Lugols Iodine

[Narelle01]

I have been a labby for almost 3 years and I have never been asked for this horid chemical.
Been in this school for almost 2 years - same.
Does anyone use it? Should i just dispose of it?

[RosalieM]

We use it but I don't remember what for. Starch staining perhaps? Actually, I think it is for something in biology - leaf stains. It is just a stronger solution of iodine, (other than 0.1M which is the other iodine solution I have on hand).

[Xenon]

Lugol's I use is 1% w/v Iodine in 2% w/v Potassium Iodide solution (aqueous). Used as starch indicator - goes purple in presence of starch. Useful in brewing process to check whether starches in mashed grains have converted to maltose. Corrosive, but can be stored in dropper-bottles.

[estelle]

we use this for biology experiments for starches etc.

[Narelle01]

hmm, ok, then it stays. But I am only going to keep one class set of it.
Its has rotted through the rubber droppers.
So I will clean them all up, replace them and keep 10.
I have made bulk mixes of chemicals today and defrosted the fridge - all the things I didn't get a chance to do before holidays and didn't get around to yesterday

[mikah]

I read an article in NEXUS over easter regarding bromine in the food supply and they recommended TAKING 2 drops of Lugols Iodine daily

I didn't think too much about it after the mag was put down but this jogged my memory.....

[RosalieM]

Serrata sells lids that fit on dropper bottles and I use these when corrosive chemicals are stored in the droppers (all acids etc) and just replace with droppers when sending them out for a class. It does take up a bit of time but in the long run it is better than having to replace the rubber bits all the time. I usually just put a small container on the shelf with the lids in where the droppers are supposed to go so when I put them back the old lids are there waiting. Then I pull the droppers apart, wash them, put them back together and store them in a drawer.

[Narelle01]

oh yes i have some of those caps for my bromine water droppers.
I am not sure how long this lugols has been here, so best chuck it. When I replace the droppers, i will also make sure there is no chemcal in the actual glass dropper bit, cause the vapour is what rots the rubber.

[ana.santos]

Lugol's Iodine and iodine solution are almost similar-used to test for starch and for staining specimens for microscopic examination. however, this solution deteriorate with light and age, so fresh solutions are preferred or check your solutions if colour has not faded.Maximum shelf life is 1 yr.

[Lyn]

Lugol's solution seems to be the main solution that I make up for use in the science labs. Mind you in all the years that I had been making up the iodine solution, I had no idea that what I was making up was Lugol's solution. For years I worked with a handwritten recipe provided by the previous lab tech. It was only when I got the "Lab bible" and looked for the recipe that I normally made that I discovered it had a specific name. It is used as a starch indicator and for staining onion when making up slides. I store iodine solution in amber glass bottles. It keeps fairly well in glass. I have class sets of plastic dropper bottles which I fill with iodine solution. The solution in the plastic dropper bottles leaches colour into the plastic and eventually the plastic turns dark brown. You can also see the leaching effect if you stand the plastic bottles on white plastic trays, with yellow staining occurring. If the stored iodine starts to look an insipid yellow I usually chuck it. If it has maintained a deep rich reddish-brown colour it is still viable. If in doubt test on starch on a white tile and if starch still turns blue-black it is still useable.
I have outlined in another area how I make up my iodine solution. I am not patient when it comes to waiting overnight for iodine to dissolve and if I need the solution quickly, like right now, I know I can have the iodine dissolved and the solution ready within ten minutes or so.

Lyn.

[RosalieM]

Hi Lyn,
I have just been searching for your quick dissolving iodine recipe but can't see it anywhere. I am not particularly patient when making up solutions either! Would you mind re-posting it for us?
Thanks!
Rosalie

[RosalieM]

Oh! I found it crush the iodine first Will give that a go next time!

[Graham Kemp]

Oh! I found it crush the iodine first Will give that a go next time!

Aye. A crush disolves so much faster than the flakes -- which take something like ... forever.

Crush the iodine together with the potassium iodide to aid disolution into just a small wash of water. Let it disolve before diluting.

[DavidPeterson]

Do you add any alcohol when you dissolve iodine? Or try and dissolve only in water?

[rosaliemb]

Lugols iodine is used to preserve algae . The iodine solution is added to the sample so it looks like weak tea. The algae are killed and sink to the bottom and then this can be subsampled. Best though is looking at fresh live specimens as you can view motility and their real colour.

The KI of Lugols recipe aids the dissolving of the solid iodine. Best left overnight. The solution deteriorates with time - decolours. And keep it in brown storagae bottle as mentioned by othes.

Rosalie (another one)

[Lyn]

I don't crush the iodine first before putting it into the potassium iodide solution. I only start breaking it up with a stirring rod when the potassium iodide solution doesn't dissolve the iodine quick enough. If you dissolve the potassium iodide in 50-100ml of water first then add the iodine to this concentrate then swirl the solution around in the beaker the iodine starts to dissolve fairly quickly. Once the iodine is completely dissolved then you add the remaining quantity of water required. I don't think it would be necessary to stand overnight if the iodine is already completely dissolved. Just try it and see what you think.

Lyn.

[lizzieb]

I've found it keeps without losing colour if stored in the dark.