BIO-ORGANIC CHEMISTRY QUARTERLY REPORT DEC. 1960 THROUGH FEB.1961

The current interest in the subject of fiber optics has brought about, among its many achievements, the development of a new technique for measuring refractive index. An instrument designed as a light-pipe refractometer or rod photorefractometer has been described by Kapany and Pike. these authors have presented both a theoretical study of the phenomenon and experimental results arising from a prototype apparatus. The range of applicability of such a device is limited, however, by the availability of rod materials having suitable refractive indices. In particular, the available solid material which has the lowest refractive index and which is also transparent is fused quartz (n{sub D} = 1.458). For reasons inherent in the geometry of the photorefractometer optics, the use of quartz rods does not permit high sensitivity of measurement on liquids having refractive index values less than 1.44. Aqueous solutions, therefore, are beyond the range of study of a system using solid rods. Kapany and Pike suggested the possibility of replacing the solid rod with a hollow cylindrical glass tube filled with a standard liquid. In this manner the effective refractive index of the light pipe is that of the reference liquid and can be varied over the complete range of refractive index for which liquids are available. Under these conditions the refractive index of the solid tube material now serves as an upper limit to the range of applicability. To date no experimental results using a hollow-tube refractometer have been reported, however. In the study presented here a photorefractometer cell incorporating a liquid light pipe has been constructed, and experimental results are reported on solutions in both water and methanol as solvents. These solutions would not be capable of sensitive refractive index measurement using a solid-rod photorefractometer. In addition, some experiments have been carried out toward determining the refractive dispersion curves of colored substances, and some difficulties inherent in these measurements are discussed