Automatic Refractometer, J357 Offers Highest Performance for Research Labs. Designed as a research quality instrument the Rudolph J357 Automatic Digital Refractometer offers one of the highest measurement ranges of any instrument in the Rudolph refractometer product line. This instrument offers the same extra wide RI measurement range as our chemical industry refractometer models combined with the high accuracy of our food industry refractometer models. It also offers very powerful automatic electronic temperature control (heating and cooling) and is able to make RI and BRIX measurements at up to 100 °C. The J357 is a perfect choice for the most demanding pharmaceutical, chemical, petroleum, essential oils, fragrance and cosmetic refractometer users.