Jean Charles Galissard de Marignac

Life and work Jean Charles Galissard de Marignac was born in Geneva on 24 April 1817, to Jacob Galissard de Marignac, a judge, and Susanne Le Royer, a sister of well-known chemist and physiologist Elie Le Royer. Le Royer's pharmacy was in the same building as their home. The following year was spent traveling and visiting well-known scientists. Marignac worked briefly with Justus von Liebig,

Marignac's name is well known for the careful and exact determinations of atomic weights. Whenever possible, he used at least two independent methods to assess a sample. He carried these out for long-identified elements and for newly proposed elements. By establishing well-defined values for a wide variety of elements, he seriously contributed to the underlying basis of inorganic chemistry. In 1880 he found gadolinium and samarium in the samarskite earths.

In 1858, he pointed out the isomorphism of the fluostannates and the fluosilicates, thus settling the then vexed question of the composition of silicic acid. Subsequently Marignac studied the fluorides of boron, tungsten, and other elements. He prepared silicotungstic acid, one of the first examples of the complex inorganic acids.

Marignac discovered that niobium and tantalum could be separated by fractional crystallization separation of potassium heptafluorotantalate from potassium oxypentafluoroniobate monohydrate, a process which was used commercially until displaced by solvent extraction separation of the same fluorides starting in the 1950s.

In physical chemistry, he carried out extensive research on the nature and process of solutions, investigating in particular the thermal effects produced by the dilution of saline solutions, the variation of the specific heat of saline solutions with temperature and concentration, and the phenomena of liquid diffusion.

Galissard de Marignac is buried with his wife Marie, née Dominicé, and their son Edouard (1849-1871) at the Cimetière des Rois, which is considered the Pantheon of Geneva.