Saturday, February 20, 2010

International Mother Language Day (21 February )

International Mother Language Day was proclaimed by UNESCO's General Conference in November 1999. The International Day has been observed every year since February 2000 to promote linguistic and cultural diversity and multilingualism.

Languages are the most powerful instruments of preserving and developing our tangible and intangible
heritage.

Virtual Bangladesh : History : Ekushe February

2nd Wave


January 26, 1952

The Basic Principles Committee of the Constituent Assembly of Pakistan announces its recommendation that Urdu should be the only state language.

In a public meting at Paltan Maidan, Dhaka, Prime Minister Nazimuddin declares that Urdu alone will be the state language of Pakistan.

Both the developments spark off the second wave of language agitation in East Bengal.

January 28, 1952

The students of Dhaka University in a protest meeting call the Prime Minister and the Provincial Ministers as stooges of West Pakistan.

January 30, 1952

In a secret meeting called by the Awami League, which is attended by a number of communist front as well as other organizations, it is agreed that the language agitation can not be successfully carried by the students alone. To mobilize full political and student support, it is decided that the leadership of the movement should be assumed by the Awami League under Bhashani.

Virtual Bangladesh : History : Ekushe February


1st Wave

September 15, 1947

Tamuddun Majlis (Cultural Society, an organization by scholars, writers and journalists oriented towards Islamic ideology) in a booklet titled State Language of Pakistan : Bengali or Urdu? demands Bengali as one of the state language of Pakistan.

The Secretary of the Majlis, at that time a Professor of Physics in Dhaka University, [Abul Kashem] was the first person to convene a literary meeting to discuss the State Language issue in the Fazlul Huq Muslim Hall, a student residence of Dhaka University. Supporters and sympathizers soon afterwards formed a political party, the Khilafate-Rabbani Party with Abul Hasim as the Chairman. (-- Talukder Maniruzzaman)

November 1947

In Karachi, the representatives of East Bengal attending the Pakistan Educational Conference, called by the Minister of Education Fazlur Rahman, a Bengali, oppose Urdu as the only national language.

February 23, 1948

Direndra Nath Dutta, a Bengali opposition member, moves a resolution in the first session of Pakistan's Constituent Assembly for recognizing Bengali as a state language along with Urdu and English.

The resolution "... was opposed by Liakat Ali, the Prime Minister of Pakistan and other non-Bengali members in the Assembly. Regrettably, this was opposed by Khawaja Nazimuddin - hailing from the eastern wing - and a few other Bengali collaborators of the West Pakistanis in the Assembly. Later, D. N. Dutta came up with a few amendments to the original resolution, and everytime these were opposed by the west Pakistanis and their Bengali stooges. The West Pakistanis were uncompromising to such a genuine demand of the majority Bengalis." (-- Rafiqul Islam)

Monday, February 15, 2010

Grow Potassium Alum or 'Ruby' Crystals


This is one of the most beautiful and largest crystals you can grow overnight. All you need is hot water and potassium alum, also known as potash alum. Potassium alum may be sold as a 'deodorant crystal' or in solution for use as an astringent. I got the powder for growing this crystal from a Smithsonian crystal-growing kit (labeled as potassium alum).
Prepare the Solution
All you need to do to prepare the crystal solution is to mix as much potassium alum as will dissolve into 1 cup of very hot water. You can add food coloring to tint the crystals. The natural color of the crystals would be clear or white.
Grow Crystals
I poured the solution into a clean bowl, trying to avoid getting any undissolved material into the new container. Allow the crystals to grow overnight. If your solution is very darkly colored, you won't be able to see whether or not you have crystal growth. You can use a spoon or fork to scrape crystals from the bottom. To get a large single crystal like this one, remove all of the crystals and return a few that have the desired form to the solution so they can continue growing. Remove them and allow them to dry when you are satisfied with their appearance.
Synthetic Rubies
One common form taken by this crystal is a regular octahedron with flattened corners. The colored crystal resembles a ruby. In fact, the first synthetic ruby was produced by Gaudin in 1837 by fusing potassium alum with a little chromium (for color) at a high temperature. A synthetic or natural ruby has a Mohs hardness of 9, while a potassium alum crystal only has a hardness of 2 and is readily soluble in water. Therefore, while your overnight-crystals may resemble a ruby, they are too soft and fragile for any purpose besides display. Even though they aren't real rubies, these crystals are well worth your time since they are so so easy and quick to grow and have such a beautiful form.

