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#26 Re: Jai Ganesh's Puzzles » General Quiz » 2025-11-05 16:01:22
Hi,
#10649. What does the term in Biology Egg mean?
#10650. What does the term in Biology Electrochemical gradient mean?
#27 Re: Jai Ganesh's Puzzles » English language puzzles » 2025-11-05 15:42:12
Hi,
#5845. What does the verb (used with object) downplay mean?
#5846. What does the noun downpour mean?
#28 Re: Jai Ganesh's Puzzles » Doc, Doc! » 2025-11-05 15:24:20
Hi,
#2517. What does the medical term HELLP syndrome mean?
#29 Jokes » Blackberry Jokes » 2025-11-05 14:29:03
- Jai Ganesh
- Replies: 0
Q: What do you call blackberries playing the guitar?
A: A jam session.
* * *
Q: What did one blackberry say to the other blackberry?
A: If you weren't so sweet, we wouldn't be in this jam!
* * *
Patient: Doctor, there is a berry growing out of my head.
Doctor: Oh, that's easy. Just put some cream on it!
* * *
Q: What do you call a blackberry that uses foul language?
A: Berry Rude.
* * *
Q: How many grams of protein are in a blackberry pi?
A: 3.14159265...
* * *
#30 Re: Jai Ganesh's Puzzles » 10 second questions » 2025-11-05 14:12:16
Hi,
#9796.
#31 Re: Jai Ganesh's Puzzles » Oral puzzles » 2025-11-05 13:56:01
Hi,
#6291.
#32 Re: Exercises » Compute the solution: » 2025-11-05 13:44:32
Hi,
2639.
#33 Science HQ » Boiling Point » 2025-11-04 22:17:49
- Jai Ganesh
- Replies: 0
Boiling Point
Gist
The boiling point is the temperature at which a liquid turns into a vapor or gas. This occurs when the liquid's vapor pressure equals the surrounding environmental pressure, and the substance's particles gain enough energy to break free from their intermolecular forces. For example, water boils at 100 degrees Centigrade (212 degrees Fahrenheit) under standard atmospheric pressure.
The boiling point is the specific temperature at which a liquid transitions to gas, occurring when its vapor pressure matches the external atmospheric pressure.
Summary
The boiling point of a substance is the temperature at which the vapor pressure of a liquid equals the pressure surrounding the liquid and the liquid changes into a vapor.
The boiling point of a liquid varies depending upon the surrounding environmental pressure. A liquid in a partial vacuum, i.e., under a lower pressure, has a lower boiling point than when that liquid is at atmospheric pressure. Because of this, water boils at 100°C (or with scientific precision: 99.97 °C (211.95 °F)) under standard pressure at sea level, but at 93.4 °C (200.1 °F) at 1,905 metres (6,250 ft) altitude. For a given pressure, different liquids will boil at different temperatures.
The normal boiling point (also called the atmospheric boiling point or the atmospheric pressure boiling point) of a liquid is the special case in which the vapor pressure of the liquid equals the defined atmospheric pressure at sea level, one atmosphere. At that temperature, the vapor pressure of the liquid becomes sufficient to overcome atmospheric pressure and allow bubbles of vapor to form inside the bulk of the liquid. The standard boiling point has been defined by IUPAC since 1982 as the temperature at which boiling occurs under a pressure of one bar.
The heat of vaporization is the energy required to transform a given quantity (a mol, kg, pound, etc.) of a substance from a liquid into a gas at a given pressure (often atmospheric pressure).
Liquids may change to a vapor at temperatures below their boiling points through the process of evaporation. Evaporation is a surface phenomenon in which molecules located near the liquid's edge, not contained by enough liquid pressure on that side, escape into the surroundings as vapor. On the other hand, boiling is a process in which molecules anywhere in the liquid escape, resulting in the formation of vapor bubbles within the liquid.
Details
At the boiling point, the transition from the liquid to the gaseous phase occurs in a pure substance. Therefore, the boiling point is the temperature at which the vapor pressure of the liquid is equal to the applied pressure on the liquid. The boiling point at a pressure of 1 atmosphere is called the normal boiling point
For a pure substance at a particular pressure P, the stable phase is the vapor phase at temperatures immediately above the boiling point and is the liquid phase at temperatures immediately below the boiling point. The liquid-vapor equilibrium line on the phase diagram of a pure substance gives the boiling point as a function of pressure. Alternatively, this line gives the vapor pressure of the liquid as a function of temperature. The vapor pressure of water is 1 atm (101.325 kilopascals) at 100°C, the normal boiling point of water. The vapor pressure of water is 3.2 kPa (0.031 atm) at 25°C, so the boiling point of water at 3.2 kPa is 25°C. The liquid-vapor equilibrium line on the phase diagram of a pure substance begins at the triple point (where solid, liquid, and vapor coexist in equilibrium) and ends at the critical point, where the densities of the liquid and vapor phases have become equal. For pressures below the triple-point pressure or above the critical-point pressure, the boiling point is meaningless. Carbon dioxide has a triple-point pressure of 5.11 atm (518 kPa), so carbon dioxide has no normal boiling point.
The normal boiling point is high for liquids with strong intermolecular attractions and low for liquids with weak intermolecular attractions. Helium has the lowest normal boiling point, 4.2 kelvin (−268.9°C). Some other normal boiling points are 111.1 K (−162°C) for methane (CH4), 450°C for triacontane (n-C30H62), 1465°C for sodium chloride (NaCl), and 5555°C for tungsten (W).
When a pure liquid is boiled at fixed pressure, the temperature remains constant until all the liquid has vaporized. When a solution is boiled at fixed pressure, the composition of the vapor usually differs from that of the liquid, and the change in liquid composition during boiling changes the boiling point. Thus the boiling process occurs over a range of temperatures for a solution. An exception is an azeotrope, which is a solution that boils entirely at a constant temperature because the vapor in equilibrium with the solution has the same composition as the solution. In fractional distillation, the variation of boiling point with composition is used to separate liquid mixtures into their components.
Additional Information
Boiling point is the temperature at which the pressure exerted by the surroundings upon a liquid is equaled by the pressure exerted by the vapour of the liquid; under this condition, addition of heat results in the transformation of the liquid into its vapour without raising the temperature.
At any temperature a liquid partly vaporizes into the space above it until the pressure exerted by the vapour reaches a characteristic value called the vapour pressure of the liquid at that temperature. As the temperature is increased, the vapour pressure increases; at the boiling point, bubbles of vapour form within the liquid and rise to the surface. The boiling point of a liquid varies according to the applied pressure; the normal boiling point is the temperature at which the vapour pressure is equal to the standard sea-level atmospheric pressure (760 mm [29.92 inches] of mercury). At sea level, water boils at 100° C (212° F). At higher altitudes the temperature of the boiling point is lower.
#34 This is Cool » Alum » 2025-11-04 20:26:06
- Jai Ganesh
- Replies: 0
Alum
Gist
Alum is a natural crystalline compound with antiseptic, astringent, and deodorizing properties, commonly known as a double sulfate salt of aluminum. It is used for water purification, in skincare for acne and tightening, and in traditional medicine for issues like bleeding gums and as a deodorant. It is also used in the food and textile industries.
