The ratio of the activity of sucrose with 0.95 Ox was first measured by Polach at 1.50070.0052 (Polach, 1976b:122).
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.The Oxalic acid standard which was developed is no longer commercially available. In the early 1980's, a group of 12 laboratories measured the ratios of the two standards.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.When finding the age of an organic organism we need to consider the half-life of carbon 14 as well as the rate of decay, which is –0.693.For example, say a fossil is found that has 35% carbon 14 compared to the living sample. We can use a formula for carbon 14 dating to find the answer.Obviously, this activity is additional and must be removed from calculations.