What Is the Chemical Composition of Air?

There aren't any 'air' molecules, but you already knew this, right? Nearly all of the Earth's atmosphere is made up of only five gases: nitrogen, oxygen, water vapor, argon, and carbon dioxide. Several other additional elements and compounds are present. Although this CRC table does not list water vapor, air can contain as much as 5% water vapor, more commonly ranging from 1-3%. The 1-5% range places water vapor as the third most common gas (which alters the other percentages accordingly). This is composition of air in percent by volume, at sea level at 15°C and 101325 Pa.
Nitrogen -- N2 -- 78.084%
Oxygen -- O2 -- 20.9476%
Argon -- Ar -- 0.934%
Carbon Dioxide -- CO2 -- 0.0314%
Neon -- Ne -- 0.001818%
Methane -- CH4 -- 0.0002%
Helium -- He -- 0.000524%
Krypton -- Kr -- 0.000114%
Hydrogen -- H2 -- 0.00005%
Xenon -- Xe -- 0.0000087%
Ozone -- O3 -- 0.000007%
Nitrogen Dioxide -- NO2 -- 0.000002%
Iodine -- I2 -- 0.000001%
Carbon Monoxide -- CO -- trace
Ammonia -- NH3 -- trace
Reference: CRC Handbook of Chemistry and Physics, edited by David R. Lide, 1997

Cement

In the most general sense of the word, a cement is a binder, a substance which sets and hardens independently, and can bind other materials together. The word "cement" traces to the Romans, who used the term "opus caementicium" to describe masonry which resembled concrete and was made from crushed rock with burnt lime as binder. The volcanic ash and pulverized brick additives which were added to the burnt lime to obtain a hydraulic binder were later referred to as cementum, cimentum, cäment and cement. Cements used in construction are characterized as hydraulic or non-hydraulic.
The most important use of cement is the production of mortar and concrete—the bonding of natural or artificial aggregates to form a strong building material which is durable in the face of normal environmental effects.
Concrete should not be confused with cement because the term cement refers only to the dry powder substance used to bind the aggregate materials of concrete. Upon the addition of water and/or additives the cement mixture is referred to as concrete, especially if aggregates have been added.

History of the origin of cement

Early uses

It is uncertain where it was first discovered that a combination of hydrated non-hydraulic lime and a pozzolan produces a hydraulic mixture (see also: Pozzolanic reaction), but concrete made from such mixtures was first used on a large scale by Roman engineers.[1] They used both natural pozzolans (trass or pumice) and artificial pozzolans (ground brick or pottery) in these concretes. Many excellent examples of structures made from these concretes are still standing, notably the huge monolithic dome of the Pantheon in Rome and the massive Baths of Caracalla.[2] The vast system of Roman aqueducts also made extensive use of hydraulic cement.[3] The use of structural concrete disappeared in medieval Europe, although weak pozzolanic concretes continued to be used as a core fill in

