What Is a Desiccator?
A desiccator is a chamber or box that is
designed to absorb water vapor from
reactants that are hygroscopic . Hygroscopic
reagents are able to absorb water. This can
cause a problem when it comes to measuring
the appropriate amounts of a particular
chemical. The desiccator reduces this effect
and helps to ensure accurate measurements
of chemicals prior to the start of a chemical
reaction. In other words, desiccators are used
to dry any chemicals that may be used in
reactions.
A Dessicator Containing a Dessicant
Desiccators are usually sealed so that outside
air cannot enter the chamber. In some cases,
desiccators may also be fitted with a vacuum
hose in order to remove excess air from the
inside of the chamber. A desiccant , or drying
material, is usually added to the desiccator to
absorb water vapor whenever the desiccator
is opened. Calcium chloride (a salt) and silica
gel (a non-reactive solid) are two typical
desiccants that are used routinely. The
desiccants ensure that water vapor is
absorbed before it reaches the reactant
Wednesday 11 November 2015
Dessicator 2
Dessicator 1
Desiccators are sealable enclosures
containing desiccants used for preserving
moisture -sensitive items such as cobalt
chloride paper for another use. A common use
for desiccators is to protect chemicals which
are hygroscopic or which react with water
from humidity .
The contents of desiccators are exposed to
atmospheric moisture whenever the
desiccators are opened. It also requires some
time to achieve a low humidity. Hence they
are not appropriate for storing chemicals
which react quickly or violently with
atmospheric moisture such as the alkali
metals; a glovebox or Schlenk -type apparatus
may be more suitable for these purposes.
Desiccators are sometimes used to remove
traces of water from an almost-dry sample.
Where a desiccator alone is unsatisfactory,
the sample may be dried at elevated
temperature using Abderhalden's drying pistol .
Use
In order to weigh a substance, watch glass or
weighing bottles or crucibles are used. But to
be accurate, the weighed object must be of
the same temperature of the analytical
balance . If a hotter (or colder) object is
placed on a balance pan this has the effect of
lengthening (or shortening) the corresponding
arm of the beam resulting in incorrect
reading. Moreover, a hot object warms the air
in contact with it and makes it rise. The
moving air pushes the corresponding balance
pan upwards and therefore the error is
increased further. Conversely, if a cold object
is weighed, a current of air flows downwards
and this gives rise to an error of the opposite
sign. Thus, the object must be left 20 minutes
to reach room temperature .
To prevent adsorption of moisture from the
surrounding air, glassware is cooled in a
desiccator. [1]
Constituents
The lower compartment of the desiccator
contains lumps of silica , freshly calcined
quicklime or (not as effective) anhydrous
calcium chloride to absorb water. The
substance is put in the upper compartment.
The ground-glass rim of the desiccator lid
must be greased with a thin layer of
petroleum jelly or other lubricant to ensure an
airtight seal
In order to prevent damage to a desiccator
the lid should be carefully slid on and off
instead of being directly placed onto the base.
[1]
Operation
In laboratory use, the most common
desiccators are circular and made of heavy
glass . There is usually a removable platform
on which the items to be stored are placed.
The desiccant, usually an otherwise-inert solid
such as silica gel, fills the space under the
platform. Colour changing silica may be used
to indicate when it should be refreshed.
Indication gels typically change from blue to
pink as they absorb moisture but other
colours may be used.
A stopcock may be included to permit the
desiccator to be evacuated. Such models are
usually known as vacuum desiccators. When a
vacuum is to be applied, it is a common
practice to criss-cross the vacuum desiccator
with tape, or to place it behind a screen to
minimize damage or injury caused by an
implosion . To maintain a good seal, vacuum
grease is usually applied to the flanges .
Chevron, others lift Ogun school with science laboratory
The Star Deep Water Petroleum Limited, a Chevron Company, has deepened the teaching and learning of science subjects by inaugurating modern science laboratory in Ibogun Comprehensive High School, Ibogun, Ogun State.
Apart from SDWPL, other partners involved in the initiative were Famfa Oil Ltd, Nigerian National Petroleum Corporation, Statoil Nigeria Ltd and Petroleo Brasileiro Nigeria Ltd.
The Managing Director, Star Deep Water Petroleum Limited, Mr. Clay Neff, said the donation of the science laboratory was one of the company’s programmes in its social investment plan aimed at improving the teaching and learning of science subjects in Nigeria’s secondary schools.
Neff, who was represented by a director in the company, Mr. Jeffery Ewing, noted that education was key to unlocking the potential of youths and developing their capacity for societal relevance.
He said, “This particular project is a product of our efforts to help generate improved access to education for all Nigerians through the donation of science laboratory complexes, electronic libraries and scholarships.”
