Posted on August 9, 2018August 13, 2018 by admin Microbiology: Lab 23-24, citrate test. Citrate test. Hydrogen sulfide test. Methyl red. Reference Cappuccino, J. G., & Welsh, C. (2018). Microbiology: A laboratory manual. Post navigationPrevious post: Microbiology: Lab 9, Gram stain examples.Next post: Microbiology: Lab 25, urease test.