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

Reconciling predictions of climate change

Harvard University researchers have resolved a conflict in estimates of how much the Earth will warm in response to a doubling of carbon dioxide in the atmosphere.

That conflict - between temperature ranges based on global climate models and paleoclimate records and ranges generated from historical observations - prevented the United Nations' Intergovernmental Panel on Climate Change (IPCC) from providing a best estimate in its most recent report for how much the Earth will warm as a result of a doubling of CO2 emissions.

The researchers found that the low range of temperature increase - between 1 and 3 degrees Celsius - offered by the historical observations did not take into account long-term warming patterns. When these patterns are taken into account, the researchers found that not only do temperatures fall within the canonical range of 1.5 to 4.5 degrees Celsius but that even higher ranges, perhaps up to 6 degrees, may also be possible.

The research is published in Science Advances.

CO2 in Earth's atmosphere if half of global-warming emissions are not absorbed (NASA simulation). By NASA/GSFC [Public domain], via Wikimedia Commons

It's well documented that different parts of the planet warm at different speeds. The land over the northern hemisphere, for example, warms significantly faster than water in the Southern Ocean.

"The historical pattern of warming is that most of the warming has occurred over land, in particular over the northern hemisphere," said Cristian Proistosescu, PhD '17, and first author of the paper. "This pattern of warming is known as the fast mode - you put CO2 in the atmosphere and very quickly after that, the land in the northern hemisphere is going to warm."

But there is also a slow mode of warming, which can take centuries to realize. That warming, which is most associated with the Southern Ocean and the Eastern Equatorial Pacific, comes with positive feedback loops that amplify the process. For example, as the oceans warm, cloud cover decreases and a white reflecting surface is replaced with a dark absorbent surface.

The researchers developed a mathematical model to parse the two different modes within different climate models.

"The models simulate a warming pattern like today's, but indicate that strong feedbacks kick in when the Southern Ocean and Eastern Equatorial Pacific eventually warm, leading to higher overall temperatures than would simply be extrapolated from the warming seen to date," said Peter Huybers, Professor of Earth and Planetary Sciences and of Environmental Science and Engineering at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) and co-author of the paper.

Huybers and Proistosescu found that while the slow mode of warming contributes a great deal to the ultimate amount of global warming, it is barely present in present-day warming patterns. "Historical observations give us a lot of insight into how climate changes and are an important test of our climate models," said Huybers, "but there is no perfect analogue for the changes that are coming."

For more information visit:- 

https://www.sciencedaily.com/releases/2017/07/170705164530.htm

http://www.prlabs.co.uk/lab-supplies.php?N=gastube-carbon-dioxide-lr-013-6&Id=11736

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

Tipping points are real: Gradual changes in CO2 levels can induce abrupt climate changes

During the last glacial period, within only a few decades the influence of atmospheric CO2 on the North Atlantic circulation resulted in temperature increases of up to 10 degrees Celsius in Greenland - as indicated by new climate calculations from researchers at the Alfred Wegener Institute and the University of Cardiff. Their study is the first to confirm that there have been situations in our planet's history in which gradually rising CO2 concentrations have set off abrupt changes in ocean circulation and climate at "tipping points." These sudden changes, referred to as Dansgaard-Oeschger events, have been observed in ice cores collected in Greenland. The results of the study have just been released in the journal Nature Geoscience.

Ice core sample taken from drill. Photo by Lonnie Thompson, Byrd Polar Research Center, Ohio State University. [Public domain], via Wikimedia Commons

Previous glacial periods were characterised by several abrupt climate changes in the high latitudes of the Northern Hemisphere. However, the cause of these past phenomena remains unclear. In an attempt to better grasp the role of CO2 in this context, scientists from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) recently conducted a series of experiments using a coupled atmosphere-ocean-sea ice model.

First author Xu Zhang explains: "With this study, we've managed to show for the first time how gradual increases of CO2 triggered rapid warming." This temperature rise is the result of interactions between ocean currents and the atmosphere, which the scientists used the climate model to explore. According to their findings, the increased CO2 intensifies the trade winds over Central America, as the eastern Pacific is warmed more than the western Atlantic. This is turn produces increased moisture transport from the Atlantic, and with it, an increase in the salinity and density of the surface water. Finally, these changes lead to an abrupt amplification of the large-scale overturning circulation in the Atlantic. "Our simulations indicate that even small changes in the CO2 concentration suffice to change the circulation pattern, which can end in sudden temperature increases," says Zhang.

