The spectroscopy we studied in class was first used in the early 60's. In infrared NMR, the position of the peaks represent the functional groups the protons attached to. In proton NMR, the integral (area) under the peaks represent the number of the group of chemically equivalent protons. There were no computer to help draw the diagram or calculate the integral. How did the early chemists complete the task?
My chemistry professor said, they adjusted the infrared frequency a little each time, dotted down the absorption, and then hand-curved the dots.
How about proton NMR? Did they used grid paper and calculated the integral by calculus? It would be hard to do because the peaks are not perfect, smooth curves. They used a even more primitive method: printed out the diagram on paper of uniform thickness, cut the peaks, and weighed them to obtain the ratio.
Early scientists are great people ... Phew, I'm so glad that we don't have to do that today
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