The amazing properties of Borosilicate Glass

Borosilicate glass is a type of glass with the main glass-forming constituents silica and boron oxide. Borosilicate glasses are known for having very low coefficients of thermal expansion (~3 × 10⁻⁶ /°C at 20°C), making them resistant to thermal shock, more so than any other common glass. Such glass is less subject to thermal stress and is commonly used for the construction of reagent bottles, flasks, beakers and many other laboratory glassware items. Borosilicate glass is sold under such trade names as Pyrex, Schott & Simax.

 

Borosilicate glass was first developed by German glassmaker Otto Schott in the late 19th century and sold under the brand name "Duran" in 1893. After Corning Glass Works introduced Pyrex in 1915, the name became a synonym for borosilicate glass in the English-speaking world.

Chemical Properties
Borosilicate glass has a very high resistance to attack from water, acids, salt solutions, halogens and organic solvents. Only hydrofluoric acid, hot concentrated phosphoric acid and strong alkaline solutions cause appreciable corrosion of the glass.

Hydrolytic resistance For many applications, it is important that laboratory glassware has excellent hydrolytic resistance; e.g. during steam sterilisation procedures, where repeated exposure to water vapour at high temperature can leach out alkali (Na+) ions. Pyrex borosilicate glass for example has a relatively low alkali metal oxide content and consequently a high resistance to attack from water. Pyrex fits into Class 1 of glasses for hydrolytic resistance according to ISO 719 (98°C) and ISO 720 (121°C).

Acid resistance
Glasses with a high percentage weight of silica (SiO2) are less likely to be attacked by acids. Pyrex borosilicate glass is over 80% silica and therefore remarkably resistant to acids (with the exception of hot concentrated phosphoric acid and hydrofluoric acid). Glass is separated into 4 acid resistance classes and Pyrex corresponds to Class 1 in accordance with DIN 12116 and meets the requirements of ISO 1776.

Alkali resistance
Alkaline solutions attack all glasses and Pyrex can be classified as moderately resistant. The alkali resistance of Pyrex borosilicate glass meets Class 2 requirements as defined by ISO 695 and DIN 52322.

High usage temperature

           

The maximum permissible operating temperature for DURAN® borosilicate glass is 500 °C. Above a temperature of 525 °C the glass begins to soften and above a temperature of 860 °C it changes to the liquid state.

DURAN® can be cooled down to the maximum possible negative temperature and is therefore suitable for use with liquid nitrogen (approx. – 196 °C). During such use/ freezing. In general DURAN® products are recommended for use down to – 70 °C. During thawing ensure that the temperature difference does not exceed 100 K.

 

The link below shows how Duran glass is made
http://www.duran-group.com/en/about-duran/how-duran-is-made.html

For more information visit
http://www.scilabware.com/Glass_technical/
http://www.duran-group.com/en/about-duran/duran-properties.html
http://en.wikipedia.org/wiki/Borosilicate_glass

Just a pinch of salt....

Salt, also known as table salt or rock salt (halite), is a crystalline mineral that is composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of ionic salts. It is absolutely essential for animal life, but can be harmful to animals and plants in excess. Salt is one of the oldest, most ubiquitous food seasonings and salting is an important method of food preservation. The taste of salt (saltiness) is one of the basic human tastes.
Salt for human consumption is produced in different forms: unrefined salt (such as sea salt), refined salt (table salt), and iodized salt. It is a crystalline solid, white, pale pink or light grey in colour, normally obtained from sea water or rock deposits. Edible rock salts may be slightly greyish in colour because of mineral content.
Because of its importance to survival, salt has often been considered a valuable commodity during human history. However, as salt consumption has increased during modern times, scientists have become aware of the health risks associated with high salt intake, including high blood pressure in sensitive individuals. Therefore, some health authorities have recommended limitations of dietary sodium, although others state the risk is minimal for typical western diets.

Additives in table salt

Most table salt sold for consumption contain additives which address a variety of health concerns, especially in the developing world. The identities and amounts of additives vary widely from country to country.

• Iodine and Iodide
• Fluoride
• Anti-caking agents
• Iron
• Other additives

Too much or too little salt in the diet can lead to muscle cramps, dizziness, or electrolyte disturbance, which can cause neurological problems, or death.  Drinking too much water, with insufficient salt intake, puts a person at risk of water intoxication (hyponatremia)

Lowering salt in diet

It is a misconception that sea salt has a lower sodium content than table salt, — they are both basically sodium chloride.  A low sodium diet reduces the intake of sodium by the careful selection of food. This aim can also be achieved by the use of a salt substitute, and Potassium chloride is widely used for this purpose. Although recommended limits for potassium are higher than for sodium, potassium has its own health disadvantages, and it is advised that such a salt substitute not be used by those taking certain prescription drugs.  Another possibility being researched is the use of seaweed granules in the manufacture of processed foods as an alternative to salt.