The chairman, Famfa Oil Ltd, Modupe Alakija, said the nation could only develop through science and technology.
She said, “One of the ways of achieving this is through progression in education, especially, science and technological education.”
Alakija, who was represented by the company’s facility manager, Atolagbe Oyeyemi, said the laboratory would help advance the course of science education in the school and beyond.
The representative of Statoil, Mrs Yvonne Yaduma, also said the project would assist the government in providing qualitative education to the people.
The principal of the school, Mr. Oladosu Ajao, commended the companies for the gesture and called on other corporate organisations to emulate them.
Former president Chief Olusegun Obasanjo, who is a native of Ibogun, was also there and he equally commended the donors.
Tuesday 10 November 2015
Chevron, others lift Ogun school with science laboratory
The Star Deep Water Petroleum Limited, a Chevron Company, has deepened the teaching and learning of science subjects by inaugurating modern science laboratory in Ibogun Comprehensive High School, Ibogun, Ogun State.
Apart from SDWPL, other partners involved in the initiative were Famfa Oil Ltd, Nigerian National Petroleum Corporation, Statoil Nigeria Ltd and Petroleo Brasileiro Nigeria Ltd.
The Managing Director, Star Deep Water Petroleum Limited, Mr. Clay Neff, said the donation of the science laboratory was one of the company’s programmes in its social investment plan aimed at improving the teaching and learning of science subjects in Nigeria’s secondary schools.
Neff, who was represented by a director in the company, Mr. Jeffery Ewing, noted that education was key to unlocking the potential of youths and developing their capacity for societal relevance.
He said, “This particular project is a product of our efforts to help generate improved access to education for all Nigerians through the donation of science laboratory complexes, electronic libraries and scholarships.”
The chairman, Famfa Oil Ltd, Modupe Alakija, said the nation could only develop through science and technology.
She said, “One of the ways of achieving this is through progression in education, especially, science and technological education.”
Alakija, who was represented by the company’s facility manager, Atolagbe Oyeyemi, said the laboratory would help advance the course of science education in the school and beyond.
The representative of Statoil, Mrs Yvonne Yaduma, also said the project would assist the government in providing qualitative education to the people.
The principal of the school, Mr. Oladosu Ajao, commended the companies for the gesture and called on other corporate organisations to emulate them.
Former president Chief Olusegun Obasanjo, who is a native of Ibogun, was also there and he equally commended the donors.
HISTORY OF OSAMA BIN LADEN EARLY LIFE
Osama bin Laden was born in Saudi Arabia, a country in the Middle East. His father owned a big construction company. Like most other Saudi Arabians, the bin Ladens were followers of Islam. People who follow Islam are called Muslims.
Young Osama embraced a special view of Islam. He accepted fundamentalist teachings. He believed that Muslims should live as they did when Islam began 14 centuries ago.
WHAT DID BIN LADEN WANT?
Bin Laden wanted to fight those who he saw as enemies of Muslims. In 1979, he got his chance. A communist country, the Soviet Union, invaded Afghanistan, a Muslim country. Bin Laden went to Afghanistan to fight the Soviets.
In 1988, while in Afghanistan, bin Laden founded a group called al-Qaeda. (Al-Qaeda is an Arabic phrase that means “the Base”.) Bin Laden wanted al-Qaeda to lead a jihad (holy war) against all nations that he considered to be against Islam.
In 1989, the Soviets left Afghanistan. Bin Laden returned to live in Saudi Arabia. Then in 1991, the United States led a war against the Muslim country of Iraq. During that war, the United States based troops in Saudi Arabia. Now bin Laden declared that the United States was the main enemy of Islam.
BIN LADEN AND TERRORISM
In 1992, bin Laden moved to Sudan, an African country ruled by Muslims. From there, he began to direct terrorist attacks by al-Qaeda. In a terrorist attack, individuals or small groups hurt or kill ordinary people. They do this to create fear among their enemies.
Bin Laden was accused of planning several big terrorist attacks over the next eight years. In 1993, a bomb damaged the World Trade Center in New York City. In 1996, terrorists blew up an apartment building in Saudi Arabia, where many Americans lived. In 1998, two U.S. embassies in Africa were bombed, killing hundreds of people. In 2000, an attack on the U.S. Navy ship Cole killed 17 sailors.
TERRORIST ATTACKS ON AMERICAN SOIL
Then came al-Qaeda’s biggest terrorist attack of all. On September 11, 2001, a group of men hijacked four airplanes. They flew two of them into the twin towers of the World Trade Center. Another airplane crashed into the Pentagon near Washington, D.C. Another crashed in Pennsylvania. The attacks killed about 3,000 people.
