Essentials of bacteriology; being a concise and systematic introduction to the study of bacteria and allied microörganisms . sa flocculent precipitate and carries down with the suspendedmatter much of the bacterial content. This is then filteredthrough sand and gravel. Sedimentation and filteringslowly through gravel and sand is known as the slow process;the other as the rapid, filtration. Charcoal sponge and asbestos, the materials formerly inuse, are objectionable because germs readily develop on themand clog them, so that they require frequent renewal. In EXAMINATION OF AIR, SOIL, AND WATE
Essentials of bacteriology; being a concise and systematic introduction to the study of bacteria and allied microörganisms . sa flocculent precipitate and carries down with the suspendedmatter much of the bacterial content. This is then filteredthrough sand and gravel. Sedimentation and filteringslowly through gravel and sand is known as the slow process;the other as the rapid, filtration. Charcoal sponge and asbestos, the materials formerly inuse, are objectionable because germs readily develop on themand clog them, so that they require frequent renewal. In EXAMINATION OF AIR, SOIL, AND WATER 237 very large filters, sand and gravel give the best results; thenumber of bacteria in a cubic centimeter is reduced to forty orfifty and kept at that number. This is a very pure water fora city water, though, as we stated before, not a safe one, foramong those forty germs very dangerous ones may be is then necessary for the users to refilter the water, beforedrinking it, through a material which will not allow anygerms to pass, or, in the presence of an epidemic, to boil allwater used for drinking Fig. 117.—Flask fitted with porcelain bougie for filtering large quantities of fluid. Pasteur-Chamberland Filter.—This very perfect filterconsists of a piece of polished porcelain in the form of acylinder closed at one end and pointed at the other. It isplaced in another cylinder of glass or rubber, and the pointedportion connected with a bottle containing the water, ordirectly with the faucet of the water-pipe. The water coursesthrough the porcelain very slowly and comes out nearly freefrom germs; pipe-clay, bisque, infusorial earth, and kaolin arealso good filters. The only disadvantage is the long time ittakes for the water to pass through. Pressure in the form 238 ESSENTIALS OF BACTERIOLOGY of an aspirator or air-pump is used to accelerate the pas-sage. These porcelain cylinders can easily be sterilized and thepores washed out. All the cylinders or bou
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Keywords: ., bookcentury1900, bookdecade1910, bookpublisherphila, bookyear1913