Alum is a crystalline double sulfate salt of a monovalent cation (like potassium) and aluminium, which has properties like antiseptic, astringent, and deodorizing effects. It is used in various applications including water purification, food, and medicine.
Summary
An alum is a type of chemical compound, usually a hydrated double sulfate salt of aluminium with the general formula XAl(SO4)2·12H2O, such that X is a monovalent cation such as potassium or ammonium. By itself, alum often refers to potassium alum, with the formula KAl(SO4)2·12H2O. Other alums are named after the monovalent ion, such as sodium alum and ammonium alum.
The name alum is also used, more generally, for salts with the same formula and structure, except that aluminium is replaced by another trivalent metal ion like chromiumIII, or sulfur is replaced by another chalcogen like selenium. The most common of these analogs is chrome alum KCr(SO4)2·12H2O.
In most industries, the name alum (or papermaker's alum) is used to refer to aluminium sulfate, Al2(SO4)3·n2O, which is used for most industrial flocculation (the variable n is an integer whose size depends on the amount of water absorbed into the alum). For medicine, the word alum may also refer to aluminium hydroxide gel used as a vaccine adjuvant.
Production
Some alums occur as minerals, the most important being alunite.
The most important alums – potassium, sodium, and ammonium – are produced industrially. Typical recipes involve combining aluminium sulfate and the sulfate monovalent cation. The aluminium sulfate is usually obtained by treating minerals like alum schist, bauxite and cryolite with sulfuric acid.
Details
Alum is a type of chemical compound that is commonly used in everyday and industrial applications. You'll find alum in everything from baking powder and toothpaste to cosmetics and some fire extinguishers, but there are also various types of alum with different use cases.
Usually, when you hear about alum it is in reference to potassium alum, which is the hydrated form of potassium aluminum sulfate and has the chemical formula KAl(SO4)2·12H2O.
However, any of the compounds with the empirical formula AB(SO4)2·12H2O are also considered to be alum. Sometimes alum is seen in its crystalline form, although it is most often sold as a powder. Potassium alum is a fine white powder that you can find sold with kitchen spices or pickling ingredients. It is also sold as a large crystal as a "deodorant rock" for underarm use.
Key Takeaways: Alum
* Alum refers to a collection of chemical compounds that are hydrated sulfate salts of aluminum and usually one other metal.
* Common forms of alum include hydrated potassium aluminum sulfate, ammonium aluminum sulfate, and sodium aluminum sulfate.
* The different compounds have different functions. Alum finds use in vaccines, baking powder, tanning agents, deodorants, and antiseptics.
What Are the Types of Alum?
* Potassium Alum: Potassium alum is also known as potash alum or tawas. It is aluminum potassium sulfate. This is the type of alum that you find in the grocery store for pickling. It is also used in leather tanning, as a flocculant in water purification, as an ingredient in aftershave, and as a treatment for fireproof textiles. Its chemical formula is KAl(SO4)2.
* Soda Alum: Soda alum has the formula NaAl(S O4)2·12H2O. It is used in baking powder and as an acidulant in food.
* Ammonium Alum: Ammonium alum has the formula NH4Al(SO4)2·12H2O. Ammonium alum is used for many of the same purposes as potassium alum and soda alum. Ammonium alum finds applications in tanning, dyeing textiles, purifying water, and making textiles flame retardant. It's also used in the manufacture of porcelain cement, vegetable glues, and some deodorants.
* Chrome Alum: Chrome alum or chromium alum has the formula KCr(S O4)2·12H2O. This deep violet compound is used in tanning and can be added to other alums to grow lavender or purple crystals.
* Selenate Alums: Selenate alums occur when selenium takes the place of sulfur so that instead of a sulfate you get a selenate, (SeO42-). The selenium-containing alums are strong oxidizing agents, so they can be used as antiseptics, among other uses.
* Aluminum Sulfate: This compound is also known as papermaker's alum. However, it is not technically an alum.
What Is Alum Used for?
Alum has several household and industrial uses. Potassium alum is used most often, although ammonium alum, ferric alum, and soda alum may be used for many of the same purposes.
* purification of drinking water as a chemical flocculant
* in styptic pencil to stop bleeding from minor cuts
* the adjuvant in vaccines ( a chemical that enhances the immune response)
* deodorant "rock"
* pickling agent to help keep pickles crisp
* flame retardant
* the acidic component of some types of baking powder
* an ingredient in some homemade and commercial modeling clay
* an ingredient in some depilatory (hair removal) waxes
* skin whitener
* ingredient in some brands of toothpaste.
Alum in Science Projects
Several interesting science projects use alum. In particular, it is used to grow stunning non-toxic crystals. Clear crystals result from potassium alum, while purple crystals grow from chrome alum.
How Is Alum Produced?
Several minerals are used as the source material to produce alum, including alum schist, alunite, bauxite, and cryolite.
The specific process used to obtain the alum depends on the original mineral. When alum is obtained from alunite, the alunite is calcined. The resulting material is kept moist and exposed to air until it turns to a powder, which is lixiviated, or extracted, with sulfuric acid and hot water. The liquid is decanted, and the alum crystallizes out of the solution.
Additional Information
Alum is any of a group of hydrated double salts, usually consisting of aluminum sulfate, water of hydration, and the sulfate of another element. A whole series of hydrated double salts results from the hydration of the sulfate of a singly charged cation (e.g., K+) and the sulfate of any one of a number of triply charged cations (e.g., Al3+). Aluminum sulfate can thus form alums with sulfates of the singly charged cations of potassium, sodium, ammonium, cesium, and other elements and compounds. In similar fashion, sulfates of the triply charged cations of iron, chromium, manganese, cobalt, and other metals may take the place of aluminum sulfate. The most important alums are potassium aluminum sulfate, ammonium aluminum sulfate, and sodium aluminum sulfate. Potassium aluminum sulfate, also known as potassium alum or potash alum, has a molecular formula of K2(SO4)·Al2(SO4)3·24H2O or KAl(SO4)2·12H2O.
Alums can easily be produced by precipitation from an aqueous solution. In producing potassium alum, for example, aluminum sulfate and potassium sulfate are dissolved in water, and then upon evaporation the alum crystallizes out of the solution. A more common production method is to treat bauxite ore with sulfuric acid and then with potassium sulfate. Ammonium alum is produced by the evaporation of a water solution containing ammonium sulfate and aluminum sulfate. It can also be obtained by treating a mixture of aluminum sulfate and sulfuric acid with ammonia. Alums occur naturally in various minerals. Potassium alum, for example, is found in the minerals kalinite, alunite, and leucite, which can be treated with sulfuric acid to obtain crystals of the alum.
Most alums have an astringent and acid taste. They are colourless, odourless, and exist as a white crystalline powder. Alums are generally soluble in hot water, and they can be readily precipitated from aqueous solutions to form large octahedral crystals.
Alums have many uses, but they have been partly supplanted by aluminum sulfate itself, which is easily obtainable by treating bauxite ore with sulfuric acid. The commercial uses of alums mainly stem from the hydrolysis of the aluminum ions, which results in the precipitation of aluminum hydroxide. This chemical has various industrial uses. Paper is sized, for example, by depositing aluminum hydroxide in the interstices of the cellulose fibres. Aluminum hydroxide adsorbs suspended particles from water and is thus a useful flocculating agent in water-purification plants. When used as a mordant (binder) in dyeing, it fixes dye to cotton and other fabrics, rendering the dye insoluble. Alums are also used in pickling, in baking powder, in fire extinguishers, and as astringents in medicine.
