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#1 This is Cool » Iodized Salt » Today 19:45:33
- Jai Ganesh
- Replies: 0
Iodized Salt
Gist
Iodized salt is regular table salt with added iodine to prevent iodine deficiency disorders. The human body cannot produce iodine, a vital mineral needed for thyroid hormone production, which regulates metabolism and is critical for brain development. Adding iodine to salt is a global public health measure to ensure people get enough of this essential nutrient.
Is iodized salt good for you?
Yes, iodized salt is good for you because it provides essential iodine, which is crucial for brain development and the production of thyroid hormones that regulate metabolism. It is an effective public health strategy to prevent iodine deficiency disorders, which can lead to goiter, mental retardation, and other developmental issues. However, salt should be consumed in moderation, as excess sodium can cause health problems like high blood pressure.
Summary
Iodised salt (also spelled iodized salt) is table salt mixed with a minuscule amount of various iodine salts. The ingestion of iodine prevents iodine deficiency. Worldwide, iodine deficiency affects about two billion people and is the leading preventable cause of intellectual and developmental disabilities. Deficiency also causes thyroid gland problems, including endemic goitre. In many countries, iodine deficiency is a major public health problem that can be cheaply addressed by purposely adding small amounts of iodine to the sodium chloride salt.
Iodine is a micronutrient and dietary mineral that is naturally present in the food supply in some regions (especially near sea coasts) but is generally quite rare in the Earth's crust. Where natural levels of iodine in the soil are low and vegetables do not take up the iodine, iodine added to salt provides the small but essential amount of iodine needed by humans.
An opened package of table salt with iodide may rapidly lose its iodine content in high temperature and high relative humidity conditions through the process of oxidation and iodine sublimation. Poor manufacturing techniques and storage processes can also lead to insufficient amounts of iodine in table salt.
Chemistry, biochemistry, and nutritional aspects
Four inorganic compounds are used as iodide sources, depending on the producer: potassium iodate, potassium iodide, sodium iodate, and sodium iodide. Any of these compounds supplies the body with the iodine required for the biosynthesis of thyroxine (T4) and triiodothyronine (T3) hormones by the thyroid gland. Animals also benefit from iodine supplements, and the hydrogen iodide derivative of ethylenediamine is the main supplement to livestock feed.
Salt is an effective vehicle for distributing iodine to the public because it does not spoil and is consumed in more predictable amounts than most other commodities. For example, the concentration of iodine in salt has gradually increased in Switzerland: 3.75 mg/kg in 1922, 7.5 mg/kg in 1962, 15 mg/kg in 1980, 20 mg/kg in 1998, and 25 mg/kg since 2014. These increases were found to improve iodine status in the general Swiss population.
Salt that is iodized with iodide may slowly lose its iodine content by exposure to excess air over long periods. Salts fortified with iodate are relatively stable to storage and heat; the main concern is reducing impurities in the salt itself, which can be removed relatively easily. Moisture accelerates the decomposition of iodate, but ceases to do so once reducing impurities are removed.
Contrary to popular belief, iodised salt cannot be used as a substitute for potassium iodide (KI) to protect a person's thyroid gland in the event of a nuclear emergency. There is not enough iodine in iodised salt to block the uptake of radioactive iodine by the thyroid.
Details
Salt iodization is an effective, safe and economical strategy to increase iodine intake in populations and ensure adequate iodine intakes. It is considered to be the most appropriate strategy for iodine fortification. Salt iodization has several advantages. Table salt is usually consumed in similar quantities throughout the year and is easily distributed. Its low cost means all socio-economic classes use it. In many countries, salt is produced in a few locations, which allows for easier quality control of iodization.
Salt is iodized using iodate or iodide, but iodate is a better choice in humid tropical areas because it is more stable and less soluble. Salt with 15–40 mg of iodine per kg is considered adequately iodized. This is based on a daily per capita consumption of 10 g of salt. When salt iodization is initiated in iodine-deficient regions, there is a rapid shift of the urine iodine concentration curve to the right indicating increased iodine intake. Successful implementation of a salt iodization program is defined as ≥ 90% of households consuming adequately iodized salt. In countries that monitor use of iodized salt, coverage ranges from less than 35% to ≥ 90%.
The efficacy of salt iodization programs depend on a number of factors including household economic status, education level and quality control efforts during preparation. At present, policies and regulations on salt iodization vary among countries. For example, in Canada iodization of table salt is mandatory, whereas in the United States salt iodization is voluntary. Regulations or recommendations on levels of iodine fortification of salt also differ among countries. Rapid test kits, despite limitations, are predominantly used to measure use of iodized salt in households and assess coverage of salt iodization programs. However, in many high-income countries including Canada, United States and Australia use of iodized salt is not regularly monitored.
Additional Information
Iodized salt is table salt with small amounts of iodine added, usually as potassium iodide, to ensure against dietary deficiency of iodine. Where iodized salt is used, particularly in Switzerland and the United States, endemic goitre has disappeared.
In the United States, iodized salt contains 1 part in 10,000 iodide; in Switzerland, 1 part in 200,000. The World Health Organization recommends 1 part in 100,000.
Iodine is a micronutrient which has a very crucial part to play in the development and functioning of our body. Although needed in a small quantity, it can have grave ramifications if not consumed in the recommended dose. Iodine deficiency causes serious health issues in pregnant women and in children. Iodine insufficiency may adversely affect mental development in children.
The Significance of iodine
Iodine is naturally found in seafood, dairy products, eggs and grains. Most countries iodize their salt to prevent iodine deficiency and its awful consequences. Iodine deficiency triggers a horde of symptoms ranging from mildly discomforting to severe to even perilous.
Here are the essential uses of the mineral in our body:
* Principally, the thyroid gland needs iodine to synthesize thyroid hormones, which are pivotal for the physical and mental growth and development, tissue repair and to regulate metabolism.
