How to use a refractometer?

pprmntshrmps · 01/10/2009, 03:10 PM

I bought a never used refractometer from someone. It is a bix refractometer with a scale of 0-30. Can I use this to test my salinity? If so how?

ajger · 01/10/2009, 04:01 PM

Google is your friend: http://www.grapestompers.com/article...ometer_use.asp

To get 1.025 SG, the line separating the dark and light color should be midway between the 1.020 and 1.030 scale on the left side.

I wouldn't trust it unless you've calibrated it with good RODI or distilled water and adjusted it to read zero.

Pulp Fishin · 01/10/2009, 04:03 PM

If its anything like ither one of my refractometers you put a drop of water on the flat end and look though the eye-peace towards the light and it will show your reading.

MotherFish · 01/10/2009, 06:53 PM

Do NOT use FW (ro/di, distilled, etc.) to calibrate a refractometer.

I just wanted to get that out there first. I'll explain why in a moment.

pprmntshrmps, I may have some bad news for you...
It sounds like you've bought a brix refractometer for measuring the sugar content of alcohol/juices.
A refractometer for measuring salinity normally has two scales on the lens.
One scale reads ppt (0/00), which is 0 to 100 parts per thousand, and the other side of the scale reads specific gravity (d 20/20), which is 1.000 to 1.070

To find out what type of refractometer you have, hold it up to a light and look thru the eyepiece.

You have a proper salinity meter if what you see is this:

However, if what you see is this:

...then what you have is a sugar meter.

Now if you have the proper refractometer then you simply put 3 drops of your tank water on the glass lens, close the clear plastic cover, and look thru the eyepiece to read your salinity.
Most SW aquarists advise trying to keep a stable reading of 35ppt or 1.026sg on the average, which is a mid-level match for natural seawater.

Now getting back to the overly large, bold and red words at the top...
The reason you never use fresh water to calibrate a salinity meter is because the lens can have several different types of defects.
This is the reason there is a calibration screw in the first place.

If you calibrate a refractometer using FW then the only thing you can be 100% certain it will measure accurately is... yep, you guessed it,... fresh water.
It's not uncommon for a lens to read accurately at the precise point on the scale where it is calibrated to, yet get more and more out-of-whack the farther away the sample is from that point.
This is know as a slope defect.
Here is a visual example of what I am talking about from reefkeeping magazine:

The full article on everything you ever wanted to know about refractometers is here: http://reefkeeping.com/issues/2006-12/rhf/index.php
Happy reading!

Bottomline is, if you want to accurately measure 35ppt on your refractometer then you must calibrate it to 35ppt.
The best way (only way, in my book) is to use American Marine's Pinpoint salinity calibration fluid.

It has both the conductive property to calibrate digital meters as well as the refractive property to calibrate refractometers exactly to 35ppt.
You should be able to find a bottle of it at a LFS for about $5 and it will be enough to last you several lifetimes.
Happy reefing!

Chris&Mel · 01/10/2009, 07:43 PM

Quote:

Originally posted by MotherFish
Do NOT use FW (ro/di, distilled, etc.) to calibrate a refractometer.

I just wanted to get that out there first. I'll explain why in a moment.

pprmntshrmps, I may have some bad news for you...
It sounds like you've bought a brix refractometer for measuring the sugar content of alcohol/juices.
A refractometer for measuring salinity normally has two scales on the lens.
One scale reads ppt (0/00), which is 0 to 100 parts per thousand, and the other side of the scale reads specific gravity (d 20/20), which is 1.000 to 1.070

To find out what type of refractometer you have, hold it up to a light and look thru the eyepiece.

You have a proper salinity meter if what you see is this:

However, if what you see is this:

...then what you have is a sugar meter.

Now if you have the proper refractometer then you simply put 3 drops of your tank water on the glass lens, close the clear plastic cover, and look thru the eyepiece to read your salinity.
Most SW aquarists advise trying to keep a stable reading of 35ppt or 1.026sg on the average, which is a mid-level match for natural seawater.

Now getting back to the overly large, bold and red words at the top...
The reason you never use fresh water to calibrate a salinity meter is because the lens can have several different types of defects.
This is the reason there is a calibration screw in the first place.

If you calibrate a refractometer using FW then the only thing you can be 100% certain it will measure accurately is... yep, you guessed it,... fresh water.
It's not uncommon for a lens to read accurately at the precise point on the scale where it is calibrated to, yet get more and more out-of-whack the farther away the sample is from that point.
This is know as a slope defect.
Here is a visual example of what I am talking about from reefkeeping magazine:

The full article on everything you ever wanted to know about refractometers is here: http://reefkeeping.com/issues/2006-12/rhf/index.php
Happy reading!