#35 Re: Dark Discussions at Cafe Infinity » crème de la crème » 2025-11-04 16:52:57
2384) George Porter
Gist:
Work
During chemical reactions, atoms and molecules regroup and form new constellations. Chemical reactions are affected by heat and light, among other things. The sequence of events can proceed very quickly. At the end of the 1940s, George Porter and Ronald Norrish built an extremely powerful lamp that emitted very short bursts of light. The light’s energy triggered reactions among the molecules or split them into parts that were inclined to react. By registering the light spectrums that are characteristic for different substances, the progress of the reaction could be monitored.
Summary
Sir George Porter, Baron Porter of Luddenham (born December 6, 1920, Stainforth, Yorkshire, England—died August 31, 2002, Canterbury) was an English chemist, corecipient with fellow Englishman Ronald George Wreyford Norrish and Manfred Eigen of West Germany of the 1967 Nobel Prize for Chemistry. All three were honoured for their studies in flash photolysis, a technique for observing the intermediate stages of very fast chemical reactions.
After undergraduate work at the University of Leeds, Porter earned a doctorate at the University of Cambridge under Norrish in 1949. He continued on there, developing the technique of flash photolysis with Norrish. In this technique, a gas or liquid in equilibrium is illuminated with an ultrashort burst of light that causes photochemical reactions in the substance. The extremely short-lived intermediate products of these reactions are illuminated by a second burst of light that enables an absorption spectrum to be taken of the reaction products before the gas has returned to a state of equilibrium. Porter specifically studied the equilibrium of chlorine atoms and molecules. In 1955 he joined the faculty of chemistry at the University of Sheffield, where he taught until 1966, becoming in that year director of the Royal Institution of Great Britain and Fullerian professor of chemistry. Porter was knighted in 1972 and created a life peer in 1990.
Details
George Porter, Baron Porter of Luddenham, (6 December 1920 – 31 August 2002) was a British chemist. He was awarded the Nobel Prize in Chemistry in 1967.
Education and early life
Porter was born in Stainforth, near Thorne, in the then West Riding of Yorkshire. He was educated at Thorne Grammar School, then won a scholarship to the University of Leeds and gained his first degree in chemistry. During his degree, Porter was taught by Meredith Gwynne Evans, who he said was the most brilliant chemist he had ever met. He was awarded a PhD from the University of Cambridge in 1949 for research investigating free radicals produced by photochemical means. He later became a Fellow of Emmanuel College, Cambridge.
Career and research
Porter served in the Royal Naval Volunteer Reserve during the Second World War. Porter then went on to do research at the University of Cambridge supervised by Ronald George Wreyford Norrish where he began the work that ultimately led to them becoming Nobel Laureates.
His original research in developing the technique of flash photolysis to obtain information on short-lived molecular species provided the first evidence of free radicals. His later research utilised the technique to study the detailed aspects of the light-dependent reactions of photosynthesis, with particular regard to possible applications to a hydrogen economy, of which he was a strong advocate.
He was Assistant Director of the British Rayon Research Association from 1953 to 1954, where he studied the phototendering of dyed cellulose fabrics in sunlight.
Porter served as professor in the Chemistry department at the University of Sheffield in 1954–65. It was here he started his work on flash photolysis with equipment designed and made in the departmental workshop. During this tenure he also took part in a television programme describing his work. This was in the "Eye on Research" series. Porter became Fullerian Professor of Chemistry and Director of the Royal Institution in 1966. During his directorship of the Royal Institution, Porter was instrumental in the setting up of Applied Photophysics, a company created to supply instrumentation based on his group's work. He was awarded the Nobel Prize in Chemistry in 1967 along with Manfred Eigen and Ronald George Wreyford Norrish. In the same year he became a visiting professor in University College London.
Porter was a major contributor to the Public Understanding of science. He became president of the British Association in 1985 and was the founding Chair of the Committee on the Public Understanding of Science (COPUS). He gave the Romanes Lecture, entitled "Science and the human purpose", at the University of Oxford in 1978; and in 1988 he gave the Dimbleby Lecture, "Knowledge itself is power." From 1990 to 1993 he gave the Gresham lectures in astronomy.
Awards and honours
Porter was elected a Fellow of the Royal Society (FRS) in 1960, a member of the American Academy of Arts and Sciences in 1979, a member of the American Philosophical Society in 1986, and served as President of the Royal Society from 1985 to 1990. He was also awarded the Davy Medal in 1971, the Rumford Medal in 1978, the Ellison-Cliffe Medal in 1991 and the Copley Medal in 1992.
Porter also received an Honorary Doctorate from Heriot-Watt University in 1971.
He was knighted in 1972, appointed to the Order of Merit in 1989, and was made a life peer as Baron Porter of Luddenham, of Luddenham in the County of Kent, in 1990. In 1995, he was awarded an Honorary Degree (Doctor of Laws) from the University of Bath.
In 1976 he gave the Royal Institution Christmas Lecture on The Natural History of a Sunbeam.
Porter served as Chancellor of the University of Leicester between 1984 and 1995. In 2001, the university's chemistry building was named the George Porter Building in his honour.
Family
In 1949 Porter married Stella Jean Brooke.
#36 Re: This is Cool » Miscellany » 2025-11-04 16:26:45
2436) Citric Acid
Gist
Citric acid is used in various applications, including acting as a flavoring agent and preservative in food and drinks, a descaling and cleaning agent in household products, an ingredient in cosmetics and personal care items, and a chelating agent in industrial processes. It is also used in some pharmaceuticals and supplements to aid mineral absorption, buffer solutions, or prevent kidney stone formation.
Summary
Citric acid is a colourless crystalline organic compound belonging to the family of carboxylic acids, present in practically all plants and in many animal tissues and fluids. It is one of a series of compounds involved in the physiological oxidation of fats, proteins, and carbohydrates to carbon dioxide and water.
Citric acid was first isolated from lemon juice by Swedish chemist Carl Wilhelm Scheele in 1784 and is manufactured by fermentation of cane sugar or molasses in the presence of a fungus, Aspergillus niger. It is used in confections and soft drinks (as a flavouring agent), in metal-cleaning compositions, and in improving the stability of foods and other organic substances (by suppressing the deleterious action of dissolved metal salts).
Details
Citric acid is an important natural compound that has been known since the late 18th century. The pioneering Swedish–German chemist Carl Wilhelm Scheele isolated it from lemon juice in 1784. It has since been found in other citrus fruits, pineapples, and even animal tissues.
Citric acid is a major industrial chemical, produced at >2 million t/year worldwide. Its main source is not from fruit, but from the fermentation of crude sugars (e.g., molasses and corn starch) by the mold Aspergillus niger. It has a myriad of uses, mostly in foods and pharmaceuticals; these uses include acidifying agent/pH adjustment, antioxidant, flavoring agent, and as metal salts in dietary supplements. In industry and domestic applications, citric acid is a chelating and buffering agent in many cleaning products and a starting material for synthesizing citrate esters, itaconic acid, acetonedicarboxylic acid, and other compounds.
