"Mendeleev was not concerned in 1869 with establishing a basic law of chemistry. He was concerned with writing a textbook for young chemists at St. Petersburg University. ...From 1871 on, Mendeleev himself would repeatedly abstract periodicity from its context... making it seem an emblem of pure science. ...it is how those sketches turned into an immutable law that requires explaining....Mendeleev's predictions themselves had naturalized periodicity by demonstrating the predictive power of his system. He then used this success to naturalize other components of the Great Reforms model."