* Thyroid hormones, and indirectly iodine, have a part to play in the monitoring of body temperature, blood pressure, and heart rate.
* Iodine also has a huge bearing on the functioning of the immune system.
The Relation Between Iodine and Mental Health
When the body’s iodine requirement is not met, the thyroid gland fails to manufacture adequate amounts of the thyroid hormones. Consequently, the amount of the thyroid hormones in the blood is low and it causes grave functional and developmental anomalies.
Iodine deficit is a major cause of poor mental developmental in children, causing a low IQ in school- going kids. The consequence of iodine deficiency during pregnancy is - an inadequate manufacture of the thyroid hormones by the mother and the foetus. As a result, there can be mental retardation in the child. In fact, impairment to the brain and irreversible mental retardation are the most severe disorders linked to a lack of iodine.
Experts state that a daily intake of salt that has been fortified with iodine is an efficient stratagem to prevent iodine deficiency. Consumption of iodized salt is sufficient to meet your everyday iodine requirement.
Iodized Salt – Vitally Important For Health
In India, iodine deficiency disorders comprise of an important causative factor of avoidable brain damage. The ramifications of iodine deficiency disorders are invisible and irreversible; but - preventable. We are prone to iodine deficiency disorders because of an iodine deficit in the soil of the subcontinent and accordingly in the food derived from it. Statistics reveal that about 350 million people do not consume iodized salt and are prone to iodine deficiency disorders. To circumvent the risk, our salt is reinforced with iodine. Iodized salt is a very efficient way to increase iodine intake in the population. As of today, iodized salt coverage in our country is 91% with only 71% people consuming sufficiently iodized salt. The National Iodine Deficiency Disorders Control Program’s (NIDDCP) goal in India is to decrease the prevalence of iodine deficiency disorders below 10%.
Tata Salt ensures purity as well as the right amount of iodine. In fact, if you are wondering which is the best salt for your health requirements Tata Salt offers a whole range to choose from– Tata salt, Tata Salt Lite (Iodized and Low Sodium), Tata Salt Plus (Double Fortified Salt: Iron & Iodine), Tata Rock Salt and Tata Black Salt. Consult your physician and choose the right alternative from this range.
#2 Re: Dark Discussions at Cafe Infinity » crème de la crème » Today 17:07:19
2386) Haldan Keffer Hartline
Gist:
Work
Our vision functions because light from the surrounding world is captured by many light-sensitive cells in the retina at the back of the eye. A series of reconnections and transformations of chemical and electrical signals finally result in visual impressions. In studies of the horseshoe crab around 1950, Keffer Hartline analyzed how the primary signals from visual cells are processed in a network of nerve cells. Among other things, he showed that when a cell is stimulated, signals from surrounding cells are suppressed. This makes it easier to understand the concept of contrasts.
Summary
Haldan Keffer Hartline (born Dec. 22, 1903, Bloomsburg, Pa., U.S.—died March 17, 1983, Fallston, Md.) was an American physiologist who was a co-winner (with George Wald and Ragnar Granit) of the 1967 Nobel Prize for Physiology or Medicine for his work in analyzing the neurophysiological mechanisms of vision.
Hartline began his study of retinal electrophysiology as a National Research Council Fellow at Johns Hopkins University, Baltimore, receiving his M.D. in 1927. After attending the universities of Leipzig and Munich as an Eldridge Johnson traveling research scholar, he became professor of biophysics and chairman of the department at Johns Hopkins in 1949. He joined the staff of Rockefeller University, New York City, in 1953 as professor of neurophysiology.
Hartline investigated the electrical responses of the retinas of certain arthropods, vertebrates, and mollusks because their visual systems are much simpler than those of humans and are thus easier to study. He concentrated his studies on the eye of the horseshoe crab (Limulus polyphemus). Using minute electrodes in his experiments, he obtained the first record of the electrical impulses sent by a single optic nerve fibre when the receptors connected to it are stimulated by light. He found that the receptor cells in the eye are interconnected in such a way that when one is stimulated, others nearby are depressed, thus enhancing the contrast in light patterns and sharpening the perception of shapes. Hartline thus built up a detailed understanding of the workings of individual photoreceptors and nerve fibres in the retina, and he showed how simple retinal mechanisms constitute vital steps in the integration of visual information.
Details
Haldan Keffer Hartline (December 22, 1903 – March 17, 1983) was an American physiologist who was a co-recipient (with George Wald and Ragnar Granit) of the 1967 Nobel Prize in Physiology or Medicine for his work in analyzing the neurophysiological mechanisms of vision.
Biography
Haldan Hartline did his undergraduate studies at Lafayette College in Easton, Pennsylvania, graduating in 1923. He began his study of retinal electrophysiology as a National Research Council Fellow at Johns Hopkins School of Medicine, receiving his medical degree in 1927.
Scientific career
After attending the universities of Leipzig and Munich as an Eldridge Johnson traveling research scholar from the University of Pennsylvania, he returned to the US to take a position in the Eldridge Reeves Johnson Foundation for Medical Physics at Penn, which was under the directorship of Detlev W. Bronk at that time. In 1940–1941, he was Associate Professor of Physiology at Cornell Medical College in New York City but returned to Penn and stayed until 1949. Then he became professor of biophysics and chairman of the Jenkins Department of Biophysics at Johns Hopkins University in 1949. One of Hartline's graduate students at Johns Hopkins, Paul Greengard, also won the Nobel Prize. Hartline joined the staff of Rockefeller University, New York City, in 1953 as professor of neurophysiology.
