Dissolve or dilute 10 g or 10 ml of the preparation being examined, unless otherwise prescribed, in Lactose broth or another suitable medium shown not to have anti-microbial activity under the conditions of the test and adjust the volume to 100 ml with the same medium. If necessary, adjust the pH to about 7.0 ± 0.2. Staphylococcus aureus , Bacteriological Incubator, Analytical Balance