How to make my own test reagent?

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owkaye

0
Jul 11, 2015
37
Biloxi MS
I have a HDX (Home Depot) branded 5-way test kit -- the same kit that's manufactured and sold by Poolmaster. I use far more #3 reagent than the others so my #3 bottle is running low yet all the others are still nearly full.

The front side of the label says "#3 - Count Drops - For Acid Demand & Alkalinity Test" and the back says "Contains Hydrochloric Acid ..." but the HCl concentration is not specified.

How can I determine the HCl concentration of this reagent so I can make my own?
 
Seems like more hassle than needed. For one, you do not even need to use the demand tests since PoolMath will do the calculation for you. Second, I would recommend sticking with the tried and trusted Taylor brand test kits ... which have easily available refills for each reagent.
 
jblizzle said:
Seems like more hassle than needed. For one, you do not even need to use the demand tests since PoolMath will do the calculation for you. Second, I would recommend sticking with the tried and trusted Taylor brand test kits ... which have easily available refills for each reagent.
Click to expand...

Some people would say the testing and maintenance we do in the TFP method seems like more hassle than needed...it appears OP may be a chemist or have a chemistry background if he's going to do a titration to determine the concentration---I say let him enjoy his hobby and please post what you find!
 
PoolMath is actually more accurate than the acid demand test in this particular kit, or at least that's been my experience so far. The chart that comes with the test kit tells how much acid to add, but I always seem to need about twice as much as the chart suggests.

I've done more testing for TA than acid demand so that's where most of my reagent was used. I'm still working to get my TA down to70- 80 ppm so I can add Boric Acid at the recommended levels and create a pool chemistry that's stable and prevents algae from getting a foothold according to this recommendation.

Yes I have a chemistry background so I'm comfortable doing the titration. If I actually get around to it some day I'll post the results.
 
Quite frankly, the concentration of reagent for the acid and base demand tests even in the Taylor test kits is too high as you can tell by looking at their tables. If you're going to roll-your-own, so to speak, you might as well make it weaker so you have finer granularity in the results. So just figure out the concentration needed based on the water volume of your sample and scale up so that your table matches your pool water volume.

If you use Taylor bottles, their bottle tips form 24 drops per milliliter. So in a 44 ml water sample that's a 1:1056 dilution. For your 1200 gallon pool, one drop would represent 1200/1056 = 1.1 gallons. So to get that to 1 cup you'd need to dilute your acid by a factor of (1200/1056)*16 = 18.18 so instead of 31.45% HCl you'd use 31.45/18.18 = 1.73% HCl. Does that help?
 
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