APPARATUS FOR INTENDING MEASUREMENT OF REFRACTIVE INDEX AND PARTICULARLY OF DENSITY OF LIQUID OR SUBSTANCE SOLVED IN LIQUID

摘要

PURPOSE: To enhance resistance against a liquid corroding a metal and the like by encasing a part of a rod having refractive index slightly larger than that of a liquid in a gas or vacuum thereby forming a total reflection surface. CONSTITUTION: A quartz tube 8 is fixed around a part of a rod 1. The tube 8 has a base part coupled with the rod 1 and an open top and an air layer 10 is formed between the wall of the rod 1 and the wall of the tube 8. When the rod 1 is immersed into a liquid 7 and irradiated with light from a light source 3, the light is reflected totally because the incident angle is larger than the critical angle on the boundary face between the quartz and the air. The light is reflected or refracted on the lower end 11 depending on the fact whether the incident angle is larger than the critical angle or not on the boundary face between the quartz and the air. Consequently, the quantity of light reflected on the lower end 11 depending on the concentration of liquid toward the rod 1 and impinging on a detector 5 is increased or decreased. According to the arrangement, the casing is not corroded and the refractive index or the concentration of the liquid 7 in a trough 6 can be measured.