For more information visit:-
http://www.nhs.uk/Livewell/Goodfood/Pages/salt.aspx
http://en.wikipedia.org/wiki/Salt

How Boomerangs Work

Classic boomerangs have two arms or wings normally of equal length. They are joined at the elbow, at an angle of between 105° and 110°. The reason for this angle lies in the origins of boomerang manufacture; most boomerangs were made from the junction of a tree with its lateral (sideways) root. Each arm usually has a tapered tip, which is a carry-over from the ancestor of the boomerang - the killer stick.

All boomerangs are either right or left-handed - one is an exact mirror image of the other. This is to allow right and left-handed throwers to launch their boomerangs with relative ease because it's far more comfortable to throw away from, rather than across, the body. Having said this, it is possible to throw an opposite handed boomerang, with a few adjustments to your throwing action.

During the flight of the boomerang, the effect of many different aerodynamic principles can be seen. Bernoulli's theorem, Newton's laws of motion, gyroscopic stability, gyroscopic precession and many others all have a bearing on the action of the boomerang.

When the boomerang leaves the thrower's hand, it will be spinning very fast. As each arm of the boomerang has an aerofoil shape, similar in cross-section to that of an aircraft wing, air moving over the top of each wing has to travel further, and therefore faster, than air passing beneath the wings. Bernoulli's theorem states that 'air travelling at a higher speed creates less pressure than slower moving air'. As a result, the boomerang experiences a 'lift'¹ force.

Newton's second law of motion states that 'the rate of change of momentum of an object is equal to the force applied to that object'. For an object with constant mass, this reduces to the well-known formula Force applied = Mass x Acceleration. The force here is a combination of friction and other resistive forces. To reduce the acceleration (or deceleration, since the force is negative), the mass needs to be large, but not so large that the boomerang falls quickly to the ground.

The length of the boomerang's arms, and the angle at which they are joined, allow the boomerang to spin in a stable plane as a result of the spin imparted on launching. This is known as gyroscopic stability. If this were not the case, the motion of the boomerang would at best be unpredictable. At worst, the boomerang would lose its spin rapidly, and be unable to sustain flight.

We now have a stable, rapidly spinning boomerang, moving forward from the force of the throw. We now need to take a slightly closer look at the effect of Bernoulli's theorem. As each wing rotates forward, into the direction of travel, it creates more lift than the other wing because the relative air speed is higher. If you imagine the spinning boomerang as a clock face, sideways on, this leads to the maximum force being created near the 12 o'clock position.

Due to the gyroscopic stability of the spinning boomerang, the effect of this force manifests itself at 90° further round the cycle of spin - at the 9 o'clock position of our clock face. The action of this force is to change the direction of flight - to the left for a right-handed boomerang and vice versa. Compare this with a 'no hands' bicycle turn - the only difference being the magnitude of the force. A small force over most of the duration of the flight produces a large, smooth turn for the boomerang, while a sudden strong force produces an abrupt bicycle turn.

As the boomerang travels, it loses velocity². Eventually, gyroscopic precession becomes the dominant force. Coupled with the initial 'off-vertical' tilt, the effect is to push the boomerang over on its side, so that it spins in a horizontal plane.

The effect of each of these principles varies with the way in which the boomerang is thrown. The basic flight path of a boomerang is circular, although advanced throwers can produce a virtually triangular flight path.

¹This is slightly misleading - the boomerang is thrown in a near vertical position, so the resulting 'lift' actually acts sideways.

²As it is rare to get absolutely dead-calm conditions, the wind starts to have an effect. This means that it is necessary to launch the boomerang 50° off the wind - the flight path should curl across the wind, and end with the boomerang being almost 'blown back' to the thrower.

 

Origins

 

The origin of the term is uncertain, and many researchers have different theories on how the word entered the English vocabulary. One source asserts that the term entered the language in 1827, adapted from an extinct Aboriginal language of New South Wales, Australia, but mentions a variant, wo-mur-rang, which it dates from 1798. The boomerang was first encountered by western people at Farm Cove (Port Jackson), Australia, in December 1804 where its use as a weapon was witnessed during a tribal skirmish.

 

http://www.h2g2.com/approved_entry/A407521

http://en.wikipedia.org/wiki/Boomerang

 

 

Want to extract your own DNA?

