Trisodium Phosphate Potency

[timqmana]

Does trisodium phosphate go bad/lose it's potency? I mix 2g Loudwolf trisodium phosphate to 1L of RODI.

I just tested .5ml of the phosphate solution in 1L of freshly mixed saltwater and got a reading of 0.32ppm with the Hanna ULR checker. According to the James' Planted Tank calculator, I should be around 0.7ppm.

I checked the Hanna against the Hanna calibration solution and it is testing correctly.

 

[Randy Holmes-Farley Verified Community Expert]

No, it does not lose potency. The Hanna fluid only checks the electronics, not the reagents or procedures, which a true calibration fluid would.

 

[timqmana]

No, it does not lose potency. The Hanna fluid only checks the electronics, not the reagents or procedures, which a true calibration fluid would.

Could trisodium phosphate absorb enough moisture from the air to that measuring 2 grams of it would lead to ~40% potency (due to the extra weight of whatever humidity was absorbed)?

 

[timqmana]

No, it does not lose potency. The Hanna fluid only checks the electronics, not the reagents or procedures, which a true calibration fluid would.

Could trisodium phosphate absorb enough moisture from the air to that measuring 2 grams of it would lead to ~40% potency (due to the extra weight of whatever humidity was absorbed)?

 

[GSPClown94]

Could the error be coming from your weight or volume measurements?

 

[Randy Holmes-Farley Verified Community Expert]

What did you use and how did you determine the expected potency?

 

[timqmana]

I used a 100g capacity scale that I have verified is accurate with a calibration weight set.

I weighed out 2 grams of Loudwolf Trisodium Phosphate and mixed it into 1L RODI to get my phosphate solution, which should raise phosphate in 25 gallons by 0.01ppm.

I put 0.5ml of that solution into 1L of new saltwater. I should be at 0.7ppm phosphate per this calculator:

 

[Randy Holmes-Farley Verified Community Expert]

Note that the calculator is not exactly the material you dosed.

Anhydrous trisodium phosphate has a molecular weight of 163.94.

Phosphate weighs 95 g/mole.

That material is thus 58% phosphate by weight (note that the google search ai gets this wrong, remarkably).

2 grams thus contains 1.16 g phosphate.

Put into 1 L water, it contains 1.16 mg/mL

Adding 0.5 mL (0.58 mg) into 1 L of salt water gives a concentration of 0.58 mg/L.

If the solid was left open to the air for any lengthy period of time, the solid can absorb moisture. That would drop the potency.

Also, if the bottle actually contained trisodium phosphate dodecahydrate, that material is only 25% phosphate by weight.

 

[timqmana]

Note that the calculator is not exactly the material you dosed.

Anhydrous trisodium phosphate has a molecular weight of 163.94.

Phosphate weighs 95 g/mole.

That material is thus 58% phosphate by weight (note that the google search ai gets this wrong, remarkably).

2 grams thus contains 1.16 g phosphate.

Put into 1 L water, it contains 1.16 mg/mL

Adding 0.5 mL (0.58 mg) into 1 L of salt water gives a concentration of 0.58 mg/L.

If the solid was left open to the air for any lengthy period of time, the solid can absorb moisture. That would drop the potency.

Also, if the bottle actually contained trisodium phosphate dodecahydrate, that material is only 25% phosphate by weight.

Thank you Randy, that was what I was looking for!