Service chemistry : being a short manual of chemistry and metallurgy and their application in the naval and military services / by Vivian Byam Lewes and J.S.S. Brame.

  • Vivian Byam Lewes
Date:
1913
Catalogue details

Licence: In copyright

Credit: Service chemistry : being a short manual of chemistry and metallurgy and their application in the naval and military services / by Vivian Byam Lewes and J.S.S. Brame. Source: Wellcome Collection.

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    if the iiiiiiiial charcoal has not been burnt at a sufficiently high temperature, which is rarely done, as it means a certain loss of carbon, some of the nitrogenised organic matter of the bone remains and Ijecomes a breeding-place for myriads of minute organisms which find their way into the water. Also, fresh organic matter like the white of an egg (albumen), which has not yet entered into putrefactive change, passes through animal charcoal almost unacted upon. Biologists have shown that domestic filters of all these classes are w^orse than useless for the removal of germs and bacteria, and that while they act satisfactorily in arresting suspended particles, many filters, especially those dependent ui)on carbon blocks, servo as breeding grounds for the growth of various organ- isms, which are generally found in enormousl} greater numbers in the filtered than the unfiltered water, and although the majority of these bacteria may have no specific action, it is clear that such filtration would be also unavailing against those liable to set up disease. It has moreover been shown that even though such filters be repeatedly cleaned and sterilised, they are absolutely useless as a safeguard against dangerous germs. Pasteur-Chamberland Filters.—The filters which recent re- searches have shown to be the only effective ones are those con- sisting of a cylinder of unglazed porcelain cla}' of the Pasteur- Chamberland type, in which water under the pressure present in the supply pipes passes through the porcelain from without mwards. This form of filter, according to the researches of Plagge, seems to be absolutely impermeable to bacteria, and is so arranged that as the surface of the porcelain tube becomes choked with solid particles, it can be removed and scrubbed. Other filters like the Berkefeld, which are also made on this principle but of infusorial earth instead of porcelain clay, have not the same effect in yielding a sterile filtrate for any length of time. Fig. 21 shows a section of a single cell tap filter of t he Pasteur- Chambeiiand type, in which (a), the cylinder of unglazed porcelain, is closed at the top, whilst the bottom is provided with an external flange and open nozzle. Surrounding the cylinder is a metal tube (b) suffici('ntly large in bore to leave a space between it and the side's and to}) of the porcelain tube. The u])pt'r end of this jacket is soldered to the water tap, whilst the lower end can
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