Sciencemadness Discussion Board - Ferrous Sulfate Heptahydrate

Ferrous Sulfate Heptahydrate

ScopeGuy - 20-12-2015 at 18:09

I wanted to try to make some Crystals out of
Ferrous Sulfate Heptahydrate
https://www.youtube.com/watch?v=tjBhumIr3OM

Anyone know where to get it? Lowes or Homedepot or some type of place I could pick it up locally.

I have some Ferrous sulfate monohydrate I do not know if that will work.

I looked in the forum and saw a few ways to make it with sulfuric acid but I want to be able to hold the crystals so I was looking for a safer way to make them.

Thank you

JJay - 20-12-2015 at 18:38

Dissolving ferrous sulfate monohydrate in room temperature water will give you a solution of the heptahydrate. Removing the water of solution is a bit tricky since oxygen will destroy the ferrous sulfate chemically and heat will alter the heptahydrate complex... but you can do it under vacuum below 56.6 C.

Making it from sulfuric acid shouldn't make handling the crystals a problem as long as you completely neutralize the acid and wash/recrystalize the product, but of course that also requires working with sulfuric acid, so it's not ideal....

[Edited on 21-12-2015 by JJay]

Amos - 20-12-2015 at 20:24

If you don't have as much ferrous sulfate as you'd like already, you can do a single-replacement reaction between a solution of copper(II) sulfate (available in most hardware stores as root killer) and steel wool, usually with a tiny amount of catalytic sodium chloride added.

ScopeGuy2 - 24-12-2015 at 20:10

Thank you both so much. I could not sign back on here for some reason. I had to create a new account but wanted to wait a few days and unsuccessfully tried to get it to work.

I got Copper II sulfate and the steel wool today. 2 pounds to try to make the ferrous sulfate and 2 pounds for some thing else at a later time.

Is there any instructions how to make the ferrous and the amounts of everything that I should use.

Thank you

Texium - 25-12-2015 at 06:58

Well, do you remember stoichiometry from high school? It'll come in handy for things like this. Here's your equation:

CuSO₄ + Fe —> FeSO₄ + Cu

It's a single replacement reaction, and a 1:1 molar ratio, so you'll need to find the molar masses of each of your reactants, and that will tell you how much of each you need to use.

Amos - 25-12-2015 at 12:37

In addition, your steel wool should be as fine as possible, and you'll want to use more steel wool than copper sulfate in the stoichiometry; this will prevent any copper sulfate from remaining afterward. Give it a stir every now and then while it reacts so that your steel wool doesn't get covered in copper and prevent it from fully reacting. At the end, you can just filter the solution and then either chill it or boil it down a bit to crystallize it.

ScopeGuy2 - 27-12-2015 at 13:45

Very useful thank you.

So I figured out that 2 pounds of CuSO4 =5.66 moles
I would need 1.06 pounds of steel wool

Then add a little extra steel wool

What should I do to figure out how much water to add when mixing the steel wool with the CuSO4? How do I figure out how much water I need?

Also how much sodium chloride should I add?

Xenoid - 27-12-2015 at 14:47

ScopeGuy2 - Why are you MAKING ferrous sulphate, you have stated in your first post that you already have some!

Ferrous sulphate can be made to crystallise with several different amounts of "water of crystallisation". Under normal circumstances it will crystallise with 7 water molecules (the heptahydrate).

Just dissolve your MONOhydrate as in the video, it will crystallise as the heptahydrate.

You should note however the crystals will soon oxidise and get a rusty coating of Fe2O3, they will not remain the pristine emerald appearance unless special precautions are taken!

ScopeGuy2 - 28-12-2015 at 00:20

I do have some ferrous sulphate. I guess the reason I want to make it is to make more is because it sounded fun when I heard that it could be made from copper sulfate. I figure that I will probably need more in a few years and thought why not make it now. I am a new to making chemicals, unlike all the experts on here, there are a few things that I want to make but they are acids and it scares me some. I thought it would be great to make some thing simple and less dangerous first.

