On this day in science history: oxygen was identified

In 1774, Joseph Priestley, British Presbyterian minister and chemist, identified a gas which he called "dephlogisticated air" - later known as oxygen. Priestley found that mercury heated in air became coated with "red rust of mercury," which, when heated separately, was converted back to mercury with "air" given off. Studying this "air" given off, he observed that candles burned very brightly in it. Also, a mouse in a sealed vessel with it could breathe it much longer than ordinary air. A strong believer in the phlogiston theory, Priestley considered it to be "air from which the phlogiston had been removed." Further experiments convinced him that ordinary air is one fifth dephlogisticated air, the rest considered by him to be phlogiston.

Joseph Priestley, by Charles Turner [Public domain], via Wikimedia Commons

However, oxygen was in fact first discovered earlier, by Swedish pharmacist Carl Wilhelm Scheele. He had produced oxygen gas by heating mercuric oxide and various nitrates in 1771–2. Scheele called the gas "fire air" because it was the only known supporter of combustion, and wrote an account of this discovery in a manuscript he titled Treatise on Air and Fire, which he sent to his publisher in 1775. That document was published in 1777. 

Because Priestly published his findings first, he is usually given priority in the discovery.

The French chemist Antoine Laurent Lavoisier later claimed to have discovered the new substance independently. Priestley visited Lavoisier in October 1774 and told him about his experiment and how he liberated the new gas. Scheele also posted a letter to Lavoisier on September 30, 1774 that described his discovery of the previously unknown substance, but Lavoisier never acknowledged receiving it (a copy of the letter was found in Scheele's belongings after his death). Long before this, one of the first known experiments on the relationship between combustion and air was conducted by the 2nd century BCE Greek writer on mechanics, Philo of Byzantium. In his work Pneumatica, Philo observed that inverting a vessel over a burning candle and surrounding the vessel's neck with water resulted in some water rising into the neck. Philo incorrectly surmised that parts of the air in the vessel were converted into the classical element fire and thus were able to escape through pores in the glass. Many centuries later Leonardo da Vinci built on Philo's work by observing that a portion of air is consumed during combustion and respiration.

In the late 17th century, Robert Boyle proved that air is necessary for combustion. English chemist John Mayow (1641–1679) refined this work by showing that fire requires only a part of air that he called spiritus nitroaereus. In one experiment, he found that placing either a mouse or a lit candle in a closed container over water caused the water to rise and replace one-fourteenth of the air's volume before extinguishing the subjects. From this he surmised that nitroaereus is consumed in both respiration and combustion.

Mayow observed that antimony increased in weight when heated, and inferred that the nitroaereus must have combined with it. He also thought that the lungs separate nitroaereus from air and pass it into the blood and that animal heat and muscle movement result from the reaction of nitroaereus with certain substances in the body. Accounts of these and other experiments and ideas were published in 1668 in his work Tractatus duo in the tract "De respiratione".

Robert Hooke, Ole Borch, Mikhail Lomonosov, and Pierre Bayen all produced oxygen in experiments in the 17th and the 18th century but none of them recognized it as a chemical element. This may have been in part due to the prevalence of the philosophy of combustion and corrosion called the phlogiston theory, which was then the favored explanation of those processes.

Established in 1667 by the German alchemist J. J. Becher, and modified by the chemist Georg Ernst Stahl by 1731, phlogiston theory stated that all combustible materials were made of two parts. One part, called phlogiston, was given off when the substance containing it was burned, while the dephlogisticated part was thought to be its true form, or calx.

Highly combustible materials that leave little residue, such as wood or coal, were thought to be made mostly of phlogiston; non-combustible substances that corrode, such as iron, contained very little. Air did not play a role in phlogiston theory, nor were any initial quantitative experiments conducted to test the idea; instead, it was based on observations of what happens when something burns, that most common objects appear to become lighter and seem to lose something in the process. The fact that a substance like wood gains overall weight in burning was hidden by the buoyancy of the gaseous combustion products.

This theory, while it was on the right track, was unfortunately set up backwards. Rather than combustion or corrosion occurring as a result of the decomposition of phlogiston compounds into their base elements with the phlogiston being lost to the air, it is in fact the result of oxygen from the air combining with the base elements to produce oxides. Indeed, one of the first clues that the phlogiston theory was incorrect was that metals gain weight in rusting (when they were supposedly losing phlogiston).