Hartline investigated the electrical responses of the retinas of certain arthropods, vertebrates, and mollusks, because their visual systems are much simpler than those of humans and thus easier to study. He concentrated his studies on the eye of the horseshoe crab (Limulus polyphemus). Using minute electrodes, he obtained the first record of the electrical impulses sent by a single optic nerve fibre when the receptors connected to it are stimulated by light. He found that the photoreceptor cells in the eye are interconnected in such a way that when one is stimulated, others nearby are depressed, thus enhancing the contrast in light patterns and sharpening the perception of shapes. Hartline thus built up a detailed understanding of the workings of individual photoreceptors and nerve fibres in the retina, and he showed how simple retinal mechanisms constitute vital steps in the integration of visual information.
Awards and honors
In 1948, Hartline was elected to the United States National Academy of Sciences. He was elected to the American Philosophical Society in 1952 and the American Academy of Arts and Sciences in 1957. He was elected to the inaugural class of Fellows of the Optical Society (OSA) of America in 1959. Later, OSA elected him an Honorary Member in 1980. Hartline was elected a Foreign Member of the Royal Society in 1966. He was awarded the Nobel Prize in Physiology or Medicine in 1967.
Personal life
Hartline married Elizabeth Kraus Hartline in 1936. They had three children: Daniel, Peter, and Frederick Hartline.
#3 Re: This is Cool » Miscellany » Today 16:45:13
2438) Compressed Natural Gas
Gist
Compressed Natural Gas (CNG) is a fuel derived from natural gas, primarily methane, that has been compressed to less than 1% of its volume for storage and transport. It is used as a cleaner-burning alternative to gasoline and diesel, especially in vehicles, and offers environmental and economic benefits like lower emissions and cost savings.
Compressed Natural Gas (CNG) is a fossil fuel that is mainly composed of methane, which has been compressed to a high pressure to store it in a smaller volume, making it a viable alternative to petrol and diesel for vehicles. It is considered a cleaner-burning fuel because it emits significantly lower levels of harmful pollutants like carbon monoxide, sulfur dioxide, and nitrogen oxides, and contains no lead or benzene.
Summary
Compressed natural gas (or simply shortened as CNG) is a fuel gas mainly composed of methane (CH4), compressed to less than 1% of the volume it occupies at standard atmospheric pressure. It is stored and distributed in hard containers at a pressure of 20–25 megapascals (2,900–3,600 psi; 200–250 bar), usually in cylindrical or spherical shapes.
CNG is used in traditional petrol/internal combustion engine vehicles that have been modified, or in vehicles specifically manufactured for CNG use: either alone (dedicated), with a segregated liquid fuel system to extend range (dual fuel), or in conjunction with another fuel (bi-fuel). It can be used in place of petrol, diesel fuel, and liquefied petroleum gas (LPG). CNG combustion produces fewer undesirable gases than the aforementioned fuels. In comparison to other fuels, natural gas poses less of a threat in the event of a spill, because it is lighter than air and disperses quickly when released. Biomethane, biogas from anaerobic digestion or landfill, can be used.
In response to high fuel prices and environmental concerns, CNG has been used in auto rickshaws, pickup trucks, transit and school buses, and trains.
The cost and placement of fuel storage containers is the major barrier to wider/quicker adoption of CNG as a fuel. It is also why municipal government, public transportation vehicles were the most visible early adopters of it, as they can more quickly amortize the money invested in the new (and usually cheaper) fuel. In spite of these circumstances, the number of vehicles in the world using CNG has grown steadily (30 percent per year). Now, as a result of the industry's steady growth, the cost of such fuel storage cylinders has been brought down to a much more acceptable level. Especially, for the CNG Type 1 and Type 2 cylinders, many countries are able to make reliable and cost effective cylinders for conversion need.
Details
Compressed natural gas or CNG is simply natural gas mainly comprised of methane that is stored under high pressures (while remaining in its gaseous form), mainly as a means to transport it, or as storage for later use as vehicle fuel. In this form it remains clear, odourless, and non-corrosive. CNG is used widely as an alternative fuel for vehicles as it has a fairly high octane rating. CNG is not to be confused with liquefied natural gas, which has been turned into a liquid—and must be at very low temperatures. Although it's still in its gaseous form, compressed natural gas is under more pressure and thus takes up a smaller volume than ordinary natural gas (but more volume than LNG : Liquefied Natural Gas).
Storage and Transport
After being extracted from wells and treated, the gas travels through pipelines to a distributor. These distributors then send this fuel out to customers in pressurized tanks or sent out to fueling stations. At smaller fueling stations and in vehicles, the compressed gas is stored in thick-walled tanks made of aluminum, steel, or some composite. These high pressure tanks are kept at pressures around 20-25 MPa, 200-250 bar, or 3000-3600 psi. This high pressure reduces the volume of the natural gas to less than 1% of its volume at standard atmospheric pressure.
Use as an Alternative Fuel
CNG can be used as a gasoline alternative in a number of different vehicles and many commercial vehicles have recently become CNG fueled. Vehicles of any size from sedans to heavy-duty transit vehicles like buses and street sweepers can be fueled by CNG. Currently, natural gas powers more than 12 million vehicles on the road with about 250,000 of these located in the United States.
There are several benefits to using natural gas as an alternative fuel for transportation. For example, 99% of the natural gas the US produces comes from somewhere in North America. Moving to CNG would reduce their reliance on oil from overseas. It burns more cleanly than gasoline or diesel fuel—showing an average reduction in emissions of 80% as compared to gasoline vehicles. Additionally, current estimates say that compressed natural gas costs about 40% less than gasoline.
Safety
Natural gas is flammable, however a leak is not always extraordinarily dangerous. Because natural gas is lighter than air, it quickly dissipates when it leaks out of a tank and it is only flammable when the air/natural gas mixture is 5-15% natural gas. Additionally, a sulfur-based mercaptan—an odourant—is added to make leaks more simple to detect. This narrow flammability range makes it a safe fuel to use, but strict safety standards exist to make CNG powered vehicles as safe as those powered by gasoline. There are some safety concerns with large buses fueled by CNG compared to diesel buses. One of these is a longer breaking distance due to the added weight of the fuel storage system. Finally, the composition of natural gas itself can be an issue. CNG is mainly methane —a greenhouse gas—which could contribute to climate change if a leak existed.
