Evening star., 1941-01-26
Used in Air Conditioning.


heads of these young ladies has de-
pended in large measure, the COM
fort of all homes with air condi-
tioning" The hygrometers of which
they form the essential part serve
as automatic moisture thermoStats
IN such houses. charging the air with
amounts Of water VapOr. regulated
according to the temperature. when
ever It gets below the ideal humidity
for human beings.
The method has been crude and
costly. The Bureau OF Standards
physicists say, but there has been
no substitute for 1t before the in
surumont Just invented by Dr.. Fran
els W. DunmOre Of the bureau staff.
The hair hygrOmeter has had two
serious drawbacks. First there has
been an appreCiable time lag before
it could absorb the maximum of
moisture in the air and another
lag before it could lose it. This
lag became greater and greater at
colder temperatures, ranging from
a minute at 70 degrees Fahrenheit
~ III &C anu q IAN minutes dt L6IO.
Second, at a little below zero it
failed altogether, making It prac-
tiCally worthless for present re-
fined methods of weather fore
casting
Palladium Coils Used.
The instrument invented by DR..
DunmOre consists of two coils of
wire spun from the rare metal
palladium, wound around a tiny CYL
inder made of plastic known as
pOlvStyrene, which is absolutely
impervious to moisture. This cylin-
der is covered with an extremely
thin film containing a chemical
known as lithium chloride, which
absorbs moisture and dries again
almost inStantaneously. The two
coils of wire are so wound that they
do not touch each other. An cleo
trio current is sent through one
OF them. When the film is COM
pletely dry it is absolutely nom
conducting for electricity. The in
slant it becomes moist to any de-
gree it becomes slightly conduct
ing, and current flows through it to
the other coil. The wetter it be-
comes the less the resistance and
the greater the current. This is
measure of the humidity.
The instrument is so delicate that
a breath AGAINST it will make the
indicator attached to the second
coil jump. A. room temperatures
it reacts 20 times faster than the
blond hair. At zero it reacts nearly
20 times faster. It will react at
temperatures as low as so below
encountered from 10 to 20 miles
high in the atmospheric quality
which probably will make it indis-
pensable for certain neW-type
weather observations.
Weight Will Be Factor.
1t weighs less than an ounce
Compared to it the lightest blond
hair hygrometers are cumbersome.
This makes it valuable for use in.
the radioSondeS. the new balloon
StratOSpbere explorers now used BY
the Weather Bureau, which make
about a dozen complex observa-
tlons and radio them back to OBJ
servers on the ground. All this is
entirely automatic Humidity is one
measurement, which hitherto has
been practically impossible because
OF the Sluggisnness of the blond
hair and their failure at very low
temperatures.
The instrument measures the de-
gree OF saturation of the atmosphere
with water vapor relative to the
normal Saturation at a certain tenn
perature. This is extremely i'm
portant at heights of 2 or 3 miles,
where the various air mass fronts
come together. A highly saturated
air mass might be the only indi-
cation of coming rain.
Already, DR.. Dunmore saws. about
80 uses have been found for the
new observation-disclosures them the
prediction of forest fires from the
degree Of moisture in the soil, where
the instrument can be buried and
estimation of the strength of
concrete wall by boring a hole in
it and placing a hygrometer in
side.