I have a bag of white powder, I know it's either D-76 developer or fixer. How can I determine which one it is?

Question

I forgot to label the bag and now it's been 6 months and I can't remember which chemical it is. They are both fine white powders. I know the fixer smells pretty strong so I suppose I could put some in water and see if I can smell it. Any better ideas?

Answer

Since developers are often alkaline, you could use a red or purple litmus paper to test for that - if it contacts with alkalies, it turns blue.

Check more discussion of this question.