Isopycnic ultracentrifugation in nonaqueous solvents can be useful in identifying and studying properties of micro quantities of soluble and insoluble substances. Miscible pairs of high- and low-density solvents form the gradient in the centrifugal field. Choice of the liquid pair depends upon the refractivities as well as the densities of its components. Because of the high and unknown compressibility behavior of most useful nonaqueous solvent pairs of varying proportions, simple procedures and techniques have been devised to simultaneously calibrate the gradient and extract data pertaining to the species under study without prior thermodynamic study of the gradient pair. Schlieren optics were used in experiments with the Model E Spinco ultracentrifuge. Photographs derived from the experiments show sigmoid schlieren patterns representing soluble matter, and optically transmitting and nontransmitting bands representing insoluble matter. Cases have been observed wherein insoluble matter has shown nontransmitting bands and sigmoid patterns simultaneously. Qualitative interpretation of the photographs is discussed and quantitative treatment of the photographic data is described. A soluble polymer, insoluble soaps, and the insoluble gelled soaps of greases have been observed by the technique, and aspects of their behaviors are deduced from the data.