Hotplate Safety

Total Lab Supplies offer a wide range of hotplates and hotplate/stirrers.  The Stuart range is well known in laboratories and they offer some good advice on the operation of these units.

  • Do not use hotplates to heat inflammable liquids.
  • Never lift or carry a hotplate until it has been switched off and allowed to cool for at least 30 minutes. A hot warning light will give guidance.
  • A hotplate should be carried using both hands with the fingers under the side edges.
  • Never move or carry a unit with containers on the top plate or while still connected to the mains supply.
  • There is a danger of liquid spillage if containers are over-filled and stirred at high speed. Always build stirrer speed slowly and never stir more rapidly than necessary
  • NEVER place a cold glass vessel onto a hotplate which is already hot.

When using a ceramic hotplates like the Stuart UC152 at temperatures over 180ºC, the base of any equipment used must not make contact with the ceramic plate outside the Hot Zone or heated plate area.

The use of a Stuart SCT1 temperature controller allows accurate temperature control of aqueous and oil based samples in the laboratory and can be used in two different modes, as a precise temperature controller from 20 to 200°C or as a digital thermometer from -4 to 325°C.

Care when preparing media

Take particular care when heating liquids having a high viscosity. Viscous liquids can act as thermal insulators and can cause thermal breakage of the glassware. This is very important with media solutions as the viscosity will usually increase as the temperature rises.

  • Check that the stirring action is sufficient to agitate the whole of the liquid.  Unstirred areas in the liquid can result in uneven heat transfer and “hot spots” in the glassware. This can induce thermal stress and so cause failure.
  • Check the stirring action regularly to ensure that it remains adequate as the viscosity of the solution increases.
  • Always use the largest magnetic follower possible and if necessary, use a mechanical overhead stirrer.
  • Do not use glass vessels with thick walls, e.g. Pyrex Heavy Duty Ware or standard beakers and flasks having capacities of 5 litres or greater.
  • NEVER heat glass bottles on a hotplate.
  • Ensure that the heat is built up slowly to avoid localised overheating.
  • Ensure the glassware is completely free from scratches or other defects.
  • Place the hotplate in a tray large enough to contain the liquid in the event of glassware failure.
  • Wear the appropriate safety clothing e.g. gloves, goggles, protective apron etc.

Following these guidelines using a stirrer/hotplate should ensure trouble free use.


For all your hotplate/stirrer needs please get in touch.

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Asbestos – The dangers!

Asbestos is a set of six naturally occurring silicate minerals which all have in common their eponymous asbestiform habit: i.e. long (roughly 1:20 aspect ratio), thin fibrous crystals, with each visible fibre composed of millions of microscopic “fibrils” that can be released by abrasion and other processes. They are commonly known by their colours, as blue asbestosbrown asbestoswhite asbestos, and green asbestos


Asbestos mining existed more than 4,000 years ago, but large-scale mining began at the end of the 19th century, when manufacturers and builders began using asbestos for its desirable physical properties. Some of those properties are sound absorption, average tensile strength, affordability, and resistance to fire, heat, and electricity. It was used in such applications as electrical insulation for hotplate wiring and in building insulation. When asbestos is used for its resistance to fire or heat, the fibers are often mixed with cement or woven into fabric or mats. These desirable properties made asbestos very widely used. Asbestos use continued to grow through most of the 20th century until public knowledge of the health hazards of asbestos dust led to its outlawing by courts and legislatures in mainstream construction and fireproofing in most countries.

Many countries have discontinued these uses since the health risks of asbestos became apparent. However, their legacy is that many buildings more than 20 years old contain asbestos. It’s estimated that 94% of hospitals in London contain asbestos, and it can also be found in older homes. It does not pose a danger unless disturbed, but can be costly to remove.

For more information



The excellent Compound Chem website has a graphic as below explaining the dangers of Asbestos in simple terms.  Click on it to enlarge.

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Cæsium is a soft, silvery-gold alkali metal with the symbol Cs and atomic number 55.


It has a melting point of 28°C (82°F), which means it will be liquid on a warm summer day, and revert to a solid later that night after the ambient temperature cools. Cæsium is just one of five elemental metals that are liquids at or near room temperature.


Its name comes from the Latin word for sky-blue because when burned, cæsium turns the flame a lovely blue colour.

Since the 1990s, the largest application of the element has been as caesium formate for drilling fluids, but it has a range of applications in the production of electricity, in electronics, and in chemistry. The radioactive isotope caesium-137 has a half-life of about 30 years and is used in medical applications, industrial gauges, and hydrology. Nonradioactive caesium compounds are only mildly toxic, but the pure metal’s tendency to react explosively with water means that caesium is considered a hazardous material, and the radioisotopes present a significant health and ecological hazard in the environment.

Caesium is also know for its use in atomic clocks and use the electromagnetic transitions in the hyperfine structure of caesium-133 atoms as a reference point. The first accurate caesium clock was built by Louis Essen in 1955 at the National Physical Laboratory in the UK.