For more information visit:-

https://todayinsci.com/8/8_01.htm

https://en.wikipedia.org/wiki/Oxygen

http://www.prlabs.co.uk/lab-supplies.php?N=oxygen-electrode-cellox-325-15&Id=77440

Solar paint offers endless energy from water vapor

Researchers have developed a solar paint that can absorb water vapour and split it to generate hydrogen - the cleanest source of energy.

The paint contains a newly developed compound that acts like silica gel, which is used in sachets to absorb moisture and keep food, medicines and electronics fresh and dry.

Sun with sunspots and limb darkening as seen in visible light with solar filter. By Geoff Elston [CC BY 4.0 (http://creativecommons.org/licenses/by/4.0)], via Wikimedia Commons

But unlike silica gel, the new material, synthetic molybdenum-sulphide, also acts as a semi-conductor and catalyses the splitting of water molecules into hydrogen and oxygen.

Lead researcher Dr Torben Daeneke, from RMIT University in Melbourne, Australia, said: "We found that mixing the compound with titanium oxide particles leads to a sunlight-absorbing paint that produces hydrogen fuel from solar energy and moist air.

"Titanium oxide is the white pigment that is already commonly used in wall paint, meaning that the simple addition of the new material can convert a brick wall into energy harvesting and fuel production real estate.

"Our new development has a big range of advantages," he said. "There's no need for clean or filtered water to feed the system. Any place that has water vapour in the air, even remote areas far from water, can produce fuel."

His colleague, Distinguished Professor Kourosh Kalantar-zadeh, said hydrogen was the cleanest source of energy and could be used in fuel cells as well as conventional combustion engines as an alternative to fossil fuels.

"This system can also be used in very dry but hot climates near oceans. The sea water is evaporated by the hot sunlight and the vapour can then be absorbed to produce fuel.

"This is an extraordinary concept - making fuel from the sun and water vapour in the air."

For more information visit:-

https://www.sciencedaily.com/releases/2017/06/170614091833.htm

http://www.prlabs.co.uk/lab-supplies.php?N=silica-gel-granules&Id=58847

On this day in science – the rubber fire hose was patented

In 1821, a fire hose of cotton web lined with rubber was patented by James Boyd of Boston, Mass. He invented it to replace riveted leather hose. Leather hose had many drawbacks, including drying out, cracking and bursting from excessive pressure. The introduction of rivets (1807), to replace stitching, had allowed higher pressures and greater delivery of water on the fireground. The improved hose now was 40 to 50 feet in length and weighed more than 85 pounds with the couplings. Hose oilers were developed to keep the leather supple and pliable. Various types of oils and other substances were used to keep the hose in shape. By 1871, the Cincinnati Fire Department was using the B.F. Goodrich Company's new rubber hose reinforced with cotton ply.

Indoor fire hose with a fire extinguisher, by Raysonho @ Open Grid Scheduler / Grid Engine (Own work) [CC0], via Wikimedia Commons

Modern fire hoses use a variety of natural and synthetic fabrics and elastomers in their construction. These materials allow the hoses to be stored wet without rotting and to resist the damaging effects of exposure to sunlight and chemicals. Modern hoses are also lighter weight than older designs, and this has helped reduce the physical strain on firefighters. Various devices are becoming more prevalent that remove the air from the interior of fire hose, commonly referred to as fire hose vacuums. This process makes hoses smaller and somewhat rigid, thus allowing more fire hose to be packed or loaded into the same compartment on a fire fighting apparatus.

There are several types of hose designed specifically for the fire service. Those designed to operate under positive pressure are called discharge hoses. They include attack hose, supply hose, relay hose, forestry hose, and booster hose. Those designed to operate under negative pressure are called suction hoses.

For more information visit:-

https://todayinsci.com/5/5_30.htm

https://en.wikipedia.org/wiki/Fire_hose

http://www.prlabs.co.uk/lab-supplies.php?N=balls-rubber-20mm-&Id=46943

Why water splashes: New theory reveals secrets

New research from the University of Warwick generates fresh insight into how a raindrop or spilt coffee splashes.

Dr James Sprittles from the Mathematics Institute has created a new theory to explain exactly what happens - in the tiny space between a drop of water and a surface - to cause a splash.

Water splash

When a drop of water falls, it is prevented from spreading smoothly across a surface by a microscopically thin layer of air that it can't push aside - so instead of wetting the surface, parts of the liquid fly off, and a splash is generated.

A layer of air 1 micron in size - fifty times smaller than the width of a human hair - can obstruct a 1mm drop of water which is one thousand times larger.

