Different Solutions to measure natural seawater?

[Mickey]

I just finished reading your article in the June Reefkeeping magazine and am a bit puzzled by something.

I understand the different solutions made to calibrate the different measuring instruments when I think about each individually. But when I think about the whole concept I am confused because each solution uses a different amount of salt and a different amount of water to make a solution with the same properties as natural seawater.

Since natural seawater is constant, couldn't I use just one of the solutions to calibrate each type of device?

Then again, perhaps the article was written because most aquarists would only have one of them rather than all of them, hence the need for a solution specific to the instrument.

Did I just answer my own question?

Mickey

[Randy Holmes-Farley]

Sorry, I didn't see this until now.

You can use natural seawater, of course, as that matches natural seawater in all respects. But using table salt, which is a different chemical, you cannot make one specific solution that has all of the same properties as natural seawater (specific gravity, refractive index and conductivity) regardless of what concentration it is.