These clocks measure frequency with an error of 2 to 3 parts in 1014, which corresponding to an accuracy of 2 nanoseconds per day, or one second in 1.4 million years. The latest versions are more accurate than 1 part in 1015, about 1 second in 20 million years.  The Caesium standard is the primary standard for standards-compliant time and frequency measurements. Caesium clocks regulate the timing of cell phone networks and the Internet.

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On this day in history

On July 29th in 1927, the first iron lung (electric respirator) was installed at Bellevue hospital in New York for the post war polio epidemic. The first iron lung was developed at Harvard University by Phillip Drinker and Louis Agassiz Shaw built with two vacuum cleaners. The iron lung is a negative pressure machine which surrounds the patient’s body except for the head, and alternates a negative atmospheric pressure with the ambient one, resulting in rhythmic expansion of the chest cage (and thus inhalation) in response to the negative extra thoracic pressure. During periods of ambient extrathoracic pressure, the lungs deflate. This type of machine is rarely used today.

The first patients of the iron lung were polio sufferers with chest paralysis.

Historically, in 1670, John Mayow demonstrated that air is drawn into the lungs by enlarging the thoracic cavity. He built a model using bellows inside which was inserted a bladder. Expanding the bellows caused air to fill the bladder and compressing the bellows expelled air from the bladder. This was the principle of artificial respiration called “external negative pressure ventilation” or ENPV that would lead to the invention of the iron lung and other respirators.

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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 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 help and advice on Ultrasonic baths get in touch.
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Why is milk white?

Milk is mostly made up of water, with smaller amounts of fat, protein, minerals, and other compounds. Fats and water don’t usually mix, but in milk the fat and water form an emulsion. It is also a suspension of a multitude of different proteins in water.

In milk, proteins cluster together to form structures called micelles. These clusters grow from small clusters of calcium phosphate, which help hold them togetherThere are a number of different models of these micelles, with the exact structure still being subject to scrutiny.
It’s the protein micelles which give milk its white appearance. The micelles are on average about 150 nanometres in diameter, and this very small size means they are able to scatter light that hits them. The overall effect of this scattering by the huge number of micelles in milk is that it looks white.
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Care and Storage of pH Electrodes

The life of a pH electrode is not infinite. A number of factors affect the life span of a pH electrode. The higher the temperature that the electrode is used at, the more extreme the pH, how often the bulb dries out and needs to be rehydrated, how roughly it is used; all these factors and more shorten the life span of an electrode. An electrode that is well maintained and cared for can last up to 2 years, one that is not well maintained will not last as long, and one that is well maintained will not last significantly longer.

Storage of the pH electrode when not in use.

The pH electrode bulb needs to be moist at all times. When you are done with the electrode pour electrode storage solution into the cap that came with the electrode and put the cap over the bulb of the electrode. Keep the cap on until next use. If the electrode is being stored for a long time you may want to check the cap to be sure the storage solution is still in the cap and keeping the bulb moist. DO NOT STORE THE pH ELECTRODE IN DISTILLED WATER. Storing the pH electrode in distilled water will shorten the life of your pH electrode.


If you do not have electrode storage solution use pH 4 buffer solution. If you have neither electrode storage solution or pH 4 buffer solution you can use pH 7 buffer solution for a short time.


Rinsing the pH electrode between measurements.

You should rinse your pH electrode between measurements. This can be done with distilled water or rinsing with a sample of the next solution to be measured. Using both distilled water and then a sample of the next solution is also a good way to rinse the pH electrode between measurements.


pH electrode fill hole

Some pH electrodes have a fill hole for refreshing the electrolyte in the pH electrode; other pH electrodes do not have a fill hole. If your pH electrode has a fill hole the fill hole cap should be removed during calibration and use. This allows for the correct amount of reference electrolyte to flow into the sample. Replace the fill hole cap when done with the electrode at the end of the day

If bulb dries out, soak electrode bulb in pH 7

pH electrode bulbs should be keep moist at all times. When not in use the pH electrode bulb should be keep moist by pouring electrode storage solution in the cap provided. If the pH electrode bulb does dry out, soak it in pH 7 buffer for a couple of hours before calibrating or taking measurements.


Do not wipe the pH electrode with a cloth or any other type of material.

When you are done with the pH meter rinse off the electrode with distilled water, put storage solution in the cap, and put the cap on the end of the pH electrode as described above. If the electrode is wet do not dry it off, let the distilled water evaporate by itself.


Cleaning the pH electrode

The pH electrode needs to be cleaned in order to prevent build up of material on the surface of the glass bulb. How often it needs to be cleaned depends upon frequency of use and the material being tested. An electrode used on dark coloured and viscous material usually needs to be cleaned more often than an electrode used on clear thin material.  Material building up on the glass bulb of the electrode will cause the calibration of the electrode to be inaccurate and any subsequent reading to be inaccurate. Follow the instructions supplied with the electrode cleaning solution when cleaning the electrode bulb.