Further, the study's authors reveal that rising CO2 levels are the dominant cause of changed ocean currents during the transitions between glacial and interglacial periods. As climate researcher Gerrit Lohmann explains, "We can't say for certain whether rising CO2 levels will produce similar effects in the future, because the framework conditions today differ from those in a glacial period. That being said, we've now confirmed that there have definitely been abrupt climate changes in the Earth's past that were the result of continually rising CO2 concentrations."

For more information visit:-

https://www.sciencedaily.com/releases/2017/06/170623100414.htm

http://www.prlabs.co.uk/lab-supplies.php?N=gastube-carbon-dioxide-hr-05-20&Id=11735

Diesels pollute more than lab tests detect

Because of testing inefficiencies, maintenance inadequacies and other factors, cars, trucks and buses worldwide emit 4.6 million tons more harmful nitrogen oxide (NOx) than standards allow, according to a new study co-authored by University of Colorado Boulder researchers.

The study, published in Nature, shows these excess emissions alone lead to 38,000 premature deaths annually worldwide, including 1,100 deaths in the United States.

The findings reveal major inconsistencies between what vehicles emit during testing and what they emit in the real world - a problem that's far more severe, said the researchers, than the incident in 2015, when federal regulators discovered Volkswagen had been fitting millions of new diesel cars with "defeat devices."

Red Diesel Tank, by Meena Kadri [CC BY 2.0 (http://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons

The devices sense when a vehicle is undergoing testing and reduce emissions to comply with government standards. Excess emissions from defeat devices have been linked to about 50 to 100 U.S. deaths per year, studies show.

"A lot of attention has been paid to defeat devices, but our work emphasizes the existence of a much larger problem," said Daven Henze, an associate professor of mechanical engineering at CU Boulder who, along with postdoctoral researcher Forrest Lacey, contributed to the study. "It shows that in addition to tightening emissions standards, we need to be attaining the standards that already exist in real-world driving conditions."

The research was conducted in partnership with the International Council on Clean Transportation, a Washington, D.C.-based nonprofit organization, and Environmental Health Analytics LLC.

For the paper, the researchers assessed 30 studies of vehicle emissions under real-world driving conditions in 11 major vehicle markets representing 80 percent of new diesel vehicle sales in 2015. Those markets include Australia, Brazil, Canada, China, the European Union, India, Japan, Mexico, Russia, South Korea and the United States.

They found that in 2015, diesel vehicles emitted 13.1 million tons of NOx, a chemical precursor to particulate matter and ozone. Exposure in humans can lead to heart disease, stroke, lung cancer and other health problems. Had the emissions met standards, the vehicles would have emitted closer to 8.6 million tons of NOx.

Heavy-duty vehicles, such as commercial trucks and buses, were by far the largest contributor worldwide, accounting for 76 percent of the total excess NOx emissions.

Henze used computer modeling and NASA satellite data to simulate how particulate matter and ozone levels are, and will be, impacted by excess NOx levels in specific locations. The team then computed the impacts on health, crops and climate.

"The consequences of excess diesel NOx emissions for public health are striking," said Susan Anenberg, co-lead author of the study and co-founder of Environmental Health Analytics LLC.

China suffers the greatest health impact with 31,400 deaths annually attributed to diesel NOx pollution, with 10,700 of those deaths linked to excess NOx emissions beyond certification limits. In Europe, where diesel-passenger cars are common, 28,500 deaths annually are attributed to diesel NOx pollution, with 11,500 of those deaths linked to excess emissions.

The study projects that by 2040, 183,600 people will die prematurely each year due to diesel vehicle NOx emissions unless governments act.

The authors say emission certification tests, both prior to sale and by vehicle owners, could be more accurate if they were to simulate a broader variety of speeds, driving styles and ambient temperatures. Some European countries now use portable testing devices that track emissions of a car in motion.

"Tighter vehicle emission standards coupled with measures to improve real-world compliance could prevent hundreds of thousands of early deaths from air pollution-related diseases each year," said Anenberg.

