Sciencemadness Discussion Board

Potassium bromate and iodide long term storage

Gargamel - 29-8-2021 at 02:46

Another storage question:

I've got some potassium bromate and potassium iodide here that I want to store safe and for a long time, since poisonous stuff is increasingly hard to get here nowadays.

It once came in plastic bottles - is that good enough or should I invest in something better?
Especially considering the seals.

Tsjerk - 29-8-2021 at 03:22

They are stable salts, they won't degrade, but they could get moist over time. You could use some PTFE tape inside the threads.

Chemgineer - 29-8-2021 at 04:10

I use heat sealed plastic bags for storing hygroscopic things.

woelen - 29-8-2021 at 04:35

Both salts are stable. KBrO3 can be stored indefinitely in any reasonably sealed container, it is not hygroscopic. KI is somewhat hygroscopic. If you want to store it for a long time, then it is best to store it in a glass container, tightly sealed. Plastic containers may be somewhat porous and over the years, their contents may become humid. A glass container with a good seal does not suffer from that.

Gargamel - 30-8-2021 at 04:24

Thank you guys.


KI is somewhat hygroscopic

Does that contribute to decomposition? What's the problem with that - I suppose precision weighing is impaired somewhat?

I haven't found any values for critical relative humidity, for none of the two.

I only have one good glasbottle left, so I would prioritise the KI for now, do you agree?

Bedlasky - 30-8-2021 at 07:04

KI is just mildly hygroscopic, this isn't problem at all. Old samples contain very small amount of iodine (if I add some starch to solution of my KI, it turns blue, but I have 30+ years old bottle). You can store it in original plastic container. You don't need perfectly dry KI for synthesis and solutions. And for analytical purposes it is best to dry it before use anyway.

Jimmymajesty - 7-9-2021 at 13:41

If you store KI in a plastic bottle the bottle will be darken due to free iodine and the KI will become a solid block you have to scrape it to get some off from the block.

Cut out a circle from ~0.3mm PTFE sheet press it into a jar lid get a big glass bottle and you have glass/PTFE container that can store 99% of the chemicals indefinitely.

For valuable stuff that comes in small amounts make an ampoule from a glass tube with a sufficient thickness you can work with. A healthy propane torch can seal a 10mm glass tube just fine.

macckone - 9-9-2021 at 12:13

I would not be worried about getting KI, it is a necessary nutrient.
It is stable but mildly hygroscopic and can oxidize.
It can react with water to release small amounts of iodine which will cause the darkening described.
But it won't seriously degrade.
Worst case scenario you can always extract it from iodine tablets.

The potassium bromate is another story as far as future availability.
Since it is being phased out in flour, it is unlikely to be readily available outside of the chemical supply chain.

However bromates can be made in the same manner as chlorates and potassium, lithium and sodium bromide are available as a photography chemical, a cooling agent and a spa chemical respectively.

Sodium bromide may be hard to obtain in canada:

vano - 18-10-2021 at 06:15

I have kilos of potassium bromate, all are more than 50 years old. When i found them, all of them were in glass jars, that's enough i think.

[Edited on 18-10-2021 by vano]