FAS-DPD powder and replacment help

[duraleigh]

I agree with what Chris said. It seems to make little difference in the test regardless of the powder quantity. In the TF test kit, you use one heaping spoon....it's the smaller Taylor spoon so I just sorta' compromised between Ben's one giant spoon or Taylor's two tiny spoons.

The color of the powder seems directly related to age and moisture exposure. When I get the Taylor 1 lb packs, it is a very, very, very light gray (almost white) and the smooth consistency of granulated sugar. My older powder that I've had for four years now is quite distinctively dark gray and clumpy. The best thing is I detect absolutely no difference in the performance or test results of either. I have done them side by side with identical results.

[Poconos]

I bought a bunch of bulk reagents from the SPS place a few years ago. I keep them in the fridge and only open to refill the smaller vials used day-to-day. I used to have a color photo lab as a hobby and the developing chemicals were a heck of a lot more sensitive than the pool reagents and using the same storage techniques the color stuff lasted indefinitely. Way past the recommended shelf life. And, the test was color comparison after developing/printing, new to old chemicals. Same with color paper and films.
Al