Opinions are so firmly fixed at present that water is capable of carrying
the germs of disease that, in cases of epidemics, the recommendation is
made to drink natural mineral waters, or to boil ordinary water. This is a
wise measure, assuredly; but mineral waters are expensive, and, moreover,
many persons cannot get used to them. As for boiled water, that is a
beverage which has no longer a normal composition; a portion of its salts
has become precipitated, and its dissolved gases have been given off. In
spite of the aeration that it is afterward made to undergo, it preserves an
insipid taste, and I believe that it is not very digestible. I have
thought, then, that it would be important, from a hygienic standpoint, to
have a filter that should effectually rid water of all the microbes or
germs that it contains, while at the same time preserving the salts or
gases that it holds in solution. I have reached such a result, and,
although it is always delicate to speak of things that one has himself
done, I think the question is too important to allow me to hold back my
opinion in regard to the apparatus. It is a question of general hygiene
before which my own personality must disappear completely.
In Mr. Pasteur's laboratory, we filter the liquids in which microbes have
been cultivated, so as to separate them from the medium in which they
exist. For this purpose we employ a small unglazed porcelain tube that we
have had especially constructed therefor. The liquid traverses the porous
sides of this under the influence of atmospheric pressure, since we cause a
vacuum around the tube by means of an air-pump. We collect in this way,
after several hours, a few cubic inches of a liquid which is absolutely
pure, since animals may be inoculated with it without danger to them, while
the smallest quantity of the same liquid, when not filtered, infallibly
causes death.
This is the process that I have applied to the filtration of water. I have
introduced into it merely such modifications as are necessary to render the
apparatus entirely practical. My apparatus consists of an unglazed
porcelain tube inverted upon a ring of enameled porcelain, forming a part
thereof, and provided with an aperture for the outflow of the liquid. This
tube is placed within a metallic one, which is directly attached to a cock
that is soldered to the service pipe. A nut at the base that can be
maneuvered by hand permits, through the intermedium of a rubber washer
resting upon the enameled ring, of the tube being hermetically closed.
Under these circumstances, when the cock is turned on, the water fills the
space between the two tubes and slowly filters, under the influence of
pressure, through the sides of the porous one, and is freed from all solid
matter, including the microbes and germs, that it contains. It flows out
thoroughly purified, through the lower aperture, into a vessel placed there
to receive it.
I have directly ascertained that water thus filtered is deprived of all its
germs. For this purpose I have added some of it (with the necessary
precautions against introducing foreign organisms) to very changeable
liquids, such as veal broth, blood, and milk, and have found that there was
no alteration. Such water, then, is incapable of transmitting the germs of
disease.
[Illustration: CHAMBERLAND'S WATER FILTER.]
With an apparatus like the one here figured, and in which the filtering
tube is eight inches in length by about one inch in diameter, about four
and a half gallons of water per day may be obtained when the pressure is
two atmospheres--the mean pressure in Mr. Pasteur's laboratory, where my
experiments were made. Naturally, the discharge is greater or less
according to the pressure. A discharge of three and a half to four and a
half gallons of water seems to me to be sufficient for the needs of an
ordinary household. For schools, hospitals, barracks, etc., it is easy to
obtain the necessary volume of water by associating the tubes in series.
The discharge will be multiplied by the number of tubes.
In the country, or in towns that have no water mains, it will be easy to
devise an arrangement for giving the necessary pressure. An increase in the
porosity of the filtering tube is not to be thought of, as this would allow
very small germs to pass. This filter being a perfect one, we must expect
to see it soil quickly. Filters that do not get foul are just the ones that
do not filter. But with the arrangement that I have adopted the solid
matters deposit upon the external surface of the filter, while the inner
surface always remains perfectly clean. In order to clean the tube, it is
only necessary to take it out and wash it vigorously. As the tube is
entirely of porcelain, it may likewise be plunged into boiling water so as
to destroy the germs that may have entered the sides or, better yet, it may
be heated over a gas burner or in an ordinary oven. In this way all the
organic matter will be burned, and the tube will resume its former
porosity.--_M. Chamberland, La Nature._
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