Different forms of vitamin C

Hey all, I would like to be taking some vitamin c to alkalinize my body, and assist in general with some detox stuff I will be doing. I recently came across a kilo of brownish bulk "vitamin c" which was made in Japan. I don't know anything about it really except it's obviously not pure ascorbic acid, any ideas what this is? My question is basically what is the best form of vitamin c to take? I'm kind of a purist and If I could use a totally naturally occurring form of vit c that would be best as far as I'm concerned, but what is a totally natural form of vitamin c that is readily available? I read recently on this forum someone recommending that one NOT take normal ascorbic acid, but rather magnesium ascorbate being preferable. I'm just looking for some feedback on this in general. Any educated opinions appreciated.

Thanks
mark...