Tommy P. Just wanted to ask a question on your thread for Boomer related to specific gravity (sg).
I noticed my NaCl (not seawater) refractomer a cheap one. don't know the brand and another brand Sper scientific both have specific gravity and corresponding ppt concentration at 1.025 and 35ppt. I thought natural seawater was 1.0264 and 35 ppt (parts per thousand)
However the natural sea water refractometer sold by the Filter Guys mentioned on the previous page of this thread clearly show the corresponding sg of 1.0264 and 35ppt when looking through the prism to indicate sg.
Then I came across a dr. foster's and smith page showing the values of red sea coral pro salt as follows: So are they incorrect?
*Replicates natural seawater to help support delicate marine life *Enriched with refined minerals to safely elevate calcium levels and buffer capacity *Natural, evaporated sea salt
Coral Pro Salt is specifically formulated for use with reverse osmosis water. Natural, evaporated sea salt is enriched with refined minerals to safely elevate calcium levels and buffer capacity. Replicates natural seawater to help support delicate marine life and invertebrates in home reef aquariums. Salt is produced by small batch process to ensure homogeneity and consistency of the salt mixture. Chemically balanced formula is nitrate and phosphate free.
Table shows calcium levels of Coral Pro mixed in RO water at 24?C/75?F and salinity.
s.g.SalinityCalciumQty of Salt 1.021 30.6 ppt 420 ppm 33.4 g/l 1.4 lb/5 US gal 1.023 32.8 ppt 450 ppm 35.8 g/l 1.5 lb/5 US gal 1.025 35.0 ppt 480 ppm 38.2 g/l 1.6 lb/5 US gal Please click on "More Information" for instructions.
I have no clue why a refract would have 1.025. What the are probably looking at is corrected Density, which is about one unit lower, ie, 1.025 instead of 1.0264. Density does not equal Specific Gravity.
That RS stuff is just showing what levels you will get at different mixing rates with their salt. They do not show one for 1.0264, for oblivious reasons. Meaning, the levels of Calcium would be ~ 500 ppm. NSW Calcium is 420 ppm Calcium @ 35 ppt and the have 420 @ 1.021, 30.6 ppt. You are reading into the RS stuff, as if their last mix is 1.025, same as your refract or the Sper.
Where did you get that 1.025 =35 ppt. I do not see it on their website. They only have one Hand Held, NaCl refract. I see no image of the lens. And Sper actually does not manufacture allot of their stuff.
Boomer thanks for the response. The sper scientific salt refractometer I have and I suspect all non seawater refractomers have two scales: On the right hand side % and on the left hand side D 20/20 or Dd.
When I look through to get a reading the 35% on the right hand side exactly corresponds to 1.025 on the left hand side. The scale on the right hand side goes from 0% to 100% and on the left hand side 1.00 to 1.07
The D from what you are saying is specific density. Therefore when you calibrate with solution that is supposed to be at 1.0264 or 35% which one should you calibrate to since the scales don't line up? Looks like it should be calibrated to 35% since the left hand side is not specific gravity although sper scientifc says it is (incorrectly as you pointed out.)
I've been calibrating at 35% and not using the scale on the left hand side so I should be ok
I can try to post a pic of what I am seeing on the Sper scientific.
As far as RedSeaMax Coral Pro salt I was reading into it but I don't think they should report 35ppt as 1.025. They should just leave it at 1.025