P&R Labpak - Everything for your laboratory

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

Tuesday, 24 December 2013

Christmas.....Did You Know.....?

Did You Know…?

The celebration of the passing of mid-winter and the lengthening of the days is ancient, Norsemen lit bonfires, told stories and drank ale at the winter solstice; the Roman festival of Saturnalia ran for seven days from 17th December and was a time when ordinary rules were turned upside down (such as men dressing as women, masters as servants), houses were decorated with evergreens, candles were lit and presents given. It was the arrival in Britain of the Romans that brought many of the rituals of Saturnalia to the mid-winter celebrations of the British peoples.

·         Evergreens have long been valued for showing life in the dead of winter.

·         Mistletoe was sacred to the Druids and was thought to bring good luck, fertility and protection from witchcraft.

·         Since the Middle Ages the Yule log has been gathered and carried into the house on Christmas Eve. It is lit with the end saved from the previous year’s log and kept burning until Twelfth Night.

·         The Georgian period saw the introduction of the Christmas tree to England, however the idea wasn’t popularised until Victorian times when a drawing of the royal family gathered around a decorated tree was published in an 1848 newspaper.

·         The first Christmas card was commissioned in 1843 and by the 1880s the sending of cards had become very popular. Gift giving had traditionally taken place at New Year but with the increased focus on family at Christmas by the Victorians this tradition was moved.

·         The Christmas meal in its now familiar form began to take shape in the Victorian era, meat was replaced by fruits in mince pies, turkey started to be served instead of goose - at first just for the wealthy and later for all.

·         Father Christmas’ origins are in old English mid-winter festivals; he dressed in green and represented the returning spring. He was known as Old Father Christmas or Old Winter and roamed from home to home, feasting with families.

·         The ghost of Christmas Past in A Christmas Carol is based on Father Christmas. Images of him dressed in red started to appear on Victorian Christmas cards and our images today owe a lot to early American cards.

·         Santa Claus is based on St Nicholas of Mrya, (Sinterklaas in Dutch). St Nicholas was a 4th century Christian who had a reputation as a secret gift giver to the poor. It was Dutch settlers in America that gave us Santa Claus. St Nicholas is patron saint of children and also unmarried women, prisoners, thieves and pawnbrokers.

·         The Dutch custom of leaving shoes filled with food for St Nicholas’ donkeys is where we get our custom of Christmas stockings

·         Norwegian scientists have speculated that Rudolph’s red nose is the result of a parasitic infection of the respiratory system.

·         In Poland spiders and spiders webs are common Christmas tree decorations because according to legend a spider wove a blanket for the baby Jesus.

·         In Germany Christmas Eve is said to be a magical time when the pure of heart can hear the animals talking.

·         St Nicholas's evil accomplice in Austrian tradition, Krampus is a demon-like creature that punishes bad children. Men dressed as Krampus roam the streets during the festive period, frightening the children.

·         In some rural areas of Wales, a villager is selected each Christmas to perform the ritual of Mari Lwyd. They must then parade around the streets with a mare's skull fastened to the end of a wooden pole, while villagers sing traditional songs. White sheets are used to conceal the pole, and the person carrying it. Sometimes the horse's jaw is spring-loaded, so that it can be used to snap at passers-by.

·         In Spain the Catalonians have the traditional caga tio or defecating log. A character is made from a log by drawing a face and putting a hat on it. A fortnight is then spent ‘feeding’ the log with fruit, sweets and nuts until on Christmas Eve the whole family beats the log with sticks until all the treats are ‘excreted’.

·         For many in Japan the traditional Christmas dinner today is Kentucky Fried Chicken, reservations have to be made to eat at KFC on Christmas day.

·         Next time you moan about eating sprouts think of the folk in Greenland, for their Christmas meal they have Mattak – raw whale skin and blubber, and kiviak – auk (a small seabird) wrapped in seal skin, buried for months and eaten once decomposing.

·         The robin is strongly associated with Christmas, appearing on many Christmas cards.

