752 36 Uppsala, Sweden
Сleve began his studies of chemistry and botany in 1858 in Uppsala; he was awarded the Ph.D. in 1863.
Cleve began his studies of chemistry and botany in 1858 in Uppsala, having learned the basic principles of mineralogy in Stockholm from Mosander, the discoverer of lanthanum, didymium, erbium, and terbium. In his dissertation Cleve discussed mineral analysis; he was awarded the Ph.D. in 1863.
Through his works in widely separated areas of natural science, Cleve assumed a leading role in Swedish research in the natural sciences during the last decades of the nineteenth century and surrounded himself with an ever-increasing number of disciples.
After only five years of research, Cleve was appointed an assistant professor in chemistry at Uppsala University. He also taught chemistry at the Technological Institute in Stockholm until 1874, when he became a professor in general and agricultural chemistry in Uppsala. He was the president of the Royal Swedish Academy of Science’s Nobel Prize committee for chemistry from 1900 to 1905 and was a member of several foreign learned societies.
His first work, “Några ammoniakaliska chromföreningar” (“Some Compounds,” 1861), was soon followed by four other papers on complex metal compounds, and in still others, he described syntheses of a multiple of new complex compounds, until in 1872 he ended this series of analyses with a detailed epitome in English, “On Ammoniacal Platinum Bases.”
Cleve then began a series of analyses of the rare earth metals, in particular, ytterbium, erbium, lanthanum, and didymium. He prepared numerous new compounds of these metals and could, as a consequence, confirm Mendeleev’s prediction that they would prove to be trivalent. He also expressed the suspicion that didymium was not an element, which was confirmed eleven years later, in 1885, when Welsbach divided it into neodymium and praseodymium. Of the new element scandium, which Nilsson had discovered in 1879, Cleve isolated, in the same year, a quantity big enough to determine reliably its atomic weight; this made it possible for him to identify the element with Mendeleev’s ekabor, the existence of which had been predicted eighteen years earlier. Cleve’s exhaustive researches on the chemistry of the rare earth metals was crowned in 1879 with his discovery of two more new elements, holmium and thulium, and with the publication of a monograph on samarium, discovered by Boisbaudran in the same year.
Cleve was active in organic chemistry as well, and several of his papers testify to his interest in the chemistry of naphthalene, which he enriched with, among other things, his discoveries of six of the ten possible dichlorine naphthalenes. He also discovered those aminosulfon acids that were known for some time as “Cleve’s acids.”
Cleve devoted the last fifteen years of his life almost exclusively to completing the biological works that he had started in his youth. His earliest studies were of the Swedish freshwater algae, to which he had devoted two monographs. Little by little, he began to specialize in the plankton that creates diatoms; his intensive researches soon brought him to the position of being the greatest authority of his time in this area.
Cleve's method of determining the age and order of deposits in late glacial and postglacial stratifications, based on the diatomaceous flora in mud, proved to be scientifically useful. His idea that diatoms make good index fossils was further stated in the hypothesis that the streams in the oceans could be characterized by the plankton they transport and, conversely, that through the existence of one type of plankton one can determine the origin of the stream. His main work on this subject, The Seasonal Distribution of Atlantic Plankton Organisms, is a basic text of oceanography.
Cleve was a supporter of women's equality and Ellen Fries, the first Swedish woman to receive a Ph.D., was one of his students.
In 1874, Cleve married Alma Öhbom, a teacher; the couple had three daughters.