As shown recently by Professor Brian Cox on the BBC TV Series Wonders of Life it is possible using a few household ingredients to extract your own DNA.

 

DNA, or Deoxyribonucleic Acid, is the genetic material of nearly all living organisms on the planet Earth and, as such, can be called the basic building block of life. In 1953, James Watson and Francis Crick unveiled their discoveries about DNA and the double helix model, which formed the basis of genetic coding.

DNA - A Brief Description

DNA is located in the cell nucleus as the basic structure of the genes, and is composed of two strands of nucleic acid made up of units called nucleotides, wound around each other to form a double helix shape.

Nucleic acids, called that because they were discovered in cell nuclei, are long organic polymers that contain carbon, hydrogen, oxygen, nitrogen and phosphorus, forming the inherited genetic material inside each cell. In humans, each gene is a segment of DNA and controls protein synthesis, regulating most of the activities that take place in the cells.

The DNA molecule can make exact copies of itself by the process of replication, thereby passing on hereditary information - so determining all physical (and some would argue, personality) traits. This enables DNA to be used to identify gender, hair and eye colour, and other genetic markers.


To extract DNA at home you will need the following:
•saline solution (a glass of salty water)
•a clean glass
•1 tsp (5ml) washing-up liquid/detergent
•3 tsp (15ml) tap water
•a clean teaspoon
•a bottle of ice-cold alcohol (gin or vodka are excellent, as many people keep these in the freezer2. If you don't have strong booze available, any alcohol will do, such as rubbing alcohol.)
•a mouthful of spit

Method

1. Swill out your mouth with the saline solution for about 30 seconds. This is to collect the DNA contained in your saliva, and around the walls of your cheeks.
2. Spit the contents of your mouth into a glass containing a mix of three teaspoons of water and one teaspoon of washing-up liquid/detergent. You are thus (hopefully) transferring the DNA from your cheek cells into the solution.
3. Stir this mix slowly and gentlyfor a couple of minutes. During this process it is necessary to break up tissue (in this case, cheek cells) mechanically, and then to degrade both the cell membranes and those surrounding the nuclei - releasing the DNA contained within them
4. Now pour (slowly!) some of the ice-cold alcohol carefully down the inside of the glass, allowing it to settle on top of the solution. DNA is insoluble in cold alcohol and while there will be a few bubbles, the other compounds in the mixture will dissolve, and the DNA will separate from the other ingredients. Leave it for about two to three minutes for this to happen
5. If you are lucky you will see a spindly white substance, maybe clumps of it if you are really careful, forming on top of the salt/detergent mixture. Be patient - it will happen slowly. The resulting 'goo' is unique to you; it is your very own DNA!

For more information visit:

http://www.h2g2.com/approved_entry/A26560424

Or watch Professor Brian Cox in action below.

http://www.bbc.co.uk/programmes/p01466mm

 

The Amazing Properties of Copper

New research has revealed that the use of Antimicrobial Copper surfaces in hospital rooms can reduce the number of healthcare-acquired infections (HAIs) by 58% as compared to patients treated in Intensive Care Units with non-copper touch surfaces.

In the United States, 1 out of every 20 hospital patients develops an HAI, resulting in an estimated 100,000 deaths per year. Although numerous strategies have been developed to decrease these infections, Antimicrobial Copper is the only strategy that works continuously, has been scientifically proven to be effective and doesn’t depend on human behaviour, according to a recently published study in the SHEA Journal of Infection Control and Hospital Epidemiology.
“The implications of this study are critical,” said Dr. Harold Michels, Senior Vice President of the Copper Development Association (CDA). “Until now, the only attempts to reduce HAIs have required hand hygiene, increased cleaning and patient screening, which don’t necessarily stop the growth of these bacteria the way copper alloy surfaces do. We now know that copper is the game-changer: it has the potential to save lives.”


Intensive Care Units See the Benefit of Copper Alloys

The study, funded by the U.S. Department of Defence, was conducted in the Intensive Care Units (ICUs) of three major hospitals: The Medical University of South Carolina, Memorial Sloan-Kettering Cancer Centre in New York City and the Ralph H. Johnson Veterans Affairs Medical Centre in Charleston, South Carolina. To determine the impact of copper alloy surfaces on the rate of HAIs, copper-surfaced objects were placed in each ICU, where patients are at higher risk due to the severity of their illnesses, invasive procedures and frequent interaction with healthcare workers. Patients were randomly placed in available rooms with or without copper alloy surfaces, and the rates of HAIs were compared. A total of 650 patients and 16 rooms (8 copper and 8 standard) were studied between July 12, 2010 and June 14, 2011.

