Agar, Phenolphthalein AND Potassium Hexacyanoferrate(iii)??

[Phoenix]

Hi all,

I've been given a rpac to set up for senior chem and it requires a solution made up of
200ml distilled water
2g agar powder
1ml 0.1%ohenolphthalein solution
AND
1ml 0.1mol/liter potassium hexacyanoferrate(iii) solution [K3Fe(CN)6]

I found out via google that the potassium H is also perussian Red. My problem is I don't have any. Has anyone made this solution before, is there an acceptable substitute or can it be left out all together and still get a result?

The prac is The effects of mechanical stress and different metals on the corrosion of iron. You wrap Iron nails in either zinc or copper leave one plain and bend the fourth then put them in petri dishes and set them in the above agar.

Any help, ideas or information please

Thanks very muchly in advance
Kelli

[lizzieb]

Hi Kelli,

Do a search for Ferroxyl Gel - I've just checked and there's a page of posts on it.

At my last school we did a 'corrosion' prac, but the only info I could find here is the (very old) recipe below, and you might find something better on the thread above. I seem to remember it being green.

Hope this helps!


AGAR FERROXYL GEL

1.5 - 2g agar
100mL water
15mL of 1% potassium ferricyanide (sic)
2mL phenolphthalein solution
1mL saturated NaCl solution

Boil agar in water then add the other ingredients.

Add 2M potassium hydroxide with dropper until gel turns pink, then decolourise using 0.5M HCl.

NB: approx 20mL solution per petrie dish.

[mtg]

Follow the prac, works well. You have to wrap the nails tightly as I recall, and bend one with pliers. The bend changes colour. Note Agar-agar, not nutrient. 0.1M potassium hexacyanoferrate(111), 33g per litre of solution.

[MariaC]

We do this prac every year, its also known as potassium ferricyanide, if they are doing corrosion as the option you may have to get some, lasts for ages , you dont need much! MariaC

[mtg]

Oh. My prac is from Chemistry one, Heinemann chemistry in context. Place 200ml de-ionised water in a 500ml beaker. Heat until the water just begins to boil, remove from heat and stir in 2g of powdered agar-agar, heat gently. Add about 1ml of 0.1M Potassium hexacyanoferrate(111) (potassium ferracyanide) and 1ml of 1% phenolphthalein indicator to the agar mixture and stir. Then do the nail bit.

[Phoenix]

Thanks everyone

Looks like I'll be chasing up some potassium ferricyanide. Problem is we are quite a small rural town. Its a good thing I'm quite adapt at letting my fingers do the walking. I'll see what I can find.

Cheers and thanks again everyone

[LabTechCollegiate]

Does anyone know about the disposal of ferroxyl solution and also after the nail part?