Bottomline is, if you want to accurately measure 35ppt on your refractometer then you must calibrate it to 35ppt.
The best way (only way, in my book) is to use American Marine's Pinpoint salinity calibration fluid.

It has both the conductive property to calibrate digital meters as well as the refractive property to calibrate refractometers exactly to 35ppt.
You should be able to find a bottle of it at a LFS for about $5 and it will be enough to last you several lifetimes.
Happy reefing!

So...what do you do if you live in the mountains....and there is only one "pet store" wich you would be lucky to be able to buy salt at?

pprmntshrmps · 01/10/2009, 08:20 PM

Shortly after I got home and tried to test my salinity, and saw only the scale of 0-30, I did get on google and found ou that the brix that I have is not the one I needed. So is there no way to convert the reading on the brix to get salinity?

dwd5813 · 01/10/2009, 08:33 PM

read the article MotherFish posted.

MotherFish · 01/10/2009, 09:25 PM

Quote:

Originally posted by Chris&Mel
So...what do you do if you live in the mountains....and there is only one "pet store" wich you would be lucky to be able to buy salt at?

A quick google reveals dozens of online places you can order it from.

I just found it for $4.99 at http://www.bluewatercorals.com/ameri...ion-fluid.html

and an even better price of $3.00 over at http://www.jcaquatics.com/id47.html

A refractometer is worse than useless if it isn't calibrated correctly.
I can't count the number of times a fellow reefer has been shocked to find out that what they thought was 1.026 on their ro/di calibrated meter actually turned out to be anywhere from 1.020 to 1.035 once it was adjusted using proper calibration fluid.
Considering the amount of money we've all got invested in our tanks, this is probably the smartest $5 you'll ever spend.

MotherFish · 01/10/2009, 09:34 PM

Quote:

Originally posted by pprmntshrmps
So is there no way to convert the reading on the brix to get salinity?

Sorry, it is not made to measure salt.
Hopefully you can take it back for a refund and then you can buy the right one.
You can find the correct ones on ebay for about $30 with free shipping.

Good luck.

qfrisco · 01/11/2009, 08:14 AM

I agree that your best option is to take it back and get a proper refractometer for saltwater, however, if it is a refractometer, I don't see any reason why you can't use it for salt. Refraction of light through a liquid is the same thing regardless of whether you have sugars or salts in the solution. As long as the scale on the Brix includes the ranges of saltwater salinity that we care about (maybe 1.010 in the event you have to treat with hyposalinity sometime, to 1.0264), and you calibrate with the proper salinity standards, you should be able to make do with it.

You just need to have the proper standards to calibrate it against (like the Pinpoint solution mentioned above). Using a calibration standard like the Pinpoint solution, you should be able to tell where the 1.0264 SG equivalent is on the Brix.

If you're unable to get the Pinpoint solution, you might want to read the article below. It talks about making homemade salinity calibration standards.

http://reefkeeping.com/issues/2004-06/rhf/index.php

Having said all this, I personally don't think it's worth the trouble. If you have the option, just return it and get a proper refractometer.

pprmntshrmps · 01/11/2009, 09:30 AM

Thanks everyone for the help. I'll keep looking for one that has a salenity scale.

01/10/2009, 03:10 PM	#1
pprmntshrmps Registered Member Join Date: May 2005 Location: roanoke, va Posts: 296	How to use a refractometer? I bought a never used refractometer from someone. It is a bix refractometer with a scale of 0-30. Can I use this to test my salinity? If so how?

01/10/2009, 04:03 PM	#3
Pulp Fishin Were all mad here. Join Date: Nov 2007 Location: London Ontario Canada Posts: 608	If its anything like ither one of my refractometers you put a drop of water on the flat end and look though the eye-peace towards the light and it will show your reading. __________________ Reef Central Corner Club Aquarium Dumpster Diver Extraordinaire Money talks, mine says "Good-Bye" Current Tank Info: RIP:60g Pentagon Reef 100lbs LR 20g Sump Deltec Mce 600 Mag 750 250W Metal Halide & 2x39W T5's Phosban ReactorX2 5gal refugium 36xTO RIP:135G FOWLER /Agressive

