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This is the clock that permits levels of c14 in organic archaeological, geological, and paleontological samples to be converted into an estimate of time.
The measurement of the rate of radioactive decay is known as its half-life, the time it takes for half of a sample to decay.
Most samples require chemical pre-treatment to ensure their purity or to recover particular components of the material.
The objective of pre-treatment is to ensure that the carbon being analyzed is native to the sample submitted for dating.
The diminishing levels via decay means that the effective limit for using c14 to estimate time is about 50,000 years. Subsequent work has shown that the half-life of radiocarbon is actually 5730 ± 40 years, a difference of 3% compared to the Libby half-life.
In addition to various pre-treatments, the sample must be burned and converted to a form suitable for the counter.
Pre-treatment seeks to remove from the sample any contaminating carbon that could yield an inaccurate date.
Acids may be used to eliminate contaminating carbonates.
These so-called "solid-carbon" dates were soon found to yield ages somewhat younger than expected, and there were many other technical problems associated with sample preparation and the operation of the counters.
Gas proportional counters soon replaced the solid-carbon method in all laboratories, with the samples being converted to gases such as carbon dioxide, carbon disulfide, methane, or acetylene.
the field deflects atoms of different masses differently (heavier atoms deflect less).