KH testing discrepancy

[rawootm]

Hi Happy Reefers
I need some advice about my testing results using a recently expired Red Sea KH testing solution.
When using bottle 872 (expired in Aug 2024) I get a reading of 7.5 Kh. Using 512 (expiry Feb 2025) I get a reading of 10.5 Kh. Seems expired items testing outcomes are questionable.

 

[Dan_P]

Hi Happy Reefers
I need some advice about my testing results using a recently expired Red Sea KH testing solution.
When using bottle 872 (expired in Aug 2024) I get a reading of 7.5 Kh. Using 512 (expiry Feb 2025) I get a reading of 10.5 Kh. Seems expired items testing outcomes are questionable.

Or the new reagent is bad. Without a reference standard who can say.

If solvent evaporation occurred in the older bottle, you would get a lower result with the more concentrated reagent. Not unheard of.