P&R Labpak - Everything for your laboratory

P&R Labpak - Everything for your laboratory
Our Head Office in St Helens

Friday, 18 July 2014

How does a Laboratory Balance or Scale work?

There are two basic types of electronic balance designs.

1. Electromagnetic balancing type
2. Electrical resistance wire type (load cell type)


These are based on different principles, but both have neither directly measures mass. They measure the force that acts downward on the pan. This force is converted to an electrical signal and displayed on a digital display.
 

As a means of measuring force, the electromagnetic balance method uses the electromagnetic force generated from a magnet and coil, whereas the electrical resistance wire method uses the change in resistance value of a strain gauge attached to a piece of metal that bends in response to a force.
 
 
So why do electronic balances display mass values when that is not what they measure? It's because the reference standards for mass are weights, which are placed on a pan to inform the electronic balance that a given force is equivalent to a given number of grams, which is used for conversion. Consequently, electronic balances that do not perform this conversion accurately cannot display accurate mass values.

Readability and accuracy are not the same thing?
The readability of a balance is the smallest quantity that the balance will display. Accuracy is the difference between the known weight of a sample and the displayed weight. The accuracy of a balance can be measured only when the balance is in its operating environment

Location of the Balance

The precision and reproducibility of weighing results is closely associated with the location of the balance. To ensure that your balance can work under the best conditions, please observe the following guidelines:

Weighing bench
  • Stable (lab bench, lab table, stone bench).  Your weighing bench should not sag when work is carried out on it and should transfer as few vibrations as possible.
  • Antimagnetic (no steel plate).
  • Protected against electrostatic charges (no plastic or glass).
  • Wall or floor installation.  The weighing bench should be fixed either to the floor or on the wall.  Mounting the bench on both places at once transfers vibrations from wall and floor.
  • Reserved for the balance.

The place of installation and the weighing bench must be stable enough that the balance display does not change when someone leans on the table or steps up to the weighing station. Do not use soft pads underneath, such as writing mats.  It is better to position the balance directly over the legs of the bench, since the area is subject to the fewest vibrations.
 
The article above is a very brief outline of laboratory balances or scales.  many factors affect the weighing accuracy besides location - eg temperature, humidity etc..Visit the last link below to download a complete guide to weighing.

For more information visit:-
http://www.shimadzu.com/an/hplc/support/lib/lctalk/66/66lab.html
http://electronics.howstuffworks.com/everyday-tech/digital-scale.htm
http://www.prlabs.co.uk/news/article.php?Id=140

Friday, 11 July 2014

Xenon

Xenon is a noble gas (or inert gas) with the symbol, Xe, and the atomic number, 54. Xenon is a clear and colourless, and odorless gas that is quite heavy. Xenon gas is 4.5 times heavier than Earth's atmosphere (which consists of a mixture of a number of gaseous elements and compounds). This element's mass comes from its nucleus, which contains 54 protons and a varying (but similar) number of neutrons. Xenon has 17 naturally-occurring isotopes (the most for any element), eight of which are stable, the most for any element, except tin, which has ten.
Xenon discharge tube

Tiny amounts of two xenon isotopes, xenon-133 and xenon-135, leak from nuclear reprocessing and power plants, but are released in higher amounts after a nuclear explosion of accident, such as what occurred at Fukushima. Thus, monitoring xenon's isotopes can ensure compliance with international nuclear test-ban treaties and also to detect whether rogue nations are testing their own nuclear weapons.

Xenon was discovered in England by the Scottish chemist William Ramsay and English chemist Morris Travers on July 12, 1898, shortly after their discovery of the elements krypton and neon. They found xenon in the residue left over from evaporating components of liquid air.

During the 1930s, American engineer Harold Edgerton began exploring strobe light technology for high speed photography. This led him to the invention of the xenon flash lamp, in which light is generated by sending a brief electrical current through a tube filled with xenon gas. In 1934, Edgerton was able to generate flashes as brief as one microsecond with this method.

Xenon as well as being used in flash lamps and arc lamps is also used as a general anaesthetic. Although it is expensive, anesthesia machines that can deliver xenon are about to appear on the European market, because advances in recovery and recycling of xenon have made it economically viable.
The first excimer laser design used a xenon dimer molecule (Xe2) as its lasing medium, and the earliest laser designs used xenon flash lamps as pumps. Xenon is also being used to search for hypothetical weakly interacting massive particles and as the propellant for ion thrusters in spacecraft.  It is also used in car headlights.
Xenon is obtained commercially as a byproduct of the separation of air into oxygen and nitrogen.

