Mysterious Compound in Water: Researching What It Is

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Discussion Overview

The discussion centers around the identification of a mysterious compound found in water, which is insoluble in water and exhibits various chemical behaviors, including color changes and magnetic properties. Participants explore the nature of this compound, its potential composition, and related chemical reactions.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant describes a compound that is orange as a precipitate, turns yellow in HCl, and exhibits magnetic properties when heated, suggesting it might be rust.
  • Another participant asserts that the compound is iron, citing the yellow color in HCl, the salicylic acid test, and the magnetic properties as conclusive evidence.
  • Some participants propose that the compound consists of a mixture of iron hydroxides and iron oxides, with HCl producing iron chloride and the salicylic acid forming a purple iron(III) complex.
  • There is a question about whether a mixture of Fe2O3 and Fe3O4 could produce a brown compound, with responses confirming that such a mixture could indeed appear brown.
  • One participant emphasizes that rust is rarely pure Fe2O3 and may contain various oxides and impurities, suggesting a complex composition.
  • Another participant discusses the nature of rust as a crystal matrix containing both Fe(II) and Fe(III), indicating that the magnetic properties may be due to Fe3O4 when freshly precipitated.
  • There is a query regarding the magnetic properties of iron hydroxides, with mixed responses indicating some hydroxides may be magnetic under certain conditions.

Areas of Agreement / Disagreement

Participants express differing views on the exact composition of the compound, with some asserting it is primarily iron oxides while others highlight the complexity of rust and the presence of impurities. The discussion remains unresolved regarding the precise nature of the compound and its magnetic properties.

Contextual Notes

Participants note that the composition of rust is not straightforward, as it can include various stoichiometries and hydrated forms, which complicates the identification of the compound in question.

JGM_14
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We have this compound in our water that is insoluble in water, partially soluble in HCl (turns it yellow), it is orange when it comes out of the water as a precipitate but whenyou heat it up it turns slightly magnetic with a color change to black then brown but then degrades (or somthing like that) over time it becomes completely non-magnetic with no visible color change. I don't have the right materials to do a reduction with H2. Doesanyone have a clue what this might be? I was always told it was rust. We have methane dissolved in our water too. I have reaserch and i cannot find what it is. Salicylic acid turns it purpleish blue. it does undergo a thermite reaction when mixed with aluminum.
 
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Its iron. The yellow color in HCl, the salicylic acid test and the ferromagnetic properties are conclusive enough results. The thermite reaction is not specific.
 
I think that you have a mixture of iron hydroxides and iron oxides (rust). HCl would give iron chloride which explains the yellow color. Salicylic acid does form a purple iron(III) complex. When the mixture is heated, the hydroxides decompose to the oxide and thus you are able to initiate a thermite reaction. The magnetic behavior is due to magnetite (Fe3O4).
 
would a mixture of Fe2O3 and Fe3O4 make the compound brown?
 
Fe2O3 is reddish-brown; Fe3O4 is black.
 
JGM_14 said:
would a mixture of Fe2O3 and Fe3O4 make the compound brown?
Yes. Rust is rarely pure Fe2O3 - there are various oxides (stoichiometries) - and hydrated oxides, and even oxyhydroxides. There are most likely other impurities.
 
You can't really say the powder that makes up rust is either pure Fe2O3 or pure FeO or pure Fe3O4. It is a crystal matrix with Fe(II) and Fe(III) in it and hydroxide impurities at the crystal-air interface. The formula which indicates the crystals composition is usualyl that which best describes it.

In this case I would say you have iron oxide, when it's just precipitated it will be best described as Fe3O4 which explains why it's magnetic and when you leave it in air it will convert into orange Fe2O3 as the powder gets further oxidized.
 
Are the hydroxides of iron magnetic?
 
Not to my knowledge but when the hydroxide ions make up only a tiny portion of the total amount of anions, the crytal in it's entirety might still be mostly describable as Fe3O4 and thus magnetic.
 
  • #10
JGM_14 said:
Are the hydroxides of iron magnetic?

Yes, some are.
 

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