Karl Ernst Claus, also known as Karl Klaus or Carl Claus (; 22 January 1796 – 24 March 1864), but also as one of the first scientists who applied quantitative methods in botany.
In 1821, Claus married Ernestine Bate whom he knew since his youth. They had three daughters born in Kazan and later a son, when they moved back to Dorpat.
Chemistry
In 1828, when he already turned 32, Claus decided to continue his education at the University of Dorpat. During the course of his studies, in 1831, he started working as an assistant at the chemical laboratory of the university. He graduated in 1835, and in 1837, defended his PhD thesis on analytical phytochemistry ("Grundzüge der Analytischen Phytochemie") at the University of Dorpat. In the same year, he applied at the St. Petersburg Medical-Surgical Academy for an academic position and obtained a post of the head of chemical laboratory at Kazan State University. In 1839, he defended habilitation thesis on separation of minerals in mineral waters and was appointed an assistant professor. He became full professor in chemistry in 1844. Choosing the name for the new element, he stated: "I named the new body, in honour of my Motherland, ruthenium. I had every right to call it by this name because Mr. Osann relinquished his ruthenium and the word does not yet exist in chemistry."
Claus managed not only to isolate ruthenium, but also determine its atomic weight and chemical properties. He noted the similarity of the chemical properties of ruthenium, rhodium, palladium and platinum and meticulously documented his results. For this discovery, he was awarded the Demidov Prize of 5,000 rubles (which was of much financial help to his large family).
Health and late years
Claus was known for his negligent attitude towards his health. In particular, he often tasted his chemicals and new compounds and tested the strength of the acids by dipping a finger in them and touching his tongue with it. Once he severely burned his mouth while tasting one of the new ruthenium compounds that he had synthesized. When he isolated osmium tetroxide – a rather toxic chemical – he described its taste as astringent and pepper-like. In April 1845, he was poisoned by osmium tetroxide vapors and had to stop working for two weeks. In 1852, Klaus moved from Kazan back to the University of Dorpat and assumed position of professor in pharmacy. He died in Dorpat in 1864.