Caution for anyone using a refractometer

[Doo]

I think you need to be a Chemist to put that together!

The other solution, will it work on all Refractometers or justthe PINPOINT ones??

Can you buy this stuff at a LPS?

[jasond]

I use RO as well....I might have to give this a shot...

[fencer]

Don't forget that density is dependent on temperature of your sample. Unless you have a correction factor your salt mix will be off.

[Doo]

ok - so how do I fix that?

My temp is at 79.0

[fencer]

I think you are okay. Most instruments are have a tolerance range. So you can be off on Temperature. Just as long as you do not mix salt at below 15 and I would say not much above 20C. Just be consistent when you make a batch of saltwater up.

[Reefer Rob]

Originally Posted by fencer

Don't forget that density is dependent on temperature of your sample. Unless you have a correction factor your salt mix will be off.

The 2 or so drops that you put on your refractometer will go to room temperature pretty quick Has anyone noticed a change in reading as the sample cools on the refractometer? I think the specific gravity may change with temperature, but not the refractive index.

[Canadian]

There's quite a large difference in the reading if you don't bring your sample up to (or down to) 25C - the temperature at which your calibration solution should be in order to get a reading of 35ppt. So bring the temperature of the solution up to 25C by placing the bottle in some hot water and then letting it come down while resting at room temperature.

[Reefer Rob]

Originally Posted by Canadian

There's quite a large difference in the reading if you don't bring your sample up to (or down to) 25C - the temperature at which your calibration solution should be in order to get a reading of 35ppt. So bring the temperature of the solution up to 25C by placing the bottle in some hot water and then letting it come down while resting at room temperature.

Do you warm your refractometer to 25C?

[fencer]

I know some refractometer have temp comp built in. There is a bimetaliic strip that move the vernier scale slightly with tempearture. Having said that look at the manufacturer specs.....

[Canadian]

Originally Posted by Reefer Rob

Do you warm your refractometer to 25C?

It sits in my stand which contains my HQI ballast and has an ambient temperature around 25C (which, incidentally, makes it a really bad place to store tests kits - hence my Elos kits are kept in the basement which remains relatively cool).

I also do not allow the drops to sit on the refractometer for any length of time before I take my reading - drops on, flip the lid and take the reading for both calibration and when taking tank readings.