A RELIABLE WATER FILTER.
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.
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.