== Types of refractometers == There're four main types of refractometers: traditional handheld refractometers, digital handheld refractometers, laboratory or Abbe refractometers, and inline process refractometers. There's also the Rayleigh Refractometer used (typically) for measuring the refractive indices of gases. In veterinary medicine, a refractometer's used to measure the total plasma protein in a blood sample and urine specific gravity. The index of refraction's calculated from Snell's law… (More on Refractometer)