemistry" book that
worked well when I tried it.

HCl is used as electrolyte and the Fe forms, of course, on the cathode (Fe) as nodular chunks which are removed under water then quickly washed on the buchner with water then acetone and vacuum dried as it is air sensitive.

Very easy to do and I got over half a kilo pure Fe in a 2 liter beaker in a couple days from an iron rod (mild black steel) anode using 5-7 amperes.