35PPT solution with randy's recipe. I made a mistake or refractometer is waaay off?

[fr3n0z]

Hi all, i am tryng to see if my refractometer is well calibrated. Calibrated first with RODI at 0.

I then proceeded to make the 35ppt solution: 6.20Gr of table salt (not iodized) with 182ml of RODI

Balance it's pretty precise, i've tested against some new coin and i am in the 0.02+/- range.

refractometer reads 1.025 or 33%o at 20°....i made a mistake or refractor is really uncalibrated? NON iodised salt can be the culprit? or RODI?

(refractometer is a cheap amazon ATC refractometer)

 

[gbroadbridge]

Hi all, i am tryng to see if my refractometer is well calibrated. Calibrated first with RODI at 0.

I then proceeded to make the 35ppt solution: 6.20Gr of table salt (not iodized) with 182ml of RODI

Balance it's pretty precise, i've tested against some new coin and i am in the 0.02+/- range.

refractometer reads 1.025 or 33%o at 20°....i made a mistake or refractor is really uncalibrated? NON iodised salt can be the culprit? or RODI?

(refractometer is a cheap amazon ATC refractometer)

Did you calibrate with the solution and refractometer at 25C ?

In any case I would consider that is close enough for all practical purposes of keeping salinity stable.

 

[fr3n0z]

Did you calibrate with the solution and refractometer at 25C ?

In any case I would consider that is close enough for all practical purposes of keeping salinity stable.

In the inside of my refractometer it says at 20C so it was at 20C Problem is i tought water 35ppt while now, after calibrating with this solution, is at 37 or nearly 1.028 that it seems a bit high to me.

 

[chipmunkofdoom2]

The standard you made is likely correct. Calibrating with deioninzed water is only accurate if your refractometer has no variance over its entire range of measurement. Which is unlikely.

 

[Randy Holmes-Farley]

Hi all, i am tryng to see if my refractometer is well calibrated. Calibrated first with RODI at 0.

I then proceeded to make the 35ppt solution: 6.20Gr of table salt (not iodized) with 182ml of RODI

Balance it's pretty precise, i've tested against some new coin and i am in the 0.02+/- range.

refractometer reads 1.025 or 33%o at 20°....i made a mistake or refractor is really uncalibrated? NON iodised salt can be the culprit? or RODI?

(refractometer is a cheap amazon ATC refractometer)

Just checking, how did you measure the water? Mass or volume? How?

The recipe should be 3.65 grams of sodium chloride in 96.35 grams water.

 

[gbroadbridge]

Just checking, how did you measure the water? Mass or volume? How?

The recipe should be 3.65 grams of sodium chloride in 96.35 grams water.

Oops, just noticed the OP seems to have made the EC standard...

 

[fr3n0z]

Just checking, how did you measure the water? Mass or volume? How?

The recipe should be 3.65 grams of sodium chloride in 96.35 grams water.

I have measured by weight

 

[fr3n0z]

Just checking, how did you measure the water? Mass or volume? How?

The recipe should be 3.65 grams of sodium chloride in 96.35 grams water.

your recipe stated6.20g and 182g of water. Or I have probably misunderstood something.

If I have to calibrate a refractometer and also a digital probe, can you use the same recipe? (3.65g + 96.35g)

 

[gbroadbridge]

your recipe stated6.20g and 182g of water. Or I have probably misunderstood something.

If I have to calibrate a refractometer and also a digital probe, can you use the same recipe? (3.65g + 96.35g)

There are different 'recipes' for Refractometers and Conductivity Probes.

For a refractometer you need 3.65g of table salt + 96.35g of RODI water.

If your other 'probe' measures conductivity (rather than being a digital refractometer) the solution you have made
(6.20g table salt and 182g of water) is the correct one to use.

 

[fr3n0z]

There are different 'recipes' for Refractometers and Conductivity Probes.

For a refractometer you need 3.65g of table salt + 96.35g of RODI water.

If your other 'probe' measures conductivity (rather than being a digital refractometer) the solution you have made
(6.20g table salt and 182g of water) is the correct one to use.

ok now all is more clear

 

[Randy Holmes-Farley]

your recipe stated6.20g and 182g of water. Or I have probably misunderstood something.

If I have to calibrate a refractometer and also a digital probe, can you use the same recipe? (3.65g + 96.35g)

No, every type of device needs a different recipe when using sodium chloride.