For more information visit:-
http://en.wikipedia.org/wiki/Xenon
http://www.theguardian.com/science/grrlscientist/2012/mar/16/1?guni=Article:in%20body%20link

Friday, 4 July 2014

The Fourth of July - Independence Day for America

Independence Day, commonly known as the Fourth of July, is a federal holiday in the United States commemorating the adoption of the Declaration of Independence on July 4, 1776, declaring independence from the Kingdom of Great Britain.

Independence Day is commonly associated with fireworks, parades, barbecues, carnivals, fairs, picnics, concerts, baseball games, family reunions, and political speeches and ceremonies, in addition to various other public and private events celebrating the history, government, and traditions of the United States. Independence Day is the National Day of the United States.

Also on this day of scientific note, Mars Pathfinder, an American spacecraft landed a base station with a roving probe on Mars on 4th July 1997. The mission carried a series of scientific instruments to analyse the Martian atmosphere, climate, geology and the composition of its rocks and soil.


On 4th July 2005,  The Deep Impact collider hits the comet Tempel 1 to analyse it's make up. And on 4th July 2012, the discovery of particles consistent with the Higgs boson at the Large Hadron Collider is announced at CERN.

All in all a day of many achievements in various scientific fields and another reason to celebrate.

Friday, 27 June 2014

Potassium Hydroxide.

Potassium hydroxide is an inorganic compound with the formula KOH, commonly called caustic potash.

Potassium Hydroxide is noteworthy as the precursor to most soft and liquid soaps as well as numerous potassium-containing chemicals.

Potassium hydroxide can be found in pure form by reacting sodium hydroxide with impure potassium. Potassium hydroxide is usually sold as white or translucent pellets, sometimes yellow, which will become tacky in air because KOH is hygroscopic. Consequently, KOH typically contains varying amounts of water (as well as carbonates).

Its dissolution in water is strongly exothermic, meaning the process gives off significant heat. Concentrated aqueous solutions are sometimes called potassium lyes. Even at high temperatures, solid KOH does not dehydrate readily.

Potassium hydroxide has many uses:-
  • Precursor to other potassium compounds, eg fertilisers
  • Manufacture of biodiesel
  • Manufacture of soft soaps
  • As an electrolyte
  • Cleaning and disinfection
  • As a main active ingredient in chemical "cuticle removers" used in manicure treatments
Health information
  • Potassium Hydroxide is highly corrosive and contact can severely irritate and burn the skin and eyes leading to damage
  • Potassium Hydroxide can affect you when inhaled and by passing through the skin
  • Contact can irritate the nose and throat
  • Inhaling can irritate the lungs causing a build up of fluid
  • Exposure can cause headaches, dizziness, nausea and vomiting
  • It may cause skin allergy.

All health and safety data information must be followed when using this chemical

Friday, 20 June 2014

Ultrasonic Baths

An ultrasonic cleaner is a cleaning device that uses ultrasound (usually from 20–400 kHz) and an appropriate cleaning solvent (sometimes ordinary tap water) to clean delicate items. The ultrasound can be used with just water, but use of a solvent appropriate for the item to be cleaned and the soiling enhances the effect. Cleaning normally lasts between three and six minutes, but can also exceed 20 minutes, depending on the object to be cleaned.

Ultrasonic cleaning penetrates even microscopic openings to provide complete cleaning of the objects treated. This makes it one of the most effective, economical and powerful cleaning methods available. It has applications in laboratories, dental and medical technology, microelectronics, precision engineering, cosmetics, optics and the automotive industry. Ultrasonic cleaners are used to clean many different types of objects, including jewellery, lenses and other optical parts, watches, dental and surgical instruments, tools, coins, fountain pens, golf clubs, window blinds, firearms, musical instruments, industrial parts and electronic equipment. They are used in many jewellery workshops, watchmakers' establishments, and electronic repair workshops               
Modern baths tend to have a heavy duty ultrasonic generator which ensures that the ultrasonic output remains constant, regardless of the bath temperature, fill level and cleaning material. This feature guarantees consistent and reproducible cleaning results. 'Frequency sweeping', a frequency modulation of the ultrasonic output generated, prevents 'standing waves' from being generated and ensures extremely homogeneous energy distribution in the cleaning bath.
 
Ultrasonic cleaning uses Cavitation bubbles induced by high frequency pressure (sound) waves to agitate a liquid. The agitation produces high forces on contaminants adhering to substrates like metals, plastics, glass, rubber, and ceramics. This action also penetrates blind holes, cracks, and recesses. The intention is to thoroughly remove all traces of contamination tightly adhering or embedded onto solid surfaces. Water or other solvents can be used, depending on the type of contamination and the workpiece.
 
There are various ways to test the level of ultrasonic activity within an ultrasonic bath..
 