The United States struck back by bombing Afghanistan. That’s where bin Laden was hiding as a guest of the country’s ruling group. The bombing forced this group, the Taliban, to flee. But bin Laden was not found.
Froth Flotation
Froth flotation is considered to be the most widely used method for ore beneficiation. In ore beneficiation, flotation is a process in which valuable minerals are separated from worthless material or other valuable minerals by inducing them to gather in and on the surface of a froth layer. Sulfide and non-sulfide minerals as well as native metals are recovered by froth flotation. This process is based on the ability of certain chemicals to modify the surface properties of the mineral(s). Other chemicals are used to generate the froth and still others are used to adjust the pH. Certain chemicals are even capable of depressing the flotation of minerals that are either to be recovered at a later time or are not to be recovered.
The process of froth flotation entails crushing and grinding the ore to a fine size. This fine grinding separates the individual mineral particles from the waste rock and other mineral particles. The grinding is normally done in water with the resultant slurry called the pulp. The pulp is processed in the flotation cells, which agitate the mixture and introduce air as small bubbles.
The ability of a mineral to float depends upon its surface properties. Chemical modification of these properties enables the mineral particles to attach to an air bubble in the flotation cell. The air bubble and mineral particle rise through the pulp to the surface of the froth or foam that is present on the flotation cell. Even though the air bubbles often break at this point, the mineral remains on the surface of the froth. The mineral is physically separated from the remaining pulp material and is removed for further processing.
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Monday 9 November 2015
Cellulose
Cellulose is an organic compound with the formula (C6H10O5)
n, a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1→4) linked D-glucoseunits.[3][4] Cellulose is an important structural component of the primary cell wall of green plants, many forms ofalgae and the oomycetes. Some species of bacteria secrete it to form biofilms.[5]Cellulose is the most abundant organic polymer on Earth.[6] The cellulose content of cotton fiber is 90%, that ofwood is 40–50% and that of dried hempis approximately 45%.[7][8][9]
Cellulose is mainly used to producepaperboard and paper. Smaller quantities are converted into a wide variety of derivative products such ascellophane and rayon. Conversion of cellulose from energy crops intobiofuels such as cellulosic ethanol is under investigation as an alternative fuel source. Cellulose for industrial use is mainly obtained from wood pulp andcotton.[6]
Some animals, particularly ruminantsand termites, can digest cellulose with the help of symbiotic micro-organisms that live in their guts, such asTrichonympha. In humans, cellulose acts as a hydrophilic bulking agent for fecesand is often referred to as a "dietary fiber".
Cellulose
Cellulose is an organic compound with the formula (C6H10O5)
n, a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1→4) linked D-glucoseunits.[3][4] Cellulose is an important structural component of the primary cell wall of green plants, many forms ofalgae and the oomycetes. Some species of bacteria secrete it to form biofilms.[5]Cellulose is the most abundant organic polymer on Earth.[6] The cellulose content of cotton fiber is 90%, that ofwood is 40–50% and that of dried hempis approximately 45%.[7][8][9]
Cellulose is mainly used to producepaperboard and paper. Smaller quantities are converted into a wide variety of derivative products such ascellophane and rayon. Conversion of cellulose from energy crops intobiofuels such as cellulosic ethanol is under investigation as an alternative fuel source. Cellulose for industrial use is mainly obtained from wood pulp andcotton.[6]
Some animals, particularly ruminantsand termites, can digest cellulose with the help of symbiotic micro-organisms that live in their guts, such asTrichonympha. In humans, cellulose acts as a hydrophilic bulking agent for fecesand is often referred to as a "dietary fiber".
Magnetic Field (Definition)
A magnetic field is generated when electric charge carriers such as electrons move through space or within an electrical conductor. The geometric shapes of the magnetic flux lines produced by moving charge carriers (electric current) are similar to the shapes of the flux lines in anelectrostatic field. But there are differences in the ways electrostatic and magnetic fields interact with the environment.
Electrostatic flux is impeded or blocked by metallic objects. Magnetic flux passes through most metals with little or no effect, with certain exceptions, notably iron and nickel. These two metals, and alloys and mixtures containing them, are known asferromagnetic materials because they concentrate magnetic lines of flux. An electromagnet provides a good example. An air-core coil carrying direct currentproduces a magnetic field. If an iron core is substituted for the air core in a given coil, the intensity of the magnetic field is greatly increased in the immediate vicinity of the coil. If the coil has many turns and carries a large current, and if the core material has exceptional ferromagnetic properties, theflux density near the ends of the core (the poles of the magnet) can be such that the electromagnet can be used to pick up and move cars.
