Central to chemistry is the periodic table of elements. The order of elements is determined by several characteristics, however, how did scientists know how to order the elements in the first place?
A particularly tricky group to order was the group of platinum metals, ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), and platinum (Pt). All six of these metals have relatively similar physical and chemical properties and also are found together in mineral deposits. They are, therefore, very difficult to separate from each other. And as the period table is ordered by atomic weights, separating them was necessary to attain this information.
Julia V. Lermontova tackled this question. Lermontova was the second woman in the world to receive a doctoral degree in chemistry. She did so in 1874 and, in 1875, became the second female member of the Russian Chemical Society. Next, Lermontova conducted research in organic chemistry in August Wilhelm Hofmann’s private lab in Berlin. Hofmann (1818-1892) was a German chemist, known for his contributions to organic chemistry. In his lab, Lermontova worked on diiodomethane or methylene iodide, which is an organoiodine compound. Organoiodine compounds are simply organic compounds containing carbon-iodine bonds. They are common in organic chemistry but rare in nature.
After working with Hofmann, Lermontova was allowed to conduct research in Vladimir Vasilyevich Markovnikov’s (1837-1904) organic chemistry lab at the University of Moscow. There, she worked on the synthesis of 1,2-dibromine propane and glutaric acid. In 1880, she began work in oil research, assisting Markovnikov in investigating the composition of Caucasian petroleum.
However, Lermontova is perhaps most well known for her work on platinum residues. This work was most likely conducted in the lab of German chemist Robert Wilhelm Eberhard Bunsen (1811-1899). Within the lab, she experimented with the separation of platinum metals and detailed her results in “Work on Platinum Residues,” an unpublished manuscript that is now held at the Mendeleev Archive in St. Petersburg.
Lermontova’s experimental work involved analyzing two samples. One contained mostly platinum and also palladium, iridium, and rhodium. The other contained all of the platinum metals except for osmium. In order to analyze these samples, she found compounds that were insoluble in water or other solvents. These could then each be separated out. For example, ruthenium was first separated out as Ba[RuCl6]. Lermontova described this procedure in great detail, in turn contributing to the determination of accurate atomic weights.