How to Measure Salinity
Use this tool to accurately measure salinity in liquids., Select a refractometer designed for the liquid you wish to measure., Open the plate near the angled end of the refractometer., Add a couple drops of the liquid onto the exposed prism...
Step-by-Step Guide
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Step 1: Use this tool to accurately measure salinity in liquids.
Refractometers measure how much light bends, or refracts, when it enters the liquid.
The more salts (and other material) dissolved in the water, the more resistance the light will meet and the more it will bend.
For a cheaper, but somewhat less accurate, method, try a hydrometer.
If you are measuring the salinity of soil, use a conductivity meter. -
Step 2: Select a refractometer designed for the liquid you wish to measure.
Different liquids already refract light by different amounts, so to accurately measure additional salinity (or other solids content), use a refractometer designed specifically for the liquid you intend to measure.
If the liquid is not specifically mentioned on the packaging, the refractometer is probably designed to measure salt water.
Note:
Salt refractometers are used to measure sodium chloride dissolved in water.
Seawater refractometers are used to measure the mixture of salts typically found in seawater or saltwater aquariums.
Using the wrong one may result in a reading approximately 5% off, which may be acceptable for non-laboratory purposes.Refractometers are also designed to compensate for the expansion of a specific material due to temperature changes., A handheld refractometer has one round, open end to look through, and one angled end.
Hold the refractometer so the angled surface is on the top of the device, and find the small plate near this end which can be moved to one side.
Note:
If you have not yet used your refractometer, you may wish to calibrate it first for a more accurate reading.
This process is explained at the end of this section, but you may wish to read the following steps first so you are more familiar with how to work the device. , Take the liquid you wish to measure, and use an eyedropper to pick up a couple drops of it.
Transfer this to the translucent prism revealed when you moved the plate.
Add enough water to completely cover the prism's surface with a thin layer., Cover the prism again by gently pushing the plate back into position.
The parts on a refractometer may be small and delicate, so try not to apply much force even if they become slightly stuck.
Instead, wiggle the plate back and forth with your finger until it moves smoothly again. , Look through the round end of the device.
There should be one or more numbered scales visible.
The salinity scale is likely labeled 0/00 meaning "parts per thousand"
and ranges from 0 at the bottom of the scale, to at least 50 at the top.Look for the salinity measurement at the line where the white and blue areas meet. , Once you have the measurement you need, open the plate again and use a soft, slightly damp cloth to wipe the prism until it is free of water droplets.Leaving water in the prism, or immersing the refractometer in water, can damage the refractometer.
A damp tissue may work if you don't have a cloth flexible enough to reach the whole surface of the tiny prism. , Periodically between uses, calibrate it to the correct reading by using pure, distilled water.
Add the water to the prism as you would for any liquid, and check whether the salinity reading is "0." If not, use a small screwdriver to adjust the calibration screw, typically found beneath a small cap on the top or bottom of the device, until the salinity reading is "0."A new, high-quality refractometer may only need calibration once every few weeks or months.
A cheaper, older refractometer may need to be calibrated before each use.
Your refractometer may come with calibration instructions that specify a certain water temperature.
If none are included, use room temperature distilled water. -
Step 3: Open the plate near the angled end of the refractometer.
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Step 4: Add a couple drops of the liquid onto the exposed prism.
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Step 5: Carefully close the plate.
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Step 6: Look through the device to see the salinity reading.
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Step 7: Wipe the prism with a soft
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Step 8: damp cloth.
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Step 9: Calibrate the refractometer periodically.
Detailed Guide
Refractometers measure how much light bends, or refracts, when it enters the liquid.
The more salts (and other material) dissolved in the water, the more resistance the light will meet and the more it will bend.
For a cheaper, but somewhat less accurate, method, try a hydrometer.
If you are measuring the salinity of soil, use a conductivity meter.
Different liquids already refract light by different amounts, so to accurately measure additional salinity (or other solids content), use a refractometer designed specifically for the liquid you intend to measure.
If the liquid is not specifically mentioned on the packaging, the refractometer is probably designed to measure salt water.
Note:
Salt refractometers are used to measure sodium chloride dissolved in water.
Seawater refractometers are used to measure the mixture of salts typically found in seawater or saltwater aquariums.
Using the wrong one may result in a reading approximately 5% off, which may be acceptable for non-laboratory purposes.Refractometers are also designed to compensate for the expansion of a specific material due to temperature changes., A handheld refractometer has one round, open end to look through, and one angled end.
Hold the refractometer so the angled surface is on the top of the device, and find the small plate near this end which can be moved to one side.
Note:
If you have not yet used your refractometer, you may wish to calibrate it first for a more accurate reading.
This process is explained at the end of this section, but you may wish to read the following steps first so you are more familiar with how to work the device. , Take the liquid you wish to measure, and use an eyedropper to pick up a couple drops of it.
Transfer this to the translucent prism revealed when you moved the plate.
Add enough water to completely cover the prism's surface with a thin layer., Cover the prism again by gently pushing the plate back into position.
The parts on a refractometer may be small and delicate, so try not to apply much force even if they become slightly stuck.
Instead, wiggle the plate back and forth with your finger until it moves smoothly again. , Look through the round end of the device.
There should be one or more numbered scales visible.
The salinity scale is likely labeled 0/00 meaning "parts per thousand"
and ranges from 0 at the bottom of the scale, to at least 50 at the top.Look for the salinity measurement at the line where the white and blue areas meet. , Once you have the measurement you need, open the plate again and use a soft, slightly damp cloth to wipe the prism until it is free of water droplets.Leaving water in the prism, or immersing the refractometer in water, can damage the refractometer.
A damp tissue may work if you don't have a cloth flexible enough to reach the whole surface of the tiny prism. , Periodically between uses, calibrate it to the correct reading by using pure, distilled water.
Add the water to the prism as you would for any liquid, and check whether the salinity reading is "0." If not, use a small screwdriver to adjust the calibration screw, typically found beneath a small cap on the top or bottom of the device, until the salinity reading is "0."A new, high-quality refractometer may only need calibration once every few weeks or months.
A cheaper, older refractometer may need to be calibrated before each use.
Your refractometer may come with calibration instructions that specify a certain water temperature.
If none are included, use room temperature distilled water.
About the Author
Shirley Jenkins
With a background in realestate, Shirley Jenkins brings 5 years of hands-on experience to every article. Shirley believes in making complex topics accessible to everyone.
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