Homemade 35ppt standard

[Stelioshah]

I am about to make a homemade 35 ppt standard solution since any store bought standard I've tried is has been proven to be complete garbage. I will make it using my aquaforest reef salt, my question is why does the salt state that for a 33ppt solution I would need 39 grams of salt per litre of water and not 33 grams? What should I do to acheive an appropriate solution?

 

[Miami Reef]

I am about to make a homemade 35 ppt standard solution since any store bought standard I've tried is has been proven to be complete garbage. I will make it using my aquaforest reef salt, my question is why does the salt state that for a 33ppt solution I would need 39 grams of salt per litre of water and not 33 grams? What should I do to acheive an appropriate solution?

Is this to calibrate a refractometer?

 

[Stelioshah]

Is this to calibrate a refractometer?

Yes for a refractometer, I am currently measuring the water by testing alk ca and mg and matching based on the salt's specifications but it is tedious.. I am doing that because the typical standard I have bought for my refractometer has ended up being about 0.003-0.006 refractive index off.

 

[Stelioshah]

I have always thought ppt reffered to per grams of solvent not solution, it makes more sense now for the grams to be higher than 33 for a 33 ppt solution then, but 39 seems a little too high to me.

 

[Miami Reef]

96.35g of RO/DI water/3.65g of sodium chloride (Mortons iodized) to make a 35ppt solution for refractometers. https://reefkeeping.com/issues/2004-06/rhf/index.php

 

[Randy Holmes-Farley Verified Community Expert]

There’s no good way to make a standard from reef salt due to high and variable amounts of moisture in it.

use the sodium chloride standard above.

 

[Randy Holmes-Farley Verified Community Expert]

Details for a variety of salinity standards for different devices are given here:

Reef Aquarium Salinity: Homemade Calibration Standards by Randy Holmes-Farley - Reefkeeping.com

 

[Stelioshah]

There’s no good way to make a standard from reef salt due to high and variable amounts of moisture in it.

use the sodium chloride standard above.

I suppose this standard needs pure NaCl? Would I be ok using any table salt? Or there would be a significant deviance?

 

[Gtinnel]

I suppose this standard needs pure NaCl? Would I be ok using any table salt? Or there would be a significant deviance?

I just use Morton’s iodized table salt which Randy mentions using in the article.

 

[Randy Holmes-Farley Verified Community Expert]

I suppose this standard needs pure NaCl? Would I be ok using any table salt? Or there would be a significant deviance?

The article answers all such questions.

"This 3.65 weight percent sodium chloride solution can be made by dissolving 3.65 grams of sodium chloride in 96.35 grams (mL) of purified fresh water. That amount roughly corresponds to ¼ cup (73.1 g) of Morton's Iodized Salt dissolved into 2 liters (2000 g) of water (giving very slightly more than 2 L of total volume)."