For more information, visit:-

https://www.sciencedaily.com/releases/2017/05/170515111557.htm

http://www.prlabs.co.uk/lab-supplies.php?N=gastube-nitrogen-oxide-airtec-002-2ppm&Id=11713

https://commons.wikimedia.org/wiki/File:Red_diesel_tank.jpg

On this day in science history: Sakurai's Object was discovered

In 1996, a bright “new” star was discovered in Sagittarius by Japanese amateur astronomer Yukio Sakurai. It was found not to be a usual nova, but instead was a star going through a dramatic evolutionary state, re-igniting its nuclear furnace for one final blast of energy called the “final helium flash.” It was only the second to be identified in the twentieth century. A star like the Sun ends its active life as a white dwarf star gradually cooling down into visual oblivion. Sakurai's Object had a mass a few times that of the Sun. Its collapse after fusing most of its hydrogen fuel to helium raised its temperature so much higher it began nuclear fusion of its helium remains. This was confirmed using its light spectrum to identify the elements present.

Sakurai's Object By ESO, [CC BY 4.0 (http://creativecommons.org/licenses/by/4.0)], via Wikimedia Commons

Sakurai's Object is a highly evolved post-asymptotic giant branch star which has, following a brief period on the white dwarf cooling track, undergone a helium shell flash (also known as a very late thermal pulse). The star is thought to have a mass of around 0.6 M☉. Observations of Sakurai's Object show increasing reddening and pulsing activity, suggesting that the star is exhibiting thermal instability during its final helium-shell flash.

Prior to its reignition V4334 Sgr is thought to have been cooling towards a white dwarf with a temperature around 100,000 K and a luminosity around 100 L☉. The luminosity rapidly increased about a hundred-fold and then the temperature decreased to around 10,000 K. The star developed the appearance of an F class supergiant (F2 Ia). The apparent temperature continued to cool to below 6,000 K and the star was gradually obscured at optical wavelengths by the formation of carbon dust, similar to an R CrB star. Since then the temperature has increased to around 20,000 K.

The properties of Sakurai's Object are quite similar to that of V605 Aquilae. V605, discovered in 1919, is the only other known star observed during the high luminosity phase of a very late thermal pulse, and Sakurai's Object is modeled to increase in temperature in the next few decades to match the current state of V605.

During the second half of 1998 an optically thick dust shell obscured Sakurai's Object, causing a rapid decrease in visibility of the star, until in 1999 it disappeared from optical wavelength observations altogether. Infrared observations showed that the dust cloud around the star is primarily carbon in an amorphous form. In 2009 it was discovered that the dust shell is strongly asymmetrical, as a disc with a major axis oriented at an angle of 134°, and inclination of around 75°. The disc is thought to be growing more opaque due to the fast spectral evolution of the source towards lower temperatures.

Sakurai's Object is surrounded by a planetary nebula created following the star's red giant phase around 8300 years ago. It has been determined that the nebula has a diameter of 44 arcseconds and expansion velocity of roughly 32 km/s.

For more information visit:-

https://todayinsci.com/2/2_20.htm

https://en.wikipedia.org/wiki/Sakurai's_Object

http://www.prlabs.co.uk/lab-supplies.php?N=helium-emptied-cylinder&Id=60491

What is absolute zero?

In theory, absolute zero is the temperature where the particles of matter stop moving. Absolute zero is impossible to achieve, because all particles move, even if it is just a small vibration. Some people have created temperatures very close to absolute zero, but the record temperature was 100 pK (Picokelvin) above absolute zero.  Even getting close to absolute zero is difficult because anything that touches an object being cooled near absolute zero would give heat to the objects. Scientists use lasers to slow atoms when cooling objects to very low temperatures.

The Kelvin and Rankine temperature scales are defined so that absolute zero is 0 kelvins (K) or 0 degrees Rankine (°R). The Celsius and Fahrenheit scales are defined so that absolute zero is −273.15 °C or −459.67 °F.

At this stage the pressure of the particles is zero. If we plot a graph to it, we can see that the temperature of the particles is zero. The temperature cannot go down any further. Also, the particles cannot move in "reverse" either because as the movement of particles is vibration, vibrating in reverse would be nothing but simply vibrating again. The closer the temperature of an object gets to absolute zero, the less resistive the material is to electricity therefore it will conduct electricity almost perfectly, with no measurable resistance.

