1993 年 13 巻 Supplement2 号 p. 131-134
In flow visualization, difference of refractive indices of air, water and glass causes troubles. Some of them can be solved by making the refractive indices of glass and water, while it is impossible to match them between air and water.
Relatively low refractive index is expected in some kinds of fluoride glasses. An attempt is made to produce glass particles of a three-phase glass of MgF 2, CaF 2 and AlF 3, of which refractive index is slightly larger than that of water, i.e., 1.333. As dissolution of KI increases the refractive index of the solution, the produced particles virtually disappear in the water with addition of some KI. For the condition, the refractive index of water, which is the same as the particles, is measured by a refractometer and estimated to be 1.398.