Clerici solution

The Clerici solution is a chemical solution of equal parts of thallium (Tl ( cho2 ) ) and Thalliummalonat (Tl ( C3H3O4 ) ) in water. It is a free-flowing, odorless liquid whose color changes with decreasing thallium salt concentration of yellowish to colorless. With a density of 4.25 g / cm ³ at 20 ° C, the saturated Clerici solution is one of the heaviest known aqueous solutions. It was discovered in 1907 by the Italian chemist Enrico Clerici and introduced in mineralogy and gemology in the 1930s as useful for the separation of minerals with the traditional principle of Archimedes. Their advantages are the transparency and the easy controllable density in the range of 1 to 5 g / cm ³. Moreover, the easy measurement of the density of advantage.

The density of the solution is so high that minerals such as spinel, corundum, diamond, and most grenade float on the solution. On heating the saturated solution of 20 to 90 ° C, the density of 4.25 to rise to 5.0 g / cm ³. The refractive index varies significantly, linear and highly reproducible with the density; thus, the density can be easily measured by optical methods.

A special feature is that the color of the solution changes significantly even at slight dilution with water: The concentrated solution at room temperature at a density of 4.25 g / cc amber and is already in dilution to the density of 4.0 g / cc similarly transparent as glass or water.

The generally applicable methods for measuring the density by means of this solution is as follows: In a small test tube with the concentrated solution, the crystal grain to be examined is placed a mineral, wherein the crystal grain floats on the surface. Then water is added dropwise until the crystal grain goes down, because the density of the fluid is then the same as the density of the mineral. The now reached density of the liquid is determined either directly by weighing or indirectly through its measured with an Abbe refractometer refractive index.

The disadvantage of this solution is its high toxicity and corrosiveness.