Conserving R-870


Sep 3, 2010
Indianapolis, IN
I'm about out of R-870 solution for checking FC. Been using the 10ml test. Is there a reasonably reliable way to half that test? since I'm using about 40 to 50 drops per test I would like to extend my testing this weekend until I get a replacement early next week.
If so, please include the exact steps to take.


LifeTime Supporter
Aug 28, 2010
Boston, MA
When I was repeatedly testing FCs in the 40-50 ppm range recently, I took to using a 5 mL sample and counting each drop as 1 ppm. This increases the uncertainty in the result, but an uncertain result would be better than no result because you ran out of reagent.

It doesn't work very well for CCs, where the difference between 0.5 and 1 ppm is very significant. And it'd be problematic for FC in the ~5 ppm range or less. But for relatively high FC it seems to do OK.