

Davy used a new method of isolating elements that he had invented, electrolysis.In electrolysis, an electric current is passed through a molten (melted) compound.The idea behind radiocarbon dating is straightforward, but years of work were required to develop the technique to the point where accurate dates could be obtained.Research has been ongoing since the 1960s to determine what the proportion of in the atmosphere has been over the past fifty thousand years.Using the argonargon dating technique, by which scientists measure the decay of an isotope called Argon40 into Argon39 in order to find the age of crystals, they came up with a rough approximation of the footprints' age: 19,000 years at the oldest, 10,000 or 12,000 years at the youngest.I can't exactly follow the logic, but I'm asking here about the dating process itself. I do not think that Argon40 decays into Argon39 as the article states, at least not all by itself. Based on the atmospheric 40Ar/36Ar ratio and the 36concentration, the 40Ar concentration at the time of formation is calculated.


(See sidebar on Davy in the calcium entry in Volume 1.) There are very few uses for potassium as a pure element.The halflife of potassium40 is roughly 1.25 billion years, so four halflives are about five billion years, or older than the earth.Other radiometric techniques, like carbon14, are useful for much more recent dates.The periodic table is a chart that shows how chemical elements are related to one another.The alkali metals also include lithium, sodium, rubidium, cesium, and francium. Potassium is so active that it never occurs free in nature.There's a more basic explanation here: books.google.com/…