This is the recipe for a refractometer, and the second link below has all of the recipes::

Refractometers and Salinity Measurement - REEFEDITION

Title photo by R2R member Rskillz By Randy Holmes-Farley Salinity is one of the most important parameters measured in reef aquaria. It controls not only the salt balance between an organism and its surrounding environment, but also the levels of a host of ions Read more here...

www.reefedition.com

Do-it-yourself Refractometer Standards

In a previous article I described how to make a do-it-yourself refractometer standard matching 35 ppt seawater, and I will just summarize that recipe here.

To provide a standard for refractometers requires a solution whose refractive index is similar to normal seawater. Seawater with a salinity of 35 ppt has a refractive index of 1.3394. Likewise, the refractive index of different sodium chloride solutions can be found in the scientific literature. My CRC Handbook of Chemistry and Physics (57th Edition, Page D-252) has such a table. That table has entries for 3.6 and 3.7 weight percent solutions of sodium chloride that span the value for normal seawater. Interpolating between these data points suggests that a solution of 3.65 weight percent sodium chloride has the same refractive index as 35 ppt seawater, and therefore can be used as an appropriate standard (Table 5).

This 3.65 weight percent sodium chloride solution can be made by dissolving 3.65 grams of sodium chloride in 96.35 grams (mL) of purified freshwater. This recipe can be scaled to any appropriate size if suitable instruments are available (36.5 grams in 963.5 grams (mL) of water, 0.365 grams in 9.635 g (mL) of water, etc.).

This concentration roughly corresponds to ¼ cup (73.1 g) of Morton’s Iodized Salt dissolved into two liters (2000 g) of water (giving very slightly more than 2 L of total volume).

For a rougher measurement in the absence of an accurate water volume or weight measurement:

1. Measure ¼ cup of Morton’s Iodized Salt (about 73.1 g).
2. Add one teaspoon of salt (making about 79.3 g total salt).
3. Measure the full volume of a plastic 2 L Coke or Diet Coke bottle filled with purified freshwater (about 2104.4 g).
4. Dissolve the total salt (79.3 g) in the total water volume (2104 g) to make an approximately 3.65 weight percent solution of NaCl. The volume of this solution will be slightly larger than the Coke bottle, so dissolve it in another container.

[Note: the standard described here using soft drink bottles is subject to variation in the volume of the bottle. It turns out that such bottles can vary in total volume, and this can lead to at least a one ppt error in the salinity of standards matched to seawater of 35 ppt salinity. Standards made with accurate measurements of salt and water, however, will accurately match 35 ppt.]

Reef Aquarium Salinity: Homemade Calibration Standards by Randy Holmes-Farley - Reefkeeping.com

 

[fr3n0z]

No, every type of device needs a different recipe when using sodium chloride.

This is the recipe for a refractometer, and the second link below has all of the recipes::

Refractometers and Salinity Measurement - REEFEDITION

Title photo by R2R member Rskillz By Randy Holmes-Farley Salinity is one of the most important parameters measured in reef aquaria. It controls not only the salt balance between an organism and its surrounding environment, but also the levels of a host of ions Read more here...

www.reefedition.com

Do-it-yourself Refractometer Standards

Thanks for the clarification, my bad that i did not read thru the whole article. Thanks for your work!

 

[Sidsreef]

Hi all, i am tryng to see if my refractometer is well calibrated. Calibrated first with RODI at 0.

I then proceeded to make the 35ppt solution: 6.20Gr of table salt (not iodized) with 182ml of RODI

Balance it's pretty precise, i've tested against some new coin and i am in the 0.02+/- range.

refractometer reads 1.025 or 33%o at 20°....i made a mistake or refractor is really uncalibrated? NON iodised salt can be the culprit? or RODI?

(refractometer is a cheap amazon ATC refractometer)

High Precision Hydrometer - Tropic Marin

Ensure that your equipment is reading correctly and your aquarium is at the right salinity with Tropic Marin's High Precision Hydrometer. Many tank inhabitants are sensitive even to minor changes of the water conditions. Unfortunately as we've all experienced, salinity reading equipment as...

www.bulkreefsupply.com

Calibrate your stuff with the results on this thing.

 

[fr3n0z]

Thanks all guys, after recalibrating probe and refracto with good solutions they both reads the same salinity in tank. Thanks a lot!