·         Different legends associate the robin with Christ and Christianity however the association with Christmas is probably due to the fact that postmen in Victorian England wore red jackets and were nicknamed ‘robins’, the robin representing the postman delivering the card.


Friday, 20 December 2013

Christmas Tinsel - how did that come about?

Tinsel is a sparkling decorative material that mimics the effect of ice or icicles. When in long narrow strips (sometimes known as "lametta"), it emulates icicles. It was originally a metallic garland for Christmas decoration. The modern production of tinsel typically involves plastic, and is used particularly to decorate Christmas trees. It may be hung from ceilings or wrapped around statues, lampposts, and so on. Modern tinsel was invented in Nuremberg, Germany, in 1610, and was originally made of shredded silver.

According to the Concise Oxford Dictionary, the word is from the Old French word estincele, meaning “sparkle”.

Tinsel was invented in Nuremberg around 1610. Tinsel was originally made from extruded strands of silver. Because silver tarnishes quickly, other shiny metals were substituted. Before the 16th century, tinsel was used for adorning sculptures rather than Christmas trees. It was added to Christmas trees to enhance the flickering of the candles on the tree.

Modern tinsel is typically made from polyvinyl chloride (PVC) film coated with a metallic finish and sliced into thin strips. Coated mylar film also has been used. These plastic forms of tinsel do not hang as well as tinsel made from heavy metals such as silver and lead.

For more information, visit:-

There will be no blog article next week.  The P&R Labpak Limited Blog will return in 2014.  We wish you all a Merry Christmas and a Happy New Year!

Friday, 13 December 2013

Measuring Conductivity

The conductivity (or specific conductance) of an electrolyte solution is a measure of its ability to conduct electricity. The SI unit of conductivity is siemens per meter (S/m).

Conductivity measurements are used routinely in many industrial and environmental applications as a fast, inexpensive and reliable way of measuring the ionic content in a solution. For example, the measurement of product conductivity is a typical way to monitor and continuously trend the performance of water purification systems.

In many cases, conductivity is linked directly to the total dissolved solids (T.D.S.). High quality deionised water has a conductivity of about 5.5 μS/m, typical drinking water in the range of 5-50 mS/m, while sea water about 5 S/m (i.e., sea water's conductivity is one million times higher than that of deionised water)

Conductivity Meters - Two electrodes with an applied AC voltage are placed in the solution. This creates a current dependent upon the conductive nature of the solution. The meter reads this current and displays in either conductivity (EC) or ppm (TDS).

Our two part guide will help you to measure conductivity accurately.  The guides answer the 7 most asked questions regarding conductivity and the second part is a comprehensive guide on theory and measurement.

Just click on the links below to download your copies.

Part 1 - http://www.prlabs.co.uk/news/article.php?Id=232
Part 2 - http://www.prlabs.co.uk/news/article.php?Id=233

Tuesday, 10 December 2013

Christmas Closure

P&R Labpak closes on Tuesday 24th December 2013 and re-opens on 2nd January 2014. There will be no deliveries during this period.

P&R Labpak would like to take this opportunity now to thank you for your custom this year, and look forward to continuing our relationships in 2014.

We hope you've enjoyed our blog posts over the last year and hope you will continue to read them in future.  If you want us to feature anything or try and answer a question for you then let us know.

Remember to LIKE us on Facebook and subscribe to our Twitter feed too!

Friday, 6 December 2013


Thorium has been in the news recently as it was suggested as a safer and more readily available element than Uranium for generating power.

Thorium is a naturally occurring radioactive chemical element with the symbol Th and atomic number 90. It was discovered in 1828 by the Norwegian mineralogist Morten Thrane Esmark and identified by the Swedish chemist Jöns Jakob Berzelius and named after Thor, the Norse god of thunder.

