The Houston daily post. [volume] (Houston, Tex.) 1886-1903, 1900-04-24
I.--LIQuID AIR.
(Concluded.)

|
gases proceeded, experimenters were
I brought to more and more intimate
knowledge OF conditions which had been
matters of mathematical demonstration
rather than of experience. The measure
ment of these conditions was very difficult
The properties of substances in this ex-
IRENE cold were unknown and great
| field OF research was at once opened.
AS heat consists in the energy of motion
OF the molecules of body, the idea at
once presents itself that the point might
be reached theoretically at least, where
the molecules, having lost their energy OF
motion little by little as the temperature
was reduced, had been brought TO rest.
Such point would mark the limit OF colo
and body at that temperature would
possess no heat at all. This point, for
obvious reasons, is known as the Absolute
zero" Its value is determined by means
of the relation between expansion OF gases
and temperature. to lie between 273 de-
grees and ga degrees below the zero OF
the centigrade scale. Logically, all tenn.
peratures should be reckoned from that
point, as, indeed, for many practical pur-
poses. they are.
Now, with all known gases liqueied,
we are getting wonderfully near TO this
point Just how near is as yet somewhat
a matter of inference. Allrordinary ther-
mometers fail Even the air thermometer
is frozen solid and the hydrogen Their
mometer is Of little use. Electrical meth
DDS are doubtful because nobody knows
Just how the electrical properties Of sub
stances vary at such temperatures. Dewar,
with liquid hydrogen, has obtained tenn
perature within about u degrees of the
absolute zero--some $50 degrees centigrade
or more than 500 degrees Fahrenheit
colder than the temperature of an ordi-
nary summer day. and solid hydrogen Is
about degrees centigrade colder yet II
will be interesting to relate, so far as they
are yet known, some of the properties OF
substances at these low temperatures.
Properties of Liauefied Gases.
The beautiful experiments which 1t is
possible to perform before an audience
with liquid air In quantity have become
well known. All ordinary liquids are
frozen. Alcohol becomes ice, mercury
d solid so hard that it will drive nails
A Jet of carbon dioXide gas Bills as snow;
and to make the liquid air boil violently
II is only necessary TO set kettle of 1t
upon cake OF ice In spite Of this, liquid
air is kept for hoars in unsealod cans,
In which evaporation is comparatively
slow. For the rarer liquehed gases, in
small quantities, Dewar has devised the
vacuum flask. The liquid oxygen or
hydrogen or whatever It may be, is in
the inner vessel, and the space hetwe-n
that and the outer flask Is exhausted. the
two TASKS being sealed together at the
neck. 1t is found that the evaporation is
only about one-iitun as rapid as when this
space is filled with air.
Under such conditions air may be seen
as clear, colorless LIQUID when pure, as
as transparent solid when very cold. Tho
solid air at higher temperature is char
acterized as nitrogen Jelly. from which
a strong magnet will draw the oxygen.
Oxygen as liquid in considerable guam
tity shows a pale blue color, as does thu
solid oxygen. 1t is highly magnetic and n
good insulator. Liquid ozone is indigo blu,
and very explosive. Nitrogen forms an
opaque solid. Hydrogen as a liquid lie
colorless and transparent, and as solid
is a transparent Ice with frothy surface,
due probably to very rapid evaporation.
1t is said TO be distinctly non-metallic.
Fluorine, very difficult to liquefy, is a
clear yellow liquid, very mobile, 1t doa1
not attack glass at these low temperatures
Argon forms a colorless liquid. and at very
low temperatures an opaque solid. Thu
liquids are generally colorless and trans
parent except fluorine and chlorine, which
are both yellow.
Effects of Very Low Temperatures.
Temperatures as low as these We are
considering have very marked effect
upon the properties Of familiar materials
and upon chemical action. Wires of metal
are made much more hard and brittle and
their tensile strength is Increased. Rub
her, cork and such substances are as hard
as stones, and organic substances of all
kinds are frozen solid. Chemical action 10
..nr Int o1.a
err, and the action of light on Photographic
films Is very weak
Upon living organisms the effects OF
very low temperature are various. Cold
blooded animals show but slight resist
ance, while warm blooded animals resist
surprisingly we'll until the resources OF
the body are exhausted, Few insects can
resist very low temperatures, although
snails were subjected to a temperature
Of -120 degrees without apparent injury.
Bacteria. unfortunately. seem to be unaf-
fected by the lowest temperature to which.
they have been exposed, -213 degrees
centigrade Possibly later experiments al
ESQ degrees to 200 degrees may show
different result. The beneficial effect
of the cold bath is we'll recognized; but
probably no one, before Pictet, ever advo-
Gated one quite so cold at 10 degrees
below zero centigrGde Bv the cautious
usV VI luS air udtn NJ TINS temperature
he cured himself of chronic Indigestion Of
long standing, and a "cold we'll construct
ed unAsr his supervision was afterward
IN use by many people.
The effect of low temperatures on the
eerminating power OF seeds has twice been
tried, once at --lS2 degrees c., and again.
within the last few months at --252 de-
grees G. In the more recent experiments
number OF seeds OF different types were
EXPOSED to the temperature of LIQUID
hydrogen Some OF each were cooled
slowly, and kept for more than an hour
IN a sealed tube immersed In the hydro
gem The others were not so carefully
treated. In transmitting the second packet
OF seeds for planting. Dewar wrote: 81
nave sent you seeds tosay which /, the
treatment with cold can kill. ought TO be
aaead They have been immersed in LIQUID
nydrogen for upward OF six hours. and NJ
attempt was made 10 graduate the cool.
ing The seeds have been soaked
N LIQUID hydrogen" The seeds showed n5
trace OF their hard experience and ali
sspfouted. This experiment. Is partirulariv
interesting as the temperature TO which
me seeds were exposed is very nearly as
low as that Of the great inirrstellar spaces.
ana their survival lends additional weight
70 the idea that life may originally have
neen brought to the earth on some seed
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