Public health laboratory work, including methods employed in bacteriological research, with special reference to the examination of air, water and food contributed / by Rubert Boyce.

  • Kenwood, Henry R. (Henry Richard), 1862-1945.
Date:
1893
Catalogue details

Licence: Public Domain Mark

Credit: Public health laboratory work, including methods employed in bacteriological research, with special reference to the examination of air, water and food contributed / by Rubert Boyce. Source: Wellcome Collection.

Provider: This material has been provided by the Augustus C. Long Health Sciences Library at Columbia University and Columbia University Libraries/Information Services, through the Medical Heritage Library. The original may be consulted at the the Augustus C. Long Health Sciences Library at Columbia University and Columbia University.

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    evidence of organic pollution all along the line of the analysis), yet these characters are precisely those of our purest and best waters. For these reasons, and from what follows, it will be seen that evidence of purity or pollution furnished by the senses, is very unreliable in itself, and is not even of much corroborative value. Such tests, therefore, are not worthy of lengthy consideration here. The Physical Characters. The sample of water should be well shaken, and then about a litre (1000 c.c.) is emptied into a glass beaker, which is kept covered so as to protect from suspended matters in the air, and after the bulk of any suspended matter which may be present has settled, a thin colour- less glass tube twenty-four inches long is filled with the clear (supernatant) water, and from the appearance of this in the two-foot tube as it is called the following physical characters are judged :— 1. Clearness.—Though the best waters are always bright and clear, these qualities cannot be considered as reliable evidence of purity, for a polluted well-water may possess these characters ; and on the other hand any haziness or turbidity—which is of course created by minute particles of suspended matter—may by chemical and microscopical examination be proved either inoccu- ous or harmful. The degrees of such turbidity may be expressed as clear, very slightly turbid, slightly turbid, and turbid. 2. Colour.—To detect this the tube is held verti- cally upon a white porcelain slab, and the observer looks down through the depth of the column of water