What calibration fluid to buy for refractometer

Azedenkae

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I asked this a while back but forgot what the answer was, and could not find that reply anymore. So I guess I have to ask again. D:

I want to buy calibration fluid to well, calibrate my refractometer. What are y'alls preferences?

Not interested in making my own, by the way.
 
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Azedenkae

Azedenkae

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I just use RODI water and set refractometer to zero. Don't waste your money on calibration fluid.
I dunno, iirc there was a thread recently that pointed out the importance of calibrating to a 'target' salinity like 35ppt rather than RODI water, so I kinda just want to buy one.
 

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BRS Refracto Juice works well for me

 
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Randy Holmes-Farley

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I just use RODI water and set refractometer to zero. Don't waste your money on calibration fluid.

Sorry, that is not correct. Using pure fresh water it is not going to be accurate unless it is a perfectly made true seawater refractometer. Very few used by hobbyists are true seawater refractometers, and as to how many are perfectly made? No idea.

OTOH, using a 35 ppt seawater equivalent standard will correctly measure 35 ppt seawater regardless of the type of refractometer (brine or true seawater) even the perfection of manufacture.
 

Randy Holmes-Farley

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I bought calibration fluid for refractometer and it was significantly off. Use RODI water and check with me Apex salinity probe.

No, you are mistaken. Please do not keep repeating such posts.
 
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Azedenkae

Azedenkae

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BRS Refracto Juice works well for me

Well that was fast and easy, lol. XD Sweet, thanks!
 

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BRS Refracto Juice works well for me

I use the same stuff. It only takes a few drops. I have been using the same bottle for years and I check the salinity often (usually daily). And if you cap it after use, it stays the same (At least in my experience).
 
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Randy Holmes-Farley

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I discuss the problem with brine refractometers and RO/DI here:

Refractometers And Salinity Measurement
http://www.reefedition.com/refractometers-salinity-measurement/

Imperfect Refractometer Use: Scale Misunderstanding and Salt Refractometers


Refractometers can lead to incorrect readings in additional ways and, again, these issues abound for reef aquarists. One is that many refractometers are intended to measure sodium chloride solutions, not seawater. These are often called salt or brine refractometers. Despite the scale reading in ppt (‰) or specific gravity, they are not intended to be used for seawater. Unfortunately, many refractometers used by aquarists fall into this category. In fact, very few refractometers used by hobbyists are true seawater refractometers. If a manufacturer does not claim it is a “True Seawater” refractometer, it very likely is a brine refractometer.

Fortunately for aquarists, the differences between a salt refractometer and a seawater refractometer are not too large. A 35 ppt sodium chloride solution (3.5 weight percent sodium chloride in water) has the same refractive index as a 33.3 ppt seawater solution, so the error in using a perfectly calibrated salt refractometer is about 1.7 ppt, or 5% of the total salinity. This error is significant, in my opinion, but not usually enough to cause a reef aquarium to fail, assuming the aquarist has targeted an appropriate salinity in the first place. Figure 23 shows the relationship between a perfectly calibrated and accurate salt refractometer and a perfectly calibrated and accurate seawater refractometer when the units are reported in salinity. This figure shows the measured salinity reading for seawater being about 1.7 ppt higher than it really is.
 

Randy Holmes-Farley

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I asked this a while back but forgot what the answer was, and could not find that reply anymore. So I guess I have to ask again. D:

I want to buy calibration fluid to well, calibrate my refractometer. What are y'alls preferences?

Not interested in making my own, by the way.

I've not measured any to know which are most accurate and which are not.

What do you have against a DIY? It's not a "second rate" sort of thing.
 

monkeyCmonkeyDo

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I have tds calibration fluid as well i have yet to use. How do i use this fluid randy? Ty
D
 

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>>klong<<

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I had an issue where my calibration fluid of 35ppt was actually 42ppt. I think I left the cap open . . .

Afterward I switched to this:

 
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Randy Holmes-Farley

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I have tds calibration fluid as well i have yet to use. How do i use this fluid randy? Ty
D

The TDS fluid is not useful for seawater salinity. Much too dilute.
 

Randy Holmes-Farley

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I am lazy, that's my reason. ^_^

It should be straight forward for companies to copy my published recipe, but since that sort of chemical knowledge seems beyond some hobby supply companies, I'm concerned that some may develop things they think are right which are not.
 

Randy Holmes-Farley

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No for my fresh rodi and tds meter randy holmes. Lol.
Do i just dip my tds meter in the bottle and if it reads the 342ppm like on the bottle its good? Lol.
Im hyjacking yo. Lol.
D

For a TDS meter intended for monitoring Ro/DI, yes, if you can adjust it, set it to read 342 ppm. If you cannot adjust it, then understand the % offset (like, "it reads 7% high") and make the correction manually (although exact RO/DI numbers are not that critical).
 
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