Jelley refractometer
The Jelley refractometer is an after its inventor Jelley called refractometer and serves the refractive index of liquids to be determined.
A horizontally lying gap S illuminated by a lamp serves as a secondary light source. As can be seen from the figure, the light falls horizontally through a gap-shaped opening O, behind which a glass microprism is glued to a glass carrier, so that a prism-shaped gap is created at the top between the glued prism and glass carrier. A tiny drop of the liquid to be examined is filled into this.
If the refractive index of liquid and glass are identical, the light beam will just pass through this arrangement. In the other cases the light beam is deflected upwards or downwards. If you now look through the opening O, the light beam seems to come from below or above the actual illumination opening S. A scale then shows the refractive index of the liquid directly.
The choice of the glass material of the microprism and thereby its refractive index influences the measuring range of the arrangement. The scale must be adjusted accordingly.
properties
The Jelley refractometer consists of a mechanically particularly simple, inexpensive to manufacture structure, achieves good precision of the measurement results, and only very small amounts of the liquid to be examined are required. However, it is very sensitive to use, the microprism is easily damaged if handled improperly.