01/10/2009, 08:20 PM	#6
pprmntshrmps Registered Member Join Date: May 2005 Location: roanoke, va Posts: 296	Shortly after I got home and tried to test my salinity, and saw only the scale of 0-30, I did get on google and found ou that the brix that I have is not the one I needed. So is there no way to convert the reading on the brix to get salinity? __________________ Brian Current Tank Info: 30G

01/10/2009, 08:33 PM	#7
dwd5813 Registered Member Join Date: Oct 2005 Location: 813 Posts: 2,827	read the article MotherFish posted. __________________ order some golf shoes, otherwise we'll never get out of this place alive. what can i say? in dog beers, i have only had one. - dublo8 Current Tank Info: 40B aiptasia farm

01/11/2009, 09:30 AM	#11
pprmntshrmps Registered Member Join Date: May 2005 Location: roanoke, va Posts: 296	Thanks everyone for the help. I'll keep looking for one that has a salenity scale. __________________ Brian Current Tank Info: 30G

01/10/2009, 04:01 PM	#2
ajger Registered Member Join Date: Aug 2008 Posts: 74	Google is your friend: http://www.grapestompers.com/article...ometer_use.asp To get 1.025 SG, the line separating the dark and light color should be midway between the 1.020 and 1.030 scale on the left side. I wouldn't trust it unless you've calibrated it with good RODI or distilled water and adjusted it to read zero.

01/10/2009, 06:53 PM	#4
MotherFish Registered Member Join Date: Jan 2009 Location: Florida Posts: 208	Do NOT use FW (ro/di, distilled, etc.) to calibrate a refractometer. I just wanted to get that out there first. I'll explain why in a moment. pprmntshrmps, I may have some bad news for you... It sounds like you've bought a *brix* refractometer for measuring the sugar content of alcohol/juices. A refractometer for measuring salinity normally has two scales on the lens. One scale reads ppt (0/00), which is 0 to 100 parts per thousand, and the other side of the scale reads specific gravity (d 20/20), which is 1.000 to 1.070 To find out what type of refractometer you have, hold it up to a light and look thru the eyepiece. You have a proper salinity meter if what you see is this: However, if what you see is this: ...then what you have is a sugar meter. Now if you have the proper refractometer then you simply put 3 drops of your tank water on the glass lens, close the clear plastic cover, and look thru the eyepiece to read your salinity. Most SW aquarists advise trying to keep a stable reading of 35ppt or 1.026sg on the average, which is a mid-level match for natural seawater. Now getting back to the overly large, bold and red words at the top... The reason you never use fresh water to calibrate a salinity meter is because the lens can have several different types of defects. This is the reason there is a calibration screw in the first place. If you calibrate a refractometer using FW then the only thing you can be 100% certain it will measure accurately is... yep, you guessed it,... fresh water. It's not uncommon for a lens to read accurately at the precise point on the scale where it is calibrated to, yet get more and more out-of-whack the farther away the sample is from that point. This is know as a slope defect. Here is a visual example of what I am talking about from reefkeeping magazine: The full article on everything you ever wanted to know about refractometers is here: http://reefkeeping.com/issues/2006-12/rhf/index.php Happy reading! Bottomline is, if you want to accurately measure 35ppt on your refractometer then you must calibrate it to 35ppt. The best way (only way, in my book) is to use American Marine's Pinpoint salinity calibration fluid. It has both the conductive property to calibrate digital meters as well as the refractive property to calibrate refractometers exactly to 35ppt. You should be able to find a bottle of it at a LFS for about $5 and it will be enough to last you several lifetimes. Happy reefing!

01/11/2009, 08:14 AM	#10
qfrisco Registered Member Join Date: Dec 2007 Location: Dallas, TX Area Posts: 1,389	I agree that your best option is to take it back and get a proper refractometer for saltwater, however, if it is a refractometer, I don't see any reason why you can't use it for salt. Refraction of light through a liquid is the same thing regardless of whether you have sugars or salts in the solution. As long as the scale on the Brix includes the ranges of saltwater salinity that we care about (maybe 1.010 in the event you have to treat with hyposalinity sometime, to 1.0264), and you calibrate with the proper salinity standards, you should be able to make do with it. You just need to have the proper standards to calibrate it against (like the Pinpoint solution mentioned above). Using a calibration standard like the Pinpoint solution, you should be able to tell where the 1.0264 SG equivalent is on the Brix. If you're unable to get the Pinpoint solution, you might want to read the article below. It talks about making homemade salinity calibration standards. http://reefkeeping.com/issues/2004-06/rhf/index.php Having said all this, I personally don't think it's worth the trouble. If you have the option, just return it and get a proper refractometer.