Salinity

[Randy Holmes-Farley]

Is the iodized salt replaceable with table salt?

For this purpose, yes, especially if you are weighing it rather than by volume.

The biggest issue with volume measurement is how "fluffy" any given brand might be.

 

[Randy Holmes-Farley]

Do you have a particular brand or model you use/like?

I have used an old Orion Model 128 conductivity probe for many years, which uses a 4 electrode sensor. Some folks get them used on ebay for not that much. It has a much wider range than many cheap/modern conductivity units.

I've used the Pinpoint and it is fine, but responds more slowly to changes (reads slower when first put in water) and cannot tell you the temperature.

 

[JoshO]

For this purpose, yes, especially if you are weighing it rather than by volume.

The biggest issue with volume measurement is how "fluffy" any given brand might be.

So 6.2g salt mixed with water (I'll use RO for a level of control) would work? Then this solution at any temperature between 20 and 25 will give an accurate enough reading of 1.026 on a refractometer?

 

[Randy Holmes-Farley]

So 6.2g salt mixed with water (I'll use RO for a level of control) would work?

Depends on how much water and what device you are checking. lol

Each device has a different standard to give 35 ppt seawater equivalent. Two of them happen to use 6.2 grams with different amounts of water.

 

[JoshO]

Depends on how much water and what device you are checking. lol

Each device has a different standard to give 35 ppt seawater equivalent. Two of them happen to use 6.2 grams with different amounts of water.

I edited the previous post, wasn't quick enough doing so lol. It would be for use on a refractometer, any temperature between 20 & 25 would be accurate enough to give a reading of 1.026?

 

[Randy Holmes-Farley]

I edited the previous post, wasn't quick enough doing so lol. It would be for use on a refractometer, any temperature between 20 & 25 would be accurate enough to give a reading of 1.026?

If it is an ATC refractometer, it should not matter what the temp is within the ATC range, and I have never understood the reseller claim that it does matter. That tidbit makes no sense to me, and I've questioned it for many years.

If it is a brine refractometer, pick the ppt scale or the sg scale, and calibrate it to that one and always use that scale. 35 ppt will not match sg = 1.0264 on such a refractometer, and so you cannot simultaneously calibrate both perfectly. Pick one scale and stick to it.

In fact, this is a way to know if you have a true seawater refractometer or a brine refractometer. For seawater, 35 ppt and sg = 1.0264 will be approximately across from one another. In a brine refractometer, 35 ppt will be across from about 1.025.

 

[JoshO]

If it is an ATC refractometer, it should not matter what the temp is within the ATC range, and I have never understood the reseller claim that it does matter. That tidbit makes no sense to me, and I've questioned it for many years.

If it is a brine refractometer, pick the ppt scale or the sg scale, and calibrate it to that one and always use that scale. 35 ppt will not match sg = 1.0264 on such a refractometer, and so you cannot simultaneously calibrate both perfectly. Pick one scale and stick to it.

In fact, this is a way to know if you have a true seawater refractometer or a brine refractometer. For seawater, 35 ppt and sg = 1.0264 will be approximately across from one another. In a brine refractometer, 35 ppt will be across from about 1.025.

I'm glad you've mentioned this! It's a red sea SEAWATER refractometer, the case even mentions that sodium chloride solution would differ by about 1.5ppt...yet based off of what you've just said it's actually a brine refractometer as 35ppt is opposite 1.025.
With the solution of 6.2g salt and 161ml of water, would this register as 35ppt this?

 

[Randy Holmes-Farley]

The beauty of the calibration solution is that it doesn't matter which type of refractometer it is. You can still calibrate it to 35 ppt, or to sg = 1.0264 if you use sg more often.

 

[JoshO]

The beauty of the calibration solution is that it doesn't matter which type of refractometer it is. You can still calibrate it to 35 ppt, or to sg = 1.0264 if you use sg more often.

Thanks for the help, I'll be making some up tomorrow!

 

[Rmckoy]

Do conductive And refractometer require calibration fluid ?