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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The chemistry behind why you shouldn’t eat laundry pods

Laundry pods have featured in the news this week after cases of people eating them in what’s being referred to as the ‘Tide Pod Challenge’. In case you didn’t already realise that this is a pretty terrible idea, this graphic looks at the chemical reasons why you really don’t want them anywhere near your mouth

The Chemistry of Laundry pods



Eating laundry pods is particularly risky since the detergents are at a higher concentration than in liquid detergents. They are highly alkaline; just as highly acidic substances can cause burns, so too can very alkaline ones. If you eat a laundry pod, you run the risk of burns to your throat and stomach from the high concentration detergent they contain. As they pop in your mouth, they can also be accidentally inhaled – definitely not good for your airway and lungs either.

In addition, eating them can also cause breathing problems. Why exactly this is is currently unclear. It seems that in some laundry pod formulations, a sedative effect is seen when they are ingested. This can lead to drowsiness and breathing difficulties. It’s been speculated that a solvent used in the pods, propylene glycol, might contribute. Alternatively, it might be an unknown effect of certain ethoxylated alcohols.


Laundry pods like this also contain a bitter substance to deter children from putting them in their mouths.  For more information visit the full article at the excellent Compound Interest


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On this day in science history: the first U.S. patent for a liquid soap was issued

In 1865, the first U.S. patent for a liquid soap was issued to William Sheppard of New York City (No. 49,561). The patent described his “discovery that by the addition of comparatively small quantities of common soap to a large quantity of spirits of ammonia or hartshorn is thickened to the consistency of molasses, and a liquid soap is obtained of superior detergent qualities.” The proportions given were to dissolve one pound of common soap in water or steam, and then add 100-lbs of ammonia such that the liquid thickens to the consistency of molasses. The product was expected to be useful for both domestic and manufacturing purposes. (Hartshorn is an ancient name for an aqueous solution of ammonia).
 
Decorative soaps, by Phanton at English Wikipedia (Transferred from en.wikipedia to Commons.) [Public domain], via Wikimedia Commons
So, how does soap clean?
 
Action of soap
 
When used for cleaning, soap allows insoluble particles to become soluble in water, so they can then be rinsed away. For example: oil/fat is insoluble in water, but when a couple of drops of dish soap are added to the mixture, the oil/fat dissolves in the water. The insoluble oil/fat molecules become associated inside micelles, tiny spheres formed from soap molecules with polar hydrophilic (water-attracting) groups on the outside and encasing a lipophilic (fat-attracting) pocket, which shields the oil/fat molecules from the water making it soluble. Anything that is soluble will be washed away with the water.
 
Effect of the alkali
 
The type of alkali metal used determines the kind of soap product. Sodium soaps, prepared from sodium hydroxide, are firm, whereas potassium soaps, derived from potassium hydroxide, are softer or often liquid. Historically, potassium hydroxide was extracted from the ashes of bracken or other plants. Lithium soaps also tend to be hard—these are used exclusively in greases.
 
Effects of fats
 
Soaps are derivatives of fatty acids. Traditionally they have been made from triglycerides (oils and fats). Triglyceride is the chemical name for the triesters of fatty acids and glycerin. Tallow, i.e., rendered beef fat, is the most available triglyceride from animals. Its saponified product is called sodium tallowate. Typical vegetable oils used in soap making are palm oil, coconut oil, olive oil, and laurel oil. Each species offers quite different fatty acid content and hence, results in soaps of distinct feel. The seed oils give softer but milder soaps. Soap made from pure olive oil is sometimes called Castile soap or Marseille soap, and is reputed for being extra mild. The term “Castile” is also sometimes applied to soaps from a mixture of oils, but a high percentage of
olive oil.
 
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On this day in science history: oxygen was identified

In 1774, Joseph Priestley, British Presbyterian minister and chemist, identified a gas which he called “dephlogisticated air” – later known as oxygen. Priestley found that mercury heated in air became coated with “red rust of mercury,” which, when heated separately, was converted back to mercury with “air” given off. Studying this “air” given off, he observed that candles burned very brightly in it. Also, a mouse in a sealed vessel with it could breathe it much longer than ordinary air. A strong believer in the phlogiston theory, Priestley considered it to be “air from which the phlogiston had been removed.” Further experiments convinced him that ordinary air is one fifth dephlogisticated air, the rest considered by him to be phlogiston.
 