Thorium produces a radioactive gas, radon-220, as one of its decay products. Secondary decay products of thorium include radium and actinium. In nature, virtually all thorium is found as thorium-232, which undergoes alpha decay with a half-life of about 14.05 billion years. Other isotopes of thorium are short-lived intermediates in the decay chains of higher elements, and only found in trace amounts. Thorium is estimated to be about three to four times more abundant than uranium in the Earth's crust, and is chiefly refined from monazite sands as a by-product of extracting rare earth metals.

Pure thorium is a soft, lustrous silvery-white metal. If it doesn't burst into flames first, thorium will slowly tarnish when exposed to air, becoming grey, as you see above, and then finally black in colour. Thorium is very ductile and, like all actinoids, thorium is radioactive.
Monazite, a rare earth and thorium phosphate mineral, is the primary source of the world's thorium
When compared to uranium, there is a growing interest in developing a thorium fuel cycle due to its greater safety benefits, absence of non-fertile isotopes and its higher occurrence and availability.

India's Kakrapar-1 reactor is the world's first reactor which uses thorium rather than depleted uranium to achieve power flattening across the reactor core. India, which has about 25% of the world's thorium reserves, is developing a 300 MW prototype of a thorium-based Advanced Heavy Water Reactor (AHWR). The prototype is expected to be fully operational by 2016, after which five more reactors will be constructed. The reactor is a fast breeder reactor and uses a plutonium core rather than an accelerator to produce neutrons. As accelerator-based systems can operate at sub-criticality they could be developed too, but that would require more research. India currently envisages meeting 30% of its electricity demand through thorium-based reactors by 2050.

For more information visit:-

Friday, 29 November 2013

The Magnetic Stirrer

A magnetic stirrer is a piece of laboratory equipment that uses a rotating magnetic field to cause a stirrer bar (also called "flea") immersed in a liquid to spin very quickly, thus stirring it.  The rotating field may be created either by a rotating magnet or a set of stationary electromagnets, placed beneath the vessel with the liquid.

Glass does not affect a magnetic field and most chemical reactions take place in glass vessels (i.e. beakers or flasks) and magnetic stirrer bars work well in glass vessels. However, the limited size of the bar means that magnetic stirrers can only be used for relatively small (under 4 litres) experiments.  They also have difficulty dealing with viscous liquids or thick suspensions.  For larger volumes or more viscous liquids, some sort of mechanical stirring is typically needed.

Ika C-MAG HS 7
Magnetic stirrers are preferred over gear-driven motorized stirrers because they are quieter, more efficient, and have no moving external parts to break or wear out (other than the simple bar magnet itself).  Due to its small size, a stirrer bar is more easily cleaned and sterilised than other stirring devices.  They do not require lubricants which could contaminate the reaction vessel and the product. They can be used inside hermetically closed vessels or systems, without the need for complicated rotary seals. Magnetic stirrers may also include a heating element to heat the liquid being stirred.

Arthur Rosinger of Newark, New Jersey, U.S.A. obtained US Patent 2,350,534, titled Magnetic Stirrer on 6 June 1944, having filed an application on 5 October 1942.   His patent includes a description of a coated bar magnet placed in a vessel, which is driven by a rotating magnet in a base below the vessel. His patent explains that coating the magnet in plastic or covering it with glass or porcelain makes it chemically inert.

The plastic-coated bar magnet was independently invented in the late 1940s by Edward McLaughlin, of the Torpedo Experimental Establishment (TEE), Greenock, Scotland, who named it the 'flea' because of the way it jumps about if the rotating magnet is driven too fast.

An even earlier patent for a magnetic mixer is US 1,242,493, issued 9 October 1917 to Richard H. Stringham of Bountiful, Utah, U.S.A. Mr. Stringman's mixer used stationary electromagnets in the base, rather than a rotating permanent magnet, to rotate the stirrer.

For more information visit:-

Wednesday, 27 November 2013

Looking for laboratory consumables, equipment or chemicals?

If you want to find and order laboratory supplies quickly from our website, enter a key word or product code into the search box and we'll help you find it!

P&R Labpak Limited has built its reputation for a commitment to quality and customer care with over 25 years experience serving science across all economic sectors.