Additional Information:
Introducing CNG
Have you ever wondered what makes Compressed Natural Gas (CNG) a more environmentally friendly alternative to traditional fuel?
CNG is natural gas under pressure which remains clear, odourless, and non-corrosive. This means CNG is not just friendlier on our naturally lush landscape, but it can be used as an economical alternative as well.
Compressed Natural Gas (CNG), is natural gas under pressure which remains clear, odourless, and non-corrosive. It is also a cheaper, greener, and more efficient alternative to the traditional petrol and diesel fuels for vehicles.
CNG is comprised of:
• Mostly methane gas which, like gasoline, produces engine power when mixed with air and fed into your engine’s combustion chamber.
• When CNG reaches the combustion chamber, it mixes with air, is ignited by a spark and the and the energy from the explosion moves the vehicle.
• CNG is compressed so that enough fuel can be stored in your vehicle to extend driving range, much like the gasoline tank in vehicle.
• Although vehicles can use natural gas as either a liquid or a gas, most vehicles use the gaseous form compressed to 3,000 psi.
CNG vs Liquid Fuels
Still wondering why CNG is better than traditional petrol?
We break it down for you here:
• CNG is one of the most viable alternatives to traditional liquid fuels for vehicles here in Trinidad and Tobago.
• CNG is one fifth the price of super gasoline, resulting in substantial savings in fuel costs.
• CNG reduces maintenance costs since it contains no additives and burns cleanly leaving no by-products of combustion to contaminate your spark plugs and engine oil.
• The combustion chamber parts function at peak output for longer periods before requiring service. The engine oil also remains clean which minimizes engine wear and requires less frequent changes.
• CNG is more environment friendly and CNG engines are much quieter due to the higher octane rating of CNG over gasoline.
• CNG produces less exhaust emissions and as a result, harmful emissions such as carbon monoxide (CO), carbon dioxide (CO2 and nitrous oxide (N2O) are generally reduced by as much as 95% when compared to gasoline powered vehicles.
• CNG is the safe bet as its components are designed and made to international standards and are monitored to ensure safe operation.
• CNG fuel systems are also sealed, which prevents any spill or evaporation losses.
#4 Dark Discussions at Cafe Infinity » Code Quotes - IV » Today 16:04:42
- Jai Ganesh
- Replies: 0
Code Quotes - IV
1. We have a rule that if you check in code, you have to maintain it. So I mostly code on the side. I don't check in code anymore. - Mark Zuckerberg
2. Roy Rogers, Gene Autry, John Wayne - these men had the code of the West. - Chuck Norris
3. Frequent elections not only entail more burden on human resources, imposition of model code also impedes the development process. - Ram Nath Kovind
4. Simply put, when you have very large pieces of software, most of the tools look at the individual lines of code as text. It is often extremely powerful to look not at individual pieces of code but at a system as a whole. - James Gosling.
#5 Re: Jai Ganesh's Puzzles » General Quiz » Today 15:33:55
Hi,
#10651. What does the term in Biology/Chemistry Electron acceptor mean?
#10652. What does the term in Biology in Biology/Chemistry Electron transport chain mean?
#6 Re: Jai Ganesh's Puzzles » English language puzzles » Today 15:07:57
Hi,
#5847. What does the noun functionary mean?
#5848. What does the adjective fungible mean?
#7 Re: Jai Ganesh's Puzzles » Doc, Doc! » Today 14:56:39
Hi,
#2518. What does the medical term Pre-eclampsia mean?
#8 Jokes » Blue Berry Jokes » Today 14:26:59
- Jai Ganesh
- Replies: 0
Q: What do you call blueberries playing the guitar?
A: A jam session.
* * *
Q: What do you call a sad strawberry?
A: A blueberry.
* * *
Q: What did one blueberry say to the other blueberry?
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 blueberry that uses foul language?
A: Berry Rude.
* * *
Q: How many grams of protein are in a blueberry pi?
A: 3.14159265...
* * *
#9 Re: Jai Ganesh's Puzzles » 10 second questions » Today 14:16:38
Hi,
#9797.
#10 Re: Jai Ganesh's Puzzles » Oral puzzles » Today 13:49:00
Hi,
#6292.
#11 Re: Exercises » Compute the solution: » Today 13:34:53
Hi,
2640.
#12 Science HQ » Melting Point » Yesterday 21:40:16
- Jai Ganesh
- Replies: 0
Melting Point
Gist
The melting point is the temperature at which a solid substance changes into a liquid under normal atmospheric pressure. At this temperature, the solid and liquid phases of the substance exist together in equilibrium. Melting occurs when added heat provides enough energy for the particles in the solid to break free from the rigid structure and move more freely as a liquid. For example, ice melts at 0 degrees Celsius (32 degrees Fahrenheit), which is also the freezing point for water.
Melting point is the temperature at which the solid and liquid forms of a pure substance can exist in equilibrium. As heat is applied to a solid, its temperature will increase until the melting point is reached. More heat then will convert the solid into a liquid with no temperature change.
Summary
Melting point is the temperature at which the solid and liquid forms of a pure substance can exist in equilibrium. As heat is applied to a solid, its temperature will increase until the melting point is reached. More heat then will convert the solid into a liquid with no temperature change. When all the solid has melted, additional heat will raise the temperature of the liquid. The melting temperature of crystalline solids is a characteristic figure and is used to identify pure compounds and elements. Most mixtures and amorphous solids melt over a range of temperatures.
The melting temperature of a solid is generally considered to be the same as the freezing point of the corresponding liquid; because a liquid may freeze in different crystal systems and because impurities lower the freezing point, however, the actual freezing point may not be the same as the melting point. Thus, for characterizing a substance, the melting point is preferred.