Joseph Priestley, by Charles Turner [Public domain], via Wikimedia Commons
However, oxygen was in fact first discovered earlier, by Swedish pharmacist Carl Wilhelm Scheele. He had produced oxygen gas by heating mercuric oxide and various nitrates in 1771–2. Scheele called the gas “fire air” because it was the only known supporter of combustion, and wrote an account of this discovery in a manuscript he titled Treatise on Air and Fire, which he sent to his publisher in 1775. That document was published in 1777. 
 
Because Priestly published his findings first, he is usually given priority in the discovery.
 
The French chemist Antoine Laurent Lavoisier later claimed to have discovered the new substance independently. Priestley visited Lavoisier in October 1774 and told him about his experiment and how he liberated the new gas. Scheele also posted a letter to Lavoisier on September 30, 1774 that described his discovery of the previously unknown substance, but Lavoisier never acknowledged receiving it (a copy of the letter was found in Scheele’s belongings after his death). Long before this, one of the first known experiments on the relationship between combustion and air was conducted by the 2nd century BCE Greek writer on mechanics, Philo of Byzantium. In his work Pneumatica, Philo observed that inverting a vessel over a burning candle and surrounding the vessel’s neck with water resulted in some water rising into the neck. Philo incorrectly surmised that parts of the air in the vessel were converted into the classical element fire and thus were able to escape through pores in the glass. Many centuries later Leonardo da Vinci built on Philo’s work by observing that a portion of air is consumed during combustion and respiration.
 
In the late 17th century, Robert Boyle proved that air is necessary for combustion. English chemist John Mayow (1641–1679) refined this work by showing that fire requires only a part of air that he called spiritus nitroaereus. In one experiment, he found that placing either a mouse or a lit candle in a closed container over water caused the water to rise and replace one-fourteenth of the air’s volume before extinguishing the subjects. From this he surmised that nitroaereus is consumed in both respiration and combustion.
 
Mayow observed that antimony increased in weight when heated, and inferred that the nitroaereus must have combined with it. He also thought that the lungs separate nitroaereus from air and pass it into the blood and that animal heat and muscle movement result from the reaction of nitroaereus with certain substances in the body. Accounts of these and other experiments and ideas were published in 1668 in his work Tractatus duo in the tract “De respiratione”.
 
Robert Hooke, Ole Borch, Mikhail Lomonosov, and Pierre Bayen all produced oxygen in experiments in the 17th and the 18th century but none of them recognized it as a chemical element. This may have been in part due to the prevalence of the philosophy of combustion and corrosion called the phlogiston theory, which was then the favored explanation of those processes.
 
Established in 1667 by the German alchemist J. J. Becher, and modified by the chemist Georg Ernst Stahl by 1731, phlogiston theory stated that all combustible materials were made of two parts. One part, called phlogiston, was given off when the substance containing it was burned, while the dephlogisticated part was thought to be its true form, or calx.
 
Highly combustible materials that leave little residue, such as wood or coal, were thought to be made mostly of phlogiston; non-combustible substances that corrode, such as iron, contained very little. Air did not play a role in phlogiston theory, nor were any initial quantitative experiments conducted to test the idea; instead, it was based on observations of what happens when something burns, that most common objects appear to become lighter and seem to lose something in the process. The fact that a substance like wood gains overall weight in burning was hidden by the buoyancy of the gaseous combustion products.
 
This theory, while it was on the right track, was unfortunately set up backwards. Rather than combustion or corrosion occurring as a result of the decomposition of phlogiston compounds into their base elements with the phlogiston being lost to the air, it is in fact the result of oxygen from the air combining with the base elements to produce oxides. Indeed, one of the first clues that the phlogiston theory was incorrect was that metals gain weight in rusting (when they were supposedly losing phlogiston).
 
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Moon has a water-rich interior

A new study of satellite data finds that numerous volcanic deposits distributed across the surface of the Moon contain unusually high amounts of trapped water compared with surrounding terrains. The finding of water in these ancient deposits, which are believed to consist of glass beads formed by the explosive eruption of magma coming from the deep lunar interior, bolsters the idea that the lunar mantle is surprisingly water-rich.
 
