Evening star., 1937-01-12
STARS, MEN AND ATOMS
Notebook of Science Progress in Field,
Laboratory and Study.

BY THOMAS r. HENR Y.

The precious metal silver is finding a
new use as one Of the most potent known
killers of bacteria and purifiers of food
substances.
This is brought out in study of the
physical and chemical properties of the
element conducted at the Bureau OF
Standards by Drs B. A. Rogers, Irl C.
Schoonover and Louis Jordan. The
study was financed by the leading silver
producing companies in the United
States.
Ordinarily considered as material for
coinage and tableware, silver has extraor-
dinary properties which give it wide
range of uses in both engineering and
medicine, the report of the study points
out Among the most notable of these
properties are its peculiar abilities as
germ killer. 1t is a deadly poison TO
bacteria in minute amounts, but is ap-
parently almost harmless to man and
the higher animals. The only adverse
effect thus far noted from continued
injeStion of silver in such amounts as
are used in pharmaceutical preparations
is slight darkening of the skin.
Special experiments were conducted on
the so-called "oligodynamic effect"-a
term used to denote the bactericidal
action of certain metals in dilute Solu-
tion. 1t was first noted with copper. AS
long ago as 1893 the observation was
made that the presence of this element
in water in amount so minute as to be
almost indistinguishable by any chemical
methods had a very marked bacteria
killing and purifying effect.
Little interest was manifested in the
phenomenon, the Bureau of Standards
chemists report, until the World War
when there were experiments on the
publication of water by finely divided
silver. Since then there has been a
great deal of experimentation along the
same lines, mostly in Germany.
They report an experiment recently
conducted by Baltimore dairy COM
pany with water containing dangerous
bacteria in concentrations ranging from
5000 to 5000 germs per cubic centimeter.
Silver in various forms was introduced
in concentrations of about one part per
ten million parts of water. The solu-
tions became entirely sterile in from an
hour and half to little less than three
hours.
Further information was obtained from
experiments conducted in the bacteri-
illogical laboratories of DR.. Robert Keilty
In Washington. The bactericidal powers
of copper, bronze, silver and silver plated
disks were studied. 1t was found that
pure silver and ilver-plated disks might
eventually effect destruction of the bac-
terra when kept in direct contact with
them on nutrient media. Copper had
the same effect, but to somewhat less
extent. Bronze seemed to have very
little bacteria-killing power.
The experiments of DR.. G. A. Krause
on the publication of water are cited
as outstanding. Infected water is made
to dissolve silver ions in extreme minute
amounts-sometimes as small as two
hundreds of one part per million. The
water then Is allowed to stand for a
period of from half an hour to several
hours, according to the dosage of silver
and other conditions. Then its path
ogenic bacteria, such as those which
cause typhoid fever, are found to be
completely killed and the water safe to
drink.
The bactericidal use of silver, they
report, is not confined to the purif1ca-
tion of drinking water. 1t has been used
for the sterilization of spirit vinegar,
water used in making ice, bottled min
eral water, preservation of fish. prepara-
ton of mouth washes and gargles and
tn various antiseptic soaps and salves.