A compound able to inhibit the growth of bacteria and other microorganisms, used as a medical disinfectant and preservative for biological products.
Chemical formula: C₉H₉O₂SHgNa
 Example sentencesExamples
-  The removal of the mercury-based preservative, thiomersal, comes weeks after researchers in the US suggested that it could be linked to the development of autism.
 -  This was strengthened a few weeks ago when US researchers suggested a mercury-based preservative, thiomersal used in the vaccine for whooping cough could be linked to the development of the condition.
 -  The third change is that the new vaccine does not contain the mercury-based preservative thiomersal.
 -  We are told that the mercury-based preservative thiomersal will no longer be used in the whooping cough vaccine ‘as part of a worldwide aim of reducing exposure to the element.’
 -  The vaccine does not contain the mercury-based preservative thiomersal, unlike the existing version.