Is there any calibration fluid that is actual seawater not just nacl? Any experts out there?

BRS

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My red sea refractometer says to use ro/di water to calibrate. While using 35ppt solution seems better, do the solutions on the market actually have the calcium, magnesium, etc in them that seawater does? Are they adjusted to read 35ppt on a seawater refractometer if not? 35ppt seawater and 35ppt NaCl will not give the same reading. Just as a normal refractometer will give different results than a seawater refractometer on the same solution. Every solution I find says pure or high quality na/cl at 35ppt, but will this solution be 35ppt on a seawater refractometer or will it read 35ppt on a brine refractometer? Any experts out there? I am loving my salinity for hypo and small differences mater. @Randy Holmes-Farley
 

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Accurasea is a natural seawater standard at 35ppt. Not sure what it would read on a brine refractometer though. I use it for my refractometers and a conductivity meter.
 
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Accurasea is a natural seawater standard at 35ppt. Not sure what it would read on a brine refractometer though. I use it for my refractometers and a conductivity meter.
you’re correct, the below description is exactly what i was looking for. I wonder if the other solutions are not actually 35ppt seawater as accurasea states it’s the only solution made from real seawater. Has anybody tested different solutions?




AccuraSea® Seawater Reference Solution is the only calibration solution of its kind made from real seawater. It’s pure natural seawater micron filtered and UV sterilized then adjusted with reverse osmosis water to match the standard S 35 or 53 ms/cm at 25°C (77°F).

Use it to accurately calibrate seawater refractometers and to check the accuracy of swing-arm hydrometers. You may also want to use it as a reference for test kits used to measure the concentrations of various seawater components, since it is natural seawater with the correct and well-known concentrations of all dissolved salts.
 

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Yes, I have tried 4 other "standards" and got different readings on the same refractometer!! Pinpoint's standard came the closest to the accurasea and I think it's made to match natural seawater. Also Randy's DIY standards are dead on but there are 3 different standards for different devices so make sure you use the correct one.
 
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33ppt to 36ppt. Not that big of a deal, but I like to be accurate.
It is actually showing 2 ppt at 1.000. That cannot be correct right? See picture
 

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zoa what

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Imo just buy labgrade 35ppt solution, calibrate it and roll with it.

Sweat the small stuff and you'll die of stress at 68yrs old.



.
 
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Could you return it? Doesn't look correct. I read a post on here about an issue with the sea refractometer and had to get a replacement.
 
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Could you return it? Doesn't look correct. I read a post on here about an issue with the sea refractometer and had to get a replacement.
So on the instructions it has the same scale and says to calibrate at 0 ppt which on the picture shows the specific gravity well below 1.000. So it is not an error on my particular refractometer, but it confuses the hrll out of me. @Randy Holmes-Farley, any ideas on why the red sea refractometer scale has 1.000 specific gravity equal to 2 ppt?

20210524_133716.jpg
 
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I recommend staying away from the red sea refractometer. It literally loses calibration in a matter of seconds not minutes. Sometimes 2 ppt off at a time. This this is pure garbage and expensive. Also Makes absolutely no sense to me that you calibrate it at 0 ppt using ro/di making the specific gravity well below 1.000 for pure fresh water. I’m taking it back, and if my local fish store won‘t take it, I will throw it in their trash can and leave.
 
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My regular cheap hydrometer reads 1.000 with ro/di and never waivers with the tank salinity, the same reading every day forever. 75$ refractometer can’t read the same from 1 second to the next.
 
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The scale on the Red Sea thing looks off to me too. Not only should 1.000 and 0 ppt line up, but the 0 ppt should also line up with about 1.027...which doesn't look right on that scale.

Not sure if you've seen RHF's salinity and calibration solution discussion article: http://reefkeeping.com/issues/2004-06/rhf/index.php

It can all be a little confusing. With a refractometer, it isn't measuring the salinity or even specific gravity, but the refractive index. You can buy the calibration fluid. I would guess that the 35 ppt calibration fluid is probably just salt and water.

Making your own is pretty easy and fairly full-proof. You need to weigh out 36.5 grams on a decent kitchen scale and dissolve that in RO water, for a total of salt+water = 1 Liter.

I know some instruments say to calibrate with RO. I disagree with them. And if you are going to do it that way, then you still need to use a calibration fluid as a "check standard."

Hope that helps.
 
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If my regular run of the mill hydrometer reads exactly 1.000 with rodi water, and reads exactly 35 ppt with 35 ppt calibration solution. Can this be used to accurately measure salinity for hypo, and is there any need whatsoever to get an expensive refractometer that has to be calibrated all the time?
 
BRS

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