I had three bottles of vitamins: Women's One a Day, Alive! and something very expensive from the health foods store. I took cups of warm water, plunked a vitamin in each cup and waited. Within 5 minutes, the Women's One a Day dissolved almost completely (the least expensive of the three). After 20 minutes, the Alive! vitamin's slimy coating finally came off so that the real vitamin could start to dissolve (totally dissolved within 30 minutes). The most expensive, health food store vitamin - after an hour it began to soften. After two hours there was a copper type substance that began to cloud the water. After 3 hours, I threw it out!
Here is a cool article about what can be in your vitamins: http://www.do-dietary-supplements-work.com/vitamin-supplements-solid.html Stay healthy!