H2S Medium Research Articles

H2S papers as presumptive tests for Salmonella contamination in tropical drinking water

Coliform bacteria may not be adequate as sole indicators of recent faecal contamination in tropical waters. Salmonella spp. in particular have been found in tropical waters in the absence of traditional indicator bacteria. Remote areas without access to a laboratory have no opportunity for salmonellae analysIs as portable tests are currently not available. H2S papers indicate the presence of hydrogen sulphide producing bacteria, a characteristic shared by tne majority of Salmonella spp.. The potential of H2S papers to act as a presumptive test for salmonellae in the absence of coliform bacteria was assessed. Salmonella spp. grew in the H2S medium, with an optimum incubation temperature of 37°C and a recommended length of incubation for a negative result of 48 hours. The presence of high numbers of the type of noncoliform bacteria commonly found in drinking water did not affect the performance of the H2S strips. H2S papers are recommended for use in conjunction with a coliform test as a presumptive test for the presence of Salmonella spp. in drinking water.

Catalytic decomposition of dimethyl disulfide

We have studied dimethyl disulfide conversion on heterogeneous catalysts in a flow setup at T=250–350°C and atmospheric pressure. Methyl mercaptan appears to be the main reaction product. The rate of dimethyl disulfide decomposition and its selectivity towards methyl mercaptan in H2S medium are higher than those in pure helium. Thus the process seems to involve the surface protons formed upon dissociative H2S chemisorption.