Rhenium was discovered by Walter Noddack, Ida Noddack, and Otto Berg in Germany. In 1925, they reported that they detected the element in a platinum ore and in the mineral columbite. They also found rhenium in gadolinite and molybdenite. In 1928, they were able to remove 1 g of the element from 660 kg of molybdenite.
Rhenium is a silvery-white metal. It has the third highest melting points of all elements. It is also the third densest element.
Rhenium has one stable isotope which is rhenium-185. Rhenium that is found in nature is made up of of 37.4% rhenium-185 and 62.6% rhenium-187. Rhenium has 33 known radioisotopes. They range from rhenium-160 to rhenium-194. The longest-lived radioisotope of rhenium is rhenium-183 which have a half-life of 70 days.
Rhenium is one of the rarest elements in Earth's crust. It the 77th most abundant element in the Earth's crust. Rhenium may not be found free in nature. It is found in small amounts in the mineral molybdenite.
Commercial rhenium is gotten from molybdenum roaster-flue gas. Some molybdenum ores contain 0.001% to 0.2% rhenium. Rhenium metal is made by reducing ammonium perrhenate with hydrogen at high temperatures.
Nickel-based superalloys of rhenium are used in the combustion chambers, turbine blades, and exhaust nozzles of jet engines. Rhenium is used in superalloys, such as CMSX-4 (2nd generation) and CMSX-10 (3rd generation). These superalloys are used in industrial gas turbine engines like the GE 7FA. Rhenium filaments are used in mass spectrometers, ion gauges and photoflash lamps in photography. Rhenium-platinum alloys are used as a catalyst for catalytic reforming. Rhenium-188 and Rhenium-186 are used to treat of liver cancer.
Thallium
Thallium is a chemical element. It has the chemical symbol Tl. It has the atomic number 81. Its standard atomic weight is 204.4. It is found in Group 15 of the periodic table. Thallium is a gray metal that is very toxic.
Thallium is a soft, malleable, grayish post-transition metal. It can be cut with a knife at room temperature. It melts at a low temperature, 304 °C. This is typical of a post-transition metal. Thallium has 25 isotopes and two stable (nonradioactive) ones. It is extremely toxic.
Thallium is a moderately reactive metal. It corrodes easily in air with a blue-gray color that is similar to lead. If it is kept in air for a long time, a large amount of thallium(I) oxide will build up. It corrodes in the presence of water to make the hydroxide. It burns with a greenish flame. It reacts with most acids.
Thallium makes chemical compounds in two oxidation states: +1 and +3. The +1 state is more common and less reactive. Its chemical compounds are very similar to potassium or silver compounds. It makes a hydroxide that in a strong base when dissolved in water. Most other transition metal and post-tranansition metal hydroxides do not dissolve in water. This reacts with carbon dioxide to make thallium(I) carbonate, which is also water-soluble and very heavy. It is the only heavy metal carbonate that can dissolve in water. Other compounds are similar to silver compounds. Thallium(I) bromide turns yellow when exposed to light, similar to silver(I) bromide. Thallium(I) sulfide is black, similar to silver(I) sulfide. The +3 state compounds are oxidizing agents. The black oxide, thallium(III) oxide and the hydroxide, thallium(III) hydroxide, are the only stable +3 compounds. They break down to oxygen and thallium(I) oxide when heated. Thallium and its compounds are rare because they are toxic and polluting.
+1 compounds are quite unreactive. It is the more common oxidation state. They are made when thallium dissolves in acids or corrodes in air.
+3 compounds are oxidizing agents. They are quite rare.
Thallium was found by spectroscopy in 1861 by a bright green line in its spectrum. The main use for thallium, rat poison, was banned in many countries in the 1970s. Thallium was used to poison people, similar to the more popular arsenic.
Thallium is found most in certain clays and granites. It cannot be gotten easily from these, though. Thallium is normally gotten from the waste after other ores like galena are processed. Hutchinsonite is another mineral that has thallium in it.
When lead and zinc are taken from their ores, many impurities are left behind. Sulfuric acid is used to dissolve the thallium from it as thallium(I) sulfate. Then the thallium(I) sulfate is electrolyzed to make thallium metal.
It is used in rat poisons and insecticides. The use of thallium as a poison has been reduced or banned in many countries because these countries think that thallium might cause cancers. It is also used in infrared detectors. It has been used in some murders. Like arsenic, the use of thallium in murders has given it the name "inheritance powder". Thallium compounds are used in glass for infrared light. Thallium was also used to kill skin infections, but it is too toxic to be used for that now. A superconductor that can work at higher temperatures than normal ones do uses thallium. A radioactive thallium isotope was used for nuclear scans. An alloy of thallium and mercury has a low freezing temperature and is a liquid. A very dense solution of a thallium compound was used to test minerals for specific gravity, but it is too toxic for use.
Thallium is very toxic. It can be absorbed through skin. Many of its salts easily dissolve. Some are colorless, tasteless, and odorless, but are very toxic. Some think that it is a carcinogen. Thallium can be a pollutant if the thallium waste from metal processing is washed away.
Néstor Kirchner
Néstor Kirchner (February 25, 1950 - October 27, 2010) was President of Argentina between 2003 and 2007. He was born in Santa Cruz Province, Patagonia, where he was governor. On May 4, 2010 he became the first Secretary General of UNASUR. He died in Calafate on October 27, 2010 from heart failure which was caused by an earlier case of a heart attack. He was elected President in 2003, preceded by Eduardo Duhalde. Kirchner's widow, Cristina Fernández de Kirchner, is the current president of Argentina.
The Cunning Little Vixen
The Cunning Little Vixen (original title: "Příhody lišky bystroušky", literally translates to "The Adventures of Vixen Sharp-Ears") is an opera by the Czech composer Leoš Janáček. Janáček loved animals, and in this opera some of the characters are humans but some are animals. Some of the little animals, (like the grasshopper, frog and cricket) are usually sung by children.
Janáček got the idea of this opera from a cartoon strip called “Sharp-ears” (in Czech: "Bystrouška"). The cartoon was published in a popular daily newspaper Lidové noviny. It was about a vixen (a female fox) and her adventures in the forest. He thought that the story would make a good opera. He made a few changes to the story: he left out a some characters, changed the order of the story a little, and made the humans and the animals behave in a similar way. It was first performed in Brno on 6 November 1924.
When Janáček died in 1928 the last part of the opera was played at his funeral.
A forester is sleeping under a tree. Nearby a young vixen (here, vixen means baby fox) is playing. She nearly catches a frog, but the frog jumps away and lands on the forester’s nose. He wakes up and sees the little vixen playing. He catches the vixen and take her home with him. He gave her a name: “Sharp-ears”.
Sharp-ears is unhappy at the forester’s cottage. She is tied up with a rope in the yard. The hens keep teasing her and the dog is boring. One day she tells the hens that they are silly to stay in the farmyard being bossed about by the rooster. She tells them they ought to fly away to freedom. She pretends to die, then jumps up and starts to catch them. When the forester’s wife comes out Sharp-ears bites through the rope and disappears into the forest.