(You'll find some support for this method I'll describe on the curezone Vitamin C forum) use a Mineral Ascorbate, not Ascorbic Acid - Ascorbic Acid is so acidic to the body that you can end up over-acidifying your body (the tissues, I'm not talking about the stomach here). For why being overly-acidic is bad, see the curezone Alkaline/Acid forum. To avoid this, use Sodium Ascorbate - which has the vitamin C bound to a mineral, still allows the body the use of the vitamin C, without being so acidic.
I did high dose ascorbic acid a number of years ago and go so acidic that I was breaking out in canker sores and havin symptoms of an overly acidic system. Dumped the vitamin C entirely at that time from my routine because didn't know of an alternative. Sodium Ascorbate is a good form to use that won't cause this problem.
Some people on the Vitamin C forum say it is better than Calcium Ascorbate or Magnesium Ascorbate, but I don't remember why on those two. Visit forum to see.