I wanted to make the ferrous crystals because I don't have them.
I will give the crystals a try tomorrow to see how it works

Amos - 28-12-2015 at 07:48

Let the solution of copper sulfate with the steel wool sit for a while and see if you see signs of reaction; I doubt you'll actually need any chloride, it simply accelerates the start of the reaction. I would use as little water as is needed to ensure all of the copper(II) sulfate dissolves. If it looks like ferrous sulfate crystals are appearing midway through the reaction and they're getting in the way, you can add more water and begin heating it all on a hot plate to keep any soluble compounds dissolved.

At the conclusion of the reaction, filter the solution as quickly as possible, boil it down a bit, and while still hot, put it into a container with as little room for air at the top as possible. Put a lid on this container and cool the whole thing down to force crystallization to occur. The larger the amount of solution you have, and the slower the gradual cooling process is, the larger and more attractive your crystals will be. If you're satisfied with the crystals you produce, pour off the remaining solution, saving it for later to produce more crystals, and immediately dry off the crystals you've produced with a paper towel; they're much more prone to air oxidation when they're wet on the surface. Larger, more richly crystals with fewer inclusions in my experience are also less prone to oxidation than their smaller, grainier relatives, so keep this in mind as well.

If at any time you notice a significant color change in your solution to a more nasty yellowish-green or even brownish, you've encountered partial oxidation of your iron(II) sulfate solution. Small amounts of this aren't too important, but if it appears drastic, you can add a few mL of sulfuric acid to the solution and place it in a NEARLY airtight container with any source of iron metal. This will slowly reduce it back.

[Edited on 12-28-2015 by Amos]

ScopeGuy2 - 28-12-2015 at 22:33

Thank you all vey much,
I will post a few photos when I get this done

ScopeGuy2 - 4-1-2016 at 19:37

So I checked to see if I got any crystals and nothing

ScopeGuy2 - 4-1-2016 at 19:39

I check with a plastic spoon and nothing and just sediment when I dumped it out. I will try again with sulfuric acid next time

Reply

mnm0003 - 5-1-2016 at 04:16

Quiet! FeSO4 are to combat moss and algae in any store or farmers' cooperatives erboresteria

in general is heptahydrate (maximum degree of hydration) but you can eliminate water molecules by controlled heating (see some TGA you have to be careful not decompose) or reach the heptahydrate for dissolution and crystallization

Attachment: TGA DI ALCUNI SOLFATI.pdf (1.1MB)
This file has been downloaded 486 times

Dr.Bob - 5-1-2016 at 06:40

If you are going to dissolve the FeSO4 in water at any time, then the degree of hydration of the starting FeSO4 is not creally critical, except in determining the amount to weigh out. If you simply leave FeSO4 in the air long enough, it may even make the heptahydrate.

I looked and most catalogs list iron(2) sulfate as FeSO4 * XH20, so it may be that most iron sulfate is already mostly hydrated, but simply not as well purified or characterized as the higher priced ones that specify the heptahydrate. The density and other specs look almost identical, so it may be that you are starting with mostly the heptahydrate anyway.

MolecularWorld - 5-1-2016 at 07:39

Quote: Originally posted by ScopeGuy2

So I checked to see if I got any crystals and nothing

Quote: Originally posted by ScopeGuy2

I check with a plastic spoon and nothing and just sediment when I dumped it out. I will try again with sulfuric acid next time

The product in the background there is mostly calcium sulfate. If you simply dissolved the product in water, that explains your sediment. You should be able to separate the two by decanting the liquid away from the sediment: calcium sulfate has very low solubility in water, less in a sulfate solution. The liquid will contain most of ferrous sulfate. However, based on the color, the ferrous sulfate is highly oxidized, so some sulfuric acid and iron will need to be added, and mixture kept in a covered container until it turns green (as Amos suggested). If it doesn't turn green with this treatment, then the brown is an additional unknown contaminant.

ScopeGuy2 - 8-1-2016 at 22:53

Thank you everyone. I will try this again using a slightly revised method and post some photos when I get it done.