We are able to offer a vast range of laboratory apparatus, instruments, equipment, consumables and chemicals from our catalogues. We carry stock at our St Helens site and have electronic access to our main supplier giving us live data on product availability.

This means that you get your goods quickly and efficiently.

If you would like to request a quotation for a particular item or have an enquiry, please click here.

We offer varied and flexible services to our customers. In addition to the many products available through our catalogues, we can also:
  • Supply production grades and volumes of chemicals and solvents
  • Handle all your chemical waste
  • Supply and service your microscopes
  • Offer third party procurement
  • Supply and install laboratory furniture
We do not limit our range to the products in our catalogues. Simply let us know what you are looking for and we'll do our best to meet your requirements.

P&R Labpak Limited offer a comprehensive single source of laboratory chemicals and reagents. These include general laboratory and analytical reagents, culture media, solvents, buffers, biochemicals, water test kits and many more.
  • We can supply chemicals in quantities from milligrams to tonnes
  • We can supply virtually any chemical you require using our extensive research capabilities
  • All chemicals are rigorously tested to meet the critical standards demanded by our customers
  • The BDH Prolabo and Merck range of chemicals that we supply are synonymous with quality throughout the world and certificates of analysis can be supplied at no extra charge. BDH Merck
  • We also sell a wide range of P&R Labpak Limited brand solutions and standards. We can manufacture to order so reaction to customer demand is rapid. The P&R Labpak Limited brand extends to a vast range of general purpose and AR grade chemicals.
P&R Labpak Limited offers a wide range of equipment for all your laboratory requirements from autoclaves and balances to vacuum pumps and water purification systems. A selection of products from key suppliers are shown below but please request our catalogue for details of the full ranges available.

We are able to offer technical assistance and additional product information to help you choose the correct piece of equipment. Given your requirements we will endeavour to source the best goods and put together the products and services appropriate for you at the right price.

Product Range

Laboratory glassware Disposable plastic

Sterilin disposable plastics. Pyrex, Quickfit and MBL laboratory glassware.and Azlon reusable plasticware.

Laboratory Equipment

The Bibby Scientific range of equipment covering the Stuart and Jenway brands. Items include pH meters, spectrophotometers, fluorimeters, hotplates and stirrers to name a few.

Laboratory Balances Centrifuges

Sartorius weighing technology is available from P&R Labpak Limited with a range of precision and analytical balances together with a wide range of Hettich centrifuges.

Laboratory Balances

The A&D range encompasses a range of balances covering analytical, precision and industrial requirements.

Laboratory Equipment

The Mettler range comprises a range of laboratory equipment including a range of precision & analytical balances, ph meters and instruments for density determination.

We can supply many other branded items of laboratory equipment.
Visit http://www.prlabs.co.uk to use our online webshop.  Terms and conditions apply.  Call 0870 034 2055 for more details or to enquire about the webshop or anything else.

Friday, 22 November 2013


Neodymium is a chemical element with the symbol Nd and atomic number 60. It is a soft silvery metal that tarnishes in air.

Like most metals, neodymium is a lustrous silvery white colour, and like its twin praseodymium,, it tarnishes rapidly in air so it must be stored under argon (as above) or oil. Like the other lanthanoids, it is a rare earth metal that is anything but rare. In fact, neodymium is exceedingly common -- almost as common as copper -- being the second most common of the rare earth elements in the Earth's crust, following cerium.

Neodymium compounds were first commercially used as glass dyes in 1927, and they remain a popular additive in glasses. The color of neodymium compounds—due to the Nd3+ ion—is often a reddish-purple but it changes with the type of lighting, due to fluorescent effects.

Its compounds have a variety of lovely colours -- pink, mauve, purple, violet, green -- that change based on the sort of lighting they are exposed to. For example, neodymium chloride hexahydrate, NdCl3·6H2O [see image courtesy of Walkerma (public domain)], is pink when exposed to sunlight (top) and a boring yellowish colour when exposed to fluorescent light (bottom).

