The plot thickens a bit .... I had emailed Taylor with the same question and just got this reply. Seems part of the difference is that you multiply the drops by 1.25 and not .5 to get a bromine level and then divide by the 2.25. Still doesn't work out and dividing by 2 is closer but it seems it's not linear based on my direct comparisons. Today's reading was 8 bromine drops and 12 chlorine drops.

FAS-DPD BROMINE (1 drop = 0.5 or 1.25 ppm)

"Yes, you can if it is the only titrating reagent you have available. Using the bromine instructions in the link below, obtain a bromine reading and divide by 2.25. We do strongly recommend using the R-0871 for testing chlorine."

http://www.taylortechnologies.com/pr...er&Number=5524

Sincerely,
Jody O'Grady
Manager, Customer & Technical Services