Ninety-five percent of the activity of Oxalic Acid from the year 1950 is equal to the measured activity of the absolute radiocarbon standard which is 1890 wood.
adtrader dating - Radiocarbon dating decay
Because the cosmic ray bombardment is fairly constant, there’s a near-constant level of carbon-14 to carbon-12 ratio in Earth’s atmosphere.
Organisms at the base of the food chain that photosynthesize – for example, plants and algae – use the carbon in Earth’s atmosphere.
Another standard, Oxalic Acid II was prepared when stocks of HOx 1 began to dwindle. The ratio of the activity of Oxalic acid II to 1 is 1.29330.001 (the weighted mean) (Mann, 1983). There are other secondary radiocarbon standards, the most common is ANU (Australian National University) sucrose.
The ratio of the activity of sucrose with 0.95 Ox was first measured by Polach at 1.50070.0052 (Polach, 1976b:122).
If you ever wondered why nuclear tests are now performed underground, this is why.