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Stibine

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Stibine is a chemical compound with the formula SbH3. It is a colorless and highly toxic gas. Scientists classify it as a pnictogen hydride. This means it is a hydride made from a pnictogen element. It is the main covalent hydride of antimony. You can think of it as a heavy version of ammonia. The molecule has a specific pyramidal shape. In this shape, the angles between hydrogen atoms are 91.7 degrees. The distance between the antimony and hydrogen atoms is 170.7 picometers.

Making stibine requires specific chemical reactions. One way to prepare it involves reacting antimony trioxide with lithium aluminum hydride. This reaction produces stibine, lithium oxide, and aluminum oxide. Another method uses antimony trichloride and sodium borohydride. This process results in stibine, sodium chloride, and boron trichloride. You can also produce this unstable gas by reacting sodium antimonide with protonic reagents like water. These different methods allow scientists to create the gas for study.

Stibine is a very unstable substance. It naturally wants to break down into its original elements. At room temperature, the gas decomposes at a slow rate. However, the decomposition happens very rapidly at 200 degrees Celsius. This decomposition is autocatalytic, which means the process helps itself continue. This reaction can even become explosive. The gas also reacts readily with oxygen in the air. This oxidation can result in the formation of a metastable yellow allotrope of antimony.

Researchers have studied stibine for many years. Lewis Thomson and Pfaff independently discovered the gas in 1837. For a long time, it was difficult to understand its properties. This was mainly because scientists lacked a reliable way to synthesize it. Francis Jones tested several different synthesis methods in 1876. It was not until 1901 that Alfred Stock determined most of the gas's properties. Stibine can also be detected using the Marsh test. This test was developed around 1836 by James Marsh to find arsenic.

In the modern world, stibine has specific industrial uses. It is used in the semiconductor industry to help make electronic components. Workers use a process called chemical vapour deposition, or CVD. During CVD, stibine is used to dope silicon with small amounts of antimony. Doping means adding tiny amounts of an element to change a material's properties. Stibine is also used as a dopant in epitaxial layers. While some reports claim it can be used as a fumigant, it is difficult to use. Its instability and complex preparation make it less common than phosphine.

Safety is a major concern when handling stibine. It is both an unstable and a highly flammable gas. The gas is also extremely toxic to living organisms. For example, the LC50 in mice is 100 parts per million. This number represents the concentration required to kill half of a test population. The toxicity of stibine is similar to a gas called arsine. Both gases are very dangerous to the human body.

When stibine enters the body, it affects the blood. The gas binds to the hemoglobin in red blood cells. Hemoglobin is the protein that carries oxygen through the body. This binding causes the body to destroy the red blood cells. Exposure symptoms may not appear for several hours. Initial signs include headaches, vertigo, and nausea. Eventually, this can lead to hemolytic anemia and kidney problems. These serious health effects make stibine a substance that requires extreme caution.

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