The Washington times., 1925-02-02
TESTS ARE
SUCCESS
HERE
Bureau of Standards An
nounces Results of Studies
and Experiments
BY ROBERT s.. THORNBURGH

BY ROBERT s.. THORNBURGH
Use of the ultraviolet ray as
germ exterminator, found high
~ effective in an investigation at
the United States Bureau of
Standards, is regarded by scien-
lists as marking the beginning of
. new era in the prevention of
disease.
Further development of the
idea may make, possible its en-
ployment in the successful cure or
treatment of practically all disease
germs. according > to Government
experts.
Wave Lengths Studied.
The study of the germ-kiIling
action of ultraviolet rays covered
the range of wave lengths from
just Beyond the limit of the visible
spectrum down to the shortest
wave lengths emitted by a mercury
vapor are in a quar- lamp" the
bureaus official statement said
The shortest waves were found
to have the most pronounced and
vigorous action, being capable
when sufficiently intense, of pro-
ducing death with an exposure of
only one second.
Longer Wave Lengths.
Longer wave lengths required
greater intensity and acted much
more slowly; but killing action
fn
waves as long. as 36S-millionths Of
O millilneter, which is almost as
long as the shortest wave visible
to the human, eye.
Prior to this experiment doubt
had been expressed regarding the
ability of these longer waves to kill
bacteria"
"Bacterium coli communis' was
the victim of the governmental
tests. According to scientists this
germ is always found in human
sewage, or in waters that are pol
luted and likely at some time to
contain typhoid.
Germs Liberated.
The. germs were liberated In a
large volume Of water. and some Of
the water was sprayed onto petrl
dishes containing a selidified jelly.
specially prepared to suit the tastes
OF the bacteria.
Those germs not killed by the
rays increased and multiplied and in
q few days formed colonies visible to
the human eye," officials said. "a
quartz mercury vapor lamp was
used as the source of the ultraviolet
rays, screens being interposed to cut
off successive spectral ranges Of the
wave lengths which might cause
Hermicidal action
To kill germs in one second a
320-watt mercury lamp was used at
4 distance of six inches, producing
the required intensity of the ray.
When the intensity was very low,
the killing action was greatly re-
tarded, according to the results dis
closed. In some experiments an ex-
posture of seventy-five to eighty
seconds was required.
On still lower intensities there was
some indication that the bacteria
were stimulated instead of being
killed.
"Other tests were made to com
pare the relative value Of continu
GUS and intermittent exposures" it
was explained. ''It was found that
the killing effect was proportional
to the total exposure, whether this
was given all at once or was d
vided into several short exposures,
with periods Of rest between"
To Prevent Disease
Properly developed scientists be
lieve the ultraviolet ray may be
used in a wide range of activities
looking to prevention or treatment
OF diseases and prolonging human
life.
They pointed out that the rays
may be employed in the Eurifica-
ton of water, instead OF the pres
ent filtration process, followed by
chlorine or other drug treatment
which has the advantage of af-
fecting the taste and odor If
water.