Ferrous sulfate quality

[4metals]

I have had 2 different clients recently ask me about ferrous sulfate, one is in Chicago and one in Tennessee so they are not using the same supplier. They are both experiencing the same thing though.

When I showed them how to use the stuff, I told them add 4 pounds to a gallon of hot water and add 600 ml of Hydrochloric acid and it will be a clear green. I never had trouble using this method.

Today while I was at the plant, they showed me what was happening and I was surprised. The ferrous was coming out murky and did settle in time to green but I never saw it so bad. After I filtered a batch it was the color I expected and what remained in the bucket looked like fine beach sand.

Have any of our ferrous loving members seen this before?


This is when I added it to the water.

this is it after filtering (sorry I cannot get it to rotate)

and this is the sand like insolubles

 

[butcher]

Ferrous sulfate crystals can oxidize to another oxidized form of Iron, the green crystals will turn brown or white from oxidation, keeping the crystals damp and acidic can keep them from oxidation.

I do not know if this is what you are seeing, or if the ferrous sulfate crystals were not pure?

Normally when I make ferrous sulfate i can get a fairly pure crystallization on first process, and then they can be recrystallized for a very pure crystals, I also store them damp and slightly acidic, and keep them from exposure to air, they stay as green as the day they were made with this in mind, and the fact you say the copperas in question is from two separate suppliers, I would suspect oxidation, but I am just guessing, what did the crystals look like before dissolving,were the bright clear green like in the picture here?

Most garden suppliers in my area sell oxidized iron, with ferrous sulfate on the label of the bag.



http://en.wikipedia.org/wiki/Iron%28II%29_sulfate

 

[4metals]

The crystals they had in the drum were a very light green and they told me they empty the bags it comes in, which if I remember correctly are plastic lined, into a steel 55 gallon drum. They told me a new shipment came in last week. Seems pretty fast to oxidize but apparently it did. It still works to drop the gold but it needs to be filtered first.

So how do you store yours to maintain the acidity? Dampness is easy, acidity a little more difficult.

 

[butcher]

As you crystallize the liquid ferrous sulfate solution you are concentrating the solution, in evaporation driving off water, iron sulfate forms crystals, any excess sulfuric acid in solution at this point is also more concentrated, this acid solution is normally poured off of the crystals, the crystals are rinsed (I use a plastic screen strainer which lets small pieces of other insoluble materials pass through the screen but hold back the copperas crystals), and these crystals are redissolved in a clean dilute sulfuric acid solution with the solution is heated to dissolve the crystals, and evaporated to re-form crystals again repeating the process above, these crystals once rinsed and still damp wet I put in HDPE plastic bottles and add a little free sulfuric acid, I fill the bottles fairly full, to avoid air space and the crystals are fairly damp in the acidic solution,sit below the slightly acidic solution.


I do something similar to this with some of my other metal salts like my copper sulfate, (or stannous chloride...), I have notice if I keep the crystals damp and acidic they seem to store better and longer without decomposition or oxidation, I have noticed even a sealed plastic bottle, or glass with a lid will breath, many metal salts exposed to air (sometimes light) can decompose faster, than they will when stored under a liquid solution (if the metal is a salt of an acid, storing it wet, in a little of the acid solution it its made from can help keep it from decomposition from oxidation of air or oxygen.

With many of these other metal salts like copperas, I do not add a bit of the metal they are made from, except for my stannous chloride solution here a small piece of tin is also added, with a little of the free excess HCl. The tin elemental metal, and acid, is free to react in solution as the solution is in storage on the shelf, stannous can have a very short shelf life, keeping it acidic, an with a little free metal, and keeping the bottle filled helps to keep the stannous form oxidation or hydrolysis, where the tin solution can more easily form an hydroxide or oxide of tin in solution, this can help the stannous chloride solution to last longer on the shelf.

With copperas or many of the metals salts I make, I use a similar principle for storage.