Another chief use of neodymium is as the free pure element. It is used as a component in the alloys used to make high-strength neodymium magnets – powerful permanent magnets. These magnets are widely used in such products as microphones, professional loudspeakers, in-ear headphones, and computer hard disks, where low magnet mass or volume, or strong magnetic fields are required. Larger neodymium magnets are used in high power versus weight electric motors (for example in hybrid cars) and generators.

Neodymium magnets are often referred to as "supermagnets". And they are for a reason: a one gram neodymium supermagnet can hold up a 1.3 kg (2.8 lb) iron sphere!

Neodymium metal dust is a combustion and explosion hazard. Neodymium compounds, as with all rare earth metals, are of low to moderate toxicity; however its toxicity has not been thoroughly investigated. Neodymium dust and salts are very irritating to the eyes and mucous membranes, and moderately irritating to skin. Breathing the dust can cause lung embolisms, and accumulated exposure damages the liver.

Even relatively small neodymium magnets cause all sorts of damages, even those that are just a few centimetres square. They are dangerous to people with pacemakers.  Bone fractures from flying magnets and crushing the tip off a finger are not uncommon.

Check out this video link too:-
Neodymium Magnet experiments

For more information visit:-

Friday, 15 November 2013

The House Spider!

There are about 660 different species of spider in the UK, and most of them will never come inside. Each autumn, however, male house spiders come indoors in search of a mate.

The spider species Tegenaria domestica, commonly known as the barn funnel weaver in North America and the domestic house spider in Europe, is a member of the funnel-web family Agelenidae and a close relative of the hobo spider. Domestic house spiders range worldwide from as north as Sweden to as south as Greece in Europe and from as north as Maritime Canada to as south as Louisiana in North America.

The large, hairy house spiders commonly seen in the UK belong to the Tegenaria genus.

House spiders in your bath are normally males who are trapped having fallen off the walls while looking for a female to mate with. Females usually stay in their webs, which are often found under the shed, and await a suitor. After a male has found a female's web he will stay with her for a number of weeks, mating with her repeatedly.

The female then overwinters with stored sperm, and the next spring she can produce 10 egg sacs, each containing around 40 to 60 eggs.

Like most spiders, Tegenaria species subdue their prey with venom. The house spider provides a service for home owners, eating flies and other unwanted insects. They are also ecologically important as food for birds and other animals.

Tegenaria house spiders are not the only species found indoors, and other common species include the daddy-long-legs spider, Pholcus phalangioides (which is not to be confused with the daddy long legs or crane fly, a completely harmless type of fly).

Why not visit the weblink below and get involved with the House Spider Survey being run by the Society of Biology:-
Or read more at:-

Friday, 8 November 2013

Polish that Chrome!

Chromium is the first of the group 6 transition metals. It is denoted by the symbol Cr and atomic number 24. Chromium is a grey coloured, hard and very lustrous metal.  It takes a high polish, resists tarnishing, and has a high melting point. The name of the element is derived from the Greek word "chrōma" (χρώμα), meaning colour.

Chromium is highly corrosion resistant, a character that it brings with it when added to steel to create stainless steel. Another popular use for chromium is electroplating, which gives hubcaps, bumpers and other shiny bits of cars their street-cred.

Many of its compounds are intensely coloured. Besides providing the familiar non-fading "chrome yellow" colour used on American school buses and by the German postal service, there is the bright red pigment, chrome red (PbCrO4·Pb(OH)2), a bright green (Cr2O3), a pale green ([CrCl(H2O)5]Cl2), and rich violet ([Cr(H2O)6]Cl3). Trace amounts of chromium also gives rubies and emeralds their characteristic colours.

Below is the relatively rare mineral, crocoite (PbCrO4), the state mineral of Tasmania.

