Monthly Archives: 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.

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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 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.

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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

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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:-
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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.

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mini-uniprep-g2New Whatman Mini-UniPrep filters

Mini-UniPrep™ G2 syringeless filters are all-in-one filters that replace syringe filters and autosampler vials, speeding up and simplifying UHPLC/HPLC sample preparation.  Available from P&R Labpak Limited.


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!

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