The Third Law of Thermodynamics says that nothing can ever have a temperature of absolute zero.

The Second Law of Thermodynamics says that all engines that are powered by heat (like car engines and steam train engines) must release waste heat and can not be 100% efficient. This is because the efficiency (percent of energy the engine uses up that is actually used to do the engine's job) is 100%×(1-T_outside/T_inside), which only is 100% if the outside temperature is absolute zero which it can not be. So, an engine can not be 100% efficient, but you can make its efficiency closer to 100% by making the inside temperature hotter and/or the outside temperature colder.

In September 2013, MIT scientists cooled a sodium gas to the lowest temperature ever recorded -- only half-a-billionth of a degree above absolute zero.

Absolute zero is defined to be −273.15°C, or 0 K.

 

For more information visit:-

http://web.mit.edu/newsoffice/2003/cooling.html

http://en.wikipedia.org/wiki/Absolute_zero

The Galileo Thermometer

A Galileo thermometer is a thermometer made of a sealed glass cylinder containing a clear liquid and several glass vessels of varying densities. As temperature changes, the individual floats rise or fall proportion to their respective density.

It is named after Galileo Galilei because he discovered the principle on which this thermometer is based—that the density of a liquid changes in proportion to its temperature—and invented a thermoscope based on this principle.


Floating in the liquid inside the cylinder are a number of sealed glass bulbs containing coloured liquid. Attached to each bulb is a metal disc whose weight is adjusted to give the bulb the correct buoyancy. As the liquid in the cylinder changes temperature, its density changes and the bulbs are free to move – rising or falling to reach a position where their density is either equal to that of the surrounding liquid or where they are brought to a halt by other bulbs. The bulbs differ in buoyancy by a very small amount and are ordered such that the least dense is at the top and densest at the bottom so that they form a temperature scale.


 

The temperature is typically read from the metal disc hanging from each bulb. Usually a gap separates the top bulbs from the bottom bulbs and then the temperature is between the tag readings on either side of the gap. If a bulb is free-floating in the gap, then its tag reading is closest to the ambient temperature.

To achieve satisfactory accuracy, the weights must be manufactured to a tolerance of less than 1/1000 of one gram (1 mg)


For more information please check out the following links

http://www.h2g2.com/approved_entry/A60734955

http://en.wikipedia.org/wiki/Galileo_thermometer

http://www.howstuffworks.com/question663.htm

What is Temperature?

Introduction

The accurate measurement of temperature is vital across a broad spectrum of human activities, including industrial processes (e.g. making steel), manufacturing; monitoring (in food transport and storage), and in health and safety. In fact, in almost every sector, temperature is one of the key parameters to be measured.

King of Poland

History of Thermometry

The means of accurately measuring temperatures has long fascinated people. One of the differences between temperature and other physical concepts, such as mass or length, is that it is subjective: different people will have different perceptions of what is hot and what is cold. To make objective measurements, we must use a thermometer in which some physical property of a substance changes with temperature in a reliable and reproducible way.
Thermoscopes, the ancestors of modern thermometers, have been around since about 200 BC. The first recognisable, modern thermometers were made in the 16th century by both the Italian Galileo Galilei and Santorio Santorio, a physician to the King of Poland. The latter produced a thermometer incorporating a scale, and his writings show that he understood the importance of the temperature measurement in the diagnosis of disease. The first sealed thermometer was made by the Grand Duke Ferdinand of Tuscany in 1641. This thermometer was more accurate than its predecessors since it wasn’t dependent on atmospheric pressure. Later, the scientists Fahrenheit and Celsius both made glass thermometers containing mercury, and used reference points (the melting point of pure ice and the boiling point of water) to improve the accuracy.

Types of Thermometer

Liquid-in-Glass

Liquid-in-glass, in particular mercury, thermometers have been used for almost 300 years in science, medicine, metrology and in industry. They rely on the expansion of a fluid with temperature. The fluid is contained in a sealed glass bulb and the temperature is read using a scale etched along the stem of the thermometer.