When charge carriers are accelerated (as opposed to moving at constant velocity), a fluctuating magnetic field is produced. This generates a fluctuating electric field, which in turn produces another varying magnetic field. The result is a "leapfrog" effect, in which both fields can propagate over vast distances through space. Such a synergistic field is known as anelectromagnetic field. This is the phenomenon that makes wireless communications and broadcasting possible.
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- The transistor, invented by three scientists at the Bell Laboratories in 1947, rapidly replaced the vacuum tube as an electronic signal regulator. (WhatIs.com)
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GLOSSARIES
- Terms related to electronics, including definitions about electrical components and words and phrases about computers, laptops parts, digital cameras, televisions and home appliances.
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Magnetic Field (Definition)
A magnetic field is generated when electric charge carriers such as electrons move through space or within an electrical conductor. The geometric shapes of the magnetic flux lines produced by moving charge carriers (electric current) are similar to the shapes of the flux lines in anelectrostatic field. But there are differences in the ways electrostatic and magnetic fields interact with the environment.
Electrostatic flux is impeded or blocked by metallic objects. Magnetic flux passes through most metals with little or no effect, with certain exceptions, notably iron and nickel. These two metals, and alloys and mixtures containing them, are known asferromagnetic materials because they concentrate magnetic lines of flux. An electromagnet provides a good example. An air-core coil carrying direct currentproduces a magnetic field. If an iron core is substituted for the air core in a given coil, the intensity of the magnetic field is greatly increased in the immediate vicinity of the coil. If the coil has many turns and carries a large current, and if the core material has exceptional ferromagnetic properties, theflux density near the ends of the core (the poles of the magnet) can be such that the electromagnet can be used to pick up and move cars.
When charge carriers are accelerated (as opposed to moving at constant velocity), a fluctuating magnetic field is produced. This generates a fluctuating electric field, which in turn produces another varying magnetic field. The result is a "leapfrog" effect, in which both fields can propagate over vast distances through space. Such a synergistic field is known as anelectromagnetic field. This is the phenomenon that makes wireless communications and broadcasting possible.
Related Terms
DEFINITIONS
- The transistor, invented by three scientists at the Bell Laboratories in 1947, rapidly replaced the vacuum tube as an electronic signal regulator. (WhatIs.com)
- Geo-fencing is a feature in a software program that uses the global positioning system (GPS) or radio frequency identification (RFID) to define geographical boundaries. A geofence is a virtual barr...(WhatIs.com)
- A quad-core processor is a chip with four independent units called cores that read and execute central processing unit (CPU) instructions such as add, move data, and branch.(WhatIs.com)
GLOSSARIES
- Terms related to electronics, including definitions about electrical components and words and phrases about computers, laptops parts, digital cameras, televisions and home appliances.
- This WhatIs.com glossary contains terms related to Internet applications, including definitions about Software as a Service (SaaS) delivery models and words and phrases about web sites, e-commerce ...
Non - Ferrous Metals
Non-ferrous metal
In metallurgy, a non-ferrous metal is a metal which is not ferrous, includingalloys, that does not contain iron in appreciable amounts. Generally more expensive than ferrous metals, non-ferrous metals are used because of desirable properties such as low weight (e.g., aluminium), higher conductivity (e.g., copper),[1] non-magnetic property or resistance to corrosion (e.g., zinc).[2]Some non-ferrous materials are also used in the iron and steel industries. For example, bauxite is used as flux forblast furnaces, while others such aswolframite, pyrolusite and chromite are used in making ferrous alloys.[3]
Important non-ferrous metals includealuminium, copper, lead, nickel, tin,titanium and zinc, and alloys such asbrass. Precious metals such as gold,silver and platinum and exotic or rare metals such as cobalt, mercury,tungsten, beryllium, bismuth, cerium,cadmium, niobium, indium, gallium,germanium, lithium, selenium, tantalum,tellurium, vanadium, and zirconium are also non-ferrous.[4] They are usually obtained through minerals such assulfides, carbonates, and silicates.[5]Non-ferrous metals are usually refined through electrolysis.[6]
Ferrous Metals
Summary:
The basic substance used in ferrous metals such as steel and cast iron (gray and malleable) is iron. It is used in the form of pig iron.Iron is a base metal, meaning that it is an alloying agent in many different metals.
Iron is produced from iron ore that occurs chiefly in nature as an oxide, the two most important oxides being hematite and magnetite. Iron ore is reduced to pig iron in a blast furnace, and the impurities are removed in the form of slag (figure 7-5). Raw materials charged into the furnace include iron ore, coke, and limestone. The pig iron produced is used to manufacture steel or cast iron.
Common ferrous metals include:
stainless steelstungsten carbidecarbon, tool and alloy steel