I have the older style salifert alkalinity test kit, the one with the small indicator bottle (blue/green) and the titration reagent.
Well, as anyone with a decently high alk level in their tank can confirm, I used up my titration reagent MUCH faster than the indicator. So, I tried making a new reagent at work, since I was pretty sure it is just a weak acid.
It worked!!
First, I tried calculating mathematically what molarity HCl it should be:
200ppm alk:
200mols CO3/1,000,000 mols water =
2molsCO3/10,000 mols water or 2molsCO3/180,000 g (mL)
For my 2mL water samople, that gives 0.000022mols CO3
That would require 2 fold molar ratio of H, or 0.000044 mols H
in 0.4mL of volume (the amount I use from the original kit) =
0.000044mols/0.0004L = x/1 or 0.11M HCl.
which we conveniently already have here at work used for titration