(K/Ar) Potassium Argon Dating Techniques I

Radiometric dating In , shortly after the discovery of radioactivity , the American chemist Bertram Boltwood suggested that lead is one of the disintegration products of uranium, in which case the older a uranium-bearing mineral the greater should be its proportional part of lead. Analyzing specimens whose relative geologic ages were known, Boltwood found that the ratio of lead to uranium did indeed increase with age. After estimating the rate of this radioactive change, he calculated that the absolute ages of his specimens ranged from million to 2. Though his figures were too high by about 20 percent, their order of magnitude was enough to dispose of the short scale of geologic time proposed by Lord Kelvin. Versions of the modern mass spectrometer were invented in the early s and s, and during World War II the device was improved substantially to help in the development of the atomic bomb. Soon after the war, Harold C. Wasserburg applied the mass spectrometer to the study of geochronology. This device separates the different isotopes of the same element and can measure the variations in these isotopic abundances to within one part in 10, By determining the amount of the parent and daughter isotopes present in a sample and by knowing their rate of radioactive decay each radioisotope has its own decay constant , the isotopic age of the sample can be calculated.

Potassium, Chemical Element

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The common potassium-argon dating process makes use of the decay of 40 K to 40 Ar, even though much more of the 40 K decays to 40 Ca. The reason is that 40 Ca is common in minerals, and sorting out what fraction of that calcium came from potassium decay is not practical.

Wujing Zongyao , Four Great Inventions , List of Chinese inventions , and Heilongjiang hand cannon Based on a 9th-century Taoist text, the invention of gunpowder by Chinese alchemists was likely an accidental byproduct from experiments seeking to create elixir of life. In the following centuries various gunpowder weapons such as bombs , fire lances , and the gun appeared in China. A slow match for flame throwing mechanisms using the siphon principle and for fireworks and rockets is mentioned.

However by the Song court was producing hundreds of thousands of fire arrows for their garrisons. The first proto-guns, known as “fire lances”, were first recorded to have been used at the siege of De’an in by Song forces against the Jin. By some fire lances were firing wads of bullets. From the Huolongjing ca. The oldest known depiction of rocket arrows, from the Huolongjing. The right arrow reads ‘fire arrow,’ the middle is an ‘arrow frame in the shape of a dragon,’ and the left is a ‘complete fire arrow.

Considered to be a pseudo-explosive. The top item is a through awl and the bottom one is a hook awl. A fire lance as depicted in the Huolongjing ca.


READ MORE Properties, occurrence, and uses Potassium metal is soft and white with a silvery lustre, has a low melting point , and is a good conductor of heat and electricity. Potassium imparts a lavender colour to a flame, and its vapour is green. Potash mine at Esterhazy, Sask. The waste liquors from certain saltworks may contain up to 40 grams per litre of potassium chloride and are used as a source of potassium. K Most potassium is present in igneous rocks, shale, and sediment in minerals such as muscovite and orthoclase feldspar that are insoluble in water; this makes potassium difficult to obtain.

Molten KCl is continuously fed into a packed distillation column while sodium vapour is passed up through the column.

Potassium 40 is a radioisotope that can be found in trace amounts in natural potassium, is at the origin of more than half of the human body activity: undergoing between 4 .

Wood ashes were washed with water to dissolve the potash. It was then recovered by evaporating the water. Potash was often called vegetable alkali. That name comes from the origin of the material “vegetable” plants that contain wood and the most important property of the material, alkali. The word alkali means a strong, harsh chemical that can be used for cleaning.

Common household lye such as Drano is a typical alkali. The chemical name for potash is potassium carbonate K 2 CO 3. Early humans also knew about a similar substance called mineral alkali. This material was made from certain kinds of rocks. But it also had alkali properties. The modern chemical name for soda ash is sodium carbonate Na 2 CO 3. For many centuries, people had trouble telling “vegetable alkali” and “mineral alkali” apart. The two materials looked and acted very much alike.

For example, they could both be used as cleaning materials.

Clocks in the Rocks

The Potassium Argon Reaction Ar 40 is used for several reasons. First of all, Argon is inert. It does not chemically react with other elements at all.

This dating method is based upon the decay of radioactive potassium to radioactive argon in minerals and rocks; potassium also decays to calcium Thus, the ratio of argon and potassium and radiogenic calcium to potassium in a mineral or rock is a measure of the age of the sample.

