He was ordained as a Presbyterian minister, but later rejected Galvanism and adopted Unitarian views. He studied chemistry and electricity at Warrington Aoademyo He was given an honorary LLoDo by Edinburgh University in I76/4. and became a Fellow of the Royal Society in I7660 In 177U his chemical experiments produced "dephlogisticated air", which Lavoisier named ojcygeno Priestley' s openly expressed sympathy with the aims of the French Revolution led, in 1791> "to the wrecking of his home and the destruction of his library and scientific apparatuso In IJSh he emigrated to America and settled in Northumberland, Pennsylvania, where he built a home on the banks of the Susquehanna River, Here he continued his writing and chemical experimentation until his death in 1804o-3 = atoirdo weight of oxygen iwas due to the fact that oxygen as it occurs in nature, either free or combined, is a mixture. It is a mixture of isotopes that differ in atomic weight and that are not readily detectable or separable by chemical methods.With the development of the mass spectroscope during I9I8-I920, oxygen was found to be a mixture of three isotopes , ', and , the comprising about 99.759 P©r cent of the mixture. Natural oxygen is, therefore, just a little heavier than the isotope, which is the reference standard of the physicists. For this reason, the atomic weights employed by the chemist are a little heavier than the atomic weights employed particularly by the nuclear physicists and nuclear cheraistSo Specifically these chemical atomic weights are heavier than the physical isotopic weights by a factor of 1«000272 ± 0,000005 or 272 units in 1,000,000 or about 5 in 10,000.This difference between the basic physical and chemical atomic weights arose primarily because of the limitations of the analytical techniques that were available to the chemist. It is but one of many illustrations showing that analysis is an indispensable step in the resolution of mixtures and in the description of the components^'-'.
Analysis and the Interpretation of PhotosynthesisFrom the academic standpoint of correlation, interpretation, and instruction, the role of analysis in the physical, chemical and biological sciences is frequently overlooked. But from the technical standpoint of investigation and discovery, analysis often plays a critical role.It defines and establishes the progress that has been made. It brings to light new observations and new materials that continually
