U.S. Food & Drug Administration
Center for Food Safety & Applied Nutrition

Bacteriological Analytical Manual Online
January 2001

R42
McFarland Nephelometer

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Make suspensions of barium sulfate as follows:

  1. Prepare 1.0% solution of CP (chemically pure) sulfuric acid.
  2. Prepare 1.0% solution of CP barium chloride.
  3. Prepare 10 standards as follows:
    4. Add
    (ml 1% BaCl2 solution)    		 to
    (ml 1% H2SO4 solution)
    1 99
    2 98
    3 97
    4 96
    5 95
    6 94
    7 93
    8 92
    9 91
    10 90


  4. Seal about 3 ml of each standard suspension of barium sulfate precipitate in small test tube. Select test tubes carefully for uniformity of wall thickness, diameter, and color. (These preparations are available commercially from several laboratory supply firms.)


    5. Hypertext Source: Bacteriological Analytical Manual, 8th Edition, Revision A, 1998.

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