Volume is 7 mL, durability of the open solution is 5 year (when stored in the dark place at room temperature).
The calibration should be done as close to 20 °C as possible!
The calibrated refractometer as well as the calibration liquid should have this temperature.
- TIP: leave the refractometer and calibration liquid in an environment with a temperature of 20 °C, the best for several tens of minutes, to allow their temperatures to equalize. Only then do the calibration.