Details
The melting point (or, rarely, liquefaction point) of a substance is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends on pressure and is usually specified at a standard pressure such as 1 atmosphere or 100 kPa.
When considered as the temperature of the reverse change from liquid to solid, it is referred to as the freezing point or crystallization point. Because of the ability of substances to supercool, the freezing point can easily appear to be below its actual value. When the "characteristic freezing point" of a substance is determined, in fact, the actual methodology is almost always "the principle of observing the disappearance rather than the formation of ice, that is, the melting point."
Examples
For most substances, melting and freezing points are approximately equal. For example, the melting and freezing points of mercury is 234.32 kelvins (−38.83 °C; −37.89 °F). However, certain substances possess differing solid-liquid transition temperatures. For example, agar melts at 85 °C (185 °F; 358 K) and solidifies from 31 °C (88 °F; 304 K); such direction dependence is known as hysteresis. The melting point of ice at 1 atmosphere of pressure is very close to 0 °C (32 °F; 273 K); this is also known as the ice point. In the presence of nucleating substances, the freezing point of water is not always the same as the melting point. In the absence of nucleators water can exist as a supercooled liquid down to −48.3 °C (−54.9 °F; 224.8 K) before freezing.
The metal with the highest melting point is tungsten, at 3,414 °C (6,177 °F; 3,687 K); this property makes tungsten excellent for use as electrical filaments in incandescent lamps. The often-cited carbon does not melt at ambient pressure but sublimes at about 3,700 °C (6,700 °F; 4,000 K); a liquid phase only exists above pressures of 10 MPa (99 atm) and estimated 4,030–4,430 °C (7,290–8,010 °F; 4,300–4,700 K). Hafnium carbonitride (HfCN) is a refractory compound with the highest known melting point of any substance to date and the only one confirmed to have a melting point above 4,273 K (4,000 °C; 7,232 °F) at ambient pressure. Quantum mechanical computer simulations predicted that this alloy (HfN0.38C0.51) would have a melting point of about 4,400 K. This prediction was later confirmed by experiment, though a precise measurement of its exact melting point has yet to be confirmed. At the other end of the scale, helium does not freeze at all at normal pressure even at temperatures arbitrarily close to absolute zero; a pressure of more than twenty times normal atmospheric pressure is necessary.
Melting point measurements
Many laboratory techniques exist for the determination of melting points. A Kofler bench is a metal strip with a temperature gradient (range from room temperature to 300 °C). Any substance can be placed on a section of the strip, revealing its thermal behaviour at the temperature at that point. Differential scanning calorimetry gives information on melting point together with its enthalpy of fusion.
A basic melting point apparatus for the analysis of crystalline solids consists of an oil bath with a transparent window (most basic design: a Thiele tube) and a simple magnifier. Several grains of a solid are placed in a thin glass tube and partially immersed in the oil bath. The oil bath is heated (and stirred) and with the aid of the magnifier (and external light source) melting of the individual crystals at a certain temperature can be observed. A metal block might be used instead of an oil bath. Some modern instruments have automatic optical detection.
The measurement can also be made continuously with an operating process. For instance, oil refineries measure the freeze point of diesel fuel "online", meaning that the sample is taken from the process and measured automatically. This allows for more frequent measurements as the sample does not have to be manually collected and taken to a remote laboratory.[citation needed]
Techniques for refractory materials
For refractory materials (e.g. platinum, tungsten, tantalum, some carbides and nitrides, etc.) the extremely high melting point (typically considered to be above, say, 1,800 °C) may be determined by heating the material in a black body furnace and measuring the black-body temperature with an optical pyrometer. For the highest melting materials, this may require extrapolation by several hundred degrees. The spectral radiance from an incandescent body is known to be a function of its temperature. An optical pyrometer matches the radiance of a body under study to the radiance of a source that has been previously calibrated as a function of temperature. In this way, the measurement of the absolute magnitude of the intensity of radiation is unnecessary. However, known temperatures must be used to determine the calibration of the pyrometer. For temperatures above the calibration range of the source, an extrapolation technique must be employed. This extrapolation is accomplished by using Planck's law of radiation. The constants in this equation are not known with sufficient accuracy, causing errors in the extrapolation to become larger at higher temperatures. However, standard techniques have been developed to perform this extrapolation.
Consider the case of using gold as the source (mp = 1,063 °C). In this technique, the current through the filament of the pyrometer is adjusted until the light intensity of the filament matches that of a black-body at the melting point of gold. This establishes the primary calibration temperature and can be expressed in terms of current through the pyrometer lamp. With the same current setting, the pyrometer is sighted on another black-body at a higher temperature. An absorbing medium of known transmission is inserted between the pyrometer and this black-body. The temperature of the black-body is then adjusted until a match exists between its intensity and that of the pyrometer filament. The true higher temperature of the black-body is then determined from Planck's Law. The absorbing medium is then removed and the current through the filament is adjusted to match the filament intensity to that of the black-body. This establishes a second calibration point for the pyrometer. This step is repeated to carry the calibration to higher temperatures. Now, temperatures and their corresponding pyrometer filament currents are known and a curve of temperature versus current can be drawn. This curve can then be extrapolated to very high temperatures.
In determining melting points of a refractory substance by this method, it is necessary to either have black body conditions or to know the emissivity of the material being measured. The containment of the high melting material in the liquid state may introduce experimental difficulties. Melting temperatures of some refractory metals have thus been measured by observing the radiation from a black body cavity in solid metal specimens that were much longer than they were wide. To form such a cavity, a hole is drilled perpendicular to the long axis at the center of a rod of the material. These rods are then heated by passing a very large current through them, and the radiation emitted from the hole is observed with an optical pyrometer. The point of melting is indicated by the darkening of the hole when the liquid phase appears, destroying the black body conditions. Today, containerless laser heating techniques, combined with fast pyrometers and spectro-pyrometers, are employed to allow for precise control of the time for which the sample is kept at extreme temperatures. Such experiments of sub-second duration address several of the challenges associated with more traditional melting point measurements made at very high temperatures, such as sample vaporization and reaction with the container.
