- Joined
- Sep 21, 2025
- Messages
- 2,701
- Reaction score
- 4,778
- Location
- Germany
- What state or country do you live in
- Other International
Thank you for the response, this helps!Both temperature and wavelength of
Light matter, but I could certainly have made a mistake.
Many times, refractive index is standardized at 20 deg C and the wavelength of the d emission line of sodium (589.3 nm). That is what I used.
The google AI calculates that the refractive index of 3.24% KCl under these conditions is 1.3374. Close, but not exactly what I got and that appears to be the difference. I do not have old CRC handbook handy, but it may have used a data source that has been replaced by better data (or I made a mistake).
Again using the google AI to run a calculation, it determines that the salinity of seawater matching that refractive index has a salinity of 24 ppt, matching your value. :)
Thus, I’m not sure exactly why I got the 26 ppt value, but it appears to be incorrect.
If it's not too much trouble, I would really appreciate it, if you could take a quick look at the tools I have built. I want to make them freely available to everyone (no ads, no tracking, etc.).
@Fish Fan has already seen a preview and can vouch that it's worth a look
They should fix the issue with online calculators not offering the right reagent/hydrate form for your Ammonia/Phosphate/2-Part/etc. recipes.Don't worry, you don't need to check the math
, I would just like to hear your suggestions (usability or things to add) 
So far I have:
- Salinity: hydrometer/refractometer SG ↔ ppt (PSU or g/kg) with temperature correction (incl. glass expansion), plus PDF/CSV correction tables
- Salinity balancing: how much salt to add, or how much water to swap for RO/DI
- Custom dosing recipes:
- Ammonia: NH₄HCO₃, NH₄Cl, NH₄NO₃
- Nitrate: NaNO₃, KNO₃, Ca(NO₃)₂, NH₄NO₃
- Phosphate: NaH₂PO₄, Na₂HPO₄, KH₂PO₄, K₂HPO₄
- Balling: CaCl₂ and any mix of Na₂CO₃/NaHCO₃
- All salts selectable in their hydrate forms, with a solubility check on the stock solution
- AFR dosing
- Unit conversions: volume (gal ↔ L) and nutrients for paper readers (e.g. µmol/L ↔ ppm as NH₃-N/TAN, NH₃, NH₄)
It isn't public yet, so I would like to send you the link privately. I can't send you a DM here on R2R, maybe you can start a conversation with me?