Chromium is the 24th most abundant element in Earth's crust with an average concentration of 100 ppm. Chromium compounds are found in the environment, due to erosion of chromium-containing rocks and can be distributed by volcanic eruptions. The concentrations range in soil is between 1 and 300 mg/kg, in sea water 5 to 800 µg/litre, and in rivers and lakes 26 µg/litre to 5.2 mg/litre.  Chromium is mined as chromite (FeCr2O4) ore.  About two-fifths of the chromite ores and concentrates in the world are produced in South Africa, while Kazakhstan, India, Russia, and Turkey are also substantial producers. Untapped chromite deposits are plentiful, but geographically concentrated in Kazakhstan and southern Africa

In the laboratory Chromic acid is a powerful oxidizing agent and is a useful compound for cleaning laboratory glassware of any trace of organic compounds. It is prepared in situ by dissolving potassium dichromate in concentrated sulfuric acid, which is then used to wash the apparatus. Sodium dichromate is sometimes used because of its higher solubility (50 g/L versus 200 g/L respectively). The use of dichromate cleaning solutions is now phased out due to the high toxicity and environmental concerns. Modern cleaning solutions are highly effective and chromium free. Potassium dichromate is a chemical reagent, used as a titrating agent. It is also used as a mordant (i.e., a fixing agent) for dyes in fabric.

For more information visit:-

Monday, 4 November 2013

Friday, 1 November 2013


A hangnail or agnail (also known as a stepmother's blessing particularly in the Lancashire region) is a corruption of agnail which literally means painful (anguished) nail.

Hangnails can seem rather insignificant in the grand scheme of health problems but they can become infected and lead to a handful of other issues. Fortunately, there are many ways to avoid hangnail hazards.

Hangnails don't have anything to do with your fingernails. Many people confuse hangnails with ingrown nails, a condition in which the corner of your nail grows into the soft skin of your nail bed.  In fact, hangnails are the dry, sometimes brittle triangular-shaped tags of skin around your fingernails that can tear off.  Because there are many different causes of hangnails, everyone gets them occasionally. But chronic, consistent hangnails can lead to bigger problems.

When the skin around your fingernails tears off, it opens the door to infection, especially when you consider all the bacteria your hands are exposed to every day, not to mention dishwater, cold weather and all the other things that dry out your hands in the first place. Fortunately, there are quick and easy ways to prevent hangnails that range from moisturising often to pampering your hands with cuticle soaks and manicures.

If you just can't beat hangnails, there are also easy ways to treat them. Antibacterial lotions can often do the trick, and in more serious cases, a prescription antibiotic might be in order.

Of course, before you can avoid hangnails, you need to know what causes them.

Hangnails are more common during the cold winter months. During the winter, skin dries out really fast which is one of the main causes of hangnails. Anything that can dry out your skin, such as cold winter weather, harsh chemicals or frequent immersion in water can cause hangnails to develop.

If you are a nail biter it can damage your nail bed, which is the skin underneath the actual fingernail and a weak nail bed can result in more hangnails.

Hangnails that aren't properly cared for can result in an infection called paronychia. There are three types of paronychia infection: bacterial, Candidal -- which is a type of yeast -- and fungal

Now that you know how hangnails happen, you're probably wondering how you can stop them before they start.
  • Moisturise your hands and your nail beds.  Moisturising your nail beds helps your nails and your cuticles as well which can have a big impact on your overall nail health
  • Stop biting your nails.
  • Manicure.
  • Wear gloves if you are exposed to harsh chemicals or even just soapy water from washing the dishes.
Working in a laboratory can cause a number of hand problems including latex glove allergies.  Make sure you choose the right gloves for your skin and for the job in hand.  Remember to wash your hands properly and moisturise afterwards.

Remember P&R Labpak offers a range of soaps and moisturisers for laboratories so you don’t need to suffer from hangnails!  The new VWR Safety catalogue is also available covering everything you need relating to personal protection, workplace safety, first aid and housekeeping.  Ask for your copy now!

For more information visit:-

Friday, 25 October 2013

Filter Papers and Membrane filters.

