Two triangular Liquid prisms

When light travels through a liquid, it is refracted in a certain way (refraction) and/or the light is dispersed (dispersion). A prism refracts light in separate colours. That is why it played an important role in the research into the extent to which fluids absorb light or let light pass. Most of the prisms shown here could be filled with carbon bisulphide. Carbon bisulphide has a large refractive index and a large dispersion. This makes the fluid very suited for eliminating the so-called chromatic aberration: blur and discolouration that occurs when observing through lenses. Earlier on, people solved this problem by combining different kinds of glass with different refractive indices. A combination of flint glass and crown glass was often used. However, as from around 1830, fluid prisms filled with carbon bisulphide became a popular alternative.