pH test kits

["James Purchase" <jppurchase at Home_com>]

One for the chemists......

Since LaMotte has apparently discontinued my pH test kit (Model AG-21, Code
7462) which reads from 6.0 - 7.4, it looks like I may have to look elsewhere
soon, once my supply of reagent runs out. The kit uses Bromthyol Blue
Indicator.

- are there different "strengths" of this indicator solution (i.e. to cover
different pH ranges) or would any generic Bromthyol Blue Indicator solution
refill from another manufacturer work with the kit?

As an alternative, I have been looking at the offerings from Hach. I have
found a Canadian source for Hach kits that offers several "color disk"
models which look promising:

- Model 17F  pH range: 5.5 - 8.5; Increment: 0.1 pH unit; Indicator -
Bromthymol Blue
- Model 17G pH range 6.5 - 8.5; Increment: 0.1 pH unit; Indicator - Thymol
Blue / Bromthymol Blue
- Model 17H pH range 6.5 - 8.5; Increment: 0.1 pH unit; Indicator - Phenol
Red with Thiosulphate

While the wider range of model 17F looks more useful, is there any reason(s)
for or against the different Indicators (Bromthymol Blue vs. Thymol Blue vs.
Phenol Red)?

Thanks,

James Purchase
Toronto

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