noun
definition
A nonmetallic chemical element (symbol Se) with an atomic number of 34, used mainly in glassmaking and pigments and as a semiconductor.
definition
A single atom of this element.
Examples of selenium in a Sentence
Owing to the variable illumination of the selenium thus produced, the resistance of the latter, and therefore the intensity of the current sent through the line to the receiving station by the battery, will be altered accordingly.
The mineral nearly always contains a small amount of silver, and sometimes antimony, arsenic, copper, gold, selenium, &c. Argentiferous galena is an important source of silver; this metal is present in amounts rarely exceeding %, and often less than o 03% (equivalent to 104 ounces per ton).
By means of this " light-relay " the intensity of the light acting at any moment upon the sensitized paper is made proportional to the illumination of the selenium in the transmitter.
It combines readily with fluorine, chlorine and bromine, and also with sulphur, selenium, phosphorus, &c.
A totally reflecting prism placed inside the glass cylinder projects the light which penetrates the film upon a selenium cell situated at the end of the cylinder.
To eliminate the sluggish action of the selenium transmitter a selenium cell similar to that at the transmitting station is arranged at the receiving apparatus, and exposed to precisely similar variations of light, the arrangement being such that the lag of this cell counteracts the lag of the transmitting cell.
Hittorf, who carefully investigated the effects produced by heat; crystalline selenium possesses a very striking property, viz.
The elements which go to form heterocyclic rings, in addition to carbon, are oxygen, sulphur, selenium and nitrogen.
The three primary members are furfurane, thiophene and pyrrol, each of which contains four methine or CH groups, and an oxygen, sulphur and imido (NH) member respectively; a series of compounds containing selenium is also known.
Now consider the effect of replacing sulphur by selenium.
Antimony, bismuth, selenium, tellurium, chromic iron ore, tin, nickel, cobalt, vanadium, titanium, molybdenum, uranium and tantalum are produced in the United States in small amounts, but such production in several cases has amounted to only slight discoveries, and in general they are of little importance in the market.
When there is appreciable absorption as in the case of the vapours of chlorine, bromine, iodine, sulphur, selenium and arsenic, luminosity begins at a red heat.
In the same year Berzelius discovered selenium in a deposit from sulphuric acid chambers, his masterly investigation including a study of the hydride, oxides and other compounds.
If, on the other hand, the sulphur system be replaced by a corresponding selenium system, an element of higher atomic weight, it would be expected that a slight increase would be observed in the vertical parameter, and a greater increase recorded equally in the horizontal parameters.
It may conveniently be extended to similar mixtures of sulphur and selenium or tellurium, of bismuth and sulphur, of copper and cuprous oxide, and of iron and carbon, in fact to all cases in which substances can be made to mix in varying proportions without very marked indication of chemical action.
Bismuth forms compounds similar to the trisulphide with the elements selenium and tellurium.
Small quantities are occasionally met with in iron pyrites, and hence tellurium is found with selenium in the flue dust, or chamber deposits of sulphuric acid works.
These substances, and also carbon, sulphur, selenium and tellurium, render the metal very brittle.
Such, for instance, were those of Spindler and Wrangell in the Black Sea by sinking an electric lamp, those of Paul Regnard by measuring the change of electric resistance in a selenium cell or the chemical action of the light on a mixture of chlorine and hydrogen, by which he found a very rapid diminution in the intensity of light even in the surface layers of water.
Crookes presumed that his thallium was something of the order of sulphur, selenium or tellurium; but Lamy, who anticipated him in isolating the new element, found it to be a metal.
The best raw materials for the preparation of thallium are the flue-dusts produced industrially in the roasting of thalliferous pyrites and the "chamber muds" accumulating in vitriol-chambers wrought with such pyrites; in both it is frequently associated with selenium.
Traces of gold, silver, selenium or thallium are sometimes present, and the mineral is sometimes worked as an ore of gold or silver.
The impurities contained in coarse-copper are mainly iron, lead, zinc, cobalt, nickel, bismuth, arsenic, antimony, sulphur, selenium and tellurium.
The principles have long been known on which is based the electrolytic separation of copper from the certain elements which generally accompany it, whether these, like silver and gold, are valuable, or, like arsenic, antimony, bismuth, selenium and tellurium, are merely impurities.
In this process, the residues are boiled with a dilute sulphuric acid to which nitric acid and potassium chlorate are added in order to transform the element into selenic acid, H 2 Se0 4, which is then reduced to selenious acid, H 2 Se0 3, by boiling with hydrochloric acid, and finally to selenium by sulphur dioxide.
The red crystalline variety is obtained by crystallization of selenium from carbon bisulphide, or by leaving the amorphous form in contact with the same solvent.
A colloidal selenium was obtained by C. Paal and C. Koch (Ber., 1905, 38, p. 526) by reducing selenious acid dissolved in an aqueous solution of sodium protalbate with hydrazine hydrate and hydrochloric acid, the precipitate obtained being then dissolved in sodium carbonate.
The specific gravity of selenium is 4.8; the specific heat varies from 0.0716 to 0.1147, depending upon the particular form.
Selenium combines directly with hydrogen when heated in the gas, and with fluorine in the cold.
Its aqueous solution is unstable, gradually depositing red selenium on standing.
It dissolves selenium.
Selenium dioxide, Se02, is prepared by burning selenium in oxygen, or by oxidizing selenium with nitric acid and heating the residue.
It is decomposed by hydriodic acid with liberation of selenium and iodine, and by ammonia with formation of selenium and nitrogen.
Selenious acid, H 2 SeO 3, is obtained in the crystalline form when a solution of selenium dioxide in water is concentrated over sulphuric acid.
Oxidizing agents readily convert it into selenic acid, whilst reducing agents transform it into selenium.
Selenium sulphoxide, SeS0 3, is formed as a yellowish crystalline mass when selenium is warmed with sulphur trioxide.
Selenosulphuric acid, H 2 SeS0 3, is only known in the form of its salts, which are usually obtained by the action of selenium on solutions of the metallic sulphites, a selenotrithionate being simultaneously produced.
It is readily decomposed by acids with liberation of sulphur dioxide and selenium.
It crystallizes in needles, possesses an alkaline reaction, and is readily decomposed by acids with liberation of selenium.
Numerous determinations of the atomic weight of selenium have been made.
The element combines directly with the halogens, sulphur and selenium, and most of the metals burn in its vapour forming phosphides.
All the thallium and selenium on the market is obtained from this source.
Arsenic compounds containing selenium and sulphur are known, such as arsenic seleno-sulphide, AsSeS2, and arsenic thio-selenide, AsSSe2.
Gross deficiency of dietary selenium may cause many heart problems, including arrhythmia.
Interactions Vitamin E exerts antioxidant effects in combination with other antioxidants including beta carotene, vitamin C and selenium.
Vitamin E and selenium supplements may prevent prostate cancer, although the evidence is not yet conclusive.
Lambs seriously deficient in copper, selenium or cobalt will fail to thrive.
I had the vet and it was mineral deficiency of cobalt, selenium and zinc, together with parasitic gastroenteritis caused by worms.
Selenium, itself an antioxidant, is required to activate one of the most important antioxidants found in the body, called glutathione.
Selenium Selenium is also important in the process of destroying hydrogen peroxide.