Platinum Resistance

In the modern world, mercury and spirit-filled thermometers have largely given way to electrical devices, which can be digitised and automated. Platinum resistance thermometers are electrical thermometers which make use of the variation of resistance of high-purity platinum wire with temperature. This variation is predictable, enabling accurate measurements to be performed. They are sensitive and, with sophisticated equipment, measurements, can routinely be made to better than a thousandth part of 1°C

Thermocouples

Thermocouples are the most common sensors in industrial use. They have a long history, the original paper on thermoelectricity by Seebeck being published in 1822. They consist of two dissimilar metallic conductors joined at the point of measurement. When the conductors are heated a voltage is generated in the circuit, and this can be used to determine the temperature

Radiation (or Pyrometers)

Radiation thermometers, or pyrometers, make use of the fact that all objects emit thermal radiation, as seen when looking at the bars of an electric fire or a light bulb. The amount of radiation emitted can be measured and related to temperature using the Planck law of radiation. Temperatures can be measured remotely using this technique, with the sensor situated some distance away from the object. Hence it is useful for objects that are very hot, moving or in hazardous environments

Temperature Scales

The two temperature scales commonly in use today date from the eighteenth century and are named after Gabriel Daniel Fahrenheit and the Swedish astronomy professor Anders Celsius. Fahrenheit designed his scale to have two reference points that could be set up in his workshop. He originally chose the melting point of pure ice and the temperature of a normal human body, which he took as being 32° and 96° respectively. These conveniently gave positive values for all the temperatures he encountered. Later he changed to using the boiling point of water (212°) as the upper fixed point of the scale.
Celsius also used the ice and steam points, but took them to be 0°C and 100°C respectively. Although the Celsius scale has taken precedence over the Fahrenheit scale, the latter is still familiar in weather reports in the United Kingdom: a summer’s day temperature of 75°F seems much more pleasant than one of 23°C!
A third, fundamental, temperature scale was proposed in 1854 by the Scottish physicist William Thomson, Lord Kelvin. It is based on the idea of the absolute zero, the point of no discernible energy, which is independent of any particular material substance. The Kelvin scale is widely used by physicists and engineers to determine and apply fundamental laws of thermodynamics

The International Temperature Scale of 1990 (ITS-90)

Since 1954 the unit of (thermodynamic) temperature has been defined as the kelvin, and is the fraction 1/273.16 of the thermodynamic temperature of the triple point of water. This is the unique temperature and pressure at which the three phases of water (solid, liquid and vapour) co-exist in equilibrium. It is fractionally higher than the melting point, being 0.01°C or 273.16 K. From this single point it is possible to generate a thermodynamic temperature scale using gas thermometers and radiation thermometers which accurately obey known laws.
Such experiments are not easy and are rarely done, but good values have been established for a series of fixed points: freezing points of pure metals at high temperatures and triple points of gases at low temperatures. These are incorporated into the International Temperature Scale so that standard platinum resistance thermometers and radiation thermometers can be calibrated with excellent reproducibility. The National Physical Laboratory maintains the temperature scale (currently the International Temperature Scale of 1990, the ITS-90) in the UK, and compares this with the ITS-90 maintained in other national laboratories. In this way temperature standards around the world can be accurately equivalent, and all manner of thermometers can be reliably calibrated for everyday use.

Future of Thermometry

The international temperature community is working towards a redefinition of the kelvin. This would be based on a fundamental constant of nature known as the Boltzmann constant. The advantages of this is that the new definition would be freed from any physical artefact (i.e. the triple point of water) and allow the use of any appropriate thermodynamic method for temperature measurement.

The Spectrum of Temperature

	200 million °C	The Joint European Torus (JET) nuclear fusion project, Culham Oxfordshire
	15 million °C	Temperature of the centre of the Sun
	6 000 °C	Temperature of the surface of the Sun
	1 200 °C to 1 500 °C	Molten glass / steel
	1 064 °C	Melting point of gold
	100 °C	Boiling point at one atmosphere of pressure
	0 °C	Freezing point of pure water at one atmosphere of pressure
	- 89.2 °C	All time coldest point on earth
	- 196 °C	Cryogenic storage in liquid nitrogen
	- 270 °C	Cosmic background radiation

For more information visit www.npl.co.uk