Modern cement

Modern hydraulic cements began to be developed from the start of the Industrial Revolution (around 1800), driven by three main needs:
  • Hydraulic renders for finishing brick buildings in wet climates
  • Hydraulic mortars for masonry construction of harbor works etc, in contact with sea water.
  • Development of strong concretes.
In Britain particularly, good quality building stone became ever more expensive during a period of rapid growth, and it became a common practice to construct prestige buildings from the new industrial bricks, and to finish them with a stucco to imitate stone. Hydraulic limes were favored for this, but the need for a fast set time encouraged the development of new cements. Most famous was Parker's "Roman cement."[4] This was developed by James Parker in the 1780s, and finally patented in 1796. It was, in fact, nothing like any material used by the Romans, but was a "Natural cement" made by burning septaria - nodules that are found in certain clay deposits, and that contain both clay minerals and calcium carbonate. The burnt nodules were ground to a fine powder. This product, made into a mortar with sand, set in 5–15 minutes. The success of "Roman Cement" led other manufacturers to develop rival products by burning artificial mixtures of clay and chalk.
John Smeaton made an important contribution to the development of cements when he was planning the construction of the third Eddystone Lighthouse (1755-9) in the English Channel. He needed a hydraulic mortar that would set and develop some strength in the twelve hour period between successive high tides. He performed an exhaustive market research on the available hydraulic limes, visiting their production sites, and noted that the "hydraulicity" of the lime was directly related to the clay content of the limestone from which it was made. Smeaton was a civil engineer by profession, and took the idea no further. Apparently unaware of Smeaton's work, the same principle was identified by Louis Vicat in the first decade of the nineteenth century. Vicat went on to devise a method of combining chalk and clay into an intimate mixture, and, burning this, produced an "artificial cement" in 1817. James Frost,[5] working in Britain, produced what he called "British cement" in a similar manner around the same time, but did not obtain a patent until 1822. In 1824, Joseph Aspdin patented a similar material, which he called Portland cement, because the render made from it was in color similar to the prestigious Portland stone.
All the above products could not compete with lime/pozzolan concretes because of fast-setting (giving insufficient time for placement) and low early strengths (requiring a delay of many weeks before formwork could be removed). Hydraulic limes, "natural" cements and "artificial" cements all rely upon their belite content for strength development. Belite develops strength slowly. Because they were burned at temperatures below 1250 °C, they contained no alite, which is responsible for early strength in modern cements. The first cement to consistently contain alite was made by Joseph Aspdin's son William in the early 1840s. This was what we call today "modern" Portland cement. Because of the air of mystery with which William Aspdin surrounded his product, others (e.g. Vicat and I C Johnson) have claimed precedence in this invention, but recent analysis[6] of both his concrete and raw cement have shown that William Aspdin's product made at Northfleet, Kent was a true alite-based cement. However, Aspdin's methods were "rule-of-thumb": Vicat is responsible for establishing the chemical basis of these cements, and Johnson established the importance of sintering the mix in the kiln.
William Aspdin's innovation was counter-intuitive for manufacturers of "artificial cements", because they required more lime in the mix (a problem for his father), because they required a much higher kiln temperature (and therefore more fuel) and because the resulting clinker was very hard and rapidly wore down the millstones which were the only available grinding technology of the time. Manufacturing costs were therefore considerably higher, but the product set reasonably slowly and developed strength quickly, thus opening up a market for use in concrete. The use of concrete in construction grew rapidly from 1850 onwards, and was soon the dominant use for cements. Thus Portland cement began its predominant role.
stone walls and colum

Hydrogen Peroxide Shelf Life

If you've ever poured hydrogen peroxide solution onto a cut and didn't experience the expected fizz, it's likely your bottle of hydrogen peroxide has become a bottle of plain water. The 3% hydrogen peroxide solution you can buy for use as a disinfectant typically has a shelf life of at least a year if the bottle is unopened, but only lasts 30-45 days once the seal has been broken. As soon as you expose the peroxide solution to air, it starts to react to form water. Also, if you contaminate the bottle (e.g., by dipping a swab or finger into the bottle), you can expect the effectiveness of the remaining liquid to be compromised.So, if you have a bottle of hydrogen peroxide that has been sitting in your medicine cabinet for a few years, it would be a good idea to replace it. If you've opened the bottle at any point, its activity is long-gone. If you feel like testing the solution. Solvay Chemicals describes a test you can perform to assess the remaining activi