Additional Information
1. What Is Melting Point?
Melting point is a characteristic property of solid crystalline substances. It is the temperature at which the solid phase changes to the liquid phase. Melting point determination is the thermal analysis most frequently used to characterize solid crystalline materials. It is used in research and development as well as in quality control in various industry segments to identify solid crystalline substances and to check their purity.
Melting point is a characteristic property of solid crystalline substance. It is the temperature at which the solid phase changes to the liquid phase. This phenomenon occurs when the substance is heated. During the melting process, all of the energy added to the substance is consumed as heat of fusion, and the temperature remains constant (see diagram below). During the phase transition, the two physical phases of the material exist side-by-side.
Crystalline materials consist of fine particles that for a regular, 3-dimensional arrangement – a crystalline lattice. The particles within the lattice are held together by lattice forces. When the solid crystalline material is heated, the particles become more energetic and start to move more strongly, until finally the forces of attraction between them are no longer strong enough to hold them together. The crystalline structure is destroyed and the solid material melts.
The stronger the forces of attraction between the particles, the more energy is needed to overcome them. The more energy is needed, the higher the melting point. The melting temperature of a crystalline solid is thus an indicator for the stability of its lattice.
At the melting point not only the aggregate state changes; quite a lot of other physical characteristics also change significantly. Amongst these are the thermodynamic values, specific heat capacity, enthalpy, and rheological properties such as volume or viscosity. Last but not least, the optical properties birefringence reflection and light transmission change. Compared to other physical values the change in light transmission can easily be determined and can therefore be used for melting point detection.
2. Why Measure Melting Points?
Melting points are often used to characterize organic and inorganic crystalline compounds and to ascertain their purity. Pure substances melt at a sharp, highly-defined temperature (very small temperature range of 0.5 – 1 °C) whereas impure, contaminated substances generally exhibit a large melting interval. The temperature at which all material of a contaminated substance is molten is usually lower than that of a pure substance. This behavior is known as melting point depression and can be used to obtain qualitative information about the purity of a substance.
In general, melting point determination is used in the lab in research and development as well as in quality control in various industry segments to identify and check the purity of different substances.
3. Melting Point Determination Principle
At the melting point, there is a change in light transmission. Compared to other physical values the change in light transmission can easily be determined and can therefore be used for melting point detection. Powdered crystalline materials are opaque in the crystalline state and transparent in the liquid state. This distinct difference in optical properties can be measured in order to determine the melting point by recording the percentage of light intensity shining through the substance in the capillary, the transmittance, in relation to the measured furnace temperature.
There are different stages of the melting point process of a solid crystalline substance: At the collapse point, the substance is mostly solid and comprises only a small amount of molten material. At the meniscus point, most of the substance has melted but some solid material is still present. At the clear point, the substance has completely melted.
#13 Re: Dark Discussions at Cafe Infinity » crème de la crème » Yesterday 17:26:53
2385) Ragnar Granit
Gist:
Work
Our vision works by the light around us being captured by a large number of light-sensitive cells located in the retinas at the back of our eyes. After a series of nerve switches and conversions of chemical and electrical signals, this results in visual impressions. Using very sophisticated electrodes, Ragnar Granit was able to study the electrical impulses from the retina’s cells. In studies conducted from the 1930s to the 1950s, he demonstrated that there are different types of cones (the cells that enable color vision) and that these are sensitive to light of three different wavelengths.
Summary
Ragnar Arthur Granit (born October 30, 1900, Helsinki, Finland—died March 12, 1991, Stockholm, Sweden) was a Finnish-born Swedish physiologist who was a corecipient (with George Wald and Haldan Hartline) of the 1967 Nobel Prize for Physiology or Medicine for his analysis of the internal electrical changes that take place when the eye is exposed to light.
Granit received an M.D. degree from the University of Helsinki in 1927, after which he conducted research at the University of Pennsylvania and at the laboratory of Sir Charles Scott Sherrington at Oxford, England. He was appointed professor of physiology at the University of Helsinki in 1937. A naturalized Swede, Granit joined the medical school of the Karolinska Institute, Stockholm, in 1940; he was named chairman of the institute’s department of neurophysiology in 1946. A year earlier he had also become the director of the Nobel Institute for Neurophysiology in Stockholm. In the 20 years from 1956 to 1976 Granit also served as a visiting professor or researcher at numerous institutions.
From studies of the action potentials in single fibres of the optic nerve, Granit formed his “dominator-modulator” theory of colour vision. In this theory he proposed that in addition to the three kinds of photosensitive cones—the colour receptors in the retina—which respond to different portions of the light spectrum, some optic nerve fibres (dominators) are sensitive to the whole spectrum while others (modulators) respond to a narrow band of light wavelengths and are thus colour-specific. Granit also proved that light could inhibit as well as stimulate impulses along the optic nerve. His book Sensory Mechanisms of the Retina (1947) is a classic work in the field of retinal electrophysiology.
Granit then turned his attention to the study of the control of movement, specifically the role of muscle sense-organs called muscle spindles and tendon organs. He helped to determine the neural pathways and processes by which these internal receptors regulate and coordinate muscle action.
Details
Ragnar Arthur Granit (30 October 1900 – 12 March 1991) was a Finnish-Swedish scientist who was awarded the Nobel Prize in Physiology or Medicine in 1967 along with Haldan Keffer Hartline and George Wald "for their discoveries concerning the primary physiological and chemical visual processes in the eye"
Early life and education
Ragnar Arthur Granit was born on 30 October 1900 in Riihimäki, Finland, at the time part of the Russian Empire, into a Swedish-speaking Finnish family. Granit was raised in Oulunkylä, a suburb of the Finnish capital of Helsinki, and attended the Svenska normallyceum in Helsinki.
