I just want to say how pleased we are with our Rudolph J 157 Automatic Refractometer. We use it in the Production Lab where it is just as accurate as our standard abbe type refractometers. It is preferred over the Abbes because you can put a sample on, then walk away and do other things while the refractometer reaches the desired temperature and displays the refractive index. It eliminates human error that causes one to get slightly different readings of the same sample by the same person or between different people. The Rudolph refractometer has a well to fill with the sample.
This is an advantage over the sample being placed between the prisms of the abbe refractometer. Low viscosity liquids leak out of the closed abbe prisms but not out of the Rudolph well. Also the Rudolph system works better than the abbe type when reading volatile liquids such as ethyl ether or other solvents.
Keep up the good work. My only suggestion is to increase the refractive index range to 1.300 to 1.700. This would be very useful to us.
Research and Quality Control Scientist