Results of this study, that appeared last July in the Journal of Clinical Microbiology, found that Antimicrobial Copper can continuously kill 83% of bacteria that cause HAIs within two hours, including strands resistant to antibiotics. The study compared copper to equivalent non-copper touch surfaces during active patient care between routine cleaning and sanitizing.

“Copper alloy surfaces offer an alternative way to reduce the increasing number of HAIs, without having to worry about changing healthcare worker behaviour,” said Dr. Michael Schmidt, Vice Chairman of Microbiology and Immunology at the Medical University of South Carolina and one of the authors of the study. “Because the antimicrobial effect is a continuous property of copper, the regrowth of deadly bacteria is significantly less on these surfaces, making a safer environment for hospital patients.”
In study results, 46 patients developed an HAI, while 26 patients became colonized with MRSA or VRE. Overall, the proportion of patients who developed an HAI was significantly lower among those assigned to intensive care rooms with objects fabricated using copper alloys. There are currently hundreds of Antimicrobial Copper healthcare-related products available today, including IV poles, stretchers, tray tables and door hardware.

This study was so successful that an interdisciplinary team from UCLA began replicating this research in July 2012. The team is testing ICUs with Antimicrobial Copper at Ronald Reagan UCLA Medical Centre.
For more information about Antimicrobial Copper, visit http://www.antimicrobialcopper.com.

Numerous antimicrobial efficacy studies have been conducted in the past 10 years regarding copper’s efficacy to destroy a wide range of bacteria, as well as influenza A virus, adenovirus, and fungi.
Copper-alloy touch surfaces have natural intrinsic properties to destroy a wide range of microorganisms. Some 355 copper alloys were proven to kill more than 99.9% of disease-causing bacteria within just two hours when cleaned regularly. The United States Environmental Protection Agency (EPA) has approved the registrations of these copper alloys as “antimicrobial materials with public health benefits," which allows manufacturers to legally make claims as to the positive public health benefits of products made with registered antimicrobial copper alloys. In addition, the EPA has approved a long list of antimicrobial copper products made from these alloys, such as bedrails, handrails, over-bed tables, sinks, faucets, door knobs, toilet hardware, computer keyboards, health club equipment, shopping cart handles, etc. Copper doorknobs are used by hospitals to reduce the transfer of disease, and Legionnaires' disease is suppressed by copper tubing in plumbing systems. Antimicrobial copper alloy products are now being installed in healthcare facilities in the U.K., Ireland, Japan, Korea, France, Denmark, Brazil and Chile amongst other.

Hydrofluoric Acid

Hydrofluoric acid (HF) is a solution of hydrogen fluoride in water. It is a valued source of fluorine and is a precursor to numerous pharmaceuticals such as fluoxetine (Prozac) and diverse materials such as PTFE (Teflon).

Hydrofluoric acid is a highly corrosive acid, capable of dissolving many materials, especially oxides. Its ability to dissolve glass has been known since the 17th century, even before hydrofluoric acid had been prepared in large quantities by Carl Wilhelm Scheele in 1771. Because of its high reactivity toward glass and moderate reactivity toward many metals, hydrofluoric acid is usually stored in plastic containers (although PTFE is slightly permeable to it).

Hydrogen fluoride gas is an acute poison that may immediately and permanently damage lungs and the corneas of the eyes. Aqueous hydrofluoric acid is a contact-poison with the potential for deep, initially painless burns and ensuing tissue death. By interfering with body calcium metabolism, the concentrated acid may also cause systemic toxicity and eventual cardiac arrest and fatality, after contact with as little as 160 cm² (25 square inches) of skin.

Production
Hydrofluoric acid is produced by treatment of the mineral fluorite (CaF₂) with concentrated sulphuric acid. When combined at 265 °C, these two substances react to produce hydrogen fluoride and calcium sulphate according to the following chemical equation:

CaF₂ + H₂SO₄ → 2 HF + CaSO₄

Although bulk fluorite is a suitable precursor and a major source of world HF production, HF is also produced as a by-product of the production of phosphoric acid, which is derived from the mineral apatite. Apatite sources typically contain a few percent of fluoroapatite, acid digestion of which releases gaseous stream consisting of sulphur dioxide (from the H₂SO₄), water, and HF, as well as particulates. After separation from the solids, the gases are treated with sulphuric acid and oleum to afford anhydrous HF. Owing to the corrosive nature of HF, its production is accompanied by the dissolution of silicate minerals, and, in this way, significant amounts of fluorosilicic acid is generated.

