An improved refractometer for automatically determining the refractive index of a test subject by using principles embodied in Brewster's Angle, the refractometer comprising a light source, a light detector, a subject mount for securing the test subject to the device, a positioning device to orient the light source and light detector to the subject such that the angles of the light source and light detector to the subject are substantially identical, a data gathering device to automatically retrieve relevant data regarding the angles of the light source and light detector to the subject and the light intensity of the reflected light, and a computational device to process the data using algorithms taking into account the principles embodied in Brewster's Angle and/or Fresnel Equations in order to arrive at the refractive index of the test subject.