There are 24 known isotopes of potassium, three of which occur naturally: Naturally occurring 40 K has a half-life of 1. It decays to stable 40 Ca by beta decay The conventional K-Ar dating method depends on the assumption that the rocks contained no argon at the time of formation and that all the subsequent radiogenic argon 40 Ar was quantitatively retained.

Minerals are dated by measurement of the concentration of potassium and the amount of radiogenic 40 Ar that has accumulated. The minerals best suited for dating include biotite , muscovite , metamorphic hornblende , and volcanic feldspar ; whole rock samples from volcanic flows and shallow instrusives can also be dated if they are unaltered. In healthy animals and people, 40 K represents the largest source of radioactivity, greater even than 14 C.

Potassium is principally created in Type II supernovae via an explosive oxygen-burning process. It makes up about 2. Potash Potash is primarily a mixture of potassium salts because plants have little or no sodium content, and the rest of a plant’s major mineral content consists of calcium salts of relatively low solubility in water. While potash has been used since ancient times, it was not understood for most of its history to be a fundamentally different substance from sodium mineral salts.


Chronological Methods 9 – Potassium-Argon Dating Potassium-Argon Dating Potassium-Argon dating is the only viable technique for dating very old archaeological materials. Geologists have used this method to date rocks as much as 4 billion years old. It is based on the fact that some of the radioactive isotope of Potassium, Potassium K ,decays to the gas Argon as Argon Ar By comparing the proportion of K to Ar in a sample of volcanic rock, and knowing the decay rate of K , the date that the rock formed can be determined.

How Does the Reaction Work?

Argon may be incorporated with potassium at time of formation. This is a real problem, but it is easily overcome either by careful selection of the material being dated or by using 40 Ar/ 39 Ar dating instead of K-Ar dating. In the case of the claim about recent lava yielding dates that are millions.

Davy on the bellows at a public demonstration of science at the Royal Institution in London. Image by James Gillray. Sodium and then potassium reacting with water. Discovery of Potassium Dr. Doug Stewart In English chemist Sir Humphry Davy discovered that chemical bonding was electrical in nature and that he could use electricity to split substances into their basic building blocks — the chemical elements.

In he isolated potassium for the first time at the Royal Institution, London. He electrolyzed dried potassium hydroxide potash which he had very slightly moistened by exposing it to the moist air in his laboratory. The electrolysis was powered by the combined output of three large batteries he had built. He also bravely added potassium to hydrochloric acid and saw it burn with a bright red flame. Interesting Facts aboutPotassium Potassium and its close periodic table neighbor sodium are solids at room temperature.

Their alloys however are not.

Potassium is useful for dating very old fossils because..

Updated 8 January c Introduction In a related article on geologic ages Ages , we presented a chart with the various geologic eras and their ages. In a separate article Radiometric dating , we sketched in some technical detail how these dates are calculated using radiometric dating techniques. As we pointed out in these two articles, radiometric dates are based on known rates of radioactivity, a phenomenon that is rooted in fundamental laws of physics and follows simple mathematical formulas.

Dating schemes based on rates of radioactivity have been refined and scrutinized for several decades.

Potassium–argon dating, abbreviated K–Ar dating, is a radiometric dating method used in geochronology and archaeology. It is based on measurement of the product of the radioactive decay of an isotope of potassium (K) into argon (Ar).

The treatments for hyperkalemia also vary widely and can include simply restricting dietary potassium; administering oral, intravenous or inhaled medications; and providing emergent dialysis for more extreme elevations. Given a lack of standardization, it’s not surprising that different doctors treat hyperkalemia in different ways. The new CPR guidelines from the American Heart Association provide recommendations for the treatment of hyperkalemia. Unfortunately, while these new guidelines are easy to follow, there are many potential problems, and I offer some criticisms.

In my opinion, especially for slight elevations, in most cases intravenous diuretics are unnecessary, and oral furosemide could be just as easily substituted. Kayexalate 15 to 30 g orally in sorbitol or by enema. While kayexalate is an important treatment for hyperkalemia, in my opinion, giving kayexalate routinely for any potassium elevation over 5 is a bad practice. It is often unnecessary and physicians frequently overlook the cramping, diarrhea, and discomfort it causes patients.

Rarely, kayexalate in powdered form which doesn’t cause diarrhea or occasionally florinef can be given to outpatients. Previously, many algorithms suggested first obtaining an ECG to look for changes due to hyperkalemia — “peaked” t-waves and new QRS widening — and if either of these were present, the old algorithms recommended particularly aggressive treatment.

The problem is, there is no good definition for what constitutes a peaked t-wave.

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