| slovo | definícia |
selenium
(encz) | selenium,selen n: Zdeněk Brož |
Selenium
(gcide) | Selenium \Se*le"ni*um\, n. [NL., from Gr. selh`nh the moon. So
called because of its chemical analogy to tellurium (from L.
tellus the earth), being, as it were, a companion to it.]
(Chem.)
A nonmetallic element of the sulphur group of atomic number
34, analogous to sulphur in its compounds. It is found in
small quantities with sulphur and some sulphur ores, and
obtained in the free state as a dark reddish powder or
crystalline mass, or as a dark metallic-looking substance. It
exhibits under the action of light a remarkable variation in
electric conductivity, and is used in certain electric
apparatus. Symbol Se. Atomic weight 78.96.
[1913 Webster] |
selenium
(wn) | selenium
n 1: a toxic nonmetallic element related to sulfur and
tellurium; occurs in several allotropic forms; a stable
grey metallike allotrope conducts electricity better in the
light than in the dark and is used in photocells; occurs in
sulfide ores (as pyrite) [syn: selenium, Se, {atomic
number 34}] |
selenium
(elements) | selenium
Symbol: Se
Atomic number: 34
Atomic weight: 78.96
Metalloid element, belongs to group 16 of the periodic table. Multiple
allotropic forms exist. Chemically resembles sulphur. Discovered in 1817
by Jons J. Berzelius.
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| | podobné slovo | definícia |
selenium cell
(encz) | selenium cell, n: |
Selenium
(gcide) | Selenium \Se*le"ni*um\, n. [NL., from Gr. selh`nh the moon. So
called because of its chemical analogy to tellurium (from L.
tellus the earth), being, as it were, a companion to it.]
(Chem.)
A nonmetallic element of the sulphur group of atomic number
34, analogous to sulphur in its compounds. It is found in
small quantities with sulphur and some sulphur ores, and
obtained in the free state as a dark reddish powder or
crystalline mass, or as a dark metallic-looking substance. It
exhibits under the action of light a remarkable variation in
electric conductivity, and is used in certain electric
apparatus. Symbol Se. Atomic weight 78.96.
[1913 Webster] |
selenium acids
(gcide) | Acid \Ac"id\, n.
1. A sour substance.
[1913 Webster]
2. (Chem.) One of a class of compounds, generally but not
always distinguished by their sour taste, solubility in
water, and reddening of vegetable blue or violet colors.
They are also characterized by the power of destroying the
distinctive properties of alkalies or bases, combining
with them to form salts, at the same time losing their own
peculiar properties. They all contain hydrogen, united
with a more negative element or radical, either alone, or
more generally with oxygen, and take their names from this
negative element or radical. Those which contain no oxygen
are sometimes called hydracids in distinction from the
others which are called oxygen acids or oxacids.
[1913 Webster]
Note: In certain cases, sulphur, selenium, or tellurium may
take the place of oxygen, and the corresponding
compounds are called respectively sulphur acids or
sulphacids, selenium acids, or tellurium acids.
When the hydrogen of an acid is replaced by a positive
element or radical, a salt is formed, and hence acids
are sometimes named as salts of hydrogen; as hydrogen
nitrate for nitric acid, hydrogen sulphate for
sulphuric acid, etc. In the old chemistry the name acid
was applied to the oxides of the negative or
nonmetallic elements, now sometimes called anhydrides.
[1913 Webster] |
selenium cell
(wn) | selenium cell
n 1: a photoelectric cell that uses a strip of selenium |
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