Biochemists are familiar with the citric acid cycle, which is a major life process in all respiring organisms. Also called the Krebs cycle or the tricarboxylic acid cycle, the process begins with sugar-derived pyruvate, which enzymatically generates acetyl-coenzyme A (CoA) to start the cycle. Acetate released from acetyl-CoA reacts with oxaloacetic acid produced at the end of the previous cycle to form citric acid; this is followed by several steps, during which an oxidation reaction releases energy to the body in the form of adenosine triphosphate.
Many scientists contributed to the discovery and establishment of the citric acid cycle. The two key researchers were Albert Szent-Györgyi at the University of Szeged (Hungary) and Hans Adolf Krebs at the University of Sheffield (UK); they were awarded the Nobel Prize in Physiology or Medicine in 1937 and 1953, respectively.
Additional Information
Citric acid is an organic compound with the formula C6H8O7. It is a colorless weak organic acid. It occurs naturally in citrus fruits. In biochemistry, it is an intermediate in the citric acid cycle, which occurs in the metabolism of all aerobic organisms.
More than two million tons of citric acid are manufactured every year. It is used widely as acidifier, flavoring, preservative, and chelating agent.
A citrate is a derivative of citric acid; that is, the salts, esters, and the polyatomic anion found in solutions and salts of citric acid. An example of the former, a salt is trisodium citrate; an ester is triethyl citrate.
Natural occurrence and industrial production
Citric acid occurs in a variety of fruits and vegetables, most notably citrus fruits. Lemons and limes have particularly high concentrations of the acid; it can constitute as much as 8% of the dry weight of these fruits (about 47 g/L in the juices).[a] The concentrations of citric acid in citrus fruits range from 0.005 mol/L for oranges and grapefruits to 0.30 mol/L in lemons and limes; these values vary within species depending upon the cultivar and the circumstances under which the fruit was grown.
Citric acid was first isolated in 1784 by the chemist Carl Wilhelm Scheele, who crystallized it from lemon juice.
Industrial-scale citric acid production first began in 1890 based on the Italian citrus fruit industry, where the juice was treated with hydrated lime (calcium hydroxide) to precipitate calcium citrate, which was isolated and converted back to the acid using diluted sulfuric acid. In 1893, C. Wehmer discovered Penicillium mold could produce citric acid from sugar. However, microbial production of citric acid did not become industrially important until World War I disrupted Italian Citrus exports.
In 1917, American food chemist James Currie discovered that certain strains of the mold Aspergillus niger could be efficient citric acid producers, and the pharmaceutical company Pfizer began industrial-level production using this technique two years later, followed by Citrique Belge in 1929. In this production technique, which is still the major industrial route to citric acid used today, cultures of Aspergillus niger are fed on a sucrose or glucose-containing medium to produce citric acid. The source of sugar is corn steep liquor, molasses, hydrolyzed corn starch, or other inexpensive, carbohydrate solution. After the mold is filtered out of the resulting suspension, citric acid is isolated by precipitating it with calcium hydroxide to yield calcium citrate salt, from which citric acid is regenerated by treatment with sulfuric acid, as in the direct extraction from citrus fruit juice.
In 1977, a patent was granted to Lever Brothers for the chemical synthesis of citric acid starting either from aconitic or isocitrate (also called alloisocitrate) calcium salts under high pressure conditions; this produced citric acid in near quantitative conversion under what appeared to be a reverse, non-enzymatic Krebs cycle reaction.
Although industrial-scale production of citric acid by chemical synthesis or extraction from citrus fruits are both feasible, fermentation by molds (and sometimes yeasts) is almost exclusively the only method actually practiced.
Global production was in excess of 2,000,000 tons in 2018. More than 50% of this volume was produced in China. More than 50% was used as an acidity regulator in beverages, some 20% in other food applications, 20% for detergent applications, and 10% for applications other than food, such as cosmetics, pharmaceuticals, and in the chemical industry.
#37 Dark Discussions at Cafe Infinity » Code Quotes - II » 2025-11-04 15:47:43
- Jai Ganesh
- Replies: 0
Code Quotes - II
1. The manual for WordStar, the most popular word-processing program, is 400 pages thick. To write a novel, you have to read a novel - one that reads like a mystery to most people. They're not going to learn slash q-z any more than they're going to learn Morse code. That is what Macintosh is all about. - Steve Jobs
2. Hackathons are these things where just all of the Facebook engineers get together and stay up all night building things. And, I mean, usually at these hackathons, I code too, just alongside everyone. - Mark Zuckerberg
3. I start 'The Code Book' with the story of Mary Queen of Scots and the Babington Plot, which was foiled when Mary's enciphered messages fell into the hands of Elizabeth I's codebreakers. - Simon Singh
4. Trying to read our DNA is like trying to understand software code - with only 90% of the code riddled with errors. It's very difficult in that case to understand and predict what that software code is going to do. - Elon Musk
5. Proprietary software tends to have malicious features. The point is with a proprietary program, when the users don't have the source code, we can never tell. So you must consider every proprietary program as potential malware. - Richard Stallman
6. It now seems very likely that many of the 64 triplets, possibly most of them, may code one amino acid or another, and that in general several distinct triplets may code one amino acid. - Francis Crick
7. In fact, the best thing we could do on taxes for all Americans is to simplify the individual tax code. This will be a tough job, but members of both parties have expressed an interest in doing this, and I am prepared to join them. - Barack Obama
8. I want to reform the tax code so that it's simple, fair, and asks the wealthiest households to pay higher taxes on incomes over $250,000 - the same rate we had when Bill Clinton was president; the same rate we had when our economy created nearly 23 million new jobs, the biggest surplus in history, and a lot of millionaires to boot. - Barack Obama.
#38 Re: Jai Ganesh's Puzzles » General Quiz » 2025-11-04 15:25:41
Hi,
#10647. What does the term in Biology Ectotherm mean?
#10648. What does the term in Biology Effector mean?
#39 Re: Jai Ganesh's Puzzles » English language puzzles » 2025-11-04 15:08:59
Hi,
#5843. What does the noun echelon mean?
#5844. What does the noun echinoderm mean?
#40 Re: Jai Ganesh's Puzzles » Doc, Doc! » 2025-11-04 14:58:06
Hi,
#2516. What does the medical term Leptomeningeal cancer mean?
#41 Jokes » Beverage Jokes - III » 2025-11-04 14:16:14
- Jai Ganesh
- Replies: 0
Q: What has eight arms and an IQ of 60?
A: Four guys drinking Bud Light and watching a football game!
* * *
Q: When do women drink alcohol?
A: Wine O'Clock.
* * *
Q: When does it rain money?
A: When there is "change" in the weather.
* * *
Q: What do you say when you're gonna drunk dial someone?
A: Al-cohol you.
* * *
Q: If H20 is water what is H204?
A: Drinking, bathing, washing, swimming. . .
* * *
#42 Re: Jai Ganesh's Puzzles » 10 second questions » 2025-11-04 14:07:43
Hi,
#9795.