Scientists had assumed for years that the interior of the Moon had been largely depleted of water and other volatile compounds. That began to change in 2008, when a research team including Brown University geologist Alberto Saal detected trace amounts of water in some of the volcanic glass beads brought back to Earth from the Apollo 15 and 17 missions to the Moon. In 2011, further study of tiny crystalline formations within those beads revealed that they actually contain similar amounts of water as some basalts on Earth. That suggests that the Moon’s mantle – parts of it, at least – contain as much water as Earth’s.
 
“The key question is whether those Apollo samples represent the bulk conditions of the lunar interior or instead represent unusual or perhaps anomalous water-rich regions within an otherwise ‘dry’ mantle,” said Ralph Milliken, lead author of the new research and an associate professor in Brown’s Department of Earth, Environmental and Planetary Sciences. “By looking at the orbital data, we can examine the large pyroclastic deposits on the Moon that were never sampled by the Apollo or Luna missions. The fact that nearly all of them exhibit signatures of water suggests that the Apollo samples are not anomalous, so it may be that the bulk interior of the Moon is wet.”
 
Full Moon photograph taken 10-22-2010 from Madison, Alabama, USA. By Gregory H. Revera (Own work) [CC BY-SA 3.0 (http://ift.tt/HKkdTz) or GFDL (http://ift.tt/KbUOlc)], via Wikimedia Commons
The research, which Milliken co-authored with Shuai Li, a postdoctoral researcher at the University of Hawaii and a recent Brown Ph.D. graduate, is published in Nature Geoscience.
 
Detecting the water content of lunar volcanic deposits using orbital instruments is no easy task. Scientists use orbital spectrometers to measure the light that bounces off a planetary surface. By looking at which wavelengths of light are absorbed or reflected by the surface, scientists can get an idea of which minerals and other compounds are present.
 
The problem is that the lunar surface heats up over the course of a day, especially at the latitudes where these pyroclastic deposits are located. That means that in addition to the light reflected from the surface, the spectrometer also ends up measuring heat.
 
“That thermally emitted radiation happens at the same wavelengths that we need to use to look for water,” Milliken said. “So in order to say with any confidence that water is present, we first need to account for and remove the thermally emitted component.”
 
To do that, Li and Milliken used laboratory-based measurements of samples returned from the Apollo missions, combined with a detailed temperature profile of the areas of interest on the Moon’s surface. Using the new thermal correction, the researchers looked at data from the Moon Mineralogy Mapper, an imaging spectrometer that flew aboard India’s Chandrayaan-1 lunar orbiter.
 
The researchers found evidence of water in nearly all of the large pyroclastic deposits that had been previously mapped across the Moon’s surface, including deposits near the Apollo 15 and 17 landing sites where the water-bearing glass bead samples were collected.
 
“The distribution of these water-rich deposits is the key thing,” Milliken said. “They’re spread across the surface, which tells us that the water found in the Apollo samples isn’t a one-off. Lunar pyroclastics seem to be universally water-rich, which suggests the same may be true of the mantle.”
 
The idea that the interior of the Moon is water-rich raises interesting questions about the Moon’s formation. Scientists think the Moon formed from debris left behind after an object about the size of Mars slammed into the Earth very early in solar system history. One of the reasons scientists had assumed the Moon’s interior should be dry is that it seems unlikely that any of the hydrogen needed to form water could have survived the heat of that impact.
 
“The growing evidence for water inside the Moon suggest that water did somehow survive, or that it was brought in shortly after the impact by asteroids or comets before the Moon had completely solidified,” Li said. “The exact origin of water in the lunar interior is still a big question.”
 
In addition to shedding light on the water story in the early solar system, the research could also have implications for future lunar exploration. The volcanic beads don’t contain a lot of water – about .05 percent by weight, the researchers say – but the deposits are large, and the water could potentially be extracted.
 
“Other studies have suggested the presence of water ice in shadowed regions at the lunar poles, but the pyroclastic deposits are at locations that may be easier to access,” Li said. “Anything that helps save future lunar explorers from having to bring lots of water from home is a big step forward, and our results suggest a new alternative.”
 
The research was funded by the NASA Lunar Advanced Science and Exploration Research Program (NNX12AO63G).
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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.”
 
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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://ift.tt/o655VX)], 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.
 
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