I went to buy some Glycin at my photo shop, but noticed it was a brown colour, a bit like milk chocolate. I was advised that it was still ok, and only when it turns very dark brown should it be discarded. I vaguely recall reading somewhere on www.unblinkingeye.com (?) that even when light brown in colour it is no longer usable, so I didn't buy any. The Merck Index of pharmaceuticals says that Glycin will darken over time but does not say that it changes its chemical structure or degrades. Does anyone have any definitive advice about the shelf live of Glycin and what the change in colour actually means?(posted 8245 days ago)thanks