Hand-held refractometer... what is Brix?

[hawaiiguy]

I just ordered a hand-held refractometer off of e-bay so I could measure salinity and spec. grav. It was advertized to measure both salinity and specific gravity but when I look into the eyepiece, the scale is in Brix%. My understanding is that Brix is some kind of sugar measurement. Is this refractometer useless for SW? Can you do some kind of conversion from Brix to salinity?

 

[Anonymous]

Yes, there is a "conversion" from Brix to salinity. However, if it is not what is advertized, you may want to talk to the seller regard this first.

To get it to work, you just need to "calibrate" it with some salt solution with know specific gravity.

Brix is used for testing the sweetness of grape for wine making, among others, I think.

 

[hawaiiguy]

can it be calibrated with RO/DI water?

 

[Anonymous]

The freshwater or RO/DI is for setting the zero point. You need salt water to find out what is the Brix reading for salinity of, say, 35 ‰.

Any optical refractmeter when properly calibrated, will give you 0‰ when you use tapwater or RO/DI. There is no need to set the zero point using RO/DI, but wasting three drops is no big deal.