#43 Re: Jai Ganesh's Puzzles » Oral puzzles » 2025-11-04 13:53:43
Hi,
#6290.
#44 Re: Exercises » Compute the solution: » 2025-11-04 13:41:19
Hi,
2638.
#45 This is Cool » Carbonic Acid » 2025-11-03 21:45:49
- Jai Ganesh
- Replies: 0
Carbonic Acid
Gist
Carbonic acid (H2CO3) is a weak acid formed when carbon dioxide (CO2)) dissolves in water. It is an unstable compound that can dissociate into a hydrogen ion (H+) and a bicarbonate ion (HCO3-), and it plays a critical role in regulating blood pH in the human body. Carbonic acid is also found in carbonated beverages and is responsible for weathering limestone.
Carbonic acid is used in the food and beverage industry for carbonating soft drinks, wine, and sparkling water; in medicine for its role as a blood buffer and for certain topical treatments; and in industrial applications for pH control in water treatment, as a cleaning agent, and in the production of other chemicals.
Summary
Carbonic acid is a chemical compound with the chemical formula H2CO3. The molecule rapidly converts to water and carbon dioxide in the presence of water. However, in the absence of water, it is quite stable at room temperature. The interconversion of carbon dioxide and carbonic acid is related to the breathing cycle of animals and the acidification of natural waters.
In biochemistry and physiology, the name "carbonic acid" is sometimes applied to aqueous solutions of carbon dioxide. These chemical species play an important role in the bicarbonate buffer system, used to maintain acid–base homeostasis.
Terminology in biochemical literature
In chemistry, the term "carbonic acid" strictly refers to the chemical compound with the formula H2CO3. Some biochemistry literature effaces the distinction between carbonic acid and carbon dioxide dissolved in extracellular fluid.
In physiology, carbon dioxide excreted by the lungs may be called volatile acid or respiratory acid.
Details
Carbonic acid, (H2CO3) is a compound of the elements hydrogen, carbon, and oxygen. It is formed in small amounts when its anhydride, carbon dioxide (CO2), dissolves in water.
The predominant species are simply loosely hydrated CO2 molecules. Carbonic acid can be considered to be a diprotic acid from which two series of salts can be formed—namely, hydrogen carbonates.
However, the acid-base behaviour of carbonic acid depends on the different rates of some of the reactions involved, as well as their dependence on the pH of the system.
Between pH values of 8 and 10, all the above equilibrium reactions are significant.
Carbonic acid plays a role in the assembly of caves and cave formations like stalactites and stalagmites. The largest and most common caves are those formed by dissolution of limestone or dolomite by the action of water rich in carbonic acid derived from recent rainfall. The calcite in stalactites and stalagmites is derived from the overlying limestone near the bedrock/soil interface. Rainwater infiltrating through the soil absorbs carbon dioxide from the carbon dioxide-rich soil and forms a dilute solution of carbonic acid. When this acid water reaches the base of the soil, it reacts with the calcite in the limestone bedrock and takes some of it into solution. The water continues its downward course through narrow joints and fractures in the unsaturated zone with little further chemical reaction. When the water emerges from the cave roof, carbon dioxide is lost into the cave atmosphere, and some of the calcium carbonate is precipitated. The infiltrating water acts as a calcite pump, removing it from the top of the bedrock and redepositing it in the cave below.
Carbonic acid is important in the transport of carbon dioxide in the blood. Carbon dioxide enters blood in the tissues because its local partial pressure is greater than its partial pressure in blood flowing through the tissues. As carbon dioxide enters the blood, it combines with water to form carbonic acid, which dissociates into hydrogen ions (H+) and bicarbonate ions (HCO3-). Blood acidity is minimally affected by the released hydrogen ions because blood proteins, especially hemoglobin, are effective buffering agents. (A buffer solution resists change in acidity by combining with added hydrogen ions and, essentially, inactivating them.) The natural conversion of carbon dioxide to carbonic acid is a relatively slow process; however, carbonic anhydrase, a protein enzyme present inside the red blood cell, catalyzes this reaction with sufficient rapidity that it is accomplished in only a fraction of a second. Because the enzyme is present only inside the red blood cell, bicarbonate accumulates to a much greater extent within the red cell than in the plasma. The capacity of blood to carry carbon dioxide as bicarbonate is enhanced by an ion transport system inside the red blood cell membrane that simultaneously moves a bicarbonate ion out of the cell and into the plasma in exchange for a chloride ion. The simultaneous exchange of these two ions, known as the chloride shift, permits the plasma to be used as a storage site for bicarbonate without changing the electrical charge of either the plasma or the red blood cell. Only 26 percent of the total carbon dioxide content of blood exists as bicarbonate inside the red blood cell, while 62 percent exists as bicarbonate in plasma; however, the bulk of bicarbonate ions is first produced inside the cell, then transported to the plasma. A reverse sequence of reactions occurs when blood reaches the lung, where the partial pressure of carbon dioxide is lower than in the blood.
Additional Information
Carbonic Acid is an inorganic, weak, and unstable acid. The molecule of Carbonic Acid consists of one carbon atom, two hydrogen atoms, and three oxygen atoms. Carbonic Acid is also referred to as a respiratory acid as it is the only acid that is exhaled in the gaseous state by human lungs.
Carbonic acid is studied majorly in various fields of science because of its vast applications and uses. It helps improve marine life due to its natural process of ocean acidification. It is essential for the human body as well.
What is Carbonic Acid?
Carbonic acid is a chemical compound made of carbon dioxide, oxygen, and hydrogen as its elements. It is a weak acid with the chemical formula H2CO3. It is formed when carbon dioxide is dissolved in water. Carbonic acid is a diprotic acid, which means it can form two types of salts: carbonate and bicarbonate. Carbonic Acid is also known as dihydrogen carbonate (because it is made of two hydrogen atoms and a carbonate ion), aerial acid (or acid of air), Oxidocarboxylic acid, Hydroxyformic acid, etc.
It was discovered by the French chemist Antoine Lavoisier in the late 18th century. He found that when carbon dioxide reacts with water an acidic solution is formed which he named as carbonic acid.
Formula of Carbonic Acid
The compound of carbonic acid consists of one carbon atom, two hydrogen atoms, and three oxygen atoms. It can also be represented as OC(OH)2 due to the presence of a carbon-oxygen double bond.
Structure of Carbonic Acid
Carbonic acid consists of a carboxyl functional group along with a hydroxyl group. The structure of carbonic acids consists of one carbon-oxygen double bond and further, this carbon is single bonded with two hydroxyl groups (OH).
Preparation of Carbonic Acid
When strong acid reacts with calcium carbonate, carbon dioxide gas is evolved which when dissolved in water, Carbonic acid is formed.
Properties of Carbonic Acid
Carbonic acid has a variety of properties which are classified into physical and chemical properties. The physical and chemical properties of carbonic acid are described below:
Physical Properties of Carbonic Acid
* State: Carbonic Acid generally occurs as a solution, but according to recent research it was found that Carbonic acid is also being prepared in a solid state by NASA scientists.
* Odor: Carbonic Acid are generally odorless.
* pKa value: The pKa value of Carbonic acid is 6.35. The pKa value is inversely proportional to the acidity of the compound. Hence, carbonic acid is termed under weak acid.
