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BAM R28: Gel Diffusion Agar, 1.2%

January 2001

Bacteriological Analytical Manual

Gel Diffusion Agar, 1.2%


NaCl8.5 g
Sodium barbital8.0 g
Merthiolate (crystalline)0.1 g
Noble special agar (Difco)12.0 g
Distilled water1 liter


Dissolve NaCl, sodium barbital, and merthiolate in 900 ml distilled water. Adjust pH to 7.4 with 1 N HCl and/or 1 N NaOH. Bring volume to l liter. Add Noble agar. Melt agar mixture in Arnold steamer. Filter in steamer, while hot, through 2 layers of analytical grade filter paper (e.g., No. 588, Schleicher and Schuell or equivalent). Dispense in small (15-25 ml) portions into 4 oz prescription bottles. Do not remelt more than twice.


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