Laboratory filter paper is a semi-permeable barrier placed perpendicular to a liquid or air flow. It is used to separate fine solids from liquids or air.

Filter paper comes in various porosities and grades depending on the applications it is meant for. The important parameters are wet strength, porosity, particle retention, flow rate, compatibility, efficiency and capacity.

There are two mechanisms of filtration with paper; volume and surface. By volume filtration the particles are caught in the bulk of the filter paper. By surface filtration the particles are caught on the paper surface. Filter paper is mostly used because even a small piece of filter paper will absorb a significant volume of liquid.

The raw materials are different paper pulps. The pulp may be from softwood, hardwood, fibre crops, mineral fibres.

For laboratory use filter papers are made in a variety of ways since specific applications require specific types of papers. The raw materials might be acid washed wooden fibres, carbon or quartz fibres.

In laboratories, filter paper is usually used with a filter funnel, Hirsch, or Buchner funnel.

Ashless filter paper is mainly used for gravimetric methods in quantitative chemical analysis.

The link here is useful as it contains a basic guide to choosing the right filter paper grade.

Glass fibre filters are commonly used in laboratories.  The manufacturer Whatman for example offers two types of glass microfiber filters manufactured from 100% borosilicate glass: binder free glass microfiber that is chemically inert and binder glass microfiber.

These depth filters combine fast flow rates with high loading capacity and the retention of very fine particle, extending into the sub-micron range. Glass microfiber filters can be used at temperatures up to 500°C and are ideal for use in applications involving air filtration and for gravimetric analysis of volatile materials where ignition is involved.
There are a number of manufacturers and include Whatman, Millipore, Sartorius, Munktell, Pall, Nalgene and more.
A Membrane Filter typically traps contaminants larger than the pore size on the addressed surface of the membrane. Contaminants smaller than the rated pore size may pass through the membrane or may be captured within the membrane by other mechanisms. Membrane filters are typically used for critical applications such as sterilising and final filtration.

A useful weblink can be found here.
When choosing a membrane filter a number of factors have to be considered, for example:-
  • Depth vs Membrane filtration
  • Chemical compatability
  • Hydrophilic vs Hydrophobic
  • Pore size
  • Thermal stability
Filtration is a huge area to cover with a short blog article but hopefully the links will prove useful for anyone looking to broaden their knowledge.

Friday, 18 October 2013

The Bunsen Burner

Robert Wilhelm Bunsen (1811-1899), a German chemist and inventor is credited with inventing the Bunsen burner, a gas burner used in scientific laboratories.

With Gustav R. Kirchhoff they pioneered work with spectrum analysis, inventing the spectroscope to detect chemicals by the colours they give off when burning. Using this instrument, they discovered the elements caesium (1860) and rubidium (1861).

Bunsen improved the efficiency of blast furnaces after observing gases escaping from them and devising a method of gas analysis. His other inventions include the ice calorimeter, a filter pump, a zinc-carbon electric cell, and the magnesium light. With Sir Henry Roscoe he did important work in the field of photochemistry.

The Bunsen Burner is used for heating chemicals, boiling water, sterilising small objects, preparing microscopic slides, bending glass tubing, and many other purposes.

The Bunsen burner consists of a straight metal tube, about five inches (13 cm) long, fastened to a stand. The bottom is connected by rubber tubing to a source of illuminating gas. Adjustable openings at the base of the burner admit air. The mixture of gas and air produces a very hot flame. Nozzles of various types can be fitted to the top of the burner to control the flame's shape.

Bunsen burner flames depend on air flow in the throat holes (on the burner side, not the needle valve for gas flow): 1. air hole closed (safety flame used for lighting or default), 2. air hole slightly open, 3. air hole half open, 4. hole almost fully open (roaring blue flame).

Flame Test

This is a method of detecting the presence of certain metals by the colours they give off in the flame of a Bunsen burner. A platinum or nichrome wire is dipped in a powder or solution of the compound to be tested, and the compound is then placed in the flame. Barium gives a green flame; calcium, orange; caesium, blue; copper, greenish blue; potassium, violet.

