You use this solution the same way -- put a couple of drops on the refractometer and make sure the refracto reads 1.026. RO/DI calibration doesn't work so well even though that is what the manufacturer recommends. When I calibrate my refractometer using the 1.026 solution, it reads my 1.009 refrerence dead on, and reads below 0 for RO/DI. If I calibrate with RO/DI my 1.026 reads falsely high (i.e. it reads 1.028 when it should read 1.026). That is why it is better to calibrate with the high-quality reference.