* Boiling Point: The boiling point of carbonic acid is around 127° Celsius.
* Melting Point: The melting point of carbonic acid is around -53° Celsius.
* Density: Carbonic acid has a density of around 1.668 grams per cubic centimeter.
* Molecular weight: The molecular weight of Carbonic acid is 62.024 g/mol.
* Conjugate base: The conjugate bases of Carbonic acid are bicarbonate and carbonate.
Chemical Properties of Carbonic Acid
* Stability: Carbonic acids are unstable under normal circumstances. However, they can be stabilized under high pressure and high temperatures.
* pH: Being a weak acidic, carbonic acid has a pH value of around 4.68
* Diprotic acid: It is a diprotic acid, i.e. it can form two types of salts namely carbonate and bicarbonate.
* Dissociation reaction: In the presence of water, Carbonic acid can partially dissociate into bicarbonate ions (HCO3-) and hydrogen ions (H+).
* Reaction with base: Carbonic acids form bicarbonate salt when reacted with a moderate amount of base and it form carbonate salts if reacted with excess amount of base.
* Decomposition reaction: Carbonic acid can easily decompose into carbon dioxide and water. However, this reaction is reversible under suitable conditions.
Uses of Carbonic Acid
* Carbonated Drinks: Carbonic acid provides the fizzy and bubbly taste in carbonated drinks like sparkling water, sodas, soft drinks, beer, champagne and other carbonated beverages
* Buffering System: Carbonic acid acts as a buffer system in human bodies which helps in maintaining the pH balance in the blood.
* pH regulation: Carbonic acid is also useful in regulating the pH level of water in swimming pools and in regulating pH balance in various other industrial processes.
* Medicinal uses: It is used in medications to balance acid-base levels in the body and in ointments to treat various fungal infections like ringworm. It is also consumed to induce vomiting (when required).
* pH indicator: Carbonic acid is used as a pH indicator to check whether the solution is acidic or basic.
* Precipitation: Carbonic acid is used as a solvent in the precipitation of various ammonium salts like ammonium persulfate.
Cleansing agent: Carbonic acid is also used as a cleaning agent to clean contact lenses.
#46 Science HQ » Chromosome » 2025-11-03 16:46:26
- Jai Ganesh
- Replies: 0
Chromosome
Gist
A chromosome is a thread-like structure made of proteins and a single molecule of DNA that carries the genetic information of an organism. Located in the nucleus of cells, chromosomes are a highly organized way to package the DNA, which is a very long molecule. Humans typically have 46 chromosomes in 23 pairs, with 22 pairs of autosomes and one pair of gender chromosomes (X and Y).
Chromosomes are long strings of DNA wrapped around proteins to make them compact. They're a way for cells to organize and store your DNA. Humans typically have 23 pairs of chromosomes for a total of 46 chromosomes. The first 22 are called autosomes and the last pair are gender chromosomes.
Summary
Chromosomes are threadlike structures made of protein and a single molecule of DNA that serve to carry the genomic information from cell to cell. In plants and animals (including humans), chromosomes reside in the nucleus of cells. Humans have 22 pairs of numbered chromosomes (autosomes) and one pair of gender chromosomes (XX or XY), for a total of 46. Each pair contains two chromosomes, one coming from each parent, which means that children inherit half of their chromosomes from their mother and half from their father. Chromosomes can be seen through a microscope when the nucleus dissolves during cell division.
Chromosomes vary in number and shape among living organisms. Most bacteria have one or two circular chromosomes. Humans, along with other animals and plants, have linear chromosomes . In fact, each species of plants and animals has a set number of chromosomes. A fruit fly, for example, has four pairs of chromosomes, while a rice plant has 12 and a dog, 39. In humans, the twenty-third pair is the gender chromosomes, while the first 22 pairs are called autosomes. Typically, biologically female individuals have two X chromosomes (XX) while those who are biologically male have one X and one Y chromosome (XY). However, there are exceptions to these rules. Chromosomes are also different sizes. The human X chromosome is about three times larger than the human Y chromosome, containing about 900 genes, while the Y chromosome has about 55 genes. The unique structure of chromosomes keeps DNA tightly wound around spool-like proteins, called histones. Without such packaging, DNA molecules would be too long to fit inside cells! For example, if all of the DNA molecules in a single human cell were unwound from their histones and placed end-to-end, they would stretch 6 feet.
Details
A chromosome is a package of DNA containing part or all of the genetic material of an organism. In most chromosomes, the very long thin DNA fibers are coated with nucleosome-forming packaging proteins; in eukaryotic cells, the most important of these proteins are the histones. Aided by chaperone proteins, the histones bind to and condense the DNA molecule to maintain its integrity. These eukaryotic chromosomes display a complex three-dimensional structure that has a significant role in transcriptional regulation.
Normally, chromosomes are visible under a light microscope only during the metaphase of cell division, where all chromosomes are aligned in the center of the cell in their condensed form. Before this stage occurs, each chromosome is duplicated (S phase), and the two copies are joined by a centromere—resulting in either an X-shaped structure if the centromere is located equatorially, or a two-armed structure if the centromere is located distally; the joined copies are called 'sister chromatids'. During metaphase, the duplicated structure (called a 'metaphase chromosome') is highly condensed and thus easiest to distinguish and study. In animal cells, chromosomes reach their highest compaction level in anaphase during chromosome segregation.
Chromosomal recombination during meiosis and subsequent sexual reproduction plays a crucial role in genetic diversity. If these structures are manipulated incorrectly, through processes known as chromosomal instability and translocation, the cell may undergo mitotic catastrophe. This will usually cause the cell to initiate apoptosis, leading to its own death, but the process is occasionally hampered by cell mutations that result in the progression of cancer.
The term 'chromosome' is sometimes used in a wider sense to refer to the individualized portions of chromatin in cells, which may or may not be visible under light microscopy. In a narrower sense, 'chromosome' can be used to refer to the individualized portions of chromatin during cell division, which are visible under light microscopy due to high condensation.
Additional Information
A chromosome is a microscopic threadlike part of the cell that carries hereditary information in the form of genes. A defining feature of any chromosome is its compactness. For instance, the 46 chromosomes found in human cells have a combined length of 200 nm (1 nm = {10}^{-9} metre); if the chromosomes were to be unraveled, the genetic material they contain would measure roughly 2 metres (about 6.5 feet) in length. The compactness of chromosomes plays an important role in helping to organize genetic material during cell division and enabling it to fit inside structures such as the nucleus of a cell, the average diameter of which is about 5 to 10 μm (1 μm = 0.00l mm, or 0.000039 inch), or the polygonal head of a virus particle, which may be in the range of just 20 to 30 nm in diameter.
The structure and location of chromosomes are among the chief differences between viruses, prokaryotes, and eukaryotes. The nonliving viruses have chromosomes consisting of either DNA (deoxyribonucleic acid) or RNA (ribonucleic acid); this material is very tightly packed into the viral head. Among organisms with prokaryotic cells (i.e., bacteria and blue-green algae), chromosomes consist entirely of DNA. The single chromosome of a prokaryotic cell is not enclosed within a nuclear membrane. Among eukaryotes, the chromosomes are contained in a membrane-bound cell nucleus. The chromosomes of a eukaryotic cell consist primarily of DNA attached to a protein core. They also contain RNA. The remainder of this article pertains to eukaryotic chromosomes.