This is comparable to a 1cm layer of air stopping a tsunami wave spreading across a beach.

Dr Sprittles has established exactly what happens to this miniscule layer of air during the super-fast action by developing a new theory, capturing its microscopic dynamics - factoring in different physical conditions, such as liquid viscosity and air pressure, to predict whether splashes will occur or not.

The lower the air pressure, the easier the air can escape from the squashed layer - giving less resistance to the water drop - enabling the suppression of splashes. This is why drops are less likely to splash at the top of mountains, where the air pressure is reduced.

Understanding the conditions that cause splashing enables researchers to find out how to prevent it - leading to potential breakthroughs in various fields.

In 3D printing, liquid drops can form the building blocks of tailor-made products such as hearing aids; stopping splashing is key to making products of the desired quality.

Splashes are also a crucial part of forensic science - whether blood drops have splashed or not provides insight into where they came from, which can be vital information in a criminal investigation.

Dr Sprittles comments:

"You would never expect a seemingly simple everyday event to exhibit such complexity. The air layer's width is so small that it is similar to the distance air molecules travel between collisions, so that traditional models are inaccurate and a microscopic theory is required.

"Most promisingly, the new theory should have applications to a wide range of related phenomena, such as in climate science - to understand how water drops collide during the formation of clouds or to estimate the quantity of gas being dragged into our oceans by rainfall."

The research, 'Kinetic Effects in Dynamic Wetting', is published in Physical Review Letters.

For more information, visit:-

https://www.sciencedaily.com/releases/2017/03/170317082750.htm

http://www.prlabs.co.uk/lab-supplies.php?N=nuclease-free-water&Id=62712

On this day....The flying disc, or Frisbee

Walter Frederick "Fred" Morrison (January 23, 1920 – February 9, 2010) was an American inventor and entrepreneur, best known as the inventor of the Frisbee.

Walter Frederick Morrison

Morrison claimed that the original idea for a flying disc toy came to him in 1937, while throwing a popcorn can lid with his girlfriend, Lu, whom he later married. The popcorn can lid soon dented which led to the discovery that cake pans flew better and were more common. Morrison and Lu developed a little business selling "Flyin' Cake Pans" on the beaches of Santa Monica, California..

In 1946, he sketched out a design (called the Whirlo-Way) for the world's first flying disc. In 1948 an investor, Warren Franscioni, paid for molding the design in plastic. They named it the Flyin-Saucer. After disappointing sales, Fred & Warren parted ways in early 1950. In 1954, Fred bought more of the Saucers from the original molders to sell at local fairs, but soon found he could produce his own disc more cheaply. In 1955, he and Lu designed the Pluto Platter, the archetype of all modern flying discs. On January 23, 1957, they sold the rights for the Pluto Platter to the Wham-O toy company. Initially Wham-O continued to market the toy solely as the "Pluto Platter", but by June 1957 they also began using the name Frisbee after learning that college students in the Northeast were calling the Pluto Platter by that name. Morrison also invented several other products for Wham-O, but none were as successful as the Pluto Platter.

 
How does a Frisbee fly?
Two factors influence the flight of a Frisbee, gravity and air. Gravity acts on all objects the same way, accelerating their mass towards the center of the Earth at 10 meters/second. Once in the air, lift and angular momentum act on the Frisbee giving it a ballet-type performance. Lift is generated by the Frisbee's shaped surfaces as it passes through the air. Maintaining a positive angle of attack, the air moving over the top of the Frisbee flows faster than the air moving underneath it.

Under the Bernoulli Principle, there is then a lower air pressure on top of the Frisbee than beneath it. The difference in pressure causes the Frisbee to rise or lift. This is the same principle that allows planes to take off, fly and land. Another significant factor in the Frisbee's lift is Newton's Third Law which states that for every action there is an equal and opposite reaction. The Frisbee forces air down (action) and the air forces the Frisbee upward (reaction). The air is deflected downward by the Frisbee's tilt, or angle of attack.

Spinning the Frisbee when it is thrown, or giving it angular momentum (gyroscopic inertia), provides it with stability. Angular momentum is a property of any spinning mass. Throwing a Frisbee without any spin allows it to tumble to the ground. The momentum of the spin also gives it orientational stability, allowing the Frisbee to receive a steady lift from the air as it passes through it. The faster the Frisbee spins, the greater its stability.

For more information visit:-
http://en.wikipedia.org/wiki/Walter_Frederick_Morrison

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