Iodine crystals for disinfecting water are available as a trade product called “Polar Pure” from most of the regular backpacking supply places such as REI. It comes in a small bottle with a screened top, you fill it, shake it, and then decant a capful or two of the supersaturated solution into your water. The bottle has full instructions and also a thermometer so you know how long the water should sit before use. The cost was about $8 or so, last time I bought any. – “Doc”
JWR’s Reply: A highly recommended product! One little three ounce bottle can treat up to 2,000 quarts of water. I recommend that you buy one for each of your G.O.O.D.  kits. Warning: The wire screen at the top of the bottle is there for a reason. Ingesting iodine crystals can be deadly!
Polar Pure is sold by Nitro-Pak , Campmor , Great Outdoors Depot , and several other Internet vendors. I recommend that you stock up before the Nanny State decides that the only use for iodine crystals is for cooking up methamphetamines.