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Originally Posted by SRoper  Quote:
Originally Posted by aleksanderpolo Todd, thanks for the clarification. I have always wondered how one measure the half-life of something without taking measurement point that is at least comparable to its half-life. In my mind, it's like having a plot with x-axis spanning millions of year, with data point only spanning the last couple of hours, and try to measure the slope of this line and extrapolate it all the way to y-axis. | You can make up for a long half-life by observing a large quantity of the isotope in question. It's really quite accurate if you think about just how many atoms are in a gram. |
Getting a single measurement of rate is easy, but that does not give you the half-life. You still need to make observations that are separated in time - and the longer the half-life, the longer the separation needed between observations in order to get accurate results. More is always better, of course, but I just wanted to reiterate that you cannot determine halflife (without knowing the initial concentration that was in your sample) by a single rate measurement.
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Todd K. Pedlar
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