أكاديميا - كولنز - معاجم الجيب العلمية - الكيمياء - انكليزي - فرنسي - عربي الحرف ٤_ b

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bromine (Br₂)
brome m

Bromine. One of the elements of the halogen group. It is a volatile red liquid at normal temperature.
Bromine is highly corrosive, while its vapor is irritating and toxic.

Although bromine is less reactive than chlorine, it actively reacts with metals to form bromides:

(solid) MgBr - (liquid) Br2 + (solid) Mg

Bromine is extracted from seawater by treatment with chlorine. One thousand liters of seawater contains about 75 grams of bromine. Bromine is mainly used to produce silver bromide, which is used in photographic films and in the manufacture of 2.1-dibromoethene (ethylene dibromide), which is added to gasoline to avoid engine cylinders from stopping due to the accumulation of lead deposits. See octane rating.
2,1-dibromoethne


bronze
bronze m

bronze. The combination of copper (more than 90%) and tin (less than 10%) gives an alloy that is much stronger than copper. The discovery of bronze in the Middle East (around 3000 BC) led to important changes in the way of life Bronze Age Man. Today, bronze is mainly used in spoked wheels, engine mounts, and of course medals, such as those awarded in the Olympic Games and elsewhere.

Brownian motion
Mouvement m brownien

Brownian motion. Particles suspended in a liquid or gas, such as pollen particles in water or smoke in the air, appear to move randomly. The explanation for this is that the microscopic particles that make up the liquid or gas, such as water and air molecules, move randomly and collide with the larger particles of pollen or smoke, making them move. The Brownian motion was presented as evidence of kinetic theory.


brown ring test
essai m de l'anneau brun

Brown ring test. Test for nitrates.
When concentrated sul aqueous solution is carefully poured into an aqueous solution of phuric acid
For azotate to which an acidic solution of iron (II) sulphate is added, a brown ring is formed when the two layers of the liquid meet, and the resulting nitric acid reacts with iron (Ii) sulphate to produce the brown compound.

aqueous layer
Brown layer
Concentrated acid
(thick liquid)


burette
burette f

burette. A long glass tube inserted at the end
The lower spout, and every 1 cm is graduated into graduations
The smallest value is 0.1 cm cm. The buret is used in titration to accurately measure small volumes (up to 50 cm3) of liquid. The volume without the final scale at the bottom is called “dead space” because it is not used in measurement. See pipette.

Graduation.
Dead space.
faucet .


burner (or Bunsen burner)
brûleur m. bec m

Haraq (or Haraq Bunsen). A device invented in the 19th century to burn coal-gas cleanly and produce a hot flame. Natural gas is now used there. When the air hole is open, the gas mixes with the air, ensuring that all the gas is burned and no soot is produced. If the air hole is closed, the burner produces a sooty, yellow flame because the gas does not burn completely. See flame.

flame
episode
She denied
Air hole
Gas flow to the burner


burning combustion f

See combustion.


butane
butane m

Butane is an alkane compound, which is gaseous at normal temperature, but is easily liquefied. Butane is found (in solution) in petroleum and is used in oil refineries, whether as fuel or as a starting material for the production of hydrogen compounds and petroleum. It is one of the main components of “calor gas”.
This gas burns in the air:

C4H10 + 1302→8CO2 + 10H2O

(gas) (gas) (gas) (gas)


by-product
The product is delivered

Side product The side product of a reaction is what is produced in contrast to the desired product. For example, slag is a byproduct of making iron in a blast furnace, and carbon dioxide is a byproduct of the fermentation process. In order for the operations to be economical, means must be found to sell by-products. For example, slag is sold as a material for building roads.