Cadmium discovery

A soft, silvery metal, cadmium has chemical properties that are similar to those of zinc. However, compared to zinc, cadmium is very rare. Cadmium sulfide ores are one source of this metal. It is also present in zinc ores, but in such small amounts that it is usually only produced as a by-product of zinc refining. Cadmiums discovery is even linked with zinc. In 1817, the German chemist Friedrich Strohmeyer (1776-1835) discovered cadmium when he was studying the compound zinc oxide. 

Several people in the 18th and 19th centuries attempted to produce a pure form of zinc oxide for medical purposes. They were unaware that their samples contained cadmium, which at that time was an unknown element. In 1817 Friedrich Strohmeyer (1776—1835), a German chemist, analyzed a zinc compound (calamine) he believed contained zinc oxide (ZnO). However, what he really found was zinc carbonate (ZnCO ), which, though at first unknown to him, contained some cadmium. Strohmeyer then treated his sample with acids until all the zinc was dissolved and thus removed. He then heated the residue with carbon black, resulting in a small ingot of soft, bluish-white metal that proved to be a new element—cadmium. Strohmeyer is given credit for the discovery of cadmium. 

Indium, like cadmium, was first discovered in substances of which it is only a non-essential constituent. Clemens Winkler said in 1867, "True indium minerals have not yet been discovered. So far as I know, indium has been detected up to the present only in a few zinc blendes in those of Freiberg, the spectral-analytical investigation of which led to the discovery of the new metal, and in the black blende, or christophite, of Breitenbrunn in Saxony, which I analyzed at the request of Mining Superintendent Breithaupt and found to contain 0.0062 per cent of indium. However, I could not detect indium in black blende of Turcz, Hungary, which is closely related to christophite, nor in Silesian calamine and the zinc and cadmium obtained from it. Bottger finally found indium in the flue dust of the zinc... 

Solar-based strategies for the conversion of the sun s light to electrical and chemical energy required the discovery of a new generation of specifically designed and engineered photonic materials. Examples of these inorganic semiconductors include those based on amorphous silicon, cadmium telluride, and more complex ternary or quaternary combinations such as copper iridium diselenide or dye-sensitized semiconductors. 

Since the discovery in the Eighteenth Century of scrotal cancer in young chimney sweeps caused by exposure to soot, epidemiological studies have identified a considerable number of human carcinogens. The list includes cigarette smoke, asbestos, benzene, vinyl chloride, nickel, chromium, cadmium, alcohol, ionizing radiation, radon, benzidine and arsenic (1). Many of these discoveries have come from studies of workers in various industries. 

Organozinc compounds are historically important39 since they were the first organometallic compounds to be prepared their discovery by Frank-land in 1849 played a decisive part in the development of modern ideas of chemical bonding. The zinc and cadmium compounds are also of interest since their mild reactivities toward certain organic functional groups give them unique synthetic potentialities. 

More evidence for the essentiality of cadmium is now available after the ten-fold repetition of the cadmium-deficiency experiments with growing, pregnant and lactating goats and their kids, and the discovery of a cadmium-specific carboanhydrase in the diatom Thallasia sir a weissflogii (Strasdeit... 

The neutrino plays an essential role in the models of elemoitaiy particles and in the theory of the formation and development of the universe. The existrace of the neutrino was predicted by Pauli in 1927 but it was not proven until 1956 when Reines and Cowan detected them in experiments at the Savannah River (USA) nuclear reactor. Since neutrinos are emitted in the j3-decays following fission, nuclear reactors are the most intense neutrino sources on earth. The detector in the discovery experiments consisted of a scintillating solution containing cadmium surrounded by photomultipliers to observe the scintillations which occurred as a consequoice of the following reactions ... 

The initial tests of the sodium dispersion-metal halide system were made with ferric chloride, fortunately, and with a nonaqueous solvent in which ferric chloride was soluble. Thus, ferric chloride was present as a solution and, consequently, presented maximum surface for contact with the sodium particles. This feature, coupled with the lower activation energy requirements, permitted the reaction to proceed at temperatures well below room temperature and established the operability of the method. The success of the initial (ferric chloride) tests lent encouragement to tests on other metal systems and prompted continued investigations when the initial runs at lower temperatures failed. The discovery of the threshold, or trigger, temperature for nickel (II) chloride reduction paved the way for successful reduction of other metal halides such as manganese (II) chloride, cobalt (II) chloride, and cadmium bromide. 

Even though MTs exist naturally with zinc and/or copper bound to them, the discovery of the first MT in 1957 from horse kidney was the result of a search for a cadmium protein. Since then, MTs have continuously challenged the interest of chemists and life scientists. A search in the SciFinder database with metallothionein as the entry yields about 15,000 publications and reveals more than 700 articles per year over the 1991-2001 decade. It also shows that developments in MT research have been covered by about 300 reviews. The widespread occurrence of MTs in nature suggests that they serve an important biological function not yet completely established. It would appear that MTs have no enzymatic activity, nor do they perform any catalytic role in known metabolic processes. Precise identification of the function of MTs accounts for the outstanding number of works available (as indicated by the search results) and prompts most of the research currently being undertaken. 

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