There are a number of recommended tests for establishing levels of ultrasonic activity in the bath.

The foil test involves suspending a strip of foil into various locations around the tank. The foil should not touch the base of the tank and should be held in position for around 1 minute. It should then be removed and there should be an even distribution of perforations and small holes on the surface of the foil.

Another test requires the use of Brownes soil test strips. These are plastic strips which have been contaminated to simulate the contamination which might affect surgical instruments. After running an ultrasonic cycle the strips should be taken from the bath and all contamination should have been removed.

An ultrasonic energy meter can also be used to test the level of ultrasonic activity within the tank.

For more information on ultrasonic baths visit:-
http://www.prlabs.co.uk/lab-supplies.php?N=ULTRASONIC-BATH-1L-MECH.-TIMER%26HEATER&Id=64514
http://en.wikipedia.org/wiki/Ultrasonic_bath

Friday, 13 June 2014

Pyroclastic flows

Pyroclastic flows are high-density mixtures of hot, dry rock fragments and hot gases that move away from the vent that erupted them at high speeds. They may result from the explosive eruption of molten or solid rock fragments, or both. They may also result from the nonexplosive eruption of lava when parts of dome or a thick lava flow collapses down a steep slope. Most pyroclastic flows consist of two parts: a basal flow of coarse fragments that moves along the ground, and a turbulent cloud of ash that rises above the basal flow. Ash may fall from this cloud over a wide area downwind from the pyroclastic flow.


Pyroclastic flows can reach speeds moving away from a volcano of up to 700 km/h (450 mph).  The gas can reach temperatures of about 1,000 °C (1,830 °F). Pyroclastic flows normally hug the ground and travel downhill, or spread laterally under gravity. Their speed depends upon the density of the current, the volcanic output rate, and the gradient of the slope. They are a common and devastating result of certain explosive volcanic eruptions.

A pyroclastic flow will destroy nearly everything in its path. With rock fragments ranging in size from ash to boulders traveling across the ground at speeds typically greater than 80 km per hour, pyroclastic flows knock down, shatter, bury or carry away nearly all objects and structures in their way. The extreme temperatures of rocks and gas inside pyroclastic flows can cause combustible material to burn, especially petroleum products, wood, vegetation, and houses.

Testimonial evidence from the 1883 eruption of Krakatoa, supported by experimental evidence, shows that pyroclastic flows can cross significant bodies of water. One flow reached the Sumatran coast as much as 48 km away.

Pyroclastic flows sweep down the flanks of Mayon Volcano, Philippines, in 1984

The towns of Pompeii and Herculaneum, Italy, for example, were engulfed by pyroclastic surges in 79 AD with many lives lost.

"Garden of the Fugitives". Plaster casts of victims still in situ; many casts are in the Archaeological Museum of Naples.
For more information and some video clips visit:-
http://www.geo.mtu.edu/volcanoes/hazards/primer/pyro.html
http://en.wikipedia.org/wiki/Pyroclastic_flow
http://volcanoes.usgs.gov/hazards/pyroclasticflow/

Friday, 6 June 2014

Antimony

Antimony is a chemical element with symbol Sb (from Latin: stibium) and atomic number 51. A lustrous grey metalloid, it is found in nature mainly as the sulfide mineral stibnite (Sb2S3).
 

Antimony compounds have been known since ancient times and were used for cosmetics.  Nowadays Antimony is mainly used as its trioxide in making flame-proofing compounds and in certain alloys.  The Egyptians had a hieroglyph for Antimony......


Antimony has no known biological role, but it is a potent toxin, with effects that are similar to arsenic poisoning. When ingested, antimony strongly bonds to sulfur-containing enzymes, thereby inactivating them. Antimony is even more toxic when inhaled as the gas, stibine, SbH3. Poisoning by antimony ingestion manifests as gastric distress, and large doses cause vomiting, and kidney and liver damage, followed by death a few days later.

It was thought that Mozart was a victim of poisoning at the hand of rival composer, Antonio Salieri, although historians don't give this hypothesis any credence. It is far more likely that Mozart was poisoned by his doctors. A heavy drinker, Mozart was known to also overindulge in the popular hangover cure of the day that contains antimony, tartar emetic, C4H4KO7Sb, which was provided by his doctors.

Stibnite

For some time, China has been the largest producer of antimony and its compounds, with most production coming from the Xikuangshan Mine in Hunan. The industrial methods to produce antimony are roasting and subsequent carbothermal reduction or direct reduction of stibnite with iron.

For more information visit:-
http://www.theguardian.com/science/grrlscientist/2012/feb/24/1?guni=Article:in%20body%20link
http://en.wikipedia.org/wiki/Antimony