My pH buffer solutions for calibration of my meters are out of date; I see no precipitation of salts in the bottles; are they still good? I have VWR brand 4, 7,and 10. The neutral yellow 7 buffer solution looks almost clear now, but the red 4 and blue 10 look the same as when new (still blue and red). I think the color dyes are the only things that can actually degrade. When I check the neutral against a newer but still expired 7 from cole parmer it's still within 0.1 pH unit. I assume that as long as the buffers aren't salted out they should be good. Fatman whats your take?
