Southwest-sentinel. [volume] (Silver City, N.M.) 1883-189?, 1894-03-06
BOILING POINTS.
These Are Tnnumorablo n FERN . Gu
rIona gtudr.

NAoub STUDY
Il is interesting 70 note that the tenn
p%orature as which q liquid boils Is the
same as that at which It's vapor Is con-
densed, precisely as the temperature at
which water freezes is thu same as that
at which ice melts.
It may seem superfluous 10 observe
that there are more boiling points than
the boiling point Of water. II It were
not 80, ell bodies would be In the solid,
liquid or gaseous state together, and life
would be impossible. It Is partly by
giving every substance its own boiling
point, OF rather its wa set Of boiling
points-for the hxed temperature, even
for the same substance, is a fallacy-
that nature has rendered our physical
environment suitable to our needs.
What is generally understood by the
boiling point Of water is a temperature
of ala degrees on the Fahrenheit Their
mometrio scale, but Alpine climbers
know well that, on a high mountain,
water boils at a very much lower tenn
perature-on the summit Of Mont Blanc
at 154 degrees. The reason - that, at
these attitudes, the pressure of the at
mOsphere is very much reduced, since
the density of the air decreases with the
distance above the earth's surface, and
the water expands at q correspondingly
lower temperature, passing more read
lily into the vaporous condition, in which
the volume of a given mass Of any sub
stance Is always far greater than that
Of the same mass whom liquid. The
boiling point Of liquid Is, therefore,
seen to depend not only on temperature,
but also on pressure, and the boiling
point of water at 212 degrees CORE
spends to what is called "a pressure Of
me atmosphere" approximately 10
pounds to the square inch, or the pres
sure capable of supporting the column
Of mercury in a morcurial barometer
at a height Of 1919 inches. This is
the average pressure of the atmosphere
at the sea level, and If it is reduced the
boiling point is lowered, while If it is
increased the boiling point Is raised.
A very curious result is arrived at
II we place q vessel Of water in the re-
ceiver Of an airpump and reduce the
pressure to .006 Of an atmosphere, for
then the water boils at 80 degrees-that
ia, at its freezing point under ordinary
pressure. Since it is now possible to
produce an almost perfect vacuum,
water may be boiled at still lower tenn
peratures.
All liquids do not boil at the same
temperature. Thus, while water under
a pressure of ono atmosphere boils at
ala degrees, alcohol, which passes more
readily into the state Of vapor, bcils
at 1873 degrees and ether at 93.8 de-
grees, which is below the normal tenn
perature Of the body.
Since increase of pressure retards the
vaporization Of a liquid, it of course
facilitates the liquefection Of a gas by
assisting the process Of contraction.
Consequently many gases are capable
Of being liqueied by pressure alone,
though only when they are below what
is called their critical temperature
different for every different gas, above
which cold as well as pressure becomes
necessary. Oxygen, hydrogen and nitro
gen are the most remarkable examples
of gases having low critical tempera-
lures, and 1t is only recently that theiI
l%iquefaction has been accomplished al
all. They were long thought to be
permanent gases" but it is now
known that all gases are ~liquehable.
Tho boiling points of oxygen and nj
trogen are respectively 875.s degrees
and 800 degrees F. below the freez-
ing point of water, and therefore
these are the highest temperatures al
which they can exist as liquids. To
produce these extremely low tempera-
lures 1t Is necessary to employ great
pressure along with freezing mixtures,
The most remarkable liquefaction which
has yet been accomplished is that Of
air. 1t was supposed that, the oxygeI
and nitrogen having different boiling
points, they would liquefy separately,
This is not the case; the mixture lique
hes as air and presents the appearances
Of water, but on being again evaporatet
the nitrogen evaporates first and the OK
ygen afterward. This Is q puzzle II
physics which will doubtless be ex
planned ere long.-Good Words.