Can anyone give me a sense of how much iodine would be needed to make, let's say, 3 ml of water thoroughly sanitary?
This link:http://en.wikipedia.org/wiki/Portable_water_purification suggests 12.5cm³/l of saturated iodine solution, prepared from iodine crystals, with the caveat that this may not kill giardia cysts. So it depends what you mean by "sanitary". The article explains there are other iodine preparations available, for which other treatment rates would be appropriate.
The Wikipedia article seems to be speaking of ~2.92 grams of iodine per liter of water. That would leave you with about ~666 mg of iodine in an 8 oz. glass of water. By comparison the Institute of Medicine states that the RDA of iodine for an adult male is 150 micrograms.* Please Register or Log in to view the hidden image! Actually, I made a slight error, but the true amount still seems to be massive. Let me re-do my calculations and then edit this post. Update: Correction made. *Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. Washington, DC: National Academy Press, 2001. Retrieved from http://ods.od.nih.gov/factsheets/Iodine-HealthProfessional
No. The solubility of iodine in water is about 1g in 3.45l water at 20C, according to Wiki. Don't make the error of assuming all the crystals dissolve, when the solution is made up. If you read on, in the original link I posted, you will see they can be reused. The idea, apparently, is to get a saturated supernatant solution, which you decant to use. Using the above solubility number, I get a saturated solution containing ~0.0003 g/cm³, which when added to water at the concentration they suggest (12.5g/l) gives you a final concentration of ~3.6mg/l. On the question of iodine dose for water purification vs. recommended dietary maximum, there is no reason why these need be aligned, since the short term risk from waterborne disease easily trumps long term overexposure, provided iodine is not used as a long term method of water purification. Read more here: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1638306/
What confuses me is the fact that there's going to be a lot of iodine crystals sitting on the bottom of the supernatant solution. How does one work with that in the future, after having used some of the liquid for some time? It just seems like a big complication to me and it's making my head spin. Thanks for the measurements, by the way.
I didn't measure anything. I dd a few calculations, that's all. There's nothing at all hard about this. The point about a saturated solution is that you only know you've got one when you have surplus solid left over. Provided you have enough of the remaining solid, you can make up with fresh water when you have used some, shake it up to dissolve some more and, provided there are still at least a few crystals lefts at the bottom, you will know you have, once again, a saturated solution. The concentration of a saturated solution will be the same every time, for a given temperature. (Of course, as it get warmer, water dissolves more, so this could be a source of variation. I imagine this might come in handy if you are travelling somewhere basic, having no measuring equipment and want make sure you use the right dose to protect yourself.
Bacteria... The measurement discussed in this thread works out to be several drops per liter of water. What I'd like to know is does its sanitizing action increase with an increase in its concentration or is its sanitzing action maxed out in the measurement discussed.
The commercial product Potable Aqua will sterilise about a litre of water with one tablet. http://www.amazon.co.uk/Potable-Aqua-Water-Treatment-Tablets/dp/B001949TKS The bottle contains 6 grams of tablets and there are 50 tablets. Each tablet is 6.68 % iodine. So 6000 mg Divided by 50 Divided by 100 Times 6.68 Is approximately 8 mg per litre. The amount varies according to the source of the water. To be sure, you need to buy a proprietary product and follow the instructions. The amount of iodine you need in your diet is measured in micrograms, not miligrams, so this would be an excessive amount of iodine to ingest on a regular basis.
According to this article, the Japanese consume on average 50 times more iodine in their diet than people in the US. And some people living on the Hokkaido coast ingest 200mg per day from eating seaweed. The coast dwellers are more prone to developing a disease called Hashimotos thyroiditis, so such high levels are not recommended.
The 8 mg per liter conforms to my statement of 'several drops per liter' and my last question was is the sanitizing capacity of iodine maxed out at these proportions? What if I put 8 mg in a shot glass, for example?
I don't know the answer to that. A higher concentration could be less effective. The solution as made will kill virtually 100% of bacteria within seconds. http://www.woundsinternational.com/made-easys/iodine-made-easy/page-2
DO NOT TRY ANYTHING SILLY. Iodine is an irritant and can burn the digestive tract at sufficiently high concentrations. It is very unwise indeed to exceed the recommended concentrations of such substances arbitrarily. You could end up in hospital.
When I was at school we had a teacher who showed us how to make Nitrogen Triiodide. I blame my Tinnitus on him.
No, it wasn't cool at all. I think we should only have made a crystal or two, but we caked filter pads with the stuff and left it to dry. I don't think he was a very responsible teacher.
