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A Berkefeld filter〔(Definition: Berkefeld filter from Online Medical Dictionary )〕 is a water filter made of diatomaceous earth or ''Kieselguhr''. It was invented in Germany in 1891, and by 1922 was being marketed in the United Kingdom by the Berkefeld Filter Co.〔("Berkefeld Filter Co (British)" ), ''Grace's Guide'', accessed 2010-09-22〕 Berkefeld was the name of owner of the mine in Hanover, Germany, where the ceramic material was obtained. The Berkefeld is a good bacterial water filter used in microbiological laboratories, in homes and out in the field.〔Textbook of Microbiology by Prof. C P Baveja, ISBN 81-7855-266-3〕〔Textbook of Microbiology by Ananthanarayan and Panikar, ISBN 81-250-2808-0〕 == Design and mode of action == The filter housing consists of two metal or plastic cylinders sitting one on top of the other. The upper one has a lid and can be filled with impure water. In the bottom of the upper cylinder are one or more holes fitted with porcelain filter columns. The water is forced through the filters by gravity,〔(SafeTrek Survival Foods - Dried and Dehydrated One-Year and Four-Year Packages )〕 and then trickles down to the lower cylinder where it is stored and tapped off as required. Some types of filter are fitted with a carbon core to act as a deodorizing adsorbent.〔(FAQ from British Berkefeld on New Millennium Concepts )〕 They may also be impregnated with silver to inhibit bacterial growth. Some types, depending on their grade of porosity, also remove certain microscopic fungi and particulate matter. The filters without silver impregnation are sterilized by autoclaving or by steam sterilizer after thorough cleaning. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Berkefeld filter」の詳細全文を読む スポンサード リンク
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