Every eukaryotic species has a characteristic number of chromosomes (chromosome number). In species that reproduce asexually, the chromosome number is the same in all the cells of the organism. Among sexually reproducing organisms, the number of chromosomes in the body (somatic) cells is diploid (2n; a pair of each chromosome), twice the haploid (1n) number found in the gender cells, or gametes. The haploid number is produced during meiosis. During fertilization, two gametes combine to produce a zygote, a single cell with a diploid set of chromosomes.
Somatic cells reproduce by dividing, a process called mitosis. Between cell divisions the chromosomes exist in an uncoiled state, producing a diffuse mass of genetic material known as chromatin. The uncoiling of chromosomes enables DNA synthesis to begin. During this phase, DNA duplicates itself in preparation for cell division.
Following replication, the DNA condenses into chromosomes. At this point, each chromosome actually consists of a set of duplicate chromatids that are held together by the centromere. The centromere is the point of attachment of the kinetochore, a protein structure that is connected to the spindle fibres (part of a structure that pulls the chromatids to opposite ends of the cell). During the middle stage in cell division, the centromere duplicates, and the chromatid pair separates; each chromatid becomes a separate chromosome at this point. The cell divides, and both of the daughter cells have a complete (diploid) set of chromosomes. The chromosomes uncoil in the new cells, again forming the diffuse network of chromatin.
Among many organisms that have separate sexes, there are two basic types of chromosomes: gender chromosomes and autosomes. Autosomes control the inheritance of all the characteristics except the gender-linked ones, which are controlled by the gender chromosomes. Humans have 22 pairs of autosomes and one pair of gender chromosomes. All act in the same way during cell division.
Chromosome breakage is the physical breakage of subunits of a chromosome. It is usually followed by reunion (frequently at a foreign site, resulting in a chromosome unlike the original). Breakage and reunion of homologous chromosomes during meiosis are the basis for the classical model of crossing over, which results in unexpected types of offspring of a mating.
#47 Re: Jai Ganesh's Puzzles » General Quiz » 2025-11-03 16:24:24
Hi,
#10645. What does the term in Geography Chorology mean?
#10646. What does the term in Geography Choropleth map mean?
#48 Re: Jai Ganesh's Puzzles » English language puzzles » 2025-11-03 16:09:42
Hi,
#5841. What does the noun foreword mean?
#5842. What does the verb (used with object) forfeit mean?
#49 Re: Dark Discussions at Cafe Infinity » crème de la crème » 2025-11-03 15:56:26
2383) Ronald George Wreyford Norrish
Gist:
Work
During chemical reactions, atoms and molecules regroup and form new constellations. Chemical reactions are affected by heat and light, among other things. The sequence of events can proceed very quickly. At the end of the 1940s, Ronald Norrish and George Porter built an extremely powerful lamp that emitted very short bursts of light. The light’s energy triggered reactions among the molecules or split them into parts that were inclined to react. By registering the light spectrums that are characteristic for different substances, the progress of the reaction could be monitored.
Summary
Ronald George Wreyford Norrish (born Nov. 9, 1897, Cambridge, Cambridgeshire, Eng.—died June 7, 1978, Cambridge) was a British chemist who was the corecipient, with fellow Englishman Sir George Porter and Manfred Eigen of West Germany, of the 1967 Nobel Prize for Chemistry. All three were honoured for their studies of very fast chemical reactions.
Norrish did his undergraduate and doctoral work at the University of Cambridge, served as research fellow at Emmanuel College, Cambridge, and directed the university’s physical chemistry department for 28 years. Norrish and Porter, who worked together between 1949 and 1965, used the new technique of flash photolysis to study the intermediate stages involved in extremely rapid chemical reactions. In this technique, a gaseous system in a state of equilibrium is subjected to an ultrashort burst of light that causes photochemical reactions in the gas. A second burst of light is then used to detect and record the changes taking place in the gas before equilibrium is reestablished. Norrish became a professor emeritus in 1963, though he continued to work with individual students and as an industrial consultant.
Details
Ronald George Wreyford Norrish FRS (9 November 1897 – 7 June 1978) was a British chemist who was awarded the Nobel Prize in Chemistry in 1967.
Education and early life
Norrish was born in Cambridge and was educated at The Perse School and Emmanuel College, Cambridge. He was a former student of Eric Rideal. From an early age he was interested in chemistry, walking up and down Cambridge University chemical laboratory admiring all the equipment. His father encouraged him to construct and equip a small laboratory in his garden shed in his garden and supplied all the chemicals he needed to conduct experiments. This apparatus now forms part of the Science Museum collections - reference shows copper water tank. He used to enter competitions for the analysis of mixtures sent round by the Pharmaceutical Journal and often won prizes. In 1915 Norrish won a Foundation Scholarship to Emmanuel College, but by adding a little to his age joined the Royal Field Artillery and served as a Lieutenant, first in Ireland and then on the Western Front.
Career and research
Norrish was a prisoner in World War I and later commented, with sadness, that many of his contemporaries and potential competitors at Cambridge had not survived the War. Military records show that 2nd Lieutenant Norrish of the Royal Artillery went missing (captured) on 21 March 1918.
Norrish rejoined Emmanuel College as a Research Fellow in 1925 and later became Head of the Department of Physical Chemistry at the University of Cambridge.
The skill which Norrish displayed in his laboratory work problems marked him out amongst his contemporaries as an unusually gifted and energetic experimentalist, capable of making significant advances in photo-chemistry and gas kinetics.
Awards and honours
Norrish was elected a Fellow of the Royal Society (FRS) in 1936. As a result of the development of flash photolysis, Norrish was awarded the Nobel Prize in Chemistry in 1967 along with Manfred Eigen and George Porter for their study of extremely fast chemical reactions. One of his accomplishments is the development of the Norrish reaction.
At Cambridge, Norrish supervised Rosalind Franklin, future DNA researcher and colleague of James Watson and Francis Crick, and experienced some conflict with her.
#50 Re: This is Cool » Miscellany » 2025-11-03 15:36:16
2435} Polyvinyl Chloride
Gist
Polyvinyl chloride (PVC) is a versatile synthetic plastic polymer produced from vinyl chloride monomers, widely used in applications from construction (pipes, window frames) to healthcare (IV bags, tubing) and everyday products. It can be made rigid or flexible by adding plasticizers, and is valued for its durability, low cost, and resistance to chemicals, corrosion, and fire.
Polyvinyl chloride (PVC) is used in a wide variety of products due to its versatility as a rigid or flexible material, including construction (pipes, window frames), electrical insulation, medical devices (IV bags, tubing), packaging, and consumer goods like flooring and raincoats. Its use in building and construction accounts for about three-quarters of all vinyl production, taking advantage of its durability, strength, and resistance to moisture and corrosion.
Summary
Polyvinyl chloride (alternatively: poly(vinyl chloride), colloquial: vinyl or polyvinyl; abbreviated: PVC) is the world's third-most widely produced synthetic polymer of plastic (after polyethylene and polypropylene). About 40 million tons of PVC are produced each year.