If more than one metal is present, the test is unreliable as one colour obscures another. Except in rough, preliminary analyses, the flame test is little used by chemists. There are more precise methods of identifying elements.

Other burners based on the same principle exist. The most important alternatives to the Bunsen burner are:

Teclu burner
The lower part of its tube is conical, with a round screw nut below its base. The gap, set by the distance between the nut and the end of the tube, regulates the influx of the air in a way similar to the open slots of the Bunsen burner. The Teclu burner provides better mixing of air and fuel and can achieve higher flame temperatures than the Bunsen burner.

Teclu Burner
Meker burner
The lower part of its tube has more openings with larger total cross-section, admitting more air and facilitating better mixing of air and gas. The tube is wider and its top is covered with a wire grid. The grid separates the flame into an array of smaller flames with a common external envelope, and also prevents flashback to the bottom of the tube, which is a risk at high air-to-fuel ratios and limits the maximum rate of air intake in a conventional Bunsen burner. Flame temperatures of up to 1100–1200 °C (2000–2200 °F) are achievable if properly used. The flame also burns without noise, unlike the Bunsen or Teclu burners
Meker Burner

For more information visit:-



Friday, 11 October 2013

The Northern Lights or Aurora Borealis

The Northern Lights or Aurora Borealis

An aurora is a natural light display in the sky particularly in the high latitude (Arctic and Antarctic) regions, caused by the collision of energetic charged particles with atoms in the high altitude atmosphere (thermosphere). The charged particles originate in the magnetosphere and solar wind and, on Earth, are directed by the Earth's magnetic field into the atmosphere. Most aurorae occur in a band known as the auroral zone, which is typically 3° to 6° in latitudinal extent and at all local times or longitudes. The auroral zone is typically 10° to 20° from the magnetic pole defined by the axis of the Earth's magnetic dipole. During a geomagnetic storm, the auroral zone expands to lower latitudes.

In northern latitudes, the effect is known as the aurora borealis (or the northern lights), named after the Roman goddess of dawn, Aurora, and the Greek name for the north wind, Boreas, by Pierre Gassendi in 1621.

Auroras seen near the magnetic pole may be high overhead, but from farther away, they illuminate the northern horizon as a greenish glow or sometimes a faint red, as if the Sun were rising from an unusual direction. Discrete aurorae often display magnetic field lines or curtain-like structures, and can change within seconds or glow unchanging for hours, most often in fluorescent green.

Its southern counterpart, the aurora australis (or the southern lights), has features that are almost identical to the aurora borealis and changes simultaneously with changes in the northern auroral zone. It is visible from high southern latitudes in Antarctica, South America, New Zealand, and Australia.
Aurora timelapse:-

What is happening?

The auroras, both surrounding the north magnetic pole (aurora borealis) and south magnetic pole (aurora australis) occur when highly charged electrons from the solar wind interact with elements in the earth's atmosphere. Solar winds stream away from the sun at speeds of about 1 million miles per hour. When they reach the earth, some 40 hours after leaving the sun, they follow the lines of magnetic force generated by the earth's core and flow through the magnetosphere, a teardrop-shaped area of highly charged electrical and magnetic fields.

­As the electrons enter the earth's upper atmosphere, they will encounter atoms of oxygen and nitrogen at altitudes from 20 to 200 miles above the earth's surface. The colour of the aurora depends on which atom is struck, and the altitude of the meeting.

  • Green - oxygen, up to 150 miles in altitude
  • Red - oxygen, above 150 miles in altitude
  • Blue - nitrogen, up to 60 miles in altitude
  • Purple/violet - nitrogen, above 60 miles in altitude

All of the magnetic and electrical forces react with one another in constantly shifting combinations. These shifts and flows can be seen as the auroras "dance," moving along with the atmospheric currents that can reach 20,000,000 amperes at 50,000 volts.

Structure of the Magnetosphere
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