SIR WILLIAM RAMSAY—MOUREU. 537 
cooling with liquid air. The clear liquid obtained was submitted to 
a fractional evaporation very skillfully conducted, with the purpose 
of separating the gases more or less volatile than argon. The success 
was complete. 
The first breaking up furnished a light gas, about ten times more 
dense than hydrogen, and characterized by a magnificent spectrum 
with brilliant lines in the red and the yellow. Ramsay called it neon. 
It is moreover accompanied by a certain proportion of helium, pres- 
ent also in the air, and from which it can be separated by the use 
of liquid hydrogen (—253°), which solidifies the neon and leaves 
the helium in a gaseous state. 
The end products of the distillation of liquified argon retained the 
two other new gases, which could however be separated by liquifac- 
tion and fractionating. Ramsay called them crypton and xenon; 
their densities in relation to hydrogen were 41 and 65. 
For the three new gases, neon, crypton, and xenon, the study of 
the specific heats led, as for helium and argon, to a monatomic mole- 
cule. They are likewise chemically inert.. Their atomic weights 20, 
82, and 130 were found to occupy exactly the places indicated by the 
classification of Mendeleeff. 
Thus, in the atmospheric air, which during more than a century 
had been believed to be perfectly known, Ramsay had succeeded in 
the four years from 1894 to 1898, in isolating a complete natural 
group of simple gases. Indeed a splendid achievement. Striking 
proof of the fundamental truth comprehended in the periodic law. 
Witness, just as noteworthy, of the scientific faith and the ability in 
experimentation of this master. Nearly all the apparatus had to be 
invented, and Ramsay also had to construct most of it himself. Only 
those who have handled small quantities of gas and have prepared 
absolutely pure gases, giving spectra entirely free from foreign lines, 
are able to understand all the technical difficulties of such a work. 
A little before the discovery of crypton, Ramsay thought he had 
isolated another element in the atmospheric argon; it had the same 
density as argon, but its spectrum was entirely different; he called 
it metargon and described several principal lines. Metargon was 
not, however, a new element; it was recognized that the lines indi- 
cated were due to traces of carbonic oxide, which occurs as an im- 
purity in argon. Other chemists were working on the same problem, 
and Ramsay, too much hurried, had insufficiently purified his argon. 
I will cite Ramsay himself in this connection: 
Should we under such circumstances regret the publication of an error? It 
seems to me that an occasional error should be excusable. No one can be 
infallible; and besides, in these conjectures one has always a large number of 
good friends who promptly correct the inaccuracy. 
