text: Hahn and Strassmann isolated the three radium isotopes (verified by their half-lives) and used fractional crystallisation to separate it from its barium carrier by adding barium bromide crystals in four steps. Since radium precipitates preferentially in a solution of barium bromide, at each step the fraction drawn off would contain less radium than the one before. However, they found no difference between each of the fractions. In case their process was faulty in some way, they verified it with known isotopes of radium; the process was fine. On 19 December, Hahn wrote to Meitner, informing her that the radium isotopes behaved chemically like barium. Anxious to finish up before the Christmas break, Hahn and Strassmann submitted their findings to Naturwissenschaften on 22 December without waiting for Meitner to reply. Hahn concluded the paper with: "As chemists... we should substitute the symbols Ba, La, Ce for Ra, Ac, Th. As nuclear chemists fairly close to physics we cannot yet bring ourselves to take this step which contradicts all previous experience in physics."
  Frisch normally celebrated Christmas with Meitner in Berlin, but in 1938 she accepted an invitation from Eva von Bahr to spend it with her family at Kungälv, and Meitner asked Frisch to join her there. Meitner received the letter from Hahn describing his chemical proof that some of the product of the bombardment of uranium with neutrons was barium. Barium had an atomic mass 40% less than uranium, and no previously known methods of radioactive decay could account for such a large difference in the mass of the nucleus. Nonetheless, she had immediately written back to Hahn to say: "At the moment the assumption of such a thoroughgoing breakup seems very difficult to me, but in nuclear physics we have experienced so many surprises, that one cannot unconditionally say: It is impossible."
  According to Frisch:
  Meitner and Frisch had correctly interpreted Hahns results to mean that the nucleus of uranium had split roughly in half. The first two reactions that the Berlin group had observed were light elements created by the breakup of uranium nuclei; the third, the 23-minute one, was a decay into the real element 93. On returning to Copenhagen, Frisch informed Bohr, who slapped his forehead and exclaimed "What idiots we have been!" Bohr promised not to say anything until they had a paper ready for publication. To speed the process, they decided to submit a one-page note to Nature'. At this point, the only evidence that they had was the barium. Logically, if barium was formed, the other element must be krypton, although Hahn mistakenly believed that the atomic masses had to add up to 239 rather than the atomic numbers adding up to 92, and thought it was masurium (technetium), and so did not check for it:
  :  + n →  +  + some n
  Over a series of long-distance phone calls, Meitner and Frisch came up with a simple experiment to bolster their claim: to measure the recoil of the fission fragments, using a Geiger counter with the threshold set above that of the alpha particles. Frisch conducted the experiment on 13 January, and found the pulses caused by the reaction just as they had predicted. He decided he needed a name for the newly discovered nuclear process. He spoke to William A. Arnold, an American biologist working with de Hevesy, and asked him what biologists called the process by which living cells divided into two cells. Arnold told him that biologists called it fission. Frisch then applied that name to the nuclear process in his paper. Frisch mailed both papers to Nature on 16 January; the jointly-authored note appeared in print on 11 February and Frisch's paper on recoil on 18 February.
  These three reports, the first Hahn-Strassmann publications of 6 January and 10 February 1939, and the Frisch-Meitner publication of 11 February 1939, had electrifying effects on the scientific community. In 1940 Frisch and Rudolf Peierls produced the Frisch–Peierls memorandum, which established that an atomic explosion could be generated.