Item — HN Reader

> differentiation of common salt and iodised salt

Is there any drawback with iodised salt? This is the only test that use “differentiation” instead of “detection”, not sure if that’s related

Also love the simplicity of “detection of iron filling in tea leaves”: use a magnet!

2 comments

Not only is there no drawback, in India iodised salt is mandatory. I'm guessing the language is because common salt lacks processing instead of having something adulterating it and is perfectly safe on its own.

Some fancy salts, like Himalayan rock salt, are not usually available iodised.

If you're adding salt to a fermentation vessel then you wouldn't want it to be iodized since the iodine will harm the bacteria responsible for fermentation.

IIRC you can still buy iodine free salt, you just can’t advertise it as table salt. It has to be explicitly advertised as pickling salt or rock salt or the like. This is the case in many countries, not just India. It is arguably one of the most successful public health initiatives ever.

same was as in the US it is possible to get "ethanol", which is just alcohol that can't be legally consumed. One of my chemistry professors explained that their records keeping for "ethanol" was actually more much more strict than the actual hazardous substances they had in the lab.

That must have been exaggeration to ward off clever ideas unless it's in like Utah or something -- At my grad school in a fairly puritanical state, USP grade ethanol was just on the shelf in the supply room with no more security or record keeping than on bags of pipet tips. And yes, some people did learn that undiluted pure EtOH dehydrates mucous membranes most painfully

In Alabama you can only legally get alcohol from a state designated entity. This was at a state university, so they had a state license just like a store would. Along with that came all the regulations.

I think the subtle difference is that alcohol not for human consumption must be denatured, and can be synthesised.

No, that's the point. You can't use denatured alcohol in a lab. It has to be nearly pure ethanol, with some percentage of water.

My chemistry professors told us that if someone tried to drink the ethanol in the lab their throat would seal off and they would start to choke because it will suck the moisture out of your tissue due to it being nearly anhydrous.

FWIW, I am on a doctor-prescribed high-salt diet and I'm sensitive to iodine, so I avoid iodized salt.