Health & Safety

Hydrofluoric acid is a highly corrosive liquid and is a contact poison. It should be handled with extreme care, beyond that accorded to other mineral acids. Owing to its low dissociation constant, HF as a neutral lipid-soluble molecule penetrates tissue more rapidly than typical mineral acids. Because of the ability of hydrofluoric acid to penetrate tissue, poisoning can occur readily through exposure of skin or eyes, or when inhaled or swallowed. Symptoms of exposure to hydrofluoric acid may not be immediately evident. HF interferes with nerve function, meaning that burns may not initially be painful. Accidental exposures can go unnoticed, delaying treatment and increasing the extent and seriousness of the injury.

Once absorbed into blood through the skin, it reacts with blood calcium and may cause cardiac arrest. Burns with areas larger than 25 square inches (160 cm²) have the potential to cause serious systemic toxicity from interference with blood and tissue calcium levels. In the body, hydrofluoric acid reacts with the ubiquitous biologically important ions Ca²⁺ and Mg²⁺. Formation of insoluble calcium fluoride is proposed as the etiology for both precipitous fall in serum calcium and the severe pain associated with tissue toxicity. In some cases, exposures can lead to hypocalcemia. Thus, hydrofluoric acid exposure is often treated with calcium gluconate, a source of Ca²⁺ that sequesters the fluoride ions. HF chemical burns can be treated with a water wash and 2.5% calcium gluconate gel. or special rinsing solutions. However, because it is absorbed, medical treatment is necessary; rinsing off is not enough. Intra-arterial infusions of calcium chloride have also shown great effectiveness in treating burns.

P&R Labpak can supply HF antidote gel - just ask for details.

For more information visit:-
http://en.wikipedia.org/wiki/Hydrofluoric_acid
http://www.hse.gov.uk/pubns/indg307.pdf
This link covers HF poisoning, effects and precautions

The eyes have it!

Eye colour

Structure of the Iris

The iris is made up of four layers:

• The anterior border layer (the front layer facing out)
• The stroma
• Two layers of endothelium (at the back of the iris)

The double layer is responsible for dilating the pupil and absorbing any stray light that reaches the back of the iris. It is only the first two layers that determine iris colour.

The anterior border layer contains melanocytes. Everyone's body contains about the same number of melanocytes, but the amount of melanin in these cells is genetically determined. Melanin absorbs light and is the principle pigment in hair and skin. Differing levels of melanin account for the differences in skin and hair colour between races and individuals. People with dark skin and hair have a generally higher level of melanin than pale, blond people. As a result, people with darker skin and/or hair are more likely to have brown eyes. In the eye, low levels of melanin absorb less light and have a yellow appearance, while high levels look brown.

The stroma is a connective tissue layer which contains collagen, blood vessels and the iris sphincter. The iris sphincter is the muscle which constricts the pupil. White light entering the stroma is scattered by the collagen. The collagen absorbs most of the colours apart from blue or grey, these are reflected back by the collagen. The blood vessels and sphincter scatter the light in different ways giving different patterns of flecks. The ring that can sometimes be seen in the iris is the minor iridic circle, which is the artery ring supplying the iris with blood. Freckles and darker patches on the iris are caused by round groups of pigment and are called clump cells.

Whether the eye is blue or grey depends on the arrangement of the collagen fibres: fine arrangement causes blue eyes while a coarser arrangement causes grey ones.

Different Eye Colours

In a brown eye there is a lot of melanin in the anterior border layer. This absorbs the light and gives a brown velvety appearance.

In a blue eye there is not much melanin in the anterior border layer. The light passes into the stroma where the collagen fibres scatter the light back as blue.

In a green eye (or a hazel one) there is a variable level of melanin, so that some of the light is absorbed by the melanin and some is scattered by the collagen. The brown layer looks yellow as it is thinner, and so the yellow and blue mix to make green.

Red irides¹ are a result of albinism. Albinism is where there is no melanin in the melanocytes at all. Therefore all of the blood vessels (in the iris and retina) are seen and a redder appearance is given. In practice only very few albinos have red eyes, the blue reflections of the collagen show up stronger and so most have blue/grey or even brown. The mixing of red and blue reflections can also give rise to violet eyes.

Why the Pupil Usually Looks Black

The retina of a human eye looks red because it has lots of blood vessels supplying the cells with metabolites. One reason you don't see the red colour is because the retina absorbs nearly all of the light which enters the pupil. In normal circumstances very little light is reflected and so the pupil looks dark. When a very strong light is shone on the pupil, some of the light is reflected back and the pupil looks red (so you sometimes get red-eye in photographs).

For more information:-
http://en.wikipedia.org/wiki/Eye_color
http://www.h2g2.com/approved_entry/A734933