Measures for Progress: A History of the National Bureau of Standards

HEAVY WATER 359
than in normal water, by 164 parts in a million, that is, possessing a specific
gravity of 1.000164.174
Urey's discovery of the isotope of hydrogen and Washburn's actual
separation were revolutionary.175 The new isotope, winning Urey the Nobel
Prize in chemistry in 1934, was given the name "deuterium," with the symbol
D (in the form of deuterium oxide or heavy water it is D20). Within 2
years it had been prepared in a pure state, its specific gravity 1.015.176
Another event in 1932, James Chadwick's discovery of the neutron,
was to prove even more important in subsequent events than that of heavy
water. In the atom compounded of protons and electrons (its positive-
and negative-charged particles), Chadwick in England identified yet another
fundamental particle, not electrically charged, which he called the neutron.
Its neutral characteristics made it highly penetrating and therefore very effec-
tive as an agent in nuclear transmutation. That same year, Cockcroft and
Walton, working in Rutherford's laboratory at Cambridge, bombarded a
lithium target with protons. In the experiment, a hydrogen
atom reacted with a lithium atom to produce two helium atoms. The first
artificial nuclear reaction and true transmutation of elements had occurred.177
For a time physicists showed great interest in the deuteron, the nucleus
of deuterium or heavy water that Urey had found, because of its "remarkable
properties as a projectile for producing transmutation of elements and par.
ticularly for the production of neutrons." 178 But while deuterium had a
NBS Annual Report 1932, p. 8; Washburn and Urey, "Concentration of the H'
isotope of hydrogen * * 'I'," Proc. Nati. Acad. Sci. 18, 496 (1932); Washburn, Smith,
and Frandsen, "The isotopic fractionation of water," J. Chem. Phys. 1, 288 (1933);
RP6OJ, "The isotopic fractionation of water" (Washburn, Smith, and Frandsen,
1933). Urey and Teal summarized deuterium research in Revs. Mod. Phys. 7, 34 (1935).
Dr. Edward W. Washburn came to the Bureau as its chief chemist in 1926, when he
was 45. He had recently completed a 4-year project as editor in chief of the monu-
mental International Critical Tables of Numerical Data of Physics, Chemistry, and
Technology. He was one of the best scientists ever to work at the Bureau, his research
on the fractionation of petroleum, the crystallization of rubber, and on heavy water
among his most important achievements in the 8 years there before his untimely death.
See Nati. Acad. Sci., Biographical Memoirs, XVII (1935).
Annual Report 1933, p. 54. In Science, 78, 555, (1933), Dr. Washburn urged
construction of a plant for quantity production of "deuterium water." The 6 to 10
gallons produced annually would be enough, he believed, for all current needs of physics,
chemistry, and biological and medical research. Urey was no more prescient. Many
years later he recalled that when he discovered heavy water he never dreamed that it
would become a vital ingredient in the making of the atomic bomb. "I thought it
might have some practical use in something like neon signs." Time, Feb. 19, 1965, p. 42.
E. U. Condon, "Physics," p. 143.
'78Sci. Mo., 38, 390 (1934).