PVC comes in rigid (sometimes abbreviated as RPVC) and flexible forms. Rigid PVC is used in construction for pipes, doors and windows. It is also used in making plastic bottles, packaging, and bank or membership cards. Adding plasticizers makes PVC softer and more flexible. It is used in plumbing, electrical cable insulation, flooring, signage, phonograph records, inflatable products, and in rubber substitutes. With cotton or linen, it is used in the production of canvas.
Polyvinyl chloride is a white, brittle solid. It is soluble in ketones, chlorinated solvents, dimethylformamide, THF and DMAc.
Chlorinated PVC
PVC can be usefully modified by chlorination, which increases its chlorine content to or above 67%. Chlorinated polyvinyl chloride, (CPVC), as it is called, is produced by chlorination of aqueous solution of suspension PVC particles followed by exposure to UV light which initiates the free-radical chlorination.
Adhesives
Flexible plasticized PVC can be glued with special adhesives often referred to as solvent cement as solvents are the main ingredients. PVC or polyurethane resin may be added to increase viscosity, allow the adhesive to fill gaps, to accelerate setting and to reduce shrinkage and internal stresses. Viscosity can be further increased by adding fumed silica as a filler. As molecules are mobilized by the solvents and migrating PVC polymers are interlinking at the joint the process is also referred to as welding or cold welding. PVC can be made with a variety of plasticizers. Plasticizer migration from the vinyl part into the adhesive can degrade the strength of the joint. If this is of concern the adhesives should be tested for their resistance to the plasticizer. Nitrile rubber adhesives are often used with flexible PVC film as they are known to be resistant to plasticizers. Some epoxy adhesive formulations have provide good adhesion to flexible PVC substrate. Typical formulations of common solvent cement may contain 10–50% ethyl acetate, 8–16% acetone, 12–50% butanone (methyl ethyl ketone, MEK), 0–18% methyl acetate, 12–30% polyurethane and 0-10% toluene. Alternatively methyl isobutyl ketone or tetrahydrofuran may be added as solvents, tin organic compounds as stabilizer and dioctylphthalate as a plasticizer.
Details
PVC, a synthetic resin made from the polymerization of vinyl chloride. Second only to polyethylene among the plastics in production and consumption, PVC is used in an enormous range of domestic and industrial products, from raincoats and shower curtains to window frames and indoor plumbing. A lightweight, rigid plastic in its pure form, it is also manufactured in a flexible “plasticized” form.
Vinyl chloride (CH2=CHCl), also known as chloroethylene, is most often obtained by reacting ethylene with oxygen and hydrogen chloride over a copper catalyst. It is a toxic and carcinogenic gas that is handled under special protective procedures. PVC is made by subjecting vinyl chloride to highly reactive compounds known as free-radical initiators. Under the action of the initiators, the double bond in the vinyl chloride monomers (single-unit molecules) is opened, and one of the resultant single bonds is used to link together thousands of vinyl chloride monomers to form the repeating units of polymers (large, multiple-unit molecules).
PVC was prepared by the French chemist Henri Victor Regnault in 1835 and then by the German chemist Eugen Baumann in 1872, but it was not patented until 1912, when another German chemist, Friedrich Heinrich August Klatte, used sunlight to initiate the polymerization of vinyl chloride. Commercial application of the plastic was at first limited by its extreme rigidity; however, in 1926, while trying to dehydrohalogenate PVC in a high-boiling solvent in order to obtain an unsaturated polymer that might bond rubber to metal, Waldo Lunsbury Semon, working for the B.F. Goodrich Company in the United States, produced what is now called plasticized PVC. The discovery of this flexible, inert product was responsible for the commercial success of the polymer. Under the trademark Koroseal, Goodrich made the plastic into shock-absorber seals, electric-wire insulation, and coated cloth products. One of the best-known applications of the plastic was initiated in 1930, when the Union Carbide and Carbon Corporation (later the Union Carbide Corporation) introduced Vinylite, a copolymer of vinyl chloride and vinyl acetate that became the standard material of long-playing phonograph records.
Pure PVC finds application in the construction trades, where its rigidity, strength, and flame resistance are useful in pipes, conduits, siding, window frames, and door frames. It is also blow-molded into clear, transparent bottles. Because of its rigidity, it must be extruded or molded above 100 °C (212 °F)—a temperature high enough to initiate chemical decomposition (in particular, the emission of hydrogen chloride [HCl]). Decomposition can be reduced by the addition of stabilizers, which are mainly compounds of metals such as cadmium, zinc, tin, or lead.
In order to arrive at a product that remains flexible, especially at low temperatures, most PVC is heated and mixed with plasticizers, which are sometimes added in concentrations as high as 50 percent. The most commonly used plasticizer is the compound di-2-ethylhexyl phthalate (DEHP), also known as dioctyl phthalate (DOP). Plasticized PVC is familiar to consumers as floor tile, garden hose, imitation leather upholstery, and shower curtains.
Very fine particles of PVC can be dispersed in plasticizer in excess of the amount used to make plasticized PVC (e.g., 50 percent or more), and this suspension can be heated until the polymer particles dissolve. The resultant fluid, called a plastisol, will remain liquid even after cooling but will solidify into a gel upon reheating. Plastisols can be made into products by being spread on fabric or cast into molds. Flexible gloves can be made by dipping a hand-shaped form into plastisol, and hollow objects such as overshoes can be made by casting plastisol into a mold, pouring off the excess, and solidifying the material remaining on the walls of the mold.
PVC has been an occasional object of controversy since a link between vinyl chloride monomer and cancer was established in 1973. Environmentalists and health advocates raised concerns over the possible ill effects of exposure to substances such as residual vinyl chloride monomer, hydrogen chloride, organometallic stabilizers, and phthalate plasticizers. Industry officials maintain that these substances are scrupulously controlled and are released from PVC in trace amounts that have not been proved harmful.
Rigid PVC is typically made into durable structural products such as window casings and home siding, which are not frequently recycled. PVC bottles and containers, however, can be recycled into products such as drainage pipe and traffic cones. The recycling code number of PVC is #3.
Additional Information
Polyvinyl chloride is one of the cheapest and most widely used plastics globally. It is a thermoplastic having good resistance to alkalis, salts, and highly polar solvents, and it is flame retardant due to the presence of chlorine in the structure. The presence of chlorine makes it flame retardant. But PVC is not thermally stable at higher temperatures. Plasticizers are added to PVC for safe processing due to its thermal instability at high temperature . In automobile industry, it is used for the fabrication of internal lining, protective covering of bottom flooring cars, and coating of electric cables in vehicles. It has excellent properties like good flexibility, flame retardancy, good thermal stability and high gloss and low lead content, diversity of manufacturing procedures, and easy to paste, print and weld . It is used for the large scale production of cable insulations, equipment parts, pipes, laminated materials, and in fiber manufacture. The PVC polymer can be blow molded, calendared, injection molded, and compression molded to form a large varieties of products. Depending upon the amount and type of plasticizers used, the product formed from the PVC is either rigid or flexible. Its vinyl content that gives good tensile strength. It has good resistant to chemical and solvent attack. Colored or transparent material is also available. It is used in automobile instrument panels and sheathing of electrical cables.
