Charcoal: Difference between revisions

Browse history interactively

← Previous edit Next edit →

Content deleted Content added

VisualWikitext

Inline

Revision as of 21:58, 12 April 2005

Charcoal is the blackish residue consisting of impure carbon obtained by

@@ Line 1: / Line 1: @@
 '''Charcoal''' is the blackish residue consisting of impure [[carbon]] obtained by
-removing water and other volatile constituents of animal and vegetable substances.
-It is usually produced by heating [[wood]] in the absence of [[oxygen]] (see [[char]]), but sugar
-charcoal, [[bone char|bone charcoal]] (which contains a great amount of [[calcium]] [[phosphate]]),
-and others can be produced as well.
-The light, black, porous material is 85% to 98% carbon, and resembles [[coal]].
-The first part of the word is of obscure origin.
-The independent use of "char", meaning to scorch, to reduce to carbon, is
-comparatively recent and must be a [[back-formation]] from the earlier charcoal.
-It may be a use of the word ''charren'', meaning to turn, i.e., wood changed or
-turned to coal; or it may be from the French ''charbon''. A person who manufactured charcoal was formerly known as a [[collier]], though the term was used later for those who dealt in [[coal]].
-===Production===
-Production of wood charcoal in districts where there is an abundance of wood dates
-back to a very remote period, and generally consists of piling billets of wood on
-their ends so as to form a conical pile, openings being left at the bottom to admit air,
-with a central shaft to serve as a flue.
-The whole  pile is covered with turf of moistened soil.
-The firing is begun at the bottom of the flue, and gradually spreads outwards
-and upwards.  The success of the operation depends upon the rate of the combustion.
-Under average conditions, 100 parts of wood yield about 60 parts by volume,
-or 25 parts by weight, of charcoal.
-The modern process of carbonizing wood either in small pieces or as sawdust
-in [[cast iron]] retorts is extensively practiced where wood is scarce, and also
-by reason of the recovery of valuable byproducts ([[wood spirit]], [[pyroligneous acid]],
-[[wood tar]]), which the process permits.
-The question of the temperature of the carbonization is important; according to
-J. Percy, wood becomes brown at 220&deg;C., a deep brown-black after some time at 280&deg;,
-and an easily powdered mass at 310&deg;.
-Charcoal made at 300&deg; is brown, soft and friable, and readily inflames at 380&deg;;
-made at higher temperatures it is hard and brittle, and does not fire until heated
-to about 700&deg;.
-===Use===
-One of the most important applications of wood charcoal is as a constituent of [[gunpowder]].
-It is also used in metallurgical operations as a reducing agent, but its application has been
-diminished by the introduction of [[coke (coal)|coke]], [[anthracite]] smalls, etc.
-A limited quantity is made up into the form of drawing [[crayon]]s; but the greatest
-amount is used as a [[fuel]], which burns hotter and cleaner than wood.
-Charcoal is often used by [[blacksmith]]s, for cooking, and for other industrial applications.
-The porosity of wood charcoal explains why it floats on the surface of water,
-although it is actually denser.
-This also accounts for its ability to readily absorb gases and liquids;
-charcoal is often used to filter water or absorb odors.
-Its pharmacological action depends on the same property; it absorbs the
-gases of the [[stomach]] and [[intestine]]s, and also liquids and solids (hence its
-use in the treatment of certain poisonings). Charcoal filters are used in some types of [[gas mask]] to remove poisonous gases from inhaled air.
-Wood charcoal has also the power of removing coloring matters from solutions,
-but this property is possessed in a much higher degree by animal charcoal.
-Animal charcoal or bone black is the carbonaceous residue obtained by the dry
-distillation of bones; it contains only about 10% carbon, the remainder being calcium
-and [[magnesium]] phosphates (80%) and other inorganic material originally present
-in the bones.
-It is generally manufactured from the residues obtained in the [[glue]]
-and [[gelatin]] industries.
-Its decolorizing power was applied in [[1812]] by Derosne to the clarification of
-the [[syrup]]s obtained in [[sugar]] refining; but its use in this direction has now greatly
-diminished, owing to the introduction of more active and easily managed reagents.
-It is still used to some extent in laboratory practice.
-The decolorizing power is not permanent, becoming lost after using for some time;
-it may be revived, however, by washing and reheating.
-Charcoal is used in art for drawing, making rough sketches in painting, and is one of the possible media for making a [[Surrealist_techniques#Parsemage|parsemage]].&#12288;&#12288;Bamboo charcoal is the principal tool in Japanese [[Sumi-e]] (&#28845;&#32117; lit: charcoal drawing) art.
-==See also==
-*[[Activated carbon]]
 [[da:Trækul]]
 [[de:Holzkohle]]