Granit graduated from the Faculty of Medicine at the University of Helsinki in 1927.
Career and research
In 1940, when Finland became the target of a massive Soviet attack during the Winter War, Granit sought refuge – and peaceful surroundings for his studies and research work – in Stockholm, the capital of neighbouring Sweden, at the age of 40. In 1941, Granit received Swedish citizenship, which made it possible for him to live and continue with his work without having to worry about the Continuation War, which lasted in Finland until 1944. Granit was proud of his Finnish-Swedish roots and remained a patriotic Finnish-Swede throughout his life, maintaining homes in both Finland and Sweden after the Moscow Armistice ended the Continuation War and secured Finnish independence.
Granit was professor of neurophysiology at the Karolinska Institute from 1946 to his retirement in 1967.
Awards and honors
Granit was elected an International Member of the American Philosophical Society in 1954. In 1960, Granit was elected a Foreign Member of the Royal Society.
In 1967 he was awarded the Nobel Prize in Physiology or Medicine. Granit said that he was a "fifty-fifty" Finnish and Swedish Nobel laureate. He was elected an International Member of the United States National Academy of Sciences the following year. In 1971, he was elected an International Honorary Member of the American Academy of Arts and Sciences.
Death
Granit died on 12 March 1991 in Stockholm at the age of 90. Granit and his wife Marguerite, who died the same year, were buried in a church cemetery on the Finnish island of Korpo.
#14 Re: This is Cool » Miscellany » Yesterday 17:05:37
2437) Liquified Petroleum Gas
Gist
LPG stands for Liquefied Petroleum Gas. It is a flammable mixture of hydrocarbon gases, primarily propane and butane, which is stored and transported in liquid form under pressure. This process makes it easier to handle and store, and it is commonly used for cooking, heating, and as a fuel for vehicles.
Summary
Liquefied petroleum gas (LPG) is any of several liquid mixtures of the volatile hydrocarbons propene, propane, butene, and butane. It was used as early as 1860 for a portable fuel source, and its production and consumption for both domestic and industrial use have expanded ever since. A typical commercial mixture may also contain ethane and ethylene, as well as a volatile mercaptan, an odorant added as a safety precaution.
Liquefied petroleum gas (LPG) is recovered from “wet” natural gas (gas with condensable heavy petroleum compounds) by absorption. The recovered product has a low boiling point and must be distilled to remove the lighter fractions and then be treated to remove hydrogen sulfide, carbon dioxide, and water. The finished product is transported by pipeline and by specially built seagoing tankers. Transportation by truck, rail, and barge has also developed, particularly in the United States.
LPG reaches the domestic consumer in cylinders under relatively low pressures. The largest part of the LPG produced is used in central heating systems, and the next largest as raw material for chemical plants. LPG commonly is used as fuel for gas barbecue grills and gas cooktops and ovens, for gas fireplaces, and in portable heaters. In Europe, LPG water heaters are common. It is also used as an engine fuel and for backup generators. Unlike diesel, LPG can be stored nearly indefinitely without degradation.
Details
Liquefied petroleum gas, also referred to as liquid petroleum gas (LPG or LP gas), is a fuel gas which contains a flammable mixture of hydrocarbon gases, specifically propane, n-butane and isobutane. It can also contain some propylene, butylene, and isobutylene/isobutene.
LPG is used as a fuel gas in heating appliances, cooking equipment, and vehicles, and is used as an aerosol propellant and a refrigerant, replacing chlorofluorocarbons in an effort to reduce the damage it causes to the ozone layer. When specifically used as a vehicle fuel, it is often referred to as autogas or just as gas.
Varieties of LPG that are bought and sold include mixes that are mostly propane (C3H8), mostly butane (C4H10), and, most commonly, mixes including both propane and butane. In the northern hemisphere winter, the mixes contain more propane, while in summer, they contain more butane. In the United States, mainly two grades of LPG are sold: commercial propane and HD-5. These specifications are published by the Gas Processors Association (GPA) and the American Society of Testing and Materials. Propane/butane blends are also listed in these specifications.
Propylene, butylenes and various other hydrocarbons are usually also present in small concentrations such as C2H6, CH4, and C3H8. HD-5 limits the amount of propylene that can be placed in LPG to 5% and is utilized as an autogas specification. A powerful odorant, ethanethiol, is added so that leaks can be detected easily. The internationally recognized European Standard is EN 589. In the United States, tetrahydrothiophene (thiophane) or amyl mercaptan are also approved odorants, although neither is currently being utilized.
LPG is prepared by refining petroleum or "wet" natural gas, and is almost entirely derived from fossil fuel sources, being manufactured during the refining of petroleum (crude oil), or extracted from petroleum or natural gas streams as they emerge from the ground. It was first produced in 1910 by Walter O. Snelling, and the first commercial products appeared in 1912. It currently provides about 3% of all energy consumed, and burns relatively cleanly with no soot and very little sulfur emission. As it is a gas, it does not pose ground or water pollution hazards, but it can cause air pollution. LPG has a typical specific calorific value of 46.1 MJ/kg compared with 42.5 MJ/kg for fuel oil and 43.5 MJ/kg for premium grade petrol (gasoline). However, its energy density per volume unit of 26 MJ/L is lower than either that of petrol or fuel oil, as its relative density is lower (about 0.5–0.58 kg/L, compared to 0.71–0.77 kg/L for gasoline). As the density and vapor pressure of LPG (or its components) change significantly with temperature, this fact must be considered every time when the application is connected with safety or custody transfer operations, e.g. typical cuttoff level option for LPG reservoir is 85%.
Besides its use as an energy carrier, LPG is also a promising feedstock in the chemical industry for the synthesis of olefins such as ethylene and propylene.
