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Figure 9. This is the plaque at the entrance in Slade Hall commemorating the important work by Ramsay
on the inert gases. Ever since the chemical reactivity of xenon was discovered in 1962, "noble" gases has
become the preferred label for the "inert"family of elements.
Canada, on August 19, 1897, Ramsay delivered
a presentation on "An Undiscovered Gas,"12
where he argued that a gas should exist
between helium and argon (atomic weights =
4, 40, respectively).
It is interesting that Ramsay used the
Dobereiner Law5c of 1817 instead of the
Periodic Table to predict this new element.
Ramsay was concerned about uncertainties in
predictions from the Periodic Table. He was
aware of the predictions of Locoq de
Boisbaudran, who, impressed by the prophesy
of his element (gallium) by Mendeleev,5a used
extrapolations from the Periodic Table to predict
a much lower atomic weight 36.40 for the "ele-
ment [argon] between chlorine and potassi-
um."13 In reality, the atomic weight of argon
was much greater (40), even larger than that of
the following element, potassium (39), in the
Periodic Table. In fact, "reversals" of atomic
weights had been observed twice before in the
Periodic Table (viz., Te/I and Co/Ni)5e, which
simply underscored the difficulties in predicting
of atomic weights from the Periodic Table.
Ramsay preferred the simplicity and success of
Dobereiner's Law of Triads and boldly predict-
ed 20 for the atomic weight for the
"Undiscovered Gas."
Morris Travers.'4 Morris William Travers
(1872-1961), (Figure 8) an undergraduate of
University College, London, joined the group of
Ramsay in 1894, just after the discovery of
argon. The excitement of a possible entire new
group of elements fascinated Travers and he
became Ramsay's junior partner through the
discovery of a whole series of inert gases.
Ramsay had been preoccupied with his
"undiscovered gas,"but other inert gases were
serendipitously discovered first. By 1898
Ramsay and Travers had been preparing argon
on a large scale by separating it from the atmos-
phere with liquid air, now prepared in quantity
by the new process developed 1895 by William
Hampson (1854-1926).15 One day a liter of
argon, neglected because of other tasks, evapo-
rated over the period of a week. A sudden
inspiration of Ramsay led to the study of the
residual liquid. Although it exhibited spectral
lines of argon, also visible were two new lines,
a green and a yellow-green line. It was a new
gas! Ramsay named it krypton, for "hidden."7
During another evening, on a hunch Travers
stayed late to collect a bubble of residual gas
remaining in the pump (which was usually dis-
carded). Ramsay arrived the next day to find
they had another gas with new blue lines. They
named this gas xenon, for "stranger."'
Next, upon liquifaction of a sample of air, the
remaining uncondensed gas was studied.
Along with the yellow line of helium, it also
exhibited brilliant red lines, a"blaze of crimson
light." It was named neon for"new."' Although
the other heavier gases-argon, krypton, and
xenon-could be separated and isolated by a
series of fractional low-temperature distilla-
tions, the volatile neon could not be separated
from helium. Thus, the atomic weights and
Royal Society of Chemistry
National Historic Chemical Landmark
William Ramsay, Nobel Laureate 1904
Between 1894 and 1910, in a He
laboratory near this site, Ne
William Ramsay discovered and Ar
characterized the noble gases, Kr
completing the structure of the Xe
Periodic Table of the Elements. Rn
10 December 2004 R5,C
FALL 2012/THE HEXAGON
I I II I
other physical properties were known for all the
inert gases except neon.
There was only one solution: prepare liquid
hydrogen, which would condense neon but not
helium. The separation of neon from helium
attests to the genius and tenaciousness of
Travers-he received no help whatsoever from
Dewar, who had earlier prepared"' liquid
hydrogen (May 10, 1898) but published no
details." Travers, who had always loved to tin-
ker with appliances, took it upon himself to
design and build a hydrogen liquifier from
scratch.4 By July 7, 1900, he was successful, and
the helium-neon mixture condensed out 15 mL
of neon, whose boiling point of 27K (-246C)
was only 7 degrees higher than that of hydro-
gen, 20K (-253C). On July 10, 1900, after a
final series of purifications, the atomic weight
was determined to be 19.98, incredibly close to
the prediction at the Toronto meeting12 in 1897,
(the modern value is 20.18). Ramsay exclaimed,
as he performed the final calculation beside
Travers, "No one will repeat this work for many
years to come."6 His words were most prophet-
ic6,7-this was the last experiment that Travers
carried out with Ramsay (Figure 9).
In 1904 Travers assumed a Professorship at
the University College, Bristol (now the
University of Bristol). In 1907 he set up the
Indian Institute of Science, Bangalore, India. He
returned to England in 1914, and thereafter was
involved in many industrial enterprises involv-
ing fuel technology and cryogenics.14
The science of cryogenics. Karol
Olszewski (vide infra) and Zygmunt Florenty
Wr6blewski (1845-1888) had first condensed
oxygen and nitrogen in 1883 at Krakow,
Poland.' These cyogenic techniques depended
upon a cyclic compression and then adiabatic
expansion. A decade later William Hampson in
London, and Carl von Linde (1842-1934) in
Munich, developed methods of producing liq-
uid air in quantity; they filed their patents
almost simultaneously in 1895.15 Linde had a
long history of research in refrigeration, and his
business developed into an international
endeavor; "Linde Industrial Gases" is successful
worldwide even to this day.
The pioneering work of Hampson and Linde
depended not only on adiabatic expansion, but
also on the Joule-Thomson effect, where a real
(nonideal) gas experiences van der Waals inter-
molecular effects. Liquifying hydrogen was par-
ticularly difficult, because the Joule-Thomson
effect at room temperature actually warms the
lighter gases (e.g., helium, hydrogen, and neon)
upon expansion. In order to take advantage of a
negative Joule-Thomson effect, hydrogen gas
must first be cooled below the "inversion"tem-
perature (-68oC).
39