reached. The effect is analogous to
the phenomenon of supercooling, i.e.
the cooling of a liquid below its
freezing point without freezing. See
also oscillating reaction.
bisulphate See hydrogensulphate.
bisulphite See hydrogensulphite;
aldehydes.
bite angle See chelate.
bittern The solution of salts remaining when sodium chloride is
crystallized from sea water.
bitumen See petroleum.
bituminous coal See coal.
bituminous sand See oil sand.
biuret test A biochemical test to
detect proteins in solution, named
after the substance biuret (H 2 NCONHCONH 2 ), which is formed when
urea is heated. Sodium hydroxide is
mixed with the test solution and
drops of 1% copper(II) sulphate solution are then added slowly. A positive
result is indicated by a violet ring,
caused by the reaction of *peptide
bonds in the proteins or peptides.
Such a result will not occur in the
presence of free amino acids.
bivalent (divalent) Having a valency of two.
Black, Joseph (1728–99) British
chemist and physician, born in
France. He studied at Glasgow and
Edinburgh, where his thesis (1754)
contained the Ürst accurate description of the chemistry of carbon dioxide. In 1757 he discovered latent
heat, and was the Ürst to distinguish
between heat and temperature.
blackdamp (choke damp) Air left
depleted in oxygen following the explosion of Üredamp in a mine.
black lead See carbon.
blanc Üxe See barium sulphate.
blast furnace A furnace for smelting iron ores, such as haematite
(Fe 2 O 3 ) or magnetite (Fe 3 O 4 ), to make
*pig iron. The furnace is a tall refractory-lined cylindrical structure that is
charged at the top with the dressed
ore (see beneficiation), coke, and a
Ûux, usually limestone. The conversion of the iron oxides to metallic
iron is a reduction process in which
carbon monoxide and hydrogen are
the reducing agents. The overall reaction can be summarized thus:
Fe 3 O 4 + 2CO + 2H 2 → 3Fe + 2CO 2 +
2H 2 O
The CO is obtained within the furnace by blasting the coke with hot
air from a ring of tuyeres about twothirds of the way down the furnace.
The reaction producing the CO is:
2C + O 2 → 2CO
In most blast furnaces hydrocarbons
(oil, gas, tar, etc.) are added to the
blast to provide a source of hydrogen.
In the modern direct-reduction
process the CO and H 2 may be produced separately so that the reduction process can proceed at a lower
temperature. The pig iron produced
by a blast furnace contains about 4%
carbon and further reÜning is usually
required to produce steel or cast iron.
blasting gelatin A high explosive
made from nitroglycerine and gun
cotton (cellulose nitrate).
bleaching powder A white solid
regarded as a mixture of calcium
chlorate(I), calcium chloride, and calcium hydroxide. It is prepared on a
large scale by passing chlorine gas
through a solution of calcium hydroxide. Bleaching powder is sold on
the basis of available chlorine, which
is liberated when it is treated with a
dilute acid. It is used for bleaching
paper pulps and fabrics and for sterilizing water.
bisulphate
74
b
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the phenomenon of supercooling, i.e.
the cooling of a liquid below its
freezing point without freezing. See
also oscillating reaction.
bisulphate See hydrogensulphate.
bisulphite See hydrogensulphite;
aldehydes.
bite angle See chelate.
bittern The solution of salts remaining when sodium chloride is
crystallized from sea water.
bitumen See petroleum.
bituminous coal See coal.
bituminous sand See oil sand.
biuret test A biochemical test to
detect proteins in solution, named
after the substance biuret (H 2 NCONHCONH 2 ), which is formed when
urea is heated. Sodium hydroxide is
mixed with the test solution and
drops of 1% copper(II) sulphate solution are then added slowly. A positive
result is indicated by a violet ring,
caused by the reaction of *peptide
bonds in the proteins or peptides.
Such a result will not occur in the
presence of free amino acids.
bivalent (divalent) Having a valency of two.
Black, Joseph (1728–99) British
chemist and physician, born in
France. He studied at Glasgow and
Edinburgh, where his thesis (1754)
contained the Ürst accurate description of the chemistry of carbon dioxide. In 1757 he discovered latent
heat, and was the Ürst to distinguish
between heat and temperature.
blackdamp (choke damp) Air left
depleted in oxygen following the explosion of Üredamp in a mine.
black lead See carbon.
blanc Üxe See barium sulphate.
blast furnace A furnace for smelting iron ores, such as haematite
(Fe 2 O 3 ) or magnetite (Fe 3 O 4 ), to make
*pig iron. The furnace is a tall refractory-lined cylindrical structure that is
charged at the top with the dressed
ore (see beneficiation), coke, and a
Ûux, usually limestone. The conversion of the iron oxides to metallic
iron is a reduction process in which
carbon monoxide and hydrogen are
the reducing agents. The overall reaction can be summarized thus:
Fe 3 O 4 + 2CO + 2H 2 → 3Fe + 2CO 2 +
2H 2 O
The CO is obtained within the furnace by blasting the coke with hot
air from a ring of tuyeres about twothirds of the way down the furnace.
The reaction producing the CO is:
2C + O 2 → 2CO
In most blast furnaces hydrocarbons
(oil, gas, tar, etc.) are added to the
blast to provide a source of hydrogen.
In the modern direct-reduction
process the CO and H 2 may be produced separately so that the reduction process can proceed at a lower
temperature. The pig iron produced
by a blast furnace contains about 4%
carbon and further reÜning is usually
required to produce steel or cast iron.
blasting gelatin A high explosive
made from nitroglycerine and gun
cotton (cellulose nitrate).
bleaching powder A white solid
regarded as a mixture of calcium
chlorate(I), calcium chloride, and calcium hydroxide. It is prepared on a
large scale by passing chlorine gas
through a solution of calcium hydroxide. Bleaching powder is sold on
the basis of available chlorine, which
is liberated when it is treated with a
dilute acid. It is used for bleaching
paper pulps and fabrics and for sterilizing water.
bisulphate
74
b
www.AzShimi.ir www.AzShimi.com