As its boiling point is below room temperature, LPG will evaporate quickly at normal temperatures and pressures and is usually supplied in pressurized steel vessels. They are typically filled to 80–85% of their capacity to allow for thermal expansion of the contained liquid. The ratio of the densities of the liquid and vapor varies depending on composition, pressure, and temperature, but is typically around 250:1. The pressure at which LPG becomes liquid, called its vapour pressure, likewise varies depending on composition and temperature; for example, it is approximately 220 kilopascals (32 psi) for pure butane at 20 °C (68 °F), and approximately 2,200 kilopascals (320 psi) for pure propane at 55 °C (131 °F). LPG in its gaseous phase is still heavier than air, unlike natural gas, and thus will flow along floors and tend to settle in low spots, such as basements. There are two main dangers to this. The first is a possible explosion if the mixture of LPG and air is within the explosive limits and there is an ignition source. The second is suffocation due to LPG displacing air, causing a decrease in oxygen concentration.
A full LPG gas cylinder contains 86% liquid; the ullage volume will contain vapour at a pressure that varies with temperature.
Additional Information
Liquefied Petroleum Gas (LPG) can pose a serious health hazard in the workplace. The chemical properties of LPG, combined with its potential for combustion and the associated risks of leaks and exposure to combustion byproducts, make it essential to handle, store, and use LPG safely to mitigate health hazards and prevent accidents.
What Is Liquified Petroleum Gas?
LPG is a colourless, odourless, flammable gas. It is a mixture of propane and butane with smaller amounts of isobutane, butylene, and other hydrocarbons. When sold and shipped, an odorant (such as Methyl Mercaptan) is added.
What are the Common Uses of Liquified Petroleum Gas?
LPG is widely used as a fuel for domestic or camping heating and cooking appliances. It is also used as a lighter fuel, refrigerant, propellant in aerosols, substitute for gasoline and in the production of other chemicals and plastics.
Why Is Liquified Petroleum Gas Harmful?
LPG is an asphyxiant gas that can cause unconsciousness and/or death if oxygen levels are sufficiently reduced. May displace oxygen and cause rapid suffocation. LPG is also an extremely flammable gas and is a gas under pressure; which may explode if heated.
Side Effects of Inhaling Liquified Petroleum Gas
Exposure to LPG is mainly by inhalation or by eye and skin contact. Inhaling LPG vapor at high concentration even for a short time can cause asphyxiation, seizures, comas, heart problems and death.
Inhalation of LPG may cause drowsiness or dizziness and respiratory irritation (cough, sneezing, headache, nose and throat pain). Long-term exposure may lead to central nervous system damage, nosebleeds, rhinitis, oral/nasal ulcerations, conjunctivitis, weight loss and fatigue.
Eye and skin irritation may occur due to contact with LPG. LPG released under pressure can cause frostbite burn due to rapid temperature decrease. Symptoms of frostbite include permanent eye damage or blindness, change in skin color to white or grayish-yellow.
Who Needs to Be Concerned About LPG Hazards in the Workplace
Both employers and employees need to be aware of LPG hazards so that safety precautions are taken.
Exposure to LPG may be due to accidental emissions of vapours or gases from pressurized equipment, a leak from containment or release during breaking containment in the following workplaces:
• Natural gas processing facilities.
• Crude oil treatment processes in petroleum refineries, distillation, cracking or reforming.
• Manufacture of refrigerants and aerosols.
• Manufacture of chemicals using LPG as chemical feedstock.
• Loading, unloading, transportation and storage.
• Filling/transfer stations.
#15 Dark Discussions at Cafe Infinity » Code Quotes - III » Yesterday 16:29:03
- Jai Ganesh
- Replies: 0
Code Quotes - III
1. The best book I read this year was 'The Da Vinci Code.' - Goran Ivanisevic
2. Theosophy has no code of morals, being itself the embodiment of the highest morality; it presents to its students the highest moral teachings of all religions, gathering the most fragrant blossoms from the gardens of the world-faiths. - Annie Besant
3. There has to be some kind of order and some moral code. I don't know how people can function without a belief in a deity. - Mel Gibson
4. The thing about boxers is that there's respect there. You beat me, and I may not like it, but you know what, deep down inside, I respect you. And that's the code of honor. - Sugar Ray Leonard
5. The Russian people have their own cultural code, their own tradition. - Vladimir Putin
6. A lot of people assume that creating software is purely a solitary activity where you sit in an office with the door closed all day and write lots of code. - Bill Gates
7. Proprietary software keeps users divided and helpless. Divided because each user is forbidden to redistribute it to others, and helpless because the users can't change it since they don't have the source code. They can't study what it really does. So the proprietary program is a system of unjust power. - Richard Stallman
8. We have a rule that if you check in code, you have to maintain it. So I mostly code on the side. I don't check in code anymore. - Mark Zuckerberg.
#16 Re: Jai Ganesh's Puzzles » General Quiz » Yesterday 16:01:22
Hi,
#10649. What does the term in Biology Egg mean?
#10650. What does the term in Biology Electrochemical gradient mean?
#17 Re: Jai Ganesh's Puzzles » English language puzzles » Yesterday 15:42:12
Hi,
#5845. What does the verb (used with object) downplay mean?
#5846. What does the noun downpour mean?
#18 Re: Jai Ganesh's Puzzles » Doc, Doc! » Yesterday 15:24:20
Hi,
#2517. What does the medical term HELLP syndrome mean?
#19 Jokes » Blackberry Jokes » Yesterday 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...
* * *
#20 Re: Jai Ganesh's Puzzles » 10 second questions » Yesterday 14:12:16
Hi,
#9796.
#21 Re: Jai Ganesh's Puzzles » Oral puzzles » Yesterday 13:56:01
Hi,
#6291.
#22 Re: Exercises » Compute the solution: » Yesterday 13:44:32
Hi,
2639.
#23 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.
#24 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.
#25 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.