Total Lab Supplies offer a wide range of electrodes, storage solutions, buffers and other associated accessories from all major manufacturers including Hanna Instruments, Mettler Toledo, Sentek, Jenway, Schott, WTW etc…

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On this day

In 1980, following a weeklong series of earthquakes and smaller explosions of ash and smoke, the long-dormant Mount St. Helens volcano erupted in Washington state, U.S., hurling ash 15,000 feet into the air and setting off mudslides and avalanches.

Mount St Helens


An earthquake at 8:32:17 a.m. on Sunday, May 18, 1980, caused the entire weakened north face to slide away, creating the largest landslide ever recorded. This allowed the partly molten, high-pressure gas- and steam-rich rock in the volcano to suddenly explode northwards toward Spirit Lake in a hot mix of lava and pulverized older rock.

Approximately 57 people were killed directly.  Hundreds of square miles were reduced to wasteland, causing over a billion U.S. dollars in damage, thousands of animals were killed, and Mount St. Helens was left with a crater on its north side.

Spirit Lake

Lakes nearest to Mount St. Helens have been partly covered with felled trees for more than thirty years. This photograph was taken in 2012.

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Today in Science

On this day in history, in 1947, the B.F. Goodrich Company of Akron, Ohio, announced the development of a tubeless tyre.
A technological innovation that would make cars safer and more efficient.
After more than three years of engineering, Goodrich’s tubeless tyre effectively eliminated the inner tube, trapping the pressurised air within the tire walls themselves. By reinforcing those walls, the company claimed, they were able to combine the puncture-sealing features of inner tubes with an improved ease of riding, high resistance to bruising and superior retention of air pressure.  Testing proved successful, and in 1952, Goodrich won patents for the tyre’s various features.  By 1955 tubeless tires became standard equipment on new cars.
Tyres have moved on since with run flat tyres but the basic design has remained the same.
Total Lab Supplies can’t offer tyres but we can offer other safety items.  If you have any requirements get in touch – we can supply safety storage cabinets, spill kits, safety spectacles, signs, labels, gloves and hazardous waste disposal and more
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Separated thermometer columns

Methods For Reuniting Separated Columns In Thermometers

The largest single cause for the failure of precision thermometers in the lab is the separation of mercury columns. This can occur in transit or in the lab. The life of the thermometer can be greatly extended if the following procedures are employed. Other methods may damage the thermometer.

Cooling Method

With the thermometer in an upright position, gradually immerse only the bulb in a solution of solid CO2 (Dry Ice) and alcohol so that the mercury column retreats slowly into the bulb. Do not cool the stem or mercury column. Keep the bulb in the solution until the main column and the separated portion retreat into the bulb. Remove and swing thermometer in a short arc, forcing all the mercury into the bulb.

Most mercury thermometers can be reunited using this method regardless of range (with the exception of deep immersion thermometers) provided only the bulb is immersed in the CO2 and alcohol solution.

Caution: Do not touch the bulb until it has warmed sufficiently for the mercury to emerge from the bulb into the capillary. Never subject the stem or mercury column to the CO2 solution as it will freeze the mercury column in the capillary and may cause the bulb to fracture.

Heating Method

This method applies to thermometers with a maximum range of 260°C (500°F) equipped with expansion chambers sufficiently large to accommodate the separations plus a portion of the main column. Immerse as much of the bulb and stem as possible in a large beaker containing a liquid whose flash point is well above the highest indication of the thermometer being reunited. Heat the beaker, stirring the liquid with the thermometer, until the separation and a portion of the main column enter the chamber. Tap the thermometer in the palm of gloved hand reuniting the column. Allow to cool slowly.


  1. Never use an open flame on the bulb.
  1. Never fill the expansion chamber more than two-thirds full.
  1. Make certain the flash point of the liquid is well above the highest temperature indicated on the thermometer.
  1. Thermometers whose ranges exceed 260°C (500°F) cannot be reunited using heat without damaging the instrument.

Reuniting Organic-Filled Columns

Separated columns in organic-filled (spirit) thermometers require a somewhat different technique in order to be reunited. The simplest and safest method is to force the liquid down the capillary by using a centrifuge, if one is available, with a cup deep enough to ensure that the centrifugal force is below the liquid column. Carefully insert the thermometer, bulb down, in the centrifuge. Have some cotton wadding at the bottom of the cup to prevent any damage to the bulb. Turn on the centrifuge and in just a few seconds all the liquid will be forced past the separation. If the cup is not deep enough and all the centrifugal force is not below the column, the column will split, forcing part of the liquid down. The remainder will be forced up, filling the expansion chamber.

If a centrifuge is not available, the column can be reunited by getting the liquid to run down. This can be accomplished by holding the thermometer in an upright position and gingerly tapping the stem above the separation against the palm of your hand. As you gently tap the thermometer, observe the liquid above the separation until it breaks away from the wall of the capillary and runs down to join the main column.

Remember, mercury in glass thermometers are no longer available.  Contact us for equivalent thermometers which can be supplied as they are or with UKAS calibrations.

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