Over 20 years in the hobby, I have never been happy with how I test salinity. I recently switched from using a conductivity probe double checked with my old refractometer to trying to calibrate my probe with a homemade salinity solution. This should work nicely as long as we are close and stay consistent - I don't care if my salinity is really 34 or 36 ppt as long as it stays the same - including when I change brands of table salt.
I read your article http://reefkeeping.com/issues/2004-06/rhf/index.htm and several posts on this forum but had some questions.
You suggest approximating a 3.65 by weight percent "by dissolving 3.65 grams of sodium chloride in 96.35 grams (mL) of purified fresh water".
You then suggest a 3.7 by weight percent (or 3.714) solution made from 6.2g Morton's salt in 161g fresh water for specific gravity.
You then suggest a 3.29 by weight percent solution from 6.2g Morton's salt in 182m fresh water to calibrate probes.
Why use over 12% more salt to calibrate by specific gravity than conductivity? Does the same ocean water weigh 1.0264 as much as fresh water and measure 53 mS/cm? Or are the "standards" from different places, such as conductivity being measured in the Atlantic and specific gravity in the Red Sea? If the same ocean water has both properties, than I would assume the ions besides sodium chloride play a significant role, and pure sodium chloride, Morton's and Kosher salts are not interchangeable. Why advise that we can use either? What about the water content of salt made for food?
Is there a reason "Morton's salt" and "fresh water" are appropriate for specific gravity and conductivity but "sodium chloride" and "purified fresh water" are needed for a refractometer? Does a refractometer require lab grade ingredients, or am I being to literal on the order the article was written?
I read your article http://reefkeeping.com/issues/2004-06/rhf/index.htm and several posts on this forum but had some questions.
You suggest approximating a 3.65 by weight percent "by dissolving 3.65 grams of sodium chloride in 96.35 grams (mL) of purified fresh water".
You then suggest a 3.7 by weight percent (or 3.714) solution made from 6.2g Morton's salt in 161g fresh water for specific gravity.
You then suggest a 3.29 by weight percent solution from 6.2g Morton's salt in 182m fresh water to calibrate probes.
Why use over 12% more salt to calibrate by specific gravity than conductivity? Does the same ocean water weigh 1.0264 as much as fresh water and measure 53 mS/cm? Or are the "standards" from different places, such as conductivity being measured in the Atlantic and specific gravity in the Red Sea? If the same ocean water has both properties, than I would assume the ions besides sodium chloride play a significant role, and pure sodium chloride, Morton's and Kosher salts are not interchangeable. Why advise that we can use either? What about the water content of salt made for food?
Is there a reason "Morton's salt" and "fresh water" are appropriate for specific gravity and conductivity but "sodium chloride" and "purified fresh water" are needed for a refractometer? Does a